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YEAR     BOOK     56 


July    1,    1956— June   30,    1957 


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CARNEGIE  INSTITUTION  OF  WASHINGTON 

WASHINGTON,    D.   C. 

1957 


Library  of  Congress  Catalog  Card  No.  3-16716 
THE  LORD  BALTIMORE  PRESS,  INC.,  BALTIMORE,  MARYLAND 


CONTENTS 


page 

OFFICERS  AND  STAFF  v 

REPORT  OF  THE  PRESIDENT  1 

REPORTS  OF  DEPARTMENTS  AND  SPECIAL  STUDIES  35 

Mount  Wilson  and  Palomar  Observatories  37 

Committee  on  Image  Tubes  for  Telescopes  77 

Department  of  Terrestrial  Magnetism  81 

Geophysical  Laboratory  149 

Department  of  Plant  Biology  253 

Department  of  Embryology  297 

Department  of  Genetics  357 

Department  of  Archaeology  405 

BIBLIOGRAPHY  415 

INDEX  417 

SUPPLEMENT  xiii 

Report  of  the  Executive  Committee  xv 

Report  of  Auditors  xvii 
Abstract  of  Minutes  of  the  Fifty-Ninth  Meeting  of  the  Board  of  Trustees     xxxiii 

Articles  of  Incorporation  xxxv 

By-Laws  of  the  Institution  xxxix 


in 


PRESIDENT  and  TRUSTEES 


PRESIDENT 
Caryl  P.  Haskins 

BOARD  OF  TRUSTEES 
Walter  S.  Giflford,  Chairman 

Barklie  McKee  Henry,  Vice-Chairman 

Robert  Woods  Bliss,  Secretary 

James  F.  Bell 
Robert  Woods  Bliss 
Lindsay  Bradford 
Omar  N.  Bradley 
Walter  S.  Giflord 
Crawford  H.  Greenewalt 
Caryl  P.  Haskins 
Barklie  McKee  Henry 
Ernest  O.  Lawrence 
Alfred  L.  Loomis 
Robert  A.  Lovett 
Keith  S.  McHugh 
Margaret  Carnegie  Miller 
Henry  S.  Morgan 
Seeley  G.  Mudd 
William  I.  Myers 
Henning  W.  Prentis,  Jr. 
Elihu  Root,  Jr. 
Henry  R.  Shepley 
Charles  P.  Taft 
Juan  T.  Trippe 
James  N.  White 
Robert  E.  Wilson 


TRUSTEES  Continued 


EXECUTIVE  COMMITTEE 


Barklie  McKee  Henry,  Chairman 
Robert  Woods  Bliss 
Lindsay  Bradford 
Walter  S.  GifTord 
Caryl  P.  Haskins 


Robert  A.  Lovett 
Henry  S.  Morgan 
Henning  W.  Prentis,  Jr. 
Henry  R.  Shepley 


FINANCE  COMMITTEE 

Lindsay  Bradford,  Chairman 
Walter  S.  Gififord 
Alfred  L.  Loomis 
Henry  S.  Morgan 
Henning  W.  Prentis,  Jr. 
James  N.  White 


NOMINATING  COMMITTEE 

Elihu  Root,  Jr.,  Chairman 
Walter  S.  Gifford 
Crawford  H.  Greenewalt 
William  I.  Myers 


AUDITING  COMMITTEE 

Keith  S.  McHugh,  Chairman 
Alfred  L.  Loomis 
Juan  T.  Trippe 


RETIREMENT  COMMITTEE 

Lindsay  Bradford,  Chairman 
Barklie  McKee  Henry 
Henry  S.  Morgan 


COMMITTEE  ON 
ASTRONOMY 

Seeley  G.  Mudd,  Chairman 
Crawford  H.  Greenewalt 
Elihu  Root,  Jr. 


COMMITTEE  ON 
BIOLOGICAL  SCIENCES 

Alfred  L.  Loomis,  Chairman 
Margaret  Carnegie  Miller 
William  I.  Myers 
Charles  P.  Taft 


COMMITTEE  ON 
TERRESTRIAL  SCIENCES 

Ernest  O.  Lawrence,  Chairman 
Barklie  McKee  Henry 
Henning  W.  Prentis,  Jr. 
Robert  E.  Wilson 


COMMITTEE  ON 
ARCHAEOLOGY 

Henry  R.  Shepley,  Chairman 
James  F.  Bell 
Robert  Woods  Bliss 
Juan  T.  Trippe 


VI 


FORMER  PRESIDENTS  and  TRUSTEES 


PRESIDENTS 

Daniel  Coit  Gilman,  1902-1904  Robert  Simpson  Woodward,  1904-1920 

John  Campbell  Merriam,  President  1921-1938;  President  Emeritus  1939-1945 
Vannevar  Bush,  1939-1955 


TRUSTEES 

1904-05 

Wayne  MacVeagh 

1902-07 

1925-27 

Andrew  W.  Mellon 

1924-37 

1934-46 

Roswell  Miller 

1933-55 

1902-13 

Darius  O.  Mills 

1902-09 

1910-29 

S.  Weir  Mitchell 

1902-14 

1903-14 

Andrew  J.  Montague 

1907-35 

1929-38 

William  W.  Morrow 

1902-29 

1916-32 

William  Church  Osborn 

1927-34 

1925-34 

James  Parmelee 

1917-31 

1927-49 

Wm.  Barclay  Parsons 

1907-32 

1903-23 

Stewart  Paton 

1916-42 

1902-03 

George  W.  Pepper 

1914-19 

1914-24 

John  J.  Pershing 

1930-43 

1927-52 

Henry  S.  Pritchett 

1906-36 

1910-14 

Gordon  S.  Rentschler 

1946-48 

1920-55 

David  Rockefeller 

1952-56 

1948-49 

Elihu  Root 

1902-37 

1902-15 

Julius  Rosenwald 

1929-31 

1902-12 

Martin  A.  Ryerson 

1908-28 

1924-34 

Theobald  Smith 

1914-34 

1924-35 

John  C.  Spooner 

1902-07 

1902-08 

William  Benson  Storey 

1924-39 

1902-05 

Richard  P.  Strong 

1934-48 

1915-29 

William  H.  Taft 

1906-15 

1902-03 

William  S.  Thayer 

1929-32 

1902-19 

James  W.  Wadsworth 

1932-52 

1902-09 

Charles  D.  Walcott 

1902-27 

1902-02 

Frederic  C.  Walcott 

1931-48 

1920-49 

Henry  P.  Walcott 

1910-24 

1903-09 

Lewis  H.  Weed 

1935-52 

1902-04 

William  H.  Welch 

1906-34 

1938-44 

Andrew  D.  White 

1902-03 

1933-49 

Edward  D.  White 

1902-03 

1904-06 

Henry  White 

1913-27 

1934-39 

George  W.  Wickersham 

1909-36 

1902-09 

Robert  S.  Woodward 

1905-24 

1914-24 

Carroll  D.  Wright 

1902-08 

1902-16 

Alexander  Agassiz 
George  J.  Baldwin 
Thomas  Barbour 
John  S.  Billings 
Robert  S.  Brookings 
John  L.  Cadwalader 
William  W.  Campbell 
John  J.  Carty 
Whitefoord  R.  Cole 
Frederic  A.  Delano 
Cleveland  H.  Dodge 
William  E.  Dodge 
Charles  P.  Fenner 
Homer  L.  Ferguson 
Simon  Flexner 
W.  Cameron  Forbes 
James  Forrestal 
William  N.  Frew 
Lyman  J.  Gage 
Cass  Gilbert 
Frederick  H.  Gillett 
Daniel  C.  Gilman 
John  Hay 
Myron  T.  Herrick 
Abram  S.  Hewitt 
Henry  L.  Higginson 
Ethan  A.  Hitchcock 
Henry  Hitchcock 
Herbert  Hoover 
William  Wirt  Howe 
Charles  L.  Hutchinson 
Walter  A.  Jessup 
Frank  B.  Jewett 
Samuel  P.  Langley 
Charles  A.  Lindbergh 
William  Lindsay 
Henry  Cabot  Lodge 
Seth  Low 

Under  the  original  charter,  from  the  date  of  organization  until  April  28,  1904,  the  following  were 
ex  officio  members  of  the  Board  of  Trustees:  the  President  of  the  United  States,  the  President  of  the  Senate, 
the  Speaker  of  the  House  of  Representatives,  the  Secretary  of  the  Smithsonian  Institution,  and  the  President 
of  the  National  Academy  of  Sciences. 


vn 


STAFF 


ASTRONOMY 

MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES 

813  Santa  Barbara  Street,  Pasadena  4,  California 

Mount  Wilson  Observatory  organized  in  1904;  George  E.  Hale,  Director  1904-1923,  Honorary  Director 
1923-1936;  Walter  S.  Adams,  Director  1924-1945.  Unified  operation  with  the  Palomar  Observatory  of 
the  California  Institute  of  Technology  began  in  1948. 


Ira  S.  Bowen,  Director;  Horace  W.  Babcock,  Assistant  Director 


Halton  C.  Arp 
Walter  Baade 
William  A.  Baum 
Arthur  D.  Code 
Armin  J.  Deutsch 


Jesse  L.  Greenstein 
Milton  L.  Humason  * 
Rudolph  L.  Minkowski 
Guido  Munch 
Seth  B.  Nicholson  * 


Donald  E.  Osterbrock 
Robert  S.  Richardson 
Allan  R.  Sandage 
Olin  C.  Wilson 
Fritz  Zwicky 


TERRESTRIAL  SCIENCES 


GEOPHYSICAL  LABORATORY 

2801  Upton  Street,  N.  W.,  Washington  8,  D.  C. 

Organized  in  1906,  opened  in  1907;  Arthur  L.  Day,  Director  1909-1936;  Leason  H.  Adams,  Acting 
Director  1936-1937,  Director  1938-1952;  George  W.  Morey,  Acting  Director  1952-1953. 


Francis  R.  Boyd,  Jr. 
Felix  Chayes 
Sydney  P.  Clark,  Jr. 
Gordon  L.  Davis 
Gabrielle  Donnay 
Joseph  L.  England 
Hans  P.  Eugster 


Philip  H.  Abelson,  Director 

Joseph  W.  Greig 
Gunnar  Kullerud 
George  W.  Morey  * 
J.  Frank  Schairer 
George  R.  Tilton 
Hatten  S.  Yoder,  Jr. 


Staff  Associate 
Gordon  J.  F.  MacDonald 

Visiting  Investigators 
Henry  Faul 
David  B.  Stewart 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 

5241  Broad  Branch  Road,  N.  W.,  Washington  15,  D.  C. 

Organized  in  1904;  Louis  A.  Bauer,  Director  1904-1929;  John  A.  Fleming,  Acting  Director  1929-1934, 
Director  1935-1946. 


L.  Thomas  Aldrich 
Ellis  T.  Bolton 
Roy  J.  Britten 
Bernard  F.  Burke 
Dean  B.  Cowie 
John  W.  Firor 


G.  N.  Cohen 
E.  H.  Creaser  || 
W.  C.  Erickson 
K.  L.  Franklin  I 


♦Retired  June  30,  1957. 
%  Resigned  in  1956. 
§  On  leave  of  absence. 


Merle  A.  Tuve,  Director 

Scott  E.  Forbush 
John  W.  Graham 
Norman  P.  Heydenburg 
Ellis  A.  Johnson  t 
Richard  B.  Roberts 

Visiting  Investigators 

H.  Lawrence  Heifer 

J.  J.  Leahy 

F.  T.  McClure** 


Howard  E.  Tatel 
Georges  M.  Temmer  § 
Ernest  H.  Vestinetl 
Harry  W.  Wells 
George  W.  Wetherill 


G.  F.  Pieper 
Irena  Z.  Roberts 
H.  Weaver 


||  Term  of  appointment  completed  in   1956. 

j[  Resigned  in  1957. 

**  Term  of  appointment  completed  in  1957. 


Vlll 


STAFF  Continued 


BIOLOGICAL  SCIENCES 


DEPARTMENT  OF  PLANT  BIOLOGY 

Stanford,  California 

Desert  Laboratory,  opened  in  1903,  became  headquarters  of  Department  of  Botanical  Research  in  1905; 
name  changed  to  Laboratory  for  Plant  Physiology  in  1923;  Daniel  T.  MacDougal,  Director  1906-1927. 
Reorganized  in  1928  as  Division  of  Plant  Biology,  including  Ecology;  Herman  A.  Spoehr,  Chairman  1927- 
1930  and  1931-1947,  Chairman  Emeritus  1947-1950.  Name  changed  to  Department  of  Plant  Biology 
in  1951. 


William  M.  Hiesey 
Donald  W.  Kupke  * 
Harold  W.  Milner 
Malcolm  A.  Nobs 
James  H.  C.  Smith 


C.  Stacy  French,  Director 

Visiting  Investigators 
Per  Halldal 
Wolf  Vishniac 

Investigator  Engaged  in 
Post-Retirement  Studies 
Jens  C.  Clausen 


Research  Fellows 
F.  J.  F.  Fisher 
Paul  H.  Latimer 
Kazuo  Shibata 


DEPARTMENT  OF  EMBRYOLOGY 

Wolfe  and  Madison  Streets,  Baltimore  5,  Maryland 

Organized  in  1914;  Franklin  P.  Mall,  Director   1914-1917;  George  L.  Streeter,  Director   1918-1940; 
George  W.  Corner,  Director  1941-1955. 


David  W.  Bishop 
Bent  G.  Boving 
Robert  K.  Burns 
Robert  L.  DeHaan 
Elizabeth  M.  Ramsey 
Royal  F.  Ruth 


James  D.  Ebert,  Director 

Consultant 
George  W.  Bartelmez 

Special  Investigators 
Vincent  J.  De  Feo 
Seymour  Katsh 
Malcolm  S.  Steinberg 


Research  Associates 
Arthur  T.  Hertig 
Chester  H.  Heuser 
Samuel  R.  M.  Reynolds 


DEPARTMENT  OF  GENETICS 

Cold  Spring  Harbor,  Long  Island,  New  Yor\ 

Station  for  Experimental  Evolution  opened  in  1904;  name  changed  to  Department  of  Experimental  Evo- 
lution in  1906;  combined  with  Eugenics  Record  Office  in  1921  to  form  Department  of  Genetics.  Charles  B. 
Davenport,  Director  1904-1934;  Albert  F.  Blakeslee,  Director  1935-1941. 


Alfred  D.  Hershey 
Berwind  P.  Kaufmann 
Barbara  McClintock 
Margaret  R.  McDonald 
George  Streisinger 


Milislav  Demerec,  Director 

Special  Investigators 
Elizabeth  Burgi 
Helen  Gay 
Sheila  Howarth  X 
Etta  Kafer  § 
Andrej  W.  Kozinski 


Ernest  L.  Lahr 
Joseph  D.  Mandell 
Atif  Sengiin  % 
Jun-ichi  Tomizawa 
Sibergina  Wagenaar  t 


*  Resigned  September  21,  1956. 

t  Term  of  appointment  completed  during  the  report  year. 

§  Resigned  during  the  report  year. 


IX 


STAFF  Continued 


ARCHAEOLOGY 


DEPARTMENT  OF  ARCHAEOLOGY 

10  Frisbie  Place,  Cambridge  38,  Massachusetts 

Department  of  Historical  Research  organized  in  1903;  Andrew  C.  McLaughlin,  Director  1903-1905; 
J.  Franklin  Jameson,  Director  1905-1928.  In  1930  this  Department  was  incorporated  as  a  section  of 
United  States  history  in  a  new  Division  of  Historical  Research;  Alfred  V.  Kidder,  Chairman  1930-1950. 
Name  changed  to  Department  of  Archaeology  in  1951. 


Tatiana  ProskouriakofF 
Karl  Ruppert  * 
Anna  O.  Shepard 


Harry  E.  D.  Pollock,  Director 

Edwin  M.  Shook  t 
A.  Ledyard  Smith 
Robert  E.  Smith 


Gustav  Stromsvik  § 
}.  Eric  S.  Thompson 


RESEARCH  ASSOCIATES 

of  Carnegie  Institution  of  Washington 

William  A.  Arnold,  Oak  Ridge  National  Laboratory 

Louis  B.  Flexner,  University  of  Pennsylvania 

Willard  F.  Libby,  University  of  Chicago 

Paul  W.  Merrill,  Mount  Wilson  Observatory 

John  von  Neumann,  ||  Institute  for  Advanced  Study 

Hans  Ramberg,  University  of  Chicago 

C.  E.  Tilley,  Cambridge  University 

Evelyn  M.  Witkin,  State  University  of  New  York 


♦Retired  in  1956. 

X  On  leave  of  absence. 

§  Retired  in  1957. 

||  Died  February  8,  1957. 


STAFF  C ontinued 


OFFICE  OF  ADMINISTRATION 

Caryl  P.  Haskins 
President 

Paul  A.  Scherer 

Executive  Officer 

Samuel  Callaway 

Assistant  to  the  President 

Ailene  J.  Bauer 

Director  of  Publications 

Dorothy  R.  Swift  * 
Editor 

Lucile  B.  Stryker 

Associate  Editor 

Earle  B.  Biesecker 

Bursar;  Secretary-Treasurer,  Retirement  Trust 

James  W.  Boise 

Assistant  Bursar;  Assistant  Treasurer,  Retirement  Trust 

James  F.  Sullivan 

Assistant  to  the  Bursar 

Richard  F.  F.  Nichols 

Executive  Secretary  to  the  Finance  Committee 


Retired  June  30,  1957. 


XI 


CARNEGIE   INSTITUTION  OF  WASHINGTON 


REPORT  of 


THE  PRESIDENT 


CARNEGIE   INSTITUTION   OF  WASHINGTON 

REPORT  OF  THE  PRESIDENT 

It  does  not  matter  what  a  man  does;  so  long  as  he  does  it  with  the  attention  which 
affection  engenders,  he  will  come  to  see  his  way  to  something  else.  After  long  waiting 
he  will  certainly  find  one  door  open,  and  go  through  it.  He  will  say  to  himself  that  he 
can  never  find  another.  He  has  found  this,  more  by  luck  than  cunning,  but  now  he  is 
done.  Yet  by  and  by  he  will  see  that  there  is  one  more  small,  unimportant  door  which 
he  had  overlooked,  and  he  proceeds  through  this  too.  .  .  .  Then  after  years — but  probably 
not  till  after  a  great  many — doors  will  open  up  all  round,  so  many  and  so  wide  that  the 
difficulty  will  not  be  to  find  a  door,  but  rather  to  obtain  the  means  of  even  hurriedly  sur- 
veying a  portion  of  those  that  stand  invitingly  open. — Samuel  Butler  in 
Alps  and  Sanctuaries  of  Piedmont  and  the  Canton  Ticino 

What  is  a  Golden  Age  ?  What  echoes  of  the  Age  of  Pericles,  of  Renaissance 
Italy  and  the  Low  Countries  and  Scandinavia,  of  Elizabethan  England,  mark 
each  as  a  flood  tide  in  the  vast,  slow  surge  of  human  intellectual  development  ? 
Will  such  flood  tides  come  again  ? 

It  is  interesting  to  notice,  as  James  Joll  has  recently  done,  some  of  the  char- 
acteristics that  these  ages  had  in  common.  All  of  them  were  times  of  fervent 
intellectual  excitement,  when  major  new  creations  and  new  experiences  and 
viewpoints  were  just  coming  to  wide  notice  and  were  on  the  threshold  of  gen- 
eral acceptance.  In  all  of  them  one  can  sense  a  vigorous  address  to  new  ideas — 
when  indeed  opening  vistas,  half-seen,  made  of  ideas  precious  coin.  All  of 
them  were  eras  of  some  physical  security  and  at  least  some  political  and  or- 
ganizational stability.  But  in  all  of  them,  too,  stability  and  security  were  far 
from  complete,  and  there  is  the  flavor  of  a  partnership  of  disorder  and  hazard 
with  vitality  and  creativeness.  None  of  them,  clearly,  were  especially  "com- 
fortable" times  in  which  to  live,  in  the  sense  that  static  and  secure  environments 
may  be  comfortable.  And  yet,  as  Joll  has  significantly  pointed  out,  men  knew 
that  they  were  living  in  great  times.  The  adventurous  in  all  these  periods 
would  probably  have  admitted — perhaps  bitterly  resented — the  danger  and  the 
insecurity  and  the  muddled  opacity  of  their  days.  But  if  hard  pressed  probably 
no  one  of  them  would  have  admitted  a  wish  to  be  born  in  any  other  era. 

Will  such  times  come  again?  It  is  hard  to  imagine  that  they  will  not. 
Indeed,  though  we  hear  our  own  age  criticized  as  static  and  as  anti-intellectual 
often  enough,  perhaps  we  ourselves  are  the  restless,  insecure,  anxious,  vital 
participants  in  an  era  of  contemporary  intellectual  development  that  other  men 
sometime,  somewhere,  may  well  look  back  upon  as  golden  too. 

If  we  are  in  fact  witnessing  the  earlier  phases  of  another  era  of  turbulent 
change,  when  viewpoints  shift  rapidly  and  radically,  serving  as  the  anvils  for 
new  ideas,  we  must  expect  it  to  differ  in  many  respects  from  similar  periods 
in  the  past.  One  striking  difference  will  be  that  we  cannot  hope  to  localize  it 
geographically.   The  interlocked  character  of  the  present  world,  the  growing 

3 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


similarity  of  all  its  cultures,  the  universality  of  its  communication,  must  make 
meaningless  any  such  designation  as  an  Athenian  or  an  Elizabethan  age.  But 
possibly  we  can  characterize  it  in  terms  of  subject  matter,  of  the  loci  of  ideas 
with  which  it  is  especially  concerned.  Prominent  among  such  domains,  clearly, 
will  be  the  natural  sciences. 

Such  a  situation  is  not  new,  of  course,  for  ideas  in  these  fields  have  figured 
in  the  conceptual  revolutions  of  all  the  Golden  Ages.  Aristotle  and  Plato  and 
Socrates  all  lived  in  or  close  to  the  times  of  Periclean  Athens;  Galileo  and 
Copernicus,  Da  Vinci  and  Vesalius  were  of  Renaissance  Italy,  Francis  Bacon 
and  William  Harvey  were  of  Elizabethan  England.  But,  as  any  new  Golden 
Age  will  be  impossible  to  localize  geographically,  so  will  its  contributions  of 
scientific  ideas  be  derived  over  a  wide  and  sometimes  rather  inchoate  intellec- 
tual front.  We  can  already  see  vivid  examples  of  this  development.  And  if  we 
compare  the  current  product  of  the  natural  sciences  over  the  world  for  any 
single  year,  not  only  in  volume  and  diversity  of  source  but  in  scope  of  conse- 
quences, with  the  whole  product  of  a  Periclean  Age,  we  are  all  but  forced  to 
conclude  that,  half-unknowing,  half-unrealizing,  we  are  living  in  proximity 
to  one  of  the  most  astounding  Golden  Ages  of  all  time. 

Surely  our  age  shares  many  characteristics  with  the  earlier  golden  times. 
There  is  the  relative  physical  safety  and  comparative  political  stability  over 
much  of  the  face  of  the  globe.  There  is  the  wide  feeling  of  insecurity,  the 
deep-lying  anxiety,  the  sense  of  confusion,  not  unlike  the  earlier  times  in  its 
general  character  even  though,  to  us  at  least,  its  causes  seem  far  more  complex, 
more  massive,  more  intractable.  But  there  is  likewise  the  same  intense  concern 
with  new  ideas  and  new  concepts,  the  same  eagerness  for  widened  vistas  of 
understanding.  And  there  is  another  and  an  important  characteristic  of  such 
times  in  which  our  age  also  seems  typical. 

The  classical  Golden  Ages  were  intensely  concerned  with  the  problem  of 
communicating  the  new  ideas  that  were  being  born  in  such  profusion.  In  all 
of  them  there  was  a  preoccupation  with  the  problems  of  education.  All  of 
them  were  times  for  the  establishment  of  special  schools  of  thought  and  of 
great  centers  of  learning,  from  the  Peripatetics  to  the  College  of  Merton  to 
Padua  to  Paris.  In  this  characteristic,  too,  our  age  resembles  the  earlier  ones, 
even  if  groping,  as  yet,  toward  developments  of  educational  concepts  com- 
parable to  theirs. 

In  the  field  of  communication  in  its  most  general  sense,  however,  our  age 
confronts  a  challenge  of  almost  new  dimensions,  perhaps  nowhere  more 
poignant  than  in  the  natural  sciences. 

Diversity  of  approach  is  the  very  lifeblood  of  the  scientific  effort.  Science 
enlists  men  of  the  most  unlike  temperaments  and  talents.  It  unites  workers 
whose  gifts  are  primarily  descriptive  with  workers  whose  understanding  and 


REPORT  OF  THE  PRESIDENT 


approaches  comprehend  symbolism  and  techniques  of  the  most  abstruse  and 
involved  character.  Bonded  in  a  common  effort  are  men  whose  talents  are 
primarily  synthetic  with  men  so  keenly  and  entirely  analytical  that  synthesis 
may  have  little  meaning  for  them.  United  are  investigators  of  deeply  theoretical 
bent  with  investigators  of  primarily  mechanical  skills.  And  since  in  every  in- 
vestigation the  observer  and  his  "real"  world  are  in  some  sense  in  equilibrium, 
scientists  with  divergent  gifts  and  interests,  even  when  concerned  with  the 
same  problem,  necessarily  labor  in  partly  different  universes. 

It  is  not  only  the  observers  that  differ  widely  in  their  characteristics,  under 
the  common  rubric  of  scientists.  The  subject  matter  diverges  even  more.  Scien- 
tific disciplines  vary  enormously  among  themselves  in  their  degree  of  sophisti- 
cation and  in  their  intricacy.  The  attitudes,  the  modes,  the  ways  of  "picking 
up  the  stick,"  to  use  Butterfield's  expressive  phrase,  even  the  underlying  atti- 
tudes and  aspirations  of  the  work,  may  be  almost  unrecognizably  different  in  a 
mature,  well  cultivated,  highly  differentiated  discipline  on  the  one  hand  and  in 
an  exploratory  one,  still  in  its  primarily  descriptive  phase,  on  the  other.  And 
though  the  newer  disciplines  must  always  be  in  some  measure  rooted  in  the 
old,  and  though  it  is  probable  that  the  tested  approaches  of  older  fields  always 
have  some  relevance  for  the  newer  ones,  the  transfer  is  far  from  literal.  To 
accomplish  it  successfully  requires  talent  and  sophistication  in  the  investigator, 
and,  above  all,  that  wisdom  and  sense  of  proportion  that  can  come  only  from 
broad  experience  and  a  flexible  viewpoint. 

These  profound  diversities  among  investigators  and  within  the  structure  of 
science  are  characteristic  and  immeasurably  precious.  But  they  also  harbor  all 
the  dangers  of  fragmentation  and  pose  the  most  serious  challenges  to  com- 
munication within  the  very  core  of  the  scientific  effort.  The  compartmenting 
of  subject  matter  is  a  constant  threat  to  the  unity  of  science,  and  many  factors 
promote  it.  Mere  growth  of  vocabulary  and  specialization  of  terminology  in 
a  given  field — to  the  point  where  its  jargon  becomes  unintelligible  not  only  to 
the  layman  but  even  to  an  investigator  working  in  a  nearly  adjacent  area — 
raise  practical  barriers  to  understanding,  barriers  that  may  be  formidable. 

But  there  is  a  more  serious  aspect  to  such  failures  of  communication.  Words 
are  basically  the  coin  of  ideas,  and  to  some  degree  their  generators — never 
entirely  their  consequences.  So  it  is  not  uncommon  to  find  that  not  only  the 
words  but  also  some  basic  concepts  governing  workers  in  one  field  may  be 
unintelligible  to  those  in  another.  A  particularly  vivid  historical  example  of 
this  situation  is  presented  in  the  notion,  once  quite  widely  held,  that  the  thermo- 
dynamic laws  underlying  life  processes  must  differ  in  some  essential  way  from 
those  in  force  in  the  nonliving  world — an  idea  whose  untenability  has  only 
been  generally  recognized  in  rather  recent  years. 

Differences  of  language  and  concept  tend  to  be  powerfully  reinforced  by 
many  of  the  social  factors  governing  scientific  work.  The  desire  of  a  scientist 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


to  live  and  talk  with  those  who  will  understand  what  he  means,  the  pragmatic 
influences  that  inevitably  make  him  seek  professional  identification  with  others 
in  his  immediate  field,  have  their  great  strengths,  both  for  the  investigator  and 
for  his  work.  For  the  investigator,  such  association  means  immediate  identifica- 
tion of  interest  and  the  satisfaction  that  only  group  activity  can  bring.  For  the 
research,  it  means  the  exposure  of  every  man's  work  to  intimate  and  continuing 
criticism  by  his  peers  in  the  same  general  subject  area — the  only  critical  estimate 
that  can  be  truly  meaningful  or  can  really  maintain  the  standards  of  the  field. 
Yet  there  is  a  profound  debit  in  this  process  too.  At  its  worst  it  can  harden  an 
incipient  conventionalism,  and  can  raise  the  most  serious  barriers  to  com- 
munication within  the  body  of  science,  powerfully  reinforcing  that  separation  of 
fields  which,  unchecked,  leads  to  unbridled  specialism  with  all  its  attendant  ills. 

These  challenges  to  communication  within  the  framework  of  science  are 
severe  enough.  But  today  a  further,  and  to  some  extent  an  intractable,  threat  of 
fragmentation  is  posed  by  the  very  magnitude  of  the  scientific  effort  itself  and 
by  the  tremendous  volume  of  scientific  publication  that  necessarily  goes  with  it. 
This  is  a  threat  which  has  been  increasing  with  immense  rapidity  over  the 
half -century  span  of  the  Carnegie  Institution.  It  is  the  worse  because  it  is  not 
only  the  sheer  volume  of  paper,  of  titles,  of  content  that  must  be  dealt  with. 
Some  progress  has  been  possible  here  through  modern  aids  to  storing  and 
sorting  information,  and  intensive  research  could  doubtless  carry  their  effec- 
tiveness much  further. 

But  the  hard  core  of  the  problem  remains.  It  is  the  basic  challenge  to  com- 
munication that  lies  in  all  the  diversity  of  the  natural  sciences.  It  is  the  effective 
"addition"  and  the  fruitful  synthesis  of  ideas  even  in  one  field  of  work,  and 
much  more  generally  the  transfer  of  idea-systems  from  one  field  into  another, 
that,  successfully  met,  may  lead  to  major  innovations  of  viewpoint. 

Communication  of  this  sort — the  counterweight  to  the  forces  of  fragmenta- 
tion in  science — can  be  greatly  aided  by  environments  of  a  very  particular  kind. 
There  have  been  notable  examples  of  them  in  every  scientific  age — in  the  great 
universities,  and,  more  recently,  in  the  great  research  institutes.  They  have 
comprised  communities  of  investigators,  working  together  in  a  common  mode 
but  in  divergent  fields,  in  continuous  converse,  in  sympathy  and  in  rivalry, 
without  predetermined  goal,  without  overcommitment  as  a  body  to  any  given 
sector  of  nature  or  to  any  one  approach  to  the  natural  world.  From  such  en- 
vironments has  come  a  goodly  proportion  of  the  real  conceptual  advances 
of  science. 

As  the  forces  of  fragmentation  and  diversity  in  science  are  clearly  more 
powerful,  the  barriers  to  interchange  evidently  higher  and  more  formidable, 
in  our  own  day  than  in  any  other  age,  this  kind  of  communication  within  sci- 
ence is  more  important  now  than  it  has  ever  been.  It  may,  indeed,  be  one  of 


REPORT  OF  THE  PRESIDENT        7 


the  most  important  aspects  of  the  whole  scientific  effort  if  conceptual  advance 
is  to  continue  and  to  accelerate. 

The  creation  of  such  an  environment  is  a  task  to  which  the  Carnegie  Institu- 
tion of  Washington  is  dedicated,  and  for  which  it  is  unusually  well  equipped. 
The  scientific  community  that  is  the  Institution  includes  among  its  members 
almost  the  full  range  of  gifts  and  attitudes  that  has  been  described.  The  scien- 
tific fields  to  which  it  addresses  itself  in  the  various  Departments  range  from 
the  primarily  descriptive  to  the  primarily  analytical,  from  the  pioneer  to  the 
more  sophisticated.  Yet  by  virtue  of  the  mobility  of  its  organization  and  its 
community  of  spirit,  neither  workers  nor  fields  are  isolated.  Rather  the  reverse 
is  true,  so  that  fields  of  the  most  divergent  character  are  sometimes  included 
within  the  working  frame  of  a  single  Department  and  even  within  the  purview 
of  a  single  investigator.  These  circumstances,  and  the  fact  that  the  whole  of 
the  Institution's  work  is  pointed  toward  the  end  of  uncommitted  research,  fit 
it  peculiarly  to  assist  in  the  major  task  of  scientific  synthesis. 

The  Institution  has  accomplished  much  in  this  direction,  and  its  task  in  the 
future  will  be  yet  greater.  Notably  in  the  fields  of  astronomy  and  physics,  and 
of  physics,  chemistry,  geology,  and  biology,  syntheses  of  concept  and  subject 
matter  which  have  been  and  are  being  achieved  contribute  significantly  not 
only  to  the  breakdown  of  barriers  between  those  fields  but  to  the  creation  of 
new  fields — fields  that  then  lie  open  to  be  tilled. 

Substantive  work  of  this  kind  must  always  remain  the  most  enduring  basis 
for  leadership  by  the  Institution  in  this  task.  But  there  are  other  avenues  too. 
Symposia,  carefully  considered,  painstakingly  organized,  and  sensitively  timed, 
can  be  exceedingly  fruitful  in  scientific  synthesis  and  in  the  generation  of  new 
concepts,  especially  if  they  conjoin  fields  that  are  subtly  related  and  bring 
together  scientists  from  America  and  abroad  who  would  normally  foregather 
seldom  if  at  all.  A  number  of  such  symposia  have  been  organized  by  various 
members  of  the  Institution  staff,  and  additional  ones  are  contemplated. 

The  geographic  dispersion  of  the  several  Departments  of  the  Institution  and 
the  location  of  many  of  them  near  universities  bring  further  opportunities  to 
assume  the  role  of  a  "crossroads"  in  the  scientific  effort,  through  the  many 
kinds  of  informal  working  arrangements  that  are  possible  between  the  staff 
of  the  Institution  and  of  these  and  other  educational  establishments.  These 
potentialities  have  been  considerably  explored.  They  must  be  developed  yet 
further. 

Finally,  the  various  fellowship  programs,  augmented  now  by  the  first  of  the 
Vannevar  Bush  Fellowships  from  the  Massachusetts  Institute  of  Technology, 
offer  splendid  opportunities  to  bring  investigators  to  the  Institution  for  varying 
periods  of  training,  of  collaborative  work,  or  of  independent  creative  activity. 
The  newest,  and  one  of  the  most  exciting,  of  these  programs  has  been  designed 
to  further  the  work  of  mature  and  senior  investigators  of  distinction  in  the 


8        CARNEGIE  INSTITUTION  OF  WASHINGTON 


various  fields  of  Institution  interest,  both  at  home  and  abroad.  Its  initiation 
last  year  was  made  possible  by  a  generous  gift  from  the  Carnegie  Corporation 
of  New  York.  Guests  are  currently  expected  from  Holland,  Denmark,  and 
Great  Britain,  as  well  as  from  the  United  States,  to  be  with  the  Institution  for 
varying  periods. 

Such  are  some  of  the  challenges  to  communication  presented  by  the  formi- 
dable diversities  characteristic  of  the  scientific  effort.  But  there  is  a  yet  more 
important  message  which  must  be  kept  vivid  if  the  promise  in  our  scientific 
age  is  to  be  wholly  realized.  It  is  that  of  the  deeper  unities  that  underlie  all 
the  diversities  of  the  scientific  mode — the  unities  of  value,  of  standard,  of  goal, 
of  motivation. 

To  assume  that  human  communication  must  always  be  in  words,  or  even 
that  it  must  always  take  place  at  the  level  of  consciousness,  is  an  undue  restric- 
tion of  viewpoint.  Indeed,  there  is  much  to  suggest  that  the  kinds  of  communi- 
cation which  have  had  the  most  profound  significance  in  human  affairs  have 
often  been  neither  wholly  conscious  nor  entirely  verbal.  They  have  come  in- 
stead through  the  most  powerful  of  all  media — the  sharing  of  a  common 
experience  or  a  common  view,  simply  and  grandly  symbolized.  The  sun  and 
the  moon  and  the  stellar  firmament,  that  all  men  could  see  and  equally  know, 
must  have  provided  such  symbols  to  innumerable  human  groups  far  more 
remote  in  time  than  the  great  societies  of  Peru  or  Minoa  or  the  Nile.  J.  Z. 
Young  has  drawn  attention  to  the  enormous  power  of  the  mountain  or  the 
hilltop,  first  natural,  then  man-made  as  the  tumulus  or  mound  or  pyramid  or 
temple,  as  a  towering  symbol  of  communication  in  ancient  societies,  and  it  is 
hard  to  conceive  the  whole  structure  and  orientation  of  Renaissance  Europe 
apart  from  the  glory  of  its  cathedrals,  or  to  reconstruct  that  society  in  imagina- 
tion without  them. 

If  communication  of  the  most  profound  sort  can  thus  be  nonverbal,  it  can 
also,  of  course,  be  largely  divorced  from  material  stimuli,  a  situation  well  illus- 
trated by  many  highly  evolved  systems  of  religious  belief.  Few  bonds  of  com- 
munication can  have  been  stronger,  for  instance,  or  can  have  had  a  more 
important  influence  on  the  cohesiveness  and  the  world  view  of  a  whole  people, 
for  good  and  for  ill,  than  that  Augustinian  concept  of  knowledge  and  research 
that  so  dominated  early  Puritan  America.  As  Perry  Miller  has  described,  its 
essence  was  that  men  must  believe  in  order  to  know;  that  the  conclusions  of 
all  possible  investigations  about  the  world  are  already  given  in  advance  of  the 
search ;  that  the  most  that  right  reasoning  can  possibly  do  is  to  arrive  at  them 
again  by  a  parallel  course  and  illuminate  them  in  detail ;  that  since  reason  is  in 
any  case  fallible  and  likely  to  fall  short  of  even  this  secondary  goal,  it  may  be 
wisest  to  forego  reasoning  altogether.  No  one  can  deny  the  power  of  such  a 
concept  as  an  instrument  of  communication,  as  an  integrating  and  stabilizing 


REPORT  OF  THE  PRESIDENT 


force — or,  in  some  measure,  as  a  powerful  brake  to  action  and  to  originality — 
in  the  society  of  its  day. 

But  its  very  opposite,  the  approach  to  nature  typified  by  the  sweep  of  the 
scientific  revolution  of  the  sixteenth  and  seventeenth  centuries — the  deep-lying 
belief  that  all  knowledge  about  the  world  is  not  given  in  advance  of  the  in- 
vestigation, that  there  still  are  new  and  profoundly  beautiful  and  exciting 
regions  of  nature  and  of  the  relation  between  nature  and  the  observer  that  are 
accessible  to  reason  and  experiment  and  have  not  yet  been  laid  bare,  that  the 
effort  to  explore  them  may  offer  spiritual  and  emotional  rewards  comparable 
to  the  most  exalting  of  experiences  in  other  fields — this  approach  has  long  since 
proved  itself  a  mode  of  communication  at  least  equal  in  its  sweep,  more  flexible 
and  perhaps  more  viable,  and,  above  all,  conducive  to  positive  action,  to  the 
growth  of  ideas,  and  to  human  joy.  And  so  the  whole  orientation  of  scientific 
research  can  be  considered  in  one  sense  a  powerful  symbol,  as  shining  and  as 
dominating  in  its  way  as  the  simpler  symbols  of  the  sun  or  moon,  and  in  this 
context  as  much  nonverbal,  as  much  the  sensed  epitome  of  a  shared,  and  ac- 
cepted, and  dedicated  way  of  life. 

The  symbol  itself  is  now  some  three  centuries  old.  It  has  not  dimmed  in 
those  three  hundred  years,  but  it  has  changed  extraordinarily  in  form.  From 
its  very  beginning,  moreover,  it  has  been  in  one  sense  a  dual  symbol,  and  this 
duality  has  become  emphasized  in  recent  years,  especially  in  our  own  country. 
Neither  profound  philosophy  nor  practical  experiment  was  new  to  the  seven- 
teenth century,  nor,  for  that  matter,  to  the  Greeks.  What  gave  the  scientific 
revolution  its  novel  character  and  power — what  in  fact  represented  the  very 
genesis  of  science — was  that  for  the  first  time  these  two  strands  were  effectively 
entwined.  Science  was  philosophy  joined  to  practical  experiment.  And  in  the 
early  conjunction  there  was  an  implicit  realization  that  the  concept  must  come 
first,  that  experiment  must  serve  as  the  trap  for  lines  of  evidence  already 
vaguely  conjectured,  that,  in  the  suggestive  simile  of  H.  S.  Harrison,  experiment 
is  experience  sharpened  to  a  point — less  divining  rod  than  digging  stick. 

Had  scientific  research  not  been  so  eminently  successful  in  a  practical  sense, 
or  were  our  pragmatic  genius  as  a  people  less,  it  might  not  be  so  important  to 
make  sure,  in  our  day,  not  only  that  the  symbol  of  the  scientific  way  stays 
bright,  but  that  the  strands  do  not  become  unwound.  In  the  event,  it  remains 
essential  to  recall  the  distinction  and  the  interdependence  between  the  strands — 
science  as  a  way  of  getting  things  done,  and  science  as  a  way  of  life  and  a  view- 
point of  the  world.  The  first  component  needs  little  further  emphasis  than  its 
own  extraordinary  achievements  already  bring.  But  the  second,  and  inherently 
the  more  basic,  element  does  require  constant  reaffirmation  among  us  that  it 
may  retain  all  the  vitality  and  the  allegiance  and  the  comprehension  that  are 
essential  to  its  vigor.  The  task  of  such  reaffirmation  is  especially  important  not 
only  because  this  is  the  more  subtle  as  well  as  the  more  fundamental  side  of 


10        CARNEGIE  INSTITUTION  OF  WASHINGTON 


science,  and  therefore  less  casually  appreciated,  but  also  because  it  is  in  constant 
danger  of  being  overwhelmed  by  its  lusty  partner  and  so  lost  to  view. 

This  is  the  task  to  which,  above  all,  the  Carnegie  Institution  is  dedicated. 
It  is  the  most  essential  duty  of  the  Institution  to  communicate,  in  virtue  of  its 
own  mode  and  its  own  being,  the  essential  verities  of  the  scientific  way  that 
are  too  easily  forgotten.  On  one  side  lie  the  joy  and  the  underlying  human 
values  of  the  road  of  the  investigator,  the  compelling  life  challenge  that  is 
offered  to  the  seeker  after  ideas  about  the  natural  world,  whoever  and  wherever 
he  may  be.  On  the  other  lie  the  great  unities  of  approach  and  of  preparation 
that  bind  those  dedicated  to  the  scientific  path:  the  requirements  of  verifi- 
ability;  the  discipline  of  parsimony;  the  emphasis  on  individual  effort  with  its 
exacting  demands  of  preparation  and  dedication,  of  originality  and  imagina- 
tion, of  the  maintenance  of  style.  These  are  not  new  parameters  for  the  best 
in  living.  They  are  as  old  as  civilized  humanity.  But  the  scientific  mode  offers 
one  of  the  means  by  which  those  priceless  elements,  so  often  confused  or 
threatened  with  destruction  in  a  crowded  world,  can  be  assured  their  proper 
and  their  permanent  place.  No  era  which  lacks  them  or  to  which  they  have 
been  lost  can  be  great,  whatever  may  be  its  other  assets.  Our  time  has  no  more 
precious  heritage  than  these  qualities — and  few  tasks  more  essential  than  to 
defend  and  reaffirm  them. 


REPORT  OF  THE  PRESIDENT        11 


THE  YEAR'S  WORK  IN  REVIEW 

As  always,  selection  of  the  year's  researches  for  inclusion  in  this  review  must 
be  in  large  measure  arbitrary.  It  cannot  imply  that  those  described  here  are 
necessarily  more  or  less  important,  more  or  less  striking,  more  or  less  signifi- 
cant in  the  last  analysis,  than  other  programs  going  forward  beside  them  which 
might  have  been  included.  They  are  simply  to  be  considered  as  representative 
examples  of  the  work  carried  on  during  the  year  in  the  various  programs  of 
the  Institution.  The  reader  who  is  interested  in  these  programs  in  greater 
detail  is  referred  to  the  fuller  individual  reviews  of  the  various  Departments 
that  follow. 

The  Mount  Wilson  Observatory  has  pioneered  for  many  years  in  the  study 
of  stellar  magnetic  fields.  The  first  definite  indication  of  them  was  obtained 
in  the  sun  by  Hale  in  1908,  using  the  then  newly  completed  spectrograph  of 
the  60-foot  solar  tower  on  the  mountain.  Hale's  finding  that  many  of  the  lines 
of  the  spectra  of  sunspots  were  split  into  components  which  had  the  charac- 
teristic polarization  of  a  Zeeman  pattern  provided  firm  evidence  of  the  existence 
of  such  fields.  But  subsequent  search  for  a  general  magnetic  field  of  the  sun 
gave  such  erratic  results  that  Hale  himself  was  never  satisfied  with  the  con- 
clusiveness of  the  work  that  followed. 

Almost  forty  years  later  the  problem  was  attacked  at  the  Observatory  in  a 
somewhat  different  way.  The  considerable  velocity  of  axial  rotation  attributed 
to  nearly  all  the  A-type  stars  suggested  to  Horace  W.  Babcock  that  these  stars 
might  show  relatively  large  magnetic  fields.  Early  in  1946  he  made  spectro- 
graphs observations  of  one  such  star,  78  Virginis,  and  discovered  a  general 
magnetic  field  of  between  one  and  two  thousand  gauss.  Since  that  finding, 
some  hundreds  of  stars  have  been  under  observation  with  the  coude  spectro- 
graph of  both  the  100-inch  and  the  200-inch  telescopes  on  Mount  Wilson  and 
Palomar.  Thousands  of  measurements  of  stellar  magnetic  fields  have  been 
made,  and  these  have  been  collected  for  publication  during  the  present  year. 
Eighty-four  of  the  listed  stars  show  definite  evidences  of  magnetic  fields,  55 
are  probably  magnetic,  and  a  further  55  show  no  indications  of  a  coherent 
magnetic  field. 

In  1952,  encouraged  by  these  results,  Harold  D.  Babcock  and  Horace  W. 
Babcock  returned  to  the  older  problem  of  the  magnetism  of  the  sun.  With  a 
solar  magnetograph  constructed  to  take  advantage  of  improved  gratings  and 
recent  advances  in  photoelectric  techniques  installed  at  the  Hale  Laboratory  in 
Pasadena,  evidence  has  been  obtained  of  magnetic  fields  of  the  order  of  one 
gauss  over  large  areas  of  the  sun's  surface.  Since  this  finding,  a  second  improved 
magnetograph  has  been  completed  for  the  150-foot  solar  tower  on  Mount 
Wilson,  and,  starting  with  the  end  of  this  report  year,  a  daily  record  of  the 
distribution  of  the  magnetic  field  of  the  sun's  surface  is  being  made.    The 


12        CARNEGIE  INSTITUTION  OF  WASHINGTON 


results  should  be  of  great  interest,  especially  in  view  of  the  fact  that  evidence 
from  many  sources  increasingly  suggests  that  magnetic  fields  are  of  wide 
occurrence  and  probably  play  a  much  larger  role  in  astronomical  phenomena 
than  has  hitherto  been  supposed. 

Problems  of  stellar  evolution  continue  to  occupy  a  central  position  in  the 
research  of  the  Observatories.  One  of  the  important  and  intriguing  aspects  of 
this  field  is  the  question  of  the  evolution  of  the  chemical  elements  in  stellar 
systems.  G.  R.  Burbidge  and  F.  Hoyle,  with  Dr.  W.  A.  Fowler  and  Dr.  E.  M. 
Burbidge,  of  the  Kellogg  Radiation  Laboratory  of  the  California  Institute  of 
Technology,  have  continued  their  work  on  the  synthesis  of  elements  in  the 
stars.  Eight  nuclear  processes  are  found  to  be  necessary  to  account  for  the 
known  abundances  of  the  327  isotopes  recorded  in  the  solar  system.  The  great- 
est portion  of  the  energy  production  of  stars  is  due  to  the  "burning"  of  hydrogen 
(in  a  nuclear  sense),  producing  helium.  When  the  reaction  occurs  in  a  mixture 
of  hydrogen  with  other  elements,  it  can  result  in  the  building  of  isotopes  of 
carbon,  nitrogen,  oxygen,  fluorine,  neon,  and  sodium.  In  the  second  process, 
the  nuclear  burning  of  helium  fuel  produces  C12,  and,  by  further  a-particle 
addition,  O16,  Ne20,  and  perhaps  Mg24.  In  the  third  pattern,  the  a  process, 
through  charged-particle  interactions,  builds  the  remaining  four-structure 
nuclei  Mg24,  Si28,  S32,  A36,  Ca40,  and  probably  Ca44  and  Ti48.  The  fourth  pattern, 
the  e  process,  builds  the  elements  from  vanadium  through  nickel,  comprising 
the  iron  peak  on  the  abundance  curve.  It  takes  place  at  very  high  temperatures 
and  densities.  The  a  process  and  the  e  process  are  both  thought  to  take  place 
shortly  before  the  explosion  of  a  star  as  a  supernova.  The  fifth  process  (the  s 
process)  is  a  slow  neutron-capture  chain,  thought  to  occur  in  the  interiors  of 
red  giant  stars.  The  r  process,  a  rapid  neutron-capture  chain,  is  believed  to  take 
place  in  supernovae,  and  to  build  uranium  and  thorium,  together  with  a  num- 
ber of  lighter  isotopes.  The  seventh  route  of  synthesis,  the  p  process,  is  a  proton- 
capture  or  photoneutron  process  which  is  also  thought  to  occur  in  some  super- 
novae.  The  eighth  path  of  synthesis,  the  x  process,  is  not  as  yet  fully  elaborated. 
It  may  be  responsible  for  building  deuterium,  lithium,  beryllium,  and  boron, 
elements  that  are  unstable  in  hydrogen  burning  in  stellar  interiors.  Work  on 
the  nature  of  the  x  process  is  continuing. 

One  of  the  most  striking  features  of  far  outer  space  is  the  great  clouds  of 
gas  that  occupy  it.  The  sources  of  these  clouds  may  be  various.  Some  of  them 
are  thought  to  represent  the  remains  of  great  cosmic  explosions,  such  as  those 
of  supernovae.  Two  programs  have  substantially  increased  our  knowledge  of 
these  gaseous  nebulae  during  the  past  year.  In  one  of  them  Osterbrock  has 
taken  advantage  of  the  fact  that  the  relative  intensity  of  two  forbidden  lines 
of  O  II  near  X3727  varies  markedly  with  density  in  the  range  of  densities  found 
in  these  objects.  Observations  of  these  lines  have  made  possible  direct  deter- 


REPORT  OF  THE  PRESIDENT        13 


minations  of  the  densities  (and  of  the  masses)  of  the  Crab  Nebula,  the  nebula 
in  Orion,  and  several  planetary  nebulae. 

In  the  second  program  Munch  and  Wilson,  using  a  multislit  technique,  have 
obtained  high-dispersion  spectrograms  from  which  the  detailed  distribution  of 
velocities  through  a  large  object  such  as  the  Orion  nebula  can  be  measured. 
Large  and  abrupt  changes  in  velocity  have  been  observed,  suggesting  shock- 
wave  phenomena  rather  than  a  simple  turbulence. 

In  the  last  report  it  was  mentioned  that  the  year  had  been  an  active  one  in 
the  comparatively  new  field  of  the  study  of  celestial  objects  as  radio  sources. 
These  investigations  have  been  continued  in  several  directions  in  the  current 
year,  both  at  the  Mount  Wilson  and  Palomar  Observatories  and  in  the  Depart- 
ment of  Terrestrial  Magnetism.  Preliminary  results  were  obtained  in  the  De- 
partment last  year  in  the  measurement  of  intensity  or  flux  of  radio  sources  at 
frequencies  below  30  mc.  The  greatly  increased  solar  activity  of  the  past  year, 
which  has  interfered  with  the  optical  redshift  measurements  of  the  far  distant 
galaxies,  has  also  made  the  observing  conditions  for  these  radio  sources  dim- 
cult — so  difficult  that  the  preliminary  measurements  of  1955-1956  cannot,  in  all 
probability,  be  repeated  in  the  12  to  15  mc  range  until,  perhaps,  1963-1965. 

A  review  of  intensity  measurements  on  discrete  sources  in  the  available  radio 
spectrum,  however,  has  underlined  the  present  inadequate  and  unsatisfactory 
data  in  this  important  area  of  radio  astronomy.  Accordingly,  a  program  of 
flux  measurements  on  a  few  of  the  intense  radio  sources  over  a  wide  band  of 
the  useful  spectrum  has  become  an  important  project  in  radio  astronomy  in 
the  Department.  Dipole  antenna  arrays  accurately  calibrated  and  with  very 
precise  record  scalings  have  been  employed,  and  measurements  have  been 
made  of  Cassiopeia  A  and  Virgo  A  at  frequencies  below  approximately  100  mc. 
Cygnus  A  and  Taurus  A  are  also  objects  of  investigation.  It  is  planned  to  con- 
tinue dipole  measurements  to  the  limits  of  sensitivity — possibly  several  hun- 
dred megacycles.  Thereafter  it  is  planned  to  standardize  other  antennas  of 
large  aperture  against  dipoles  at  the  transition  frequency  and  to  use  scaled 
versions  of  the  large  antenna  in  subsequent  operations.  It  may  thus  be  possible 
to  extend  the  range  of  absolute  measurements  to  1000  mc  or  more. 

Measurements  of  radio  emission  within  our  own  solar  system  have  also  con- 
tinued actively.  An  antenna  effective  for  a  detailed  examination  of  the  emis- 
sion of  radio-frequency  energy  from  the  surface  of  the  sun  presents  a  number 
of  special  requirements,  quite  different  from  those  demanded  of  antennas  used 
for  stellar  work.  Such  an  antenna  array,  specially  designed  for  detailed  ex- 
amination of  solar  radio  emission,  has  been  built  by  the  Department  at  the 
River  Road  site  near  Seneca,  Maryland.  Preliminary  scans  of  the  sun's  face 
made  with  this  equipment  have  revealed  localized  bright  sources  which  move 


14        CARNEGIE  INSTITUTION  OF  WASHINGTON 


across  the  disk  as  the  sun  rotates.  Further  work  should  reveal  much  of  interest 
in  the  finer  structure  of  solar  radio  emission. 

It  will  be  recalled  that  one  of  the  earliest  findings  in  the  Department  of 
Terrestrial  Magnetism  in  the  field  of  radio  astronomy  was  that  the  planet 
Jupiter  was  a  source  of  radio  noise.  Further  investigation  of  this  phenomenon 
has  indicated  that  there  may  well  be  a  single  center  of  activity  on  the  planet, 
with  an  approximately  uniform  rotational  period.  No  visual  observations  of 
Jupiter  report  surface  features  having  a  corresponding  rotational  period,  sug- 
gesting that  the  source  of  radio  radiation  lies  below  the  cloud  level  of  the  planet 
and  may  well  be  associated  with  its  actual  surface. 

Two  further  developments  of  note  in  radio  astronomy  are  under  way  in  the 
Department.  To  obtain  a  detailed  knowledge  of  the  nature  of  radio  sources, 
optical  identifications  must  be  made.  So  far,  only  relatively  few  celestial  objects 
have  been  so  identified  in  a  satisfactory  way,  and  the  available  evidence  suggests 
that  many  radio  sources  may  be  distant  galaxies  fainter  than  the  eighteenth 
magnitude.  To  extend  the  list  of  optical  identifications,  precise  position  de- 
terminations for  a  large  number  of  radio  sources  should  be  made.  Antennas 
constructed  for  precision  position  measurements  must  incorporate  very  special 
features.  Such  antennas  are  under  experimental  design  at  present.  At  the 
same  time,  a  beginning  has  been  made  this  year  in  the  actual  construction  of  a 
radio  telescope  to  be  equipped  with  a  60-foot  dish — a  project  that  has  been 
under  consideration  and  study  in  the  Institution  since  1955. 

It  is  a  long  way  from  considerations  of  distant  galaxies  and  stars — their  age, 
their  evolution,  their  physical  characteristics — to  similar  investigations  within 
the  confines  of  our  own  planet.  In  some  respects,  however,  the  qualities  of  our 
terrestrial  environment  have  an  even  more  vivid  and  immediate  quality  for 
the  imagination.  Both  the  Department  of  Terrestrial  Magnetism  and  the 
Geophysical  Laboratory  are  deeply  concerned  with  the  properties  of  the  earth's 
crust.  In  the  Department  special  attention  has  been  focused  for  several  years 
on  a  recognition  and  understanding  of  many  large-scale  physical  processes 
operating  over  long  periods  of  geological  time  which  have  resulted,  among 
other  things,  in  the  formation  of  the  continents  and  the  ocean  depths,  moun- 
tain ranges  and  high  plateaus.  A  sine  qua  non  for  such  understanding  is  a 
comprehensive  and  quantitative  description  of  the  crust  of  the  earth  at  the 
present  day. 

To  this  end,  seismic  and  gravity  studies  continue  to  form  an  important  pro- 
gram of  the  Department's  work.  It  will  be  recalled  that  this  program  has  in 
previous  years  included  studies  on  the  Colorado  Plateau  and,  as  reported  last 
year,  in  Alaska.  This  year  an  even  more  ambitious  seismic  study  has  been 
undertaken  in  the  Andean  highlands,  using  as  indicators  the  explosions  nor- 
mally set  oft  in  the  operation  of  large  open-pit  copper  mines  in  southern  Peru 


REPORT  OF  THE  PRESIDENT        15 


and  northern  Chile.  This  program  has  been  undertaken  by  the  Department 
in  co-operation  with  the  United  States  National  Committee  for  the  Interna- 
tional Geophysical  Year. 

The  problem  of  the  age  of  the  various  rock  deposits  of  the  earth  has  engaged 
the  attention  of  earth  scientists  since  the  beginning  of  geology.  Despite  wide- 
spread and  intensive  work  over  the  years,  however,  major  problems  remain. 
Several  years  ago  a  program  was  undertaken  jointly  by  the  Geophysical  Labora- 
tory and  the  Department  of  Terrestrial  Magnetism  to  extend  the  scope  of 
mineral  age  measurements  involving  radiogenic  products,  originally  limited  to 
rocks  containing  uranium  and  thorium — an  extension  made  possible  by  im- 
provements in  mass  spectrometric  techniques  and  finer  developments  of  chemi- 
cal analysis  by  isotope  dilution.  Particular  emphasis  has  been  given  to  the 
means  made  available  by  the  natural  radioactive  decay  of  potassium  to  argon, 
and  of  rubidium  to  strontium. 

Agreement  of  the  rubidium-strontium  and  potassium-argon  ages  for  a  sample 
of  mica  is  a  good  indication  that  the  mineral  was  formed  in  a  closed  system, 
and  such  agreement  is  now  considered  essential  to  a  satisfactory  age  determina- 
tion. During  the  year  the  Geophysical  Laboratory-Department  of  Terrestrial 
Magnetism  group  began  an  investigation  of  regional  regularities  in  the  ages  of 
the  Precambrian  rock  exposures.  As  an  early  result,  it  has  been  found  that 
over  a  large  part  of  Arizona,  New  Mexico,  Colorado,  and  Wyoming  rocks 
were  formed  during  a  period  1300  to  1400  million  years  ago.  In  Ontario  there 
exists  a  large  group  of  minerals  that  are  apparently  much  older.  Investigation 
of  these,  together  with  the  work  of  other  laboratories,  suggests  that  there  is  a 
long  band  of  rocks,  extending  from  Wyoming  through  Montana,  Minnesota, 
Manitoba,  and  Ontario  into  Quebec,  composed  of  minerals  of  approximately 
2600  million  years  of  age.  Similar  areas  of  very  ancient  rocks  are  known  in 
Africa  and  Australia. 

A  striking  specific  finding  in  the  past  year  in  this  area  of  research  has  been 
the  establishment,  by  concordant  rubidium-strontium  and  potassium-argon 
datings,  of  an  age  of  about  340  million  years  for  the  micas  in  a  number  of 
granitic  rock  samples  collected  by  Dr.  Faul,  a  guest  investigator  from  the 
United  States  Geological  Survey,  from  the  Hercynian  Chain  of  western  Europe. 
Now  the  stratigraphic  age  of  these  rocks  is  known  to  be  older  than  the  middle 
Carboniferous,  and  they  are  usually  assigned  to  the  lower  Carboniferous.  Ac- 
cording to  the  United  States  Geological  Survey  version  of  the  Holmes  time 
scale,  the  Carboniferous  began  about  265  million  years  ago.  By  this  time  scale, 
then,  these  Hercynian  rocks  according  to  the  present  findings  belong  in  the 
middle  Silurian.  Thus  there  is  a  tremendous  difference  between  the  present 
age  determinations  and  the  commonly  accepted  stratigraphic  assignment.  The 
discrepancy  is  so  great  that  it  follows  either  that  the  time  scale  is  not  correct 


16        CARNEGIE  INSTITUTION  OF  WASHINGTON 


or  that  the  accepted  stratigraphic  assignment  of  the  formation  requires  con- 
siderable revision. 

Phase-equilibrium  relations  among  the  major  mineral  groups  continue  to  be 
studied  intensively  at  the  Geophysical  Laboratory  and  are  making  available  a 
whole  series  of  geological  "thermometers"  which  may  be  applied  to  igneous 
and  metamorphic  rocks,  supplying  means  for  learning  a  great  deal  about  the 
conditions  under  which  such  processes  as  mountain  building  occurred.  Similar 
types  of  thermometers  are  being  developed  for  ore  minerals.  Thus  Kullerud 
and  his  associates  have  performed  the  basic  laboratory  work  preliminary  to 
field  tests  of  an  additional  series  of  sulfide  geological  thermometers,  including 
two  based  on  the  stability  of  pyrite  and  covellite  and  a  third  on  the  composi- 
tion of  pyrrhotite  formed  in  the  presence  of  pyrite.  The  ultimate  accumulation 
of  a  number  of  such  thermometers  will  make  possible  extensive  cross  checks 
and  permit  the  reliable  determination  of  temperatures  prevailing  during  ore 
formation. 

For  a  number  of  years  the  Geophysical  Laboratory  has  carried  forward  a 
vigorous  program  in  crystallography,  which  is  becoming  perhaps  one  of  the 
most  vital  fields  in  all  of  science  today.  Through  the  use  of  neutron  diffraction, 
nuclear  and  paramagnetic  resonance,  and  X-ray  diffraction  the  structural  chem- 
ist is  learning  how  the  precise  determination  of  molecular  arrangement  leads 
to  real  understanding  of  chemical  reactivity.  The  nature  of  the  chemical  bond 
as  manifested  in  covalent,  metallic,  ionic,  or  intermediate  types  is  related  closely 
to  structure.  Interestingly,  work  on  the  crystallography  of  alkali  phosphates, 
continued  this  year  jointly  with  Drs.  J.  W.  Gryden  and  Helen  M.  Ondik,  has 
demonstrated  the  first  crystalline  ultraphosphate  on  record. 

One  of  the  high  points  in  research  for  the  year  in  the  Institution  has  been 
the  work  of  Chayes  in  the  Geophysical  Laboratory.  Using  an  optical  analogue, 
he  has  produced  diffraction  patterns  similar  to  the  types  obtained  from  the 
interaction  of  X  rays  on  crystals.  By  making  variations  in  the  analogue  he  has 
been  studying  the  kinds  of  patterns  that  might  be  obtained  in  various  types 
of  order-disorder  in  crystals.  This  method  may  well  represent  a  major  "break- 
through" in  crystallographic  research. 

During  the  year  Libby  has  continued  his  investigations  of  simple  methods 
of  absolute  counting  of  3  radioactivity  at  the  Geophysical  Laboratory.  He  has 
evaluated  the  role  of  back-scattered  radiation  with  greater  accuracy,  and  has 
discovered  the  important  effect  of  surface  roughness  in  the  measurement  of 
soft  3  rays.  One  extremely  practical  consequence  of  these  findings  is  that  they 
may  now  make  possible  the  introduction,  into  the  high  school  and  college 
classroom  and  laboratory,  of  isotopes  of  real  chemical  interest,  convenient  life- 
time, and  low  enough  specific  activity  to  be  completely  safe,  permitting  student 
use,  for  example,  of  the  radioactive  forms  of  acetic  acid,  hydrochloric  acid, 
sulfuric  acid,  and  the  calcium  salts. 


REPORT  OF  THE  PRESIDENT        17 


Yoder  and  Tilley  have  continued  their  studies  in  the  production  of  various 
basalts,  with  particular  attention  to  the  possibility  that  they  can  be  obtained 
naturally  by  differentiation  of  a  parental  magma.  Laboratory  determinations 
of  the  products  formed  when  a  variety  of  basalts  are  melted  and  quenched,  as 
well  as  comparisons  with  minerals  obtained  from  synthetic  melts,  show  that 
the  basalts  must  have  been  formed  from  different  original  magmas.  Eugster 
has  determined  the  effects  of  oxygen  on  the  stability  of  the  iron  mica,  annite, 
thus  demonstrating  the  feasibility  of  investigating  the  important  biotite  micas. 

The  Carnegie  Institution  is  deeply  concerned  with  research  in  fundamental 
biology.  In  five  of  the  seven  Departments,  investigations  are  under  way  in 
various  aspects  of  the  life  sciences.  They  range  from  the  organization  of 
molecular  units  in  life  processes  through  questions  of  the  structure  and  function 
of  relatively  elementary  subcellular  entities  such  as  the  pools  for  amino  acid 
concentration  and  synthesis  in  single  cells,  of  more  grossly  defined  intracellular 
structures  such  as  the  chloroplasts  of  the  cells  of  green  plants,  and  of  such  ex- 
ceedingly complicated  and  critical  cellular  organelles  as  the  chromosomes,  to 
the  organization  and  functioning  of  cells  themselves  in  the  developing  meta- 
zoan  embryo,  and  finally  to  questions  of  speciation  and  experimental  taxonomy, 
involving  the  organization  and  the  interaction  of  many-celled  plants  in  natural 
populations. 

In  the  Geophysical  Laboratory,  Abelson  has  continued  his  pioneering  work 
on  the  synthesis  of  amino  acids  from  simpler  components  under  conditions 
simulating  those  believed  to  have  obtained  on  the  earth  in  remote  geological 
periods.  Analysis  of  the  available  geologic  evidence  has  led  to  the  hypothesis 
that  the  principal  constituents  of  the  early  terrestrial  atmosphere  were  carbon 
monoxide,  nitrogen,  and  lesser  amounts  of  hydrogen,  water,  and  carbon  di- 
oxide. In  a  series  of  laboratory  experiments  he  has  simulated  the  effects  of 
solar  radiation  on  such  an  atmosphere  and  the  associated  oceans  and  found  that 
a  considerable  production  of  organic  compounds  results,  including  the  amino 
acids  glycine,  alanine,  and  serine,  as  well  as  more  complicated  substances. 
These  amino  acids  are  important  starting  points  in  the  building  of  proteins  by 
living  things. 

One  of  the  very  interesting  consequences  of  the  analysis  of  probable  condi- 
tions in  the  atmosphere  and  the  oceans  of  the  earth  at  the  time  when  life  may 
have  originated  is  that  carbon  dioxide,  probably  fairly  abundant  in  the  early 
atmosphere,  must  have  served  as  a  kind  of  buffer  in  the  oxidation-reduction 
system,  guaranteeing  that  the  atmosphere  could  never  have  been  very  reducing. 
It  seems  impossible  to  visualize  that  any  great  concentration  of  such  substances 
as  methane  was  present  together  with  the  carbon  dioxide.  This  picture  con- 
trasts sharply  with  some  of  the  earlier  ones  of  the  supposed  conditions  under 
which  life-like  systems  might  have  originated  on  the  earth. 


18        CARNEGIE  INSTITUTION  OF  WASHINGTON 


For  a  number  of  years,  the  members  of  the  biophysics  group  in  the  Depart- 
ment of  Terrestrial  Magnetism  have  been  especially  concerned  in  tracing  the 
pathways  of  synthesis  of  proteins  and  nucleic  acids  in  microorganisms,  concen- 
trating their  attention  especially  upon  two  representative  forms,  a  bacterium 
and  a  yeast.  During  the  earlier  years,  attention  was  directed  especially  to  the 
synthesis  of  relatively  small  molecules.  Later  the  studies  were  shifted  to  in- 
vestigations of  the  metabolic  pools  which  are  the  precursors  of  the  macromole- 
cules.  Special  attention  this  year  has  been  concentrated  on  the  organization  of 
structure  within  the  cell  in  terms  of  some  framework  larger  than  a  protein 
molecule. 

Studies  of  the  metabolic  pools  have  revealed  the  extremely  interesting  point 
that  they  are  susceptible  to  osmotic  shock,  and  must  therefore  be  held  in  some 
osmotically  sensitive  structure.  Work  conducted  this  year  strongly  suggests 
that  when  the  osmotic  pressure  of  the  medium  is  suddenly  reduced  a  flow  of 
water  occurs  into  the  sensitive  structures,  together  with  a  slow  loss  of  solute 
from  the  cell.  The  stretching  of  the  pool  structures  that  results  leads  to  an 
increase  of  permeability,  allowing  a  faster  rate  of  loss  of  the  solute  molecules. 
It  was  found  in  one  set  of  experiments,  for  instance,  that  radioactive  S04=  and 
P04=  ions  can  be  taken  up  after  such  shock  in  an  amount  corresponding  to 
about  5  per  cent  of  the  cell  volume  at  the  external  concentrations  of  S04=  and 
P04= — a  situation  that  cannot  occur  in  the  absence  of  the  shock.  Stretching  of 
the  pool  structures  and  loss  of  solute  molecules  finally  lead  to  a  new  osmotic 
equilibrium  in  the  cell  and  to  the  recovery  of  the  normal  pool  function.  These 
experiments  are  the  first  in  which  the  properties  of  the  pool  as  a  definite, 
distensible  intracellular  structure  have  been  clearly  indicated,  and  they  are 
correspondingly  interesting. 

Through  the  use  of  amino  acid  analogues  the  mechanism  in  the  cell  which 
selects  amino  acids  for  protein  synthesis  has  been  investigated  by  observing  the 
"mistakes"  that  a  cell  can  make  in  protein  formation.  Through  collaboration 
with  Dr.  Georges  N.  Cohen,  of  the  Institut  Pasteur,  it  has  been  shown  that 
selenomethionine,  for  example,  can  completely  replace  methionine  and  sup- 
port exponential  growth  in  a  methionine-requiring  mutant  of  the  bacterium 
Escherichia  coli.  The  experiment,  together  with  related  ones  conducted  at  the 
Institut  Pasteur,  demonstrates  that  the  amino  acid  composition  of  a  protein  can 
be  altered  by  the  presence  of  such  amino  acid  analogues  in  the  medium. 

Perhaps  the  most  dramatic  finding  of  the  biophysics  group  for  the  year  has 
been  the  demonstration  that,  under  appropriate  conditions,  rather  large  parti- 
cles containing  nucleic  acids,  proteins,  and  lipids  can  be  made  to  form  "spon- 
taneously" from  disintegrated  cellular  material.  When  cultures  of  cells  of 
E.  coli  suspended  in  a  glucose-mineral  salts  medium  were  brought  to  pH  8, 
centrifuged,  resuspended,  and  broken  by  being  forced  through  a  small  hole 
at  high  pressure,  again  centrifuged  to  remove  cell  fragments  and  any  unbroken 


REPORT  OF  THE  PRESIDENT        19 


cells,  and  the  resulting  supernatant  decanted  and  once  more  centrifuged  and 
diluted,  a  quite  clear  fluid  remained.  When  to  this  fluid  MgCl2  and  MnCl2 
were  added  (only  the  manganese  being  indispensable),  the  clear  solution 
became  cloudy  and  a  few  hours  later  was  found  to  contain  in  considerable 
density  particles  which  were  nearly  spherical  and  ranged  in  size  from  about 
1  to  5  microns.  Since  the  particles  have  a  definite  size  and  shape,  are  quite 
stable,  and  are  found  to  contain  several  of  the  constituents  of  bacterial  proto- 
plasm, they  have  been  named  "protomorphs."  Further  studies  of  these  remark- 
able objects  are  planned. 

The  Department  of  Plant  Biology  has  long  maintained  a  central  concern 
with  the  nature  of  the  photosynthetic  pigment  chlorophyll  as  it  occurs  in  the 
living  plant.  The  problem  has  been  attacked  by  a  number  of  routes.  Attempts 
to  isolate  the  photochemically  active  components  of  disintegrated  chloroplasts 
made  several  years  ago  showed  that  reaggregation  of  the  finely  dispersed  frag- 
ments restored  activity.  The  size  of  the  chloroplast  fragments  used  at  that 
time,  however,  was  still  too  large  to  permit  the  isolation  of  the  chlorophyll 
complex  in  pure  form.  Considerably  more  success  has  been  achieved  in  recent 
years  by  the  characterization  and  partial  purification  of  the  protochlorophyll 
complex  from  leaves  grown  in  the  dark.  The  chlorophyll-protein  complex 
formed  by  illumination  of  etiolated  leaf  material,  being  soluble  in  water,  is 
more  suitable  for  certain  chemical  studies  than  the  natural  complex  obtained 
from  dark  green  plants.  The  complex  in  fully  developed  leaves  contains  far 
more  chlorophyll  per  unit  protein,  however,  so  that  it  is  important  that  it  be 
studied  also.  As  such  complexes  are  generally  water-insoluble,  methods  of  in- 
vestigation not  based  on  chemical  isolation  seem  more  promising  than  attempts 
at  direct  chemical  characterization. 

One  evident  method  for  investigation  is  a  study  of  the  chlorophyll  absorption 
spectrum.  Such  a  study,  concerned  with  the  detailed  shape  of  the  red  absorp- 
tion band  of  chlorophyll  in  vivo  and  of  the  way  that  its  shape  may  be  altered 
by  various  procedures,  is  under  way  in  the  Department  at  present.  The  red 
band  of  chlorophyll  in  living  material  appears  to  consist  of  two  components 
having  a  wavelength  difference  of  about  10  millimicrons.  These  two  com- 
ponents have  not  been  separated  chemically.  Their  presence,  however,  may 
be  indicated  by  the  shape  of  the  derivative  of  the  spectral  absorbance  curve — 
though  another  interpretation  is  also  possible.  The  Department  is  particularly 
fitted  to  undertake  an  investigation  of  this  kind  by  virtue  of  its  derivative 
spectrophotometer,  designed  and  built  in  past  years  by  French  and  his  group, 
and  now  in  full  operation. 

Since  the  evidence  for  the  chemical  differences  between  native  and  extracted 
chlorophyll  rests  so  largely  on  spectroscopic  data,  it  is  especially  important  to 
be  sure  that  the  methods  for  measuring  the  absorption  spectra  of  pigments  in 


20        CARNEGIE  INSTITUTION  OF  WASHINGTON 


living  cells  are  highly  reliable.  During  the  current  year  Latimer  has  shown 
that  large  errors  can  be  introduced  in  determining  the  peak  positions  of  the 
absorption  bands  of  cell  pigments  by  selective  scattering  of  the  light  by  the 
pigment  molecules — a  phenomenon  which  is  sensitively  dependent  upon  the 
wavelength  of  the  incident  light  in  the  vicinity  of  a  pigment  absorption  band. 
This  critical  work  does  not  appear  to  invalidate  the  conclusion  that  natural 
chlorophyll  is  spectroscopically  different  from  the  extracted  material,  but  it 
does  raise  grave  questions  of  the  validity  of  comparisons  of  the  peak  positions 
of  chlorophyll  in  living  cells  spectroscopically  measured  in  different  labora- 
tories, or  even  of  different  samples  in  the  same  apparatus.  It  also  raises  the 
important  question  whether  the  double  peak  of  chlorophyll  absorption  observed 
by  derivative  spectrophotometry  is  due  to  two  actual  components,  or  whether 
one  peak  may  be  an  optical  artifact. 

Attempts  to  isolate  the  naturally  occurring  protochlorophyll  holochrome 
have  been  continued  during  the  year  by  Smith,  who  explored  additional  meth- 
ods of  fractionating  the  leaf  extracts.  The  earlier  reported  purification  of  about 
75  per  cent  was  not  exceeded,  but  a  promising  new  source  of  etiolated  leaves 
has  been  found  in  the  tropical  starch-crop  plant  taro,  which  will  be  interesting 
for  future  work. 

Another  approach  to  the  study  of  the  natural  chlorophyll-protein  complex 
is  to  separate  it  into  its  protein  and  chlorophyll  moieties  and  then  to  recom- 
bine  them.  Dr.  Wolf  Vishniac,  of  Yale  University,  has  succeeded  in  this  effort, 
and  has  demonstrated  that  the  recombined  "halves"  of  the  complex  can  again 
show  photochemical  activity.  During  the  year  Vishniac  spent  some  time  at  the 
Department,  experimenting  with  and  demonstrating  his  preparations.  In  the 
course  of  the  work  he  found  that  purified  chlorophyll  a  can  be  used  in  place  of 
the  alcoholic  leaf  extract  with  which  his  earlier  experiments  had  been  done, 
and  which  contained  substances  in  addition  to  chlorophyll. 

A  more  functional  kind  of  investigation  of  the  nature  of  chlorophyll  and  its 
relation  to  growth  processes  has  been  under  way  in  the  Department  for  some 
time.  This  is  a  study  of  the  interrelated  effects  of  light  intensity  and  tempera- 
ture on  the  growth  of  various  species  of  algae,  performed  by  growing  the  cells 
on  an  agar  surface  having  a  gradient  of  temperature  from  left  to  right  and  a 
gradient  of  light  intensity  from  front  to  back.  The  growth  pattern  produced 
on  such  a  plate  was  found  to  be  very  different  in  different  species  of  algae.  In 
last  year's  report  the  L-shaped  pattern  of  Chlorella  pyrenoidosa  was  mentioned. 
It  has  been  found  recently  that  the  vertical  arm  of  this  pattern  is  accentuated  by 
a  narrow  temperature  range  around  32°  C  in  which  growth  is  very  poor  at 
high  light  intensities.  On  the  higher-temperature  side  of  this  sharply  defined 
zone  is  an  equally  narrow  range  of  luxuriant  growth.  At  temperatures  below 
32°  C  at  high  light  intensity  the  growth  is  moderately  profuse  for  a  few 
degrees,  then  weakens  gradually  toward  lower  temperatures. 


REPORT  OF  THE  PRESIDENT        21 


It  is  believed  that  the  narrow  temperature  range  occupied  by  dark  green 
cells  on  plates  several  days  old  is  artificially  sharpened  by  effects  secondary  to 
the  direct  influence  of  intensity  and  temperature  on  growth. 

Yet  another  approach  to  the  problem  of  the  role  of  light  in  the  life  of  the 
plant  is  a  study  of  the  orientation  and  behavior  of  freely  moving  unicellular 
algae  in  the  presence  of  light  of  varying  wavelengths  and  intensity.  Such 
studies  of  phototaxis  in  the  unicellular  green  algae  have  been  continued  at  the 
Department  this  year,  attention  being  focused  especially  on  the  form  Platy- 
monas  subcordiformis.  When  this  alga  exhibited  a  fixed  light  response,  the 
reaction  could  not  be  altered  immediately  by  changing  either  the  intensity  of 
illumination  or  the  absolute  or  partial  pressure  of  carbon  dioxide  or  oxygen  in 
the  medium.  On  the  other  hand,  the  ions  Ca++  and  Mg++  were  found  to  be 
directly  involved,  and  to  be  antagonistic  in  their  effects,  Ca++  causing  a  nega- 
tive and  Mg++  a  positive  phototaxis.  A  number  of  other  ions  that  were  tested 
produced  no  reaction.  The  theory  that  the  driving  power  in  the  flagellates  is 
an  "adenosine  triphosphate  motor"  has  recently  been  suggested  by  Links,  in 
Holland.  Such  a  hypothesis  implies  that  the  mechanism  supplying  the  muscu- 
lar energy  of  animals  is  similar  to  that  which  innervates  the  flagellar  apparatus 
of  algae.  From  muscle  research  it  is  thought  that  Ca++  and  Mg++  ions  may  be 
involved  with  antagonistic  effects  in  the  ATPase  activity.  Thus  the  antago- 
nistic effect  of  Ca++  and  Mg++  in  these  experiments  in  phototaxis  is  particularly 
suggestive. 

Lynch  and  French  last  year  reported  the  very  interesting  finding  that  the 
Hill  activity  can  be  restored  in  ether-extracted  chloroplasts  by  (3-carotene.  This 
year  the  work  has  been  continued  by  Dr.  Max  Milner,  visiting  the  Department 
from  Kansas  State  College,  who  used  somewhat  more  quantitative  techniques. 
The  surprising  effect  has  been  confirmed,  and  it  has  been  shown  that  the  opti- 
mum concentration  of  (3-carotene  required  for  reactivation  is  approximately 
100  times  greater  than  that  used  in  the  earlier  work.  These  and  related  experi- 
ments suggest  that  one  or  more  fat-soluble  factors  may  be  involved  in  the 
reactivation  of  petroleum  ether-extracted  chloroplasts  in  addition  to  (3-carotene. 
Further  work  is  planned  to  determine  the  nature  and  the  mode  of  action  of 
these  components. 

Perhaps  no  aspect  of  the  living  cell  presents  so  many  facets  for  investigation 
or  leads  to  consequences  of  wider  general  interest  than  the  mechanisms  through 
which  heredity  is  mediated  and  determined.  Concern  with  the  processes  of 
heredity  must  underlie  biological  work  throughout  the  Institution,  but,  in 
both  functional  and  structural  aspects,  it  is  the  particular  province  of  the  De- 
partment of  Genetics. 

On  the  functional  side,  the  remarkable  findings  of  McClintock  concerning 
systems  of  elements  in  the  cell  nucleus  which  control  the  action  of  genes  in 


22        CARNEGIE  INSTITUTION  OF  WASHINGTON 


maize  have  continued  to  open  new  vistas.  Study  has  been  concentrated  on  a 
system  that  controls  gene  actions  at  two  known  loci,  not  directly  related  to  the 
Ds-Ac  system  earlier  reported,  though  the  genes  affected  are  themselves  ones 
which,  in  other  cultures,  have  come  under  Ds-Ac  control.  Particular  attention 
has  been  directed  to  determining  the  number  of  recognizable  elements  com- 
posing the  system  and  to  studying  the  transpositions  and  the  changes  in  modes 
of  expression  that  can  occur. 

Work  has  also  continued  in  the  analysis  of  a  structural  modification  in  maize 
chromosome  9,  preliminary  investigations  of  which  were  reported  last  year. 
The  substance  of  the  chromosome  is  distributed  between  two  components,  one 
member  comprising  the  distal  third  of  the  short  arm  (the  "fragment  chromo- 
some") and  the  other  the  proximal  two-thirds  of  the  short  arm  and  all  of  the 
long  arm  (the  "deficient  chromosome").  The  fragment  chromosome  exhibits 
aberrant  behavior  in  somatic  cells,  sometimes  being  lost,  sometimes  undergoing 
changes  in  structural  organization  or  becoming  attached  to  ends  or  centromeres 
of  other  chromosomes,  or  being  incorporated  into  another  chromosome.  The 
frequency  of  occurrence  of  events  leading  to  such  consequences  and  the  time 
of  their  occurrence  during  the  development  of  a  tissue  are  both  known  to  be 
under  genetic  control.  Initial  interest  in  this  structurally  modified  chromosome 
was  aroused  by  the  aberrant  behavior  of  fragments  in  somatic  cells.  It  was  later 
discovered  that  the  fragment  could  behave  unexpectedly  in  some  of  the  meiotic 
cells  also,  and  in  plants  either  heterozygous  or  homozygous  for  the  structural 
modification.  It  has  become  clear  that  the  rules  supposed  to  apply  to  crossing 
over  in  maize  are  not  always  followed  by  the  fragment  chromosome  when  it 
participates  in  a  crossover  event.  The  genetic  significance  of  these  findings  may 
be  very  considerable  indeed. 

For  a  number  of  years  Demerec  and  his  group  have  been  concerned  with  the 
application  of  methods  of  biochemical  genetics  to  investigation  of  the  detailed 
constitution  of  bacterial  chromosomes — methods  so  quantitative  as  to  be  ca- 
pable of  resolving  loci  concerned  with  specific  amino  acid  syntheses.  In  this 
connection  they  have  paid  much  attention  to  the  phenomena  of  transduction, 
in  which  fragments  of  a  bacterial  chromosome  can  be  transferred  from  one 
bacterium  to  another  through  the  vehicle  of  a  particle  of  infective  bacteriophage, 
and  of  transformation,  in  which  genetic  changes  can  be  mediated  by  nucleic 
acid  components  of  a  cell.  Such  studies  have  been  continued  this  year  in  the 
genetic  mechanisms  of  the  bacterium  Salmonella  typhimurium.  Stocks  have 
been  constructed  having  various  combinations  of  genetic  markers  representa- 
tive of  a  cystine  locus  and  four  tryptophan  loci  so  closely  linked  that  they  are 
carried  together  in  one  transducing  fragment.  Preliminary  experiments  with 
such  stocks  have  indicated  that  three  separate  portions  of  a  fragment  may  be 
incorporated  simultaneously  into  a  newly  formed  bacterial  chromosome.  If 
incorporation  is  accomplished  through  a  process  similar  to  crossing  over  in 


REPORT  OF  THE  PRESIDENT        23 


higher  organisms,  six  simultaneous  crossovers  would  be  required  to  produce 
the  combinations  of  markers  observed  in  these  experiments.  A  most  interesting 
indication  has  been  obtained  by  Ozeki  that  a  transducing  fragment  may  not 
be  a  randomly  selected  section  of  a  bacterial  chromosome.  The  evidence  sug- 
gests that  the  chromosomes  of  donor  bacteria  (infected  with  bacteriophage) 
are  partitioned  during  the  lytic  process  into  small  sections  in  some  regular  way 
and  at  predetermined  locations,  producing  uniform  transducing  fragments  for 
any  one  region. 

New  evidence  that  the  "chromosome"  of  bacteriophage  T2  consists  exclu- 
sively of  nucleic  acid  has  been  obtained  by  Hershey  and  his  group.  They  have 
found  that  the  chromatin  material  can  multiply  in  functional  form  in  bacterial 
cultures  containing  chloramphenicol,  which  inhibits  the  synthesis  of  all  bac- 
teriophage proteins. 

The  nature  of  reverse  mutations  in  bacteriophage  has  been  investigated  dur- 
ing the  year  by  Streisinger,  with  interesting  results.  Streisinger's  previous  work 
with  bacterial  viruses  had  revealed  that  mutations  at  many  sites  within  a  certain 
genetic  region  may  result  in  a  loss  of  the  capacity  of  the  bacteriophage  to  attach 
to  certain  strains  of  bacteria.  Such  mutations,  resulting  in  a  loss  of  adsorptive 
capacity  in  the  phage  T2,  may  take  place  at  any  of  a  large  number  of  genetic 
sites.  It  is  now  clear  that  reverse  mutations  restoring  this  adsorptive  capacity 
occur  at  precisely  the  sites  of  the  forward  mutations  from  which  they  are  de- 
rived. Not  all  reverse  mutants,  however,  are  identical  with  the  original,  non- 
mutated  form. 

Work  has  also  gone  forward  actively  during  the  year  on  the  structural  side 
of  the  nature  of  the  hereditary  mechanism.  Kaufmann,  Gay,  and  their  asso- 
ciates are  combining  methods  of  enzymatic  hydrolysis  with  modern  techniques 
of  electron  microscopy.  Results  obtained  after  deoxyribonuclease  treatment  of 
salivary-gland  chromosomes  of  Drosophila  fixed  in  osmium  tetroxide  and 
stained  by  the  Feulgen  method  suggest  that  the  main  structural  fibers  are 
immune  to  nuclease  or  acid  hydrolysis.  DNA  thus  appears  to  be  attached  to 
the  main  chromosomal  axis.  Results  obtained  with  chromosomes  of  Drosophila 
and  of  plants  preserved  in  other  fixatives  are  somewhat  ambiguous ;  much  work 
remains  to  be  done  before  a  generalized  conclusion  can  be  formulated  about 
the  location  of  DNA,  RNA,  and  protein  in  chromosomes.  Inclusion  of  tritium- 
labeled  thymidine  in  the  food  of  Drosophila  larvae  has  afforded  some  spectacu- 
lar radioautographs,  prepared  in  collaboration  with  Philip  Woods,  of  the 
salivary-gland  chromosomes  at  late  third  instar.  Radioactivity  was  limited  to 
the  banded  regions.  This  finding  suggests  that  thymidine,  which  is  a  precursor 
of  DNA,  was  not  incorporated  into  the  material  that  occupies  the  intervals 
between  the  bands. 

McDonald  has  continued  her  investigations  of  the  intracellular  deoxyribo- 
nucleases,  which  appear  to  be  related  to  the  general  problem  of  DNA  me- 


24        CARNEGIE  INSTITUTION  OF  WASHINGTON 


tabolism.  These  deoxyribonucleases  are  particularly  interesting  because  of  the 
unique  biological  importance  of  their  known  substrates  as  components  of 
chromosomes.  McDonald  has  concentrated  her  efforts  this  year  on  a  survey  of 
the  deoxyribonucleases  of  various  tissues,  seeking  to  determine  their  precise 
relation  to  cell  division  and  to  the  synthesis  and  metabolism  of  DNA.  During 
these  studies  it  was  found  that  the  deoxyribonuclease  content  of  salmon  testes 
is  especially  high,  and  further  investigation  suggests  that  this  tissue  may  be  a 
potent  and  extremely  useful  source  of  the  material. 

The  organization  of  cells  into  tissues,  and  their  modification  in  the  course 
of  growth  and  metamorphosis  of  the  many-celled  animal,  is  the  peculiar  con- 
cern of  the  Department  of  Embryology.  During  the  year  some  methods  have 
been  developed  and  applied  which  are  most  noteworthy  in  their  delicacy  and 
in  the  extent  to  which  they  permit  exact  inquiry.  Perhaps  one  of  the  most 
striking  is  illustrated  by  the  current  work  of  Wilt,  concerned  with  a  system 
which  may  well  permit  study  of  the  effects  of  a  hormone  system  in  a  meta- 
morphosing vertebrate  at  a  molecular  level.  The  bullfrog  tadpole  is  trans- 
formed into  an  adult  under  the  influence  of  the  thyroid  hormone.  During  the 
process,  an  abrupt  change  takes  place  in  the  visual  pigment  of  the  retina.  The 
tadpole's  retinal  pigment,  porphyropsin,  is  rapidly  replaced  by  rhodopsin,  the 
pigment  of  the  adult  retina.  These  visual  pigments  are  composed  of  a  protein 
moiety  (opsin)  coupled  with  a  carotenoid.  The  change  at  metamorphosis  has 
been  described  as  a  shift  from  retinene2,  the  aldehyde  of  vitamin  A2,  to  retinenei, 
the  aldehyde  of  vitamin  Ai.  Wilt's  long-range  objective  is  to  determine  the 
role  of  the  thyroid  hormone  in  this  shift.  His  immediate  goal  is  to  explore  the 
metabolic  implications  of  the  predominance  of  retinene2  in  the  tadpole  and  of 
retinenei  in  the  adult.  He  first  tested  the  hypothesis  that  the  tadpole  and  adult 
differ  in  their  content  of  oxidative  enzymes,  so  that  the  tadpole  can  oxidize  only 
vitamin  A2  and  the  adult  only  vitamin  Ai.  His  work  disclosed  that  the  two 
metamorphic  stages  do  not  differ  qualitatively  with  respect  to  retinene  reductase, 
the  enzyme  required  for  the  reaction.  Both  the  tadpole  and  the  adult  can  oxidize 
vitamins  A2  and  Ai.  In  further  experiments  Wilt  succeeded  in  preparing  and 
characterizing  highly  purified  porphyropsin  and  clearly  showed  that  it  differs 
from  the  rhodopsin  of  the  adult,  after  which  he  used  this  porphyropsin  in 
experiments  of  great  interest.  The  question  has  been  raised  whether  the  pig- 
ment difference  in  the  tadpole  and  adult  was  the  result  of  a  change  in  the 
ability  of  the  opsin  moiety  to  couple  with  the  retinene.  Thus  the  larval  opsin 
might  couple  with  retinene2,  that  of  the  adult  only  with  retinenei.  Wilt  has 
been  able  to  prove  that  larval  opsin  (bleached  porphyropsin)  will  combine 
with  retinenei,  to  regenerate  rhodopsin,  the  kinetics  of  the  reaction  following 
closely  those  for  the  regeneration  of  rhodopsin  in  the  adult  retina.  He  is  now 


REPORT  OF  THE  PRESIDENT        25 


focusing  attention  on  the  pathways  of  synthesis  of  vitamin  A2  and  on  the 
mechanism  that  confines  it  to  the  eye. 

In  the  course  of  experiments  designed  to  modify  the  onset  of  synthesis  and 
functional  activity  of  acetylcholine  in  the  early  chick  embryo,  DeHaan  made 
an  unexpected  observation  that  has  led  him  to  extend  his  study  of  spontaneous 
contractility  to  include  an  analysis  of  the  morphogenetic  movements  of  meso- 
derm and  endoderm  involved  in  cardiogenesis.  It  is  often  unappreciated  that 
the  factors  regulating  cell  movements  in  the  embryo  include  perhaps  the  most 
obscure  phenomena  in  embryology.  Thus  it  proved  of  great  interest  when 
DeHaan  demonstrated  that,  in  the  chick  embryo  cultivated  in  vitro,  the  addition 
of  a  tiny  crystal  of  acetylcholine  to  the  surface  of  the  endoderm  resulted  in  the 
formation  of  two  independently  beating  hearts.  On  the  basis  of  several  lines 
of  evidence  DeHaan  has  suggested  that  acetylcholine  acts  here  by  the  sequestra- 
tion of  calcium  or  other  divalent  cations.  Particular  interest  attached  to  the 
specificity  of  the  effect.  Other  morphogenetic  movements  presumably  are  in 
progress  at  this  time,  yet  only  the  cardiogenic  movements  are  altered.  DeHaan 
continues  to  probe  this  question,  at  the  same  time  maintaining  his  interest  in 
the  onset  of  spontaneous  contractility. 

In  consultation  with  Bishop,  Dr.  Katsh  has  continued  to  explore  the  unusually 
interesting  observation  that  the  injection  into  the  male  guinea  pig  of  testicular 
extracts  combined  with  adjuvant  (a  mixture  of  oils  and  certain  killed  bacteria) 
leads  to  the  destruction  of  the  spermatogenic  elements  in  the  testes  of  the  recip- 
ient. It  is  suggested  that  damage  to  the  spermatogenic  tissue  is  the  result  of  an 
immune  reaction,  which  may  operate  in  the  following  manner.  The  prepara- 
tion of  the  testicular  homogenate  and  its  combination  with  adjuvant  result  in 
a  change  in  its  properties  sufficient  to  enable  it  to  act  as  an  antigen  in  the 
homologous  species.  The  antibodies  produced  by  the  host,  however,  are  not 
sufficiently  specific  to  distinguish  normal  and  slightly  altered  testicular  antigens; 
hence  the  animal's  own  testis  is  destroyed.  Katsh's  studies  have  disclosed  that 
sperm-immobilizing,  sperm-agglutinating,  and  complement-fixing  antibodies 
appear  in  the  sera  of  the  injected  animals  and  not  in  the  sera  of  animals  injected 
with  adjuvant  alone.  Yet  there  are  reasons  for  believing  that  these  circulating 
antibodies  may  not  be  instrumental  in  inducing  aspermatogenesis.  For  example, 
it  has  not  been  possible  to  demonstrate  a  correlation  between  antibody  content 
and  aspermatogenic  effectiveness.  Moreover,  although  other  animals  like  the 
rabbit  are  highly  effective  in  producing  circulating  antibodies  of  this  type, 
aspermatogenesis  can  be  induced  only  with  difficulty.  These  considerations  led 
to  investigations  of  other  types  of  immune  reactions,  as  a  result  of  which  Katsh 
has  found  that  the  ileum  of  the  sensitized  guinea  pig  injected  with  homologous 
testis  or  sperm  responds  in  vitro  to  a  challenging  dose  of  guinea-pig  sperm  by 
contracting,  a  finding  that  suggests  an  allergic  response  of  the  anaphylactoid 
type.  While  exploring  this  possibility,  Katsh  has  made  progress  toward  eluci- 


26        CARNEGIE  INSTITUTION  OF  WASHINGTON 


dating  the  nature  of  the  antigenic  stimulus.  He  has  demonstrated  that  the 
antigens  are  not  species-specific,  and  that  they  are  shared  by  brain  and  testis. 
Within  the  testis,  the  effective  substances  are  confined  to  the  spermatogenic 
elements,  a  fact  established  by  the  failure  of  homogenates  of  testes  depleted  of 
spermatogenic  tissue  to  elicit  a  reaction.  A  number  of  thought-provoking  ex- 
periments suggest,  but  do  not  prove,  that  the  antigenic  stimulus  is  provided  by 
a  mixture  of  bacterial  and  testicular  lipopolysaccharides. 

During  the  past  years,  Dr.  Ramsey's  morphological  studies  have  led  her  to 
conclude  that  the  circulation  in  the  maternal  placenta  of  primates  is  effected  by 
the  vis  a  tergo  of  the  maternal  blood  pressure,  a  hypothesis  that  contradicts  the 
traditional  belief  that  the  myometrial  contractions  "squeeze  the  placenta  like  a 
sponge."  Although  a  few  valuable  observations  have  been  made  in  pioneer 
studies  on  human  patients,  experiments  are  required  to  confirm  or,  if  necessary, 
modify  the  hypothesis  deduced  from  morphological  studies.  During  the  year, 
Ramsey  initiated  such  a  program  in  collaboration  with  Drs.  G.  W.  Corner,  Jr., 
and  W.  Newton  Long,  Jr.,  using  experimental  material  from  the  Carnegie 
monkey  colony.  Although  the  first  year  of  the  research  was  devoted  primarily 
to  working  out  new  techniques,  the  initial  results  have  been  encouraging. 
Standard  procedures  were  devised  for  introducing  a  polyethylene  catheter  into 
the  amniotic  cavity — the  uterus  having  been  exposed  at  laparotomy — or  into 
the  intervillous  space  or  a  uterine  vein.  Positive  results  have  indicated  that 
myometrial  contractions  are  reflected  in  heightened  amniotic  and  intervillous 
space  pressures,  and  that  variations  of  absolute  pressures  in  the  amniotic  and 
intervillous  spaces  correspond.  Data  have  been  obtained  showing  inherent 
amplitude-tonus  patterns  characteristic  on  the  one  hand  of  individual  uteri  and 
on  the  other  of  specific  developmental  periods  in  animals  studied  during  a 
single  pregnancy.  Although  the  preliminary  findings  support  Ramsey's  hypoth- 
esis, the  research  is  just  beginning. 

At  the  "highest"  level  of  biological  organization,  the  structure  of  populations, 
the  group  in  experimental  taxonomy  is  continuing  its  work  actively  at  the 
Department  of  Plant  Biology,  though  this  year  with  a  somewhat  altered  direc- 
tion. The  research  has  long  been  concerned  especially  with  morphological  and 
genetic  studies  of  widely  distributed  groups  of  plants,  directed  primarily  toward 
the  clarification  of  the  evolutionary  relationships  between  races,  species,  and 
groups  of  species,  and  toward  their  fitness  to  their  natural  habitat.  Until  re- 
cently this  work  was  done  by  comparing  the  responses  of  identical  population 
samples  of  races  and  hybrids  of  plants  in  contrasting  environments,  by  exten- 
sive genetic  studies,  and  by  examining  chromosome  behavior  in  hybrid  and 
parental  forms  of  species  variously  related.  Many  of  these  long-range  studies 
have  been  completed,  and  emphasis  is  now  shifting  to  a  study  of  the  compara- 
tive physiology  of  closely  related  but  ecologically  distinct  races.   Research  is 


REPORT  OF  THE  PRESIDENT        27 


being  carried  on  at  present  with  some  of  the  species  whose  genetic  constitution 
and  evolutionary  history  have  already  been  considered.  Current  work  is  espe- 
cially concerned  with  rates  of  respiration  and  photosynthesis  of  contrasting 
climatic  races  of  the  monkey  flower,  Mimulus  cardinalis,  and  with  comparative 
growth  and  physiology  in  many  races  of  the  aquatic  duckweeds,  the  Lemnaceae, 
and  in  various  groups  of  the  yarrow,  Achillea. 

Laboratory  analyses  and  studies  of  data  resulting  from  recent  field  work  by 
the  Department  of  Archaeology  during  the  year  revealed  a  number  of  new  and 
significant  facets  of  the  Maya  culture.  Studies  by  Proskouriakoff  have  developed 
some  extremely  interesting  information  bearing  on  the  date  of  the  introduction 
of  metal  into  Yucatan,  suggesting  that  this  event  may  have  occurred  later  than 
has  commonly  been  supposed.  Thompson,  in  a  study  of  effigy  incense  burners 
recovered  from  Mayapan,  was  able  not  only  to  identify  a  number  of  the  gods 
or  personages  represented  but  in  addition  to  show  how  considerably  the  religion 
of  Mayapan  was  influenced  by  foreign  ideologies.  He  also  succeeded  in  identi- 
fying a  number  of  glyphs  representing  diseases — a  rather  striking  finding. 

The  Department  of  Archaeology  has  this  year  given  particular  attention  to 
finishing  the  various  studies  in  hand,  preparatory  to  the  completion  of  its  work 
in  1958.  Effort  has  been  directed  especially  toward  the  production  of  pre- 
liminary reports  on  the  field  work  and  to  broader  studies  that  will  lead  to  defini- 
tive statements  covering  the  results  of  the  more  recent  program  of  researches 
in  Yucatan. 

Losses  .   •   • 

On  June  30, 1957,  Dr.  George  W.  Morey  retired  from  the  Institution,  bringing 
to  a  close  an  association  of  forty-five  years  with  the  Geophysical  Laboratory. 
On  the  following  day  he  joined  the  Geochemical  and  Petrology  Branch  of  the 
United  States  Geological  Survey  to  continue  his  work — a  vivid  demonstration 
of  his  own  conviction  that  the  work  of  true  inquiry  is  never  done. 

When  Dr.  Morey  joined  the  staff  of  the  Geophysical  Laboratory  in  1912  that 
Department  was  but  six  years  old.  Its  interest  then  was  concentrated  particu- 
larly in  the  study  of  mineral-forming  processes  in  the  interior  of  the  earth.  The 
new  staff  member  expressed  some  misgivings  about  the  value  of  the  contribu- 
tions a  physical  chemist  could  make  to  such  a  program.  Events,  of  course,  belied 
this  uncertainty.  His  initial  precise  quantitative  work  on  phase  equilibria  in 
silicate  systems,  in  fact,  provided  the  basis  for  most  of  his  subsequent  research. 
The  label  "systems  containing  water  and  carbon  dioxide,"  by  which  he  describes 
his  field  of  study,  covers  myriad  activities.  Intensive  experimentation  with 
silicates  and  other  minerals  under  extreme  conditions  of  temperature  and 
pressure,  approximating  those  prevailing  deep  in  the  interior  of  the  earth,  was 
the  starting  point  for  new  insights  into  the  processes  of  mineral  formation, 


28        CARNEGIE  INSTITUTION  OF  WASHINGTON 


ore  deposition,  and  the  chemistry  of  magmatic  differentiation.  It  also  led  to  a 
new  theory  of  volcanic  eruption  based  on  the  tremendous  pressures  developed 
when  minerals  crystallize  from  an  aqueous  magma. 

Dr.  Morey  is  noted  for  his  skill  and  ingenuity  in  devising  new  apparatus  and 
techniques.  The  "Morey  bomb"  was  an  important  tool  in  the  first  production  of 
synthetic  quartz,  which,  in  turn,  led  to  most  significant  research  in  the  devel- 
opment and  manufacture  of  optical  glass. 

During  both  world  wars,  Dr.  Morey  left  the  Laboratory  to  put  his  theoretical 
and  experimental  work  on  the  chemical  constitution  of  glass  to  practical  appli- 
cation in  the  service  of  his  country.  In  the  first  war  he  manufactured  strategic 
optical  glass  for  the  War  Industries  Board  and  was  general  manager  of  the 
Spencer  Lens  Company;  in  the  second,  he  was  a  member  of  the  optical  instru- 
ments section  of  the  National  Defense  Research  Committee  and,  as  manager 
of  a  division  of  the  Corning  Glass  Works,  he  was  responsible  for  the  design, 
construction,  and  operation  of  the  largest  optical  glass  plant  ever  built.  He 
invented  a  new  family  of  glasses  with  high  refractive  index  and  wide  disper- 
sion especially  adaptable  for  photographic  lenses,  which  have  been  extensively 
used  by  the  Army  in  aerial  cameras.  All  these  contributions  to  industry,  tech- 
nology, and  military  objectives  were  based  on  replacing  empiricism  with  pre- 
cise knowledge  of  scientific  principles.  Dr.  Morey  is  the  author  of  an  American 
Chemical  Society  monograph,  The  Properties  of  Glass,  now  in  its  second  edi- 
tion, a  treatise  that  stands  alone  in  its  field,  and  of  some  hundred  scientific 
papers. 

Dr.  Milton  L.  Humason,  who  came  to  the  Mount  Wilson  Observatory  in 
1917,  retired  on  June  30,  1957.  Beginning  as  a  janitor  at  the  Observatory,  he 
soon  became  a  night  assistant.  Here  he  showed  such  gifts  of  observation  that  in 
1922  he  was  made  a  regular  member  of  the  Staff  of  Investigators.  His  most 
important  contributions  have  been  in  the  spectrographic  study  of  very  faint 
and  distant  objects.  It  was  largely  from  the  measurements  of  velocity  furnished 
by  his  early  spectrograms  of  distant  galaxies  that  Edwin  P.  Hubble  developed 
his  famous  hypothesis  of  an  expanding  universe.  In  1928,  at  the  request  of 
Hubble,  Humason  began  a  long  series  of  spectrographic  observations  of  galaxies 
designed  to  investigate  the  relation  between  the  redshift  and  the  apparent 
brightness  of  the  objects.  These  observations  were  continued  over  a  period  of 
twenty-eight  years,  with  the  aid  of  ever  newer  and  more  sensitive  photographic 
plates  and  of  modern  spectrographs.  After  1950,  with  the  greater  light-gathering 
power  of  the  Hale  telescope,  he  was  able  to  extend  the  record  of  the  spectra  of 
galaxies  to  distances  in  space  hitherto  utterly  unattainable.  One  of  his  particu- 
lar achievements  was  the  development  of  procedures  for  locating  images  ac- 
curately on  the  slit  of  the  spectrograph  and  holding  them  there  through  long 
exposures.  In  the  course  of  his  extensive  and  precise  observations  he  accumu- 


REPORT  OF  THE  PRESIDENT        29 


lated  redshift  measurements  of  620  separate  galactic  objects.  For  this  work  on 
redshift  measurements  he  was  awarded  the  degree  of  Ph.D.  honoris  causa  by 
Lund  University  in  Sweden  in  1950. 

From  1948  until  his  retirement  Dr.  Humason  was  Secretary  of  the  Mount 
Wilson  and  Palomar  Observatories,  effectively  handling  many  of  the  adminis- 
trative tasks  in  addition  to  his  scientific  work. 

One  of  the  most  painstaking  investigators  of  the  Institution's  astronomical 
staff,  Dr.  Seth  B.  Nicholson,  retired  on  June  30,  1957,  after  forty-two  years  of 
service.  Dr.  Nicholson  came  to  the  Institution  from  Lick  Observatory,  where 
he  had  already  won  recognition  by  the  discovery  of  the  ninth  satellite  of  Jupiter 
in  1914.  Subsequently  he  detected  three  other  satellites  of  the  planet — the  tenth 
and  eleventh  in  1938  and  the  twelfth  in  1951,  all  with  the  100-inch  Hooker 
telescope  on  Mount  Wilson.  Using  the  48-inch  schmidt  camera  on  Mount 
Palomar,  he  has  recently  taken  a  series  of  photographs  of  the  region  around 
Jupiter,  which  he  expects  to  use  during  the  coming  year  to  determine  the  rela- 
tive brightnesses,  positions,  and  magnitudes  of  all  twelve  satellites. 

When  he  first  came  to  Mount  Wilson,  Nicholson  collaborated  with  the  Direc- 
tor of  the  Observatory,  Dr.  George  Ellery  Hale,  in  investigations  of  the  sun. 
Ever  since,  his  work  has  been  chiefly  concerned  with  solar  astronomy,  more 
particularly  with  the  phenomena  of  the  visible  surface  of  that  star.  He  has  car- 
ried out  extensive  studies  of  the  magnetic  polarity  of  sunspots. 

Karl  Ruppert,  a  staff  member  of  the  Department  of  Archaeology,  retired  on 
October  1, 1956.  He  joined  the  Institution  group  carrying  on  research  in  Middle 
American  archaeology  in  1925  and  took  an  active  part  in  the  excavation  and 
restoration  of  Maya  buildings  at  Chichen  Itza  in  Yucatan.  Subsequently  he 
made  explorations  in  many  other  parts  of  the  Yucatan  Peninsula,  some  of  which 
had  never  before  been  entered  by  archaeologists. 

During  World  War  II  Ruppert  took  leave  of  absence,  first  for  War  Depart- 
ment activities  connected  with  the  American  Legation  at  Guatemala  City  and 
later  for  ambulance  work  with  the  American  Field  Service  in  India,  Burma, 
Italy,  and  Germany. 

In  the  winter  of  1947  he  was  in  charge  of  a  joint  Carnegie  Institution-United 
Fruit  Company  expedition  to  Bonampak,  Chiapas,  Mexico,  the  archaeological 
site  that  has  become  famous  in  recent  years  for  its  magnificent  Maya  mural 
paintings.  Ruppert  has  described  the  location  of  the  site,  the  history  of  its  dis- 
covery, and  its  architecture  in  Bonampa\,  Chiapas,  Mexico,  written  in  col- 
laboration with  Thompson  and  Proskouriakoff. 

In  1950  the  Department  of  Archaeology  began  its  survey  of  the  ruins  of 
Mayapan.  In  this  project  Ruppert,  with  A.  L.  Smith,  conducted  extensive 
excavations  of  the  remains  of  dwellings,  obtaining  a  rich  collection  of  data  the 
analysis  of  which  should  significantly  add  to  our  knowledge  of  the  domestic 


30        CARNEGIE  INSTITUTION  OF  WASHINGTON 


architecture,  the  patterns  of  settlement,  and  the  size  and  character  of  the  popu- 
lation of  Mayapan  and  its  vicinity. 

Another  member  of  the  staff  of  the  Department  of  Archaeology,  Gustav 
Stromsvik,  retired  on  June  30,  1957.  Stromsvik  was  first  employed  in  1926  as  a 
carpenter  at  Chichen  Itza.  He  soon  acquired  such  knowledge  of  that  site  and 
such  skill  in  the  engineering  aspects  of  excavating,  restoring,  and  protecting 
the  ruins  as  to  become  one  of  the  most  valuable  staff  members  in  the  field.  In 
1933  he  carried  out  comprehensive  repairs  in  the  Temple  of  the  Phalli  at 
Chichen  Itza,  guaranteeing  its  preservation  after  excavation.  From  1935  to 
1942  he  was  in  charge  of  the  joint  undertaking  of  the  Government  of  Honduras 
and  the  Carnegie  Institution  to  excavate,  restore,  and  preserve  the  highly  sig- 
nificant ruins  at  Copan.  Here  he  re-erected  the  extraordinary  monuments  of 
that  city,  repaired  several  of  its  most  important  buildings,  and  restored  the  great 
hieroglyphic  stairway.  In  the  course  of  this  program  it  became  necessary  to 
divert  the  course  of  the  Copan  River  to  prevent  its  violent  summer  floods  from 
undermining  the  ruins — a  major  engineering  undertaking. 

Stromsvik  enlisted  in  the  Royal  Norwegian  Navy  in  1943  and  subsequently 
took  part  in  the  landing  of  Allied  forces  on  the  Normandy  beachhead.  When 
he  returned  to  the  Institution  in  1945  he  resumed  his  diverse  activities  of  ex- 
ploring, mapping,  restoring  ruins,  and  collecting  artifacts.  He  participated  in 
discussions  in  Honduras  leading  to  the  establishment  of  the  Instituto  Nacional 
de  Antropologia  e  Historia  there,  for  which  he  served  as  a  Technical  Adviser. 
He  has  now  returned  to  Norway,  where  he  plans  to  continue  his  archaeological 
investigations. 

For  the  past  twenty  years  the  Carnegie  Institution  has  been  particularly 
fortunate  in  having  as  its  editor  Miss  Dorothy  Swift,  who  retired  on  June  30, 
1957.  The  importance  of  a  gifted  editor  in  any  publications  program  cannot 
be  overemphasized.  Miss  Swift's  contributions  to  lucidity  and  exact  expression 
won  the  respect  and  admiration  of  the  staff.  Her  high  standards  and  her 
meticulous  attention  to  perfection  in  detail  are  reflected  in  the  publications  of 
the  Institution  during  the  years  of  her  service.  Miss  Swift  plans  to  continue 
her  editorial  work  in  Boston. 

The  death  of  Dr.  John  von  Neumann,  brilliant  mathematician  and  member 
of  the  Atomic  Energy  Commission,  on  February  8,  1957,  cut  short  an  associa- 
tion which  the  Institution  was  deeply  privileged  to  enjoy.  He  had  been  ap- 
pointed a  Research  Associate  on  June  1,  1955. 

Dr.  von  Neumann  was  born  in  Budapest  and  received  his  early  training  there 
and  at  Zurich.  He  came  to  the  United  States  in  1929  as  a  visiting  lecturer  at 
Princeton  University,  where  the  following  year  he  was  made  professor  of 


REPORT  OF  THE  PRESIDENT        31 


mathematical  physics.  Three  years  later  he  received  appointment  as  one  of  the 
first  full  professors  at  the  Institute  for  Advanced  Study. 

There  were  few  fields  of  physics  or  mechanics  untouched  by  von  Neumann's 
genius.  His  pioneering  investigations  of  the  phenomena  of  weather  are  well 
known.  Perhaps  the  impact  of  his  gifts  was  most  widely  felt  in  the  field  of 
military  armament.  His  discovery  and  development  of  the  implosion  method 
were  critical  to  the  development  of  the  first  atomic  bomb.  He  was  one  of  the 
principal  advisers  to  the  United  States  Air  Force  and  a  powerful  exponent  of 
the  intercontinental  ballistic  missile.  Von  Neumann's  contributions  to  the 
design  of  early  fusion  weapons  were  equally  significant.  He  was  the  recipient 
of  many  honors,  among  them  the  Medal  of  Freedom  and  the  Enrico  Fermi 
award  for  his  work  on  the  theory  and  design  of  computing  machines.  In 
October  1954,  he  was  appointed  to  the  Atomic  Energy  Commission  and  served 
actively  with  it,  in  spite  of  his  illness,  almost  to  the  time  of  his  death. 

Few  losses  to  contemporary  science  have  been  as  great  as  this  premature  and 
tragic  ending  of  the  career  of  a  man  of  extraordinary  genius. 

On  May  14  of  this  year  Dr.  Francis  G.  Benedict,  formerly  Director  of  the 
Institution's  Nutrition  Laboratory,  died  at  the  age  of  86.  He  began  his  re- 
searches in  human  nutrition  at  Wesleyan  University  under  grants  of  the 
Carnegie  Institution.  In  1907  he  became  Director  of  the  Institution's  Nutrition 
Laboratory  in  Boston  and  served  in  this  capacity  until  his  retirement  in  1937. 

The  activities  of  the  Laboratory  during  Dr.  Benedict's  thirty  years  as  Director 
were  concentrated  largely  on  establishing  standards  of  basal  metabolism  of 
normal  human  subjects  according  to  height,  weight,  age,  sex,  and  race.  Special 
researches  were  made  on  the  conditions  that  may  affect  basal  metabolism,  such 
as  position  of  the  body,  temperature,  vegetarian  diet,  athletic  activity,  environ- 
ment, season,  and  fatigue.  Notable  contributions  were  made  to  the  invention 
and  testing  of  various  types  of  apparatus  for  measuring  heat  production,  heat 
elimination,  respiratory  exchange,  and  surface  and  internal  body  temperature. 

Henry  Norris  Russell,  who  died  on  February  18,  1957,  in  his  eightieth  year, 
had  long  been  one  of  the  leading  astronomers  of  this  country.  A  brilliant  scien- 
tist with  an  encyclopedic  knowledge  of  astrophysics,  a  man  of  inexhaustible 
enthusiasms,  varied  interests,  and  boundless  energy,  he  exercised  an  inspiring 
influence  on  all  with  whom  he  came  in  contact. 

Although  his  career  was  centered  in  Princeton,  he  had  associations  with  the 
Institution  from  its  earliest  days,  first  as  a  Research  Assistant  and  later,  from 
1921  to  1945,  as  a  Research  Associate.  He  worked  in  England  at  the  Cam- 
bridge Observatory  from  1903  to  1905.  In  1911,  at  the  early  age  of  thirty-four, 
he  became  director  of  the  observatory  at  Princeton.  From  1921  until  the  late 


32        CARNEGIE  INSTITUTION  OF  WASHINGTON 


1940's  the  Institution  had  the  benefit  of  his  presence  for  a  part  of  practically 
every  academic  year  for  research  and  lectures  at  Mount  Wilson. 

Dr.  Russell's  early  investigations  in  the  field  of  stellar  constitution  and  evolu- 
tion are  of  major  significance.  The  Hertzsprung-Russell  diagram  of  the  rela- 
tion between  absolute  magnitude  and  spectral  type  of  stars  has  played  a  most 
important  part  in  the  advance  of  astrophysics.  During  the  first  World  War  he 
contributed  to  military  research  in  the  field  of  airplane  navigation.  He  was 
a  pioneer  in  the  analysis  of  complex  laboratory  spectra.  The  role  of  spectra  in 
the  interpretation  of  the  physical  characteristics  of  stars  absorbed  him  for  several 
years.  His  discovery  that  hydrogen  was  by  far  the  most  abundant  element  in 
the  atmosphere  of  the  sun  ran  contrary  to  the  accepted  belief  of  the  day.  It 
is  now  a  basic  fact  of  cosmology. 

Dr.  Arthur  S.  King  died  on  April  25,  1957,  at  the  age  of  81.  He  was  one  of 
the  early  Research  Assistants  of  the  Institution,  receiving  a  grant  in  1904  to 
investigate  emission  spectra  at  high  temperatures  at  the  Universities  of  Bonn 
and  Berlin.  On  January  1,  1908,  after  teaching  physics  at  the  University  of 
California  for  three  years,  he  was  appointed  Superintendent  of  the  new  Physical 
Laboratory  of  the  Mount  Wilson  Observatory,  which  was  equipped  with  a 
30-foot  spectrograph  and  a  large  electric  furnace  designed  by  him,  apparatus 
superior  to  anything  then  in  existence  for  spectroscopic  work. 

Over  the  years  until  his  retirement  on  February  1,  1943,  Dr.  King  concerned 
himself  with  laboratory  investigations  of  many  spectra.  His  study  of  the  tem- 
perature classification  of  the  spectra  of  chemical  elements,  as  observed  in  the 
arc,  spark,  and  electric  furnace,  had  a  far-reaching  effect,  both  on  the  analyses 
of  complex  spectra  and  on  the  interpretation  of  the  solar  spectrum,  the  sunspot 
spectrum,  and  stellar  spectra  in  general.  His  research  also  included  the  study 
of  the  spectra  of  several  of  the  rare  earths  (atomic  numbers  57  to  71),  and  he 
completed  the  wavelength  measurements  and  intensity  estimates  for  a  great 
number  of  lines  in  these  complex  spectra.  His  laboratory  observations,  in 
collaboration  with  those  of  Raymond  T.  Birge,  led  to  the  extremely  important 
discovery  of  the  carbon  isotope  of  mass  13. 

During  World  War  II,  Dr.  King  investigated  the  velocities  of  aerial  torpedoes 
for  the  Office  of  Scientific  Research  and  Development  at  the  California  Insti- 
tute of  Technology,  and  from  1946  to  1954  he  served  as  a  mathematician  with 
the  Naval  Ordnance  Test  Station  in  Pasadena. 

•   •   •  and  Gains 

In  consequence  of  a  generous  gift  from  the  Carnegie  Corporation  of  New 
York,  the  Institution  is  initiating  this  year  a  series  of  special  fellowships  in  the 
natural  sciences,  primarily  to  permit  of  travel  and  visits  of  distinguished  scholars 
to  departments  of  the  Institution  carrying  on  research  in  their  fields  of  interest. 


REPORT  OF  THE  PRESIDENT        33 


Such  awards  are  entirely  without  restriction  with  regard  to  their  specific  use, 
but  are  made  in  general  in  subject  fields  to  which  the  Institution  is  especially 
directing  its  attention. 

Current  recipients  of  the  new  fellowships  are  Dr.  Evelyn  M.  Witkin,  of  the 
College  of  Medicine,  State  University  of  New  York;  Dr.  William  A.  Arnold, 
of  the  Oak  Ridge  National  Laboratory,  Oak  Ridge,  Tennessee;  Dr.  R.  v.  d.  R. 
Woolley,  the  Astronomer  Royal  of  Great  Britain ;  and  Professor  Jan  Hendrick 
Oort,  the  Director  of  the  Observatory  of  Leyden  in  the  Netherlands. 

It  is  a  particular  pleasure  to  report  that  Dr.  Vannevar  Bush,  retired  President 
of  the  Institution,  was  elected  Chairman  of  the  Corporation  of  the  Massachu- 
setts Institute  of  Technology  on  March  4,  1957.  On  May  21,  the  New  Jersey 
Patent  Law  Association  in  Newark  presented  him  with  the  1957  Jefferson 
medal  for  his  notable  contributions  to  the  United  States  patent  system. 

It  gives  me  great  pleasure  to  announce  the  following  honors  that  have  been 
received  by  directors  and  members  of  the  staff. 

The  Catherine  Wolfe  Bruce  gold  medal  for  1957  for  distinguished  services 
to  astronomy  was  awarded  to  Dr.  Ira  S.  Bowen,  Director  of  the  Mount  Wilson 
and  Palomar  Observatories,  by  the  Astronomical  Society  of  the  Pacific.  Dr. 
Jesse  L.  Greenstein,  staff  member  of  the  Observatories,  was  elected  to  the  Na- 
tional Academy  of  Sciences.  Dr.  Milton  L.  Humason  was  elected  an  associate 
of  the  Royal  Astronomical  Society.  Dr.  Harold  D.  Babcock,  retired  staff  mem- 
ber, received  the  degree  of  Doctor  of  Laws  honoris  causa  from  the  University 
of  California. 

At  the  Department  of  Plant  Biology,  Dr.  Jens  Clausen,  retired  staff  member, 
was  awarded  the  degree  of  Doctor  of  Agronomy  honoris  causa  by  the  Royal 
College  at  Upsala,  Sweden,  on  May  31,  1957,  in  connection  with  a  celebration 
of  the  250th  anniversary  of  the  birth  of  Linnaeus. 

Dr.  M.  Demerec,  Director  of  the  Department  of  Genetics,  was  elected  a 
member  of  the  Royal  Danish  Academy  of  Sciences  and  Letters  on  April  6, 1956, 
and  on  February  3,  1957,  he  received  the  degree  of  Doctor  of  Laws  honoris 
causa  from  Hofstra  College,  Hempstead  (Long  Island,  New  York). 

The  Geophysical  Institute  of  Huancayo,  Peru,  has  been  renamed  in  honor 
of  the  late  Dr.  John  A.  Fleming,  long  associated  with  the  Department  of  Ter- 
restrial Magnetism,  as  the  "Geophysical  Observatory  John  A.  Fleming." 

Caryl  P.  Has\ins 


REPORTS  OF  DEPARTMENTS 


and  SPECIAL  STUDIES 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES 


COMMITTEE  ON  IMAGE  TUBES  FOR  TELESCOPES 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


GEOPHYSICAL  LABORATORY 


DEPARTMENT  OF  PLANT  BIOLOGY 


DEPARTMENT  OF  EMBRYOLOGY 


DEPARTMENT  OF  GENETICS 


DEPARTMENT  OF  ARCHAEOLOGY 


MOUNT  WILSON  &  PALOMAR  OBSERVATORIES 

Operated  by  the  Carnegie  Institution  of  Washington 

and  the  California  Institute  of  Technology 


Pasadena,  California 


IRA  S.  BOWEN,  Director 
HORACE  W.  BABCOCK,  Assistant  Director 


OBSERVATORY  COMMITTEE 

Ira  S.  Bowen,  Chairman  Robert  S.  Bacher 

Walter  Baade  Jesse  L.  Greenstein 

Horace  W.  Babcock  Ernest  C.  Watson 


CONTENTS 


page 

Introduction      39 

Observing  Conditions 40 

Solar  Research    40 

Solar  photography  40 

Sunspot  activity   40 

Magnetic  polarities 40 

Studies  of  geomagnetic  activity 41 

Solar  magnetic  fields 41 

Planets  and  Satellites 42 

Observations  of  Mars 42 

Spectra  of  Venus 43 

Satellites 43 

Comets 43 

Stellar  Spectroscopy  and  Photometry ....  44 

White  dwarfs  and  subdwarfs 44 

Late-type  stars 46 

Variable  stars   48 

Magnetic  stars 49 

Globular  and  galactic  clusters  and  stel- 
lar evolution   50 


page 
Chemical  composition  of  stellar  atmos- 
pheres    52 

Nuclear  reactions  in  stars 54 

Gaseous  Nebulae  55 

Internal  motions  and  radial  velocities.  55 

Densities   of   nebulae 57 

Galaxies  58 

The    Andromeda    galaxy    and    other 

members  of  the  local  group 58 

Studies  of  individual  galaxies 59 

Catalogues  and  statistics  of  galaxies.  .  60 

Clusters  of  galaxies 60 

Velocities  and  distances  of  galaxies.  .  .  61 

Radio  Sources 63 

Identification  of  radio  sources 63 

Instrumentation    64 

Guest  Investigators   64 

Staff  and  Organization 70 

Bibliography   72 


Carnegie  Institution  of  Washington  Year  Boo\  56,  1956-1957 


INTRODUCTION 


In  1908,  Hale,  using  the  newly  completed 
spectrograph  of  the  60-foot  solar  tower  on 
Mount  Wilson,  noticed  that  many  of  the 
lines  of  the  spectra  of  sunspots  were  split 
into  components  which  had  the  character- 
istic polarization  of  a  Zeeman  pattern. 
This  observation  provided  the  first  definite 
evidence  for  the  presence  of  a  magnetic 
field  in  an  astronomical  body.  Later  Hale 
and  his  collaborators  searched  for  a  gen- 
eral magnetic  field  of  the  sun,  but  the  field 
was  so  weak  that  Hale  was  never  satisfied 
with  the  conclusiveness  of  the  evidence. 

The  large  velocity  of  axial  rotation  at- 
tributed to  nearly  all  A-type  stars  suggested 
to  Horace  W.  Babcock  that  relatively  large 
general  magnetic  fields  might  exist  in  these 
objects.  Early  in  1946  he  made  the  neces- 
sary spectroscopic  observations  of  one  of 
these  stars,  78  Virginis,  with  the  100-inch 
coude  spectrograph,  and  discovered  a  gen- 
eral magnetic  field  of  between  1000  and 
2000  gauss.  Since  that  time  some  hundreds 
of  stars  have  been  under  observation  with 
the  coude  spectrographs  of  both  the  100- 
inch  and  the  200-inch.  A  few  score  of  the 
most  interesting  objects  have  been  ob- 
served many  times  in  order  to  study  the 
fluctuations  that  occur  in  the  magnetic 
fields.  Many  of  the  variations  are  irregular, 
but  in  some  stars  the  field  reverses  with  a 
regular  period  of  a  few  days.  During  the 
present  year  Babcock  has  collected  for 
publication  all  the  thousands  of  measure- 
ments of  stellar  magnetic  fields  made  in 
the  past  11  years.  Eighty-four  of  the  stars 
listed  show  definite  evidence  for  a  mag- 
netic field;  55  are  probably  magnetic;  an- 
other 55  show  no  evidence  for  a  coherent 
magnetic  field.  One  hundred  and  eleven 
of  the  stars  observed  had  lines  too  broad 
for  magnetic  measurements. 

Encouraged  by  the  discovery  of  these 
general  fields  of  rapidly  rotating  stars, 
Harold  D.  Babcock  and  Horace  W.  Bab- 
cock returned  to  the  problem  of  the  gen- 
eral  magnetic  field   of  the   sun   in   1952. 


Taking  advantage  of  improved  gratings 
and  of  current  advances  in  photoelectric 
and  electronic  techniques,  they  constructed 
a  solar  magnetograph  which  scans  the  sur- 
face of  the  sun  and  records  the  amount  of 
the  residual  polarization  at  the  side  of  a 
certain  sensitive  spectral  line  caused  by  the 
Zeeman  splitting  of  the  line  in  the  mag- 
netic field.  Installed  in  the  Hale  Solar 
Laboratory  in  Pasadena,  the  magnetograph 
immediately  gave  definite  evidence  for 
magnetic  fields  of  the  order  of  1  gauss  over 
large  areas  of  the  solar  surface.  Further- 
more, the  pattern  of  many  of  these  fields 
was  found  to  change  in  the  course  of  a  few 
days;  this  finding  explains  why  the  results 
obtained  by  Hale  and  the  other  early  ob- 
servers were  so  erratic  and  inconclusive. 
Recently  a  second,  improved  magneto- 
graph has  been  completed  for  the  150-foot 
solar  tower  on  Mount  Wilson.  Starting  at 
the  end  of  the  report  year,  a  daily  record  of 
the  distribution  of  the  magnetic  fields  over 
the  sun's  surface  is  being  made  as  a  regular 
part  of  the  solar  program. 

Meanwhile  indirect  evidence  has  been 
found  at  other  observatories  for  small  inter- 
stellar magnetic  fields  extending  through- 
out large  volumes  of  space.  In  particular 
the  discovery  in  the  USSR,  by  Dombrovsky 
and  by  Vashakidze,  of  polarization  in  the 
Crab  Nebula  led  to  the  explanation  that 
the  continuous  radiation  from  this  object 
was  synchrotron  radiation  caused  by  very- 
high-velocity  electrons  being  accelerated 
in  a  magnetic  field.  Baade  with  the  aid 
of  the  200-inch  was  able  to  study  the  de- 
tailed structures  of  the  polarization  in  the 
Crab  Nebula  and  also  to  observe  polariza- 
tion in  the  radiation  of  the  jet  in  M  87 
which  probably  has  a  similar  cause. 

All  these  observations  point  to  the  fact 
that  magnetic  fields  are  very  widespread 
and  play  a  much  larger  role  in  astronomi- 
cal phenomena  than  has  hitherto  been  sup- 
posed.  They  also  mean  that  any  attempt 


39 


40 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


to  explain  the  structure  of  stars  and  nebu- 
lae must  more  and  more  take  into  account 
the  forces  exerted  on  the  ionized  gas  or 
"plasma"  associated  with  these  fields.  Be- 
cause of  the  growing  importance  of  mag- 
netic phenomena  in  astronomy  a  Sym- 
posium on  Electromagnetic  Phenomena  in 


Cosmical  Physics  was  held  in  Stockholm 
on  August  27-31,  1956,  under  the  auspices 
of  the  International  Astronomical  Union. 
Three  representatives  from  the  Mount 
Wilson  and  Palomar  Observatories  at- 
tended, including  H.  W.  Babcock,  who  was 
one  of  the  organizers  of  the  Symposium. 


OBSERVING  CONDITIONS 

For  the  fifth  consecutive  year,  precipita-  ond  half  of  the  year.    Solar  observations 

tion  was  below  normal  on  Mount  Wilson,  were  made  on  323  days;  observations  were 

the  total  for  the  year  being  25.47  inches,  made  with  the  100-inch  on  292  nights,  and 

Nevertheless,  the  number  of  cloudy  days  with  the  60-inch  on  285  nights, 
and  nights  was  large,  especially  in  the  sec- 

SOLAR  RESEARCH 


Solar  Photography 

Solar  observations  were  made  by  Nichol- 
son, Hickox,  and  Cragg.  The  numbers 
of  photographs  of  various  kinds  taken  be- 
tween July  1, 1956,  and  June  30,  1957,  were 
as  follows : 

638 
567 
936 
921 
78,000 
942 


Direct  photographs 

Ha  spectroheliograms,  60-foot  focus 
Ha  spectroheliograms,  18-foot  focus 
K2  spectroheliograms,  18-foot  focus 
K2  spectroheliograms,  7-foot  focus. 
K  prominences,  18-foot  focus. 


Sunspot  Activity 

The  magnetic  classification  and  study  of 
sunspots  and  related  phenomena  have  been 
continued  by  Nicholson  and  Cragg.  Co- 
operative programs  have  been  carried  out 
with  the  U.  S.  Naval  Observatory,  the 
University  of  Michigan,  the  Observatory 
of  Kodaikanal,  the  Meudon  Observatory, 
and  the  Central  Radio  Propagation  Labo- 
ratory of  the  National  Bureau  of  Stand- 
ards. During  the  calendar  year  1956,  solar 
observations  were  made  on  348  days,  on 
none  of  which  was  the  sun  without  spots. 
Only  in  1953  were  observations  made  on 
more  days  than  in  1956.  The  total  num- 
ber of  spot  groups  observed  in  1956  was 
642,  compared  with  208  in  1955  and  46  in 
1954.   The  record  number  of  groups  ob- 


served here  in  one  year  is  663  in  1947.  The 
northern  hemisphere  was  again  the  more 
active,  with  53  per  cent  of  the  total  groups. 

An  unusual  number  of  spots  have  ap- 
peared in  very  high  latitudes  in  this  cycle. 
In  the  65  years  from  1878  to  1943,  during 
which  time  daily  solar  photographs  are 
available,  only  four  groups  that  lasted 
longer  than  a  day  appeared  on  the  sun 
farther  than  40°  from  the  equator.  In  the 
last  cycle,  1943  to  1954,  eight  such  groups 
were  observed.  In  the  present  cycle  thir- 
teen have  already  appeared. 

The  rate  of  increase  of  solar  activity  from 
1955  to  1956  greatly  exceeded  that  from 
1945  to  1946.  If  the  number  of  spots  con- 
tinues to  increase  for  another  year,  as  it 
did  at  a  similar  phase  last  cycle,  the  com- 
ing sunspot  maximum  will  certainly  be 
the  highest  ever  recorded.  Since  maximum 
activity  is  expected  in  1957  a  new  record 
could  be  set. 

The  monthly  means  of  the  number  of 
groups  observed  daily  for  the  past  two  and 
one-half  years  are  shown  in  table  1. 

Magnetic  Polarities 

Magnetic  polarities  in  each  spot  group 
have,  if  possible,  been  observed  at  least 
once.  The  classification  of  groups  observed 
between  July  1,  1956,  and  June  30,  1957,  is 
indicated  in  table  2.  "Regular"  groups  in 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES 


41 


the  northern  hemisphere  are  those  in 
which  the  preceding  members  have  N 
(north-seeking)  polarity;  in  the  southern 
hemisphere  the  polarities  are  reversed. 

TABLE  1 


Month 


Daily  Number  of  Sunspot  Groups 


1955 


1956 


1957 


January    2.2 

February   2.2 

March    0.6 

April    1.4 

May    2.3 

June   2.4 

July    3.2 

August 3.3 

September  4.9 

October   6.1 

November 7.3 

December 6.9 


6.4 

12.7 

9.3 

10.9 

10.6 

13.6 

10.8 

14.0 

9.9 

12.7 

9.3 

15.1 

9.3 

13.5 

15.2 

12.9 

11.8 

13.8 

Yearly  mean 


3.6 


10.2 


TABLE  2 


Hemisphere   Regular      Irregular    Unclassified 


North    

.  259 

7 

80 

South    

312 

5 

96 

Whole  sun . 

.  571 

12 

176 

Studies  of  Geomagnetic  Activity 

The  study  of  the  diurnal  variation  of 
geomagnetic  activity  on  very  disturbed 
days,  reported  last  year,  has  been  extended 
by  Nicholson  and  Dr.  Oliver  R.  Wulf,  of 
the  U.  S.  Weather  Bureau,  to  include  the 
ten  selected  quiet  days  in  each  month  and 
the  all-except-quiet  days.  The  local-time 
component  for  the  quiet  days,  which  is 
quite  significant,  seems  to  be  related  to 
deviations  from  the  normal  diurnal  change 
in  the  intensity  of  the  earth's  field.  This 
effect,  which  changes  the  phase  of  the 
local-time  component  for  all  days,  has  been 
removed  from  the  data.  The  remaining 
local-time  component  of  disturbance  re- 
flects the  known  local-time  dependence  of 


magnetic  "bays."  The  additional  Universal- 
Time  component  indicates  that  through- 
out the  year  disturbance  is  greater  when 
the  sun  is  over  certain  longitudes,  follow- 
ing a  pattern  like  that  near  the  equinoxes, 
but  that  the  variations  are  influenced  by 
the  north-and-south  position  of  the  sun  as 
well.  This  effect  may  arise  from  the  chang- 
ing position  of  the  ionization  cap  under 
the  sun  relative  to  the  earth's  magnetic 
field  and  to  the  changing  patterns  of  the 
large-scale  atmospheric  circulation. 

Solar  Magnetic  Fields 

In  the  past  year,  160  magnetograms  of 
the  sun  have  been  made  by  Harold  D.  Bab- 
cock;  a  total  of  786  has  been  obtained  since 
the  series  was  begun  in  1952.  Compilation 
of  additional  data,  not  photographically 
recorded,  up  to  the  end  of  1956,  confirms 
published  results  on  signs  and  intensities 
of  the  high-latitude  polar  fields  of  the  sun. 

Measurements  have  been  made  on  weak 
coherent  fields  of  great  area  for  17  dates 
between  December  24, 1953,  and  March  14, 
1954.  For  29  of  these  fields  the  following 
mean  values  are  found:  maximum  in- 
tensity, 1  gauss;  total  magnetic  flux,  1021 
maxwells;  areas,  0.14  of  the  sun's  disk. 

Measurements  of  magnetic  flux,  maxi- 
mum intensity,  and  area  have  been  made 
for  fields  of  each  sign  in  both  sunspot 
zones  for  21  days  between  October  8,  1955, 
and  May  13,  1956.  This  interval  includes 
the  most  notable  outburst  of  activity  in  the 
first  18  months  of  the  present  solar  cycle. 

In  22  selected  bipolar  magnetic  regions, 
each  dominated  by  one  sunspot,  the  flux, 
maximum  intensity,  and  area  have  been 
measured.  In  each  case,  the  maximum  flux 
of  the  spot  umbra  has  been  estimated,  for 
a  comparison  between  the  flux  emerging 
from  the  spot  and  the  flux  returning 
through  a  photospheric  region  of  opposite 
polarity. 

A  comparison  of  magnetograms  with 
charts  of  coronal  activity  issued  by  the 
High  Altitude  Observatory,  Boulder,  Colo- 


42        CARNEGIE  INSTITUTION  OF  WASHINGTON 


rado,  based  on  emission  of  AA5303,  6374, 
shows  a  general  correspondence  between 
magnetic  flux  and  light  flux.  In  every 
case,  the  areas  on  the  sun  are  much  more 
extensive  in  longitude  than  in  latitude. 
After  putting  the  new  solar  magneto- 


graph  at  the  150-foot  solar  tower  on  Mount 
Wilson  into  regular  operation  at  a  high 
level  of  stability  and  sensitivity,  Vrabec 
has  used  it  to  map  magnetic  fields  in  the 
neighborhood  of  sunspots  and  to  study 
their  variations. 


PLANETS  AND  SATELLITES 


Observations  of  Mars 

Mars  was  observed  at  the  opposition  of 
1956  by  Richardson  on  34  nights  for  a 
total  of  110  hours.  About  twice  as  much 
time  was  spent  on  the  planet  as  in  1954, 
under  generally  superior  conditions.  Only 
part  of  the  material  secured  has  been  re- 
duced as  yet. 

Four  hundred  and  ten  direct  photo- 
graphs of  Mars  were  taken  in  blue,  orange, 
red,  and  infrared  light  with  a  camera  and 
enlarging  lens  at  the  Cassegrain  focus  of 
the  60-inch.  The  diameter  of  the  images 
ranged  from  2  to  10  mm.  Eastman  IV  F 
emulsion  was  used  throughout  the  visual 
region,  and  IV  N  emulsion  in  the  infrared. 
Exposure  times  ranged  from  J/3  to  20 
seconds. 

The  direct  photographs,  recording  the 
appearance  of  the  planet  at  the  time  of 
observation,  can  be  used  for  photometry 
of  the  disk.  From  measures  on  the  posi- 
tions of  the  markings  the  oblateness  of  the 
planet  can  be  determined,  since  the  period 
of  rotation  is  accurately  known. 

The  effective  wavelength  of  the  red 
images  is  at  6600  A,  at  about  the  position 
of  the  chlorophyll  absorption  band.  The 
effective  wavelength  of  the  infrared  images 
is  at  8000  A,  in  the  region  where  chloro- 
phyll reflects  strongly.  Photographs  taken 
a  few  minutes  apart  show  the  intensity  of 
the  maria  relative  to  the  deserts  as  the 
same  in  both  red  and  infrared.  The  maria, 
therefore,  cannot  consist  of  vegetation  with 
a  high  chlorophyll  content,  unless  the  re- 
flectivity of  chlorophyll  on  Mars  differs 
markedly  from  that  of  terrestrial  vegeta- 
tion. 

Spectra  of  Mars  were  taken  by  Richard- 
son on  17  nights  with  the  114-inch  camera, 


using  the  grating  which  gives  a  dispersion 
in  the  first  order  of  5.6  A/mm. 

Plates  in  the  first  order  infrared  were 
taken  in  a  search  for  the  carbon  dioxide 
bands  at  A7820  and  A8688,  first  discovered 
in  the  spectrum  of  Venus.  Carbon  dioxide 
has  already  been  identified  in  the  Martian 
atmosphere  through  the  band  at  1.6  mi- 
crons. The  bands  at  A7820  and  A8688  do 
not  show  in  the  telluric  spectrum  with  a 
very  low  sun.  There  was  no  trace  of  these 
bands  in  the  spectrum  of  Mars.  Their  ab- 
sence should  allow  us  to  set  an  upper  limit 
to  the  quantity  of  carbon  dioxide  in  the 
atmosphere  of  Mars. 

The  A  band  of  oxygen  at  A7600  was 
photographed  in  the  spectrum  of  Mars  in 
July  and  December  1956,  when  the  velocity 
of  the  planet  relative  to  the  earth  was  —8.9 
and  +14.9  km/sec,  respectively.  This 
velocity  gives  a  shift  of  0.62  A,  correspond- 
ing to  0.11  mm  on  the  plates.  Previous 
measures  to  detect  oxygen  have  been  made 
on  the  (1,0)  B  band  at  A6900.  The  (0,0) 
A  band  would  seem  better  suited  to  this 
investigation,  owing  to  the  greater  intensity 
of  possible  Martian  components.  Also,  the 
isotope  lines  in  the  band  of  016018  arise 
from  molecules  about  0.004  as  abundant 
as  those  producing  the  principal  lines,  thus 
affording  a  basis  of  comparison  for  the 
intensity  of  Martian  lines. 

The  presence  of  water  vapor  might  be 
detected  from  variations  in  intensity  of  the 
H2O  lines  in  the  maria  and  polar  cap  rela- 
tive to  the  adjacent  deserts.  Inspection  of 
the  water-vapor  lines  on  several  spectra  in 
the  region  of  A8200  showed  no  variations 
in  intensity  that  seemed  significant. 

Direct  photographs  of  Mars  in  visual 
light  show  the  surface  markings  distinctly. 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES 


43 


Those  in  blue  and  violet  usually  show  only 
a  blank  disk  with  a  greatly  enlarged  polar 
cap. 

Preliminary  measures  by  Richardson  on 
the  spectra  from  7500  to  8500  A  give  a 
ratio  maria/desert «  0.78.  No  spectrograms 
were  taken  in  the  red,  but  the  direct  photo- 
graphs indicate  that  this  ratio  remains 
nearly  constant  from  6000  to  7500  A.  Be- 
ginning about  A5700  the  ratio  maria/desert 
^0.84,  and  increases  gradually  until  at 
about  A4400  the  maria  and  deserts  become 
indistinguishable. 

The  polar  cap  is  inconspicuous  in  the 
infrared,  increases  steadily  in  intensity  in 
the  visual  region  relative  to  the  deserts,  and 
is  apparently  still  increasing  at  the  limit 
of  our  spectra  at  A3600. 

Spectra  of  Venus 

Thirteen  spectra  of  Venus  were  taken 
by  Richardson  for  the  measurement  of 
rotation  in  the  A6300  region  with  the  114- 
inch  camera  in  the  second  order  with  a 
dispersion  of  2.8  A/mm.  Two  spectra  of 
Mars  were  taken  as  controls.  Fifteen  spec- 
tra of  Venus  have  also  been  taken  at  the 
Snow  telescope  with  a  dispersion  of  0.75 
A/mm.  Only  a  few  exploratory  measures 
have  been  made  on  these  plates. 

Satellites 

Perturbations  in  the  motions  of  the 
satellites  furnish  one  of  the  best  means  of 


determining  the  oblateness  and  inner  con- 
stitution of  Mars.  A  dozen  of  Richard- 
son's best  plates  which  show  both  Phobos 
and  Deimos  have  been  sent  to  the  U.  S. 
Naval  Observatory  at  their  request  for 
measurement  and  reduction. 

Photographs  of  the  satellite  field  around 
Jupiter  were  taken  by  Nicholson  with  the 
48-inch  schmidt  on  several  nights  in  April, 
May,  and  June  with  corresponding  ex- 
posures on  Selected  Areas  to  redetermine 
the  magnitudes  of  the  faint  satellites  in  a 
homogeneous  manner.  Positions  of  the 
satellites  will  also  be  measured  on  these 
plates,  each  of  which  covers  the  entire 
satellite  field,  and  their  search  should  re- 
veal all  of  Jupiter's  satellites  down  to  the 
limiting  magnitude  of  the  plates.  The 
search,  measurement,  and  reduction  of 
these  plates,  the  last  of  which  were  taken 
in  June,  have  just  been  started.  A  pre- 
liminary search  of  the  plates  taken  in  April 
located  all  the  known  distant  satellites  with 
JXII  near  the  plate  limit.  No  new  satellites 
were  found,  but  some  fifty  asteroids  were 
detected  in  the  search. 

Two  pairs  of  plates  of  Saturn  taken  in 
June  by  Osterbrock  with  the  48-inch 
schmidt  have  been  searched  for  satellites 
by  Nicholson.  No  new  satellites  were 
found.  Among  the  asteroids  detected,  one 
has  the  motion  characteristic  of  the  Trojan 
asteroids,  but  further  observations  will  be 
necessary  to  determine  its  orbit. 


COMETS 


Reduction  was  completed,  under  the 
supervision  of  Osterbrock,  of  a  two-year 
series  of  Comet  Baade  (1954h)  and  Comet 
Haro-Chavira  (1954k).  These  comets  were 
at  a  distance  of  approximately  4  astro- 
nomical units  from  the  sun  during  the 
whole  period  of  observation,  and  the  plates 
were  taken  with  the  48-inch  schmidt  in 
order  to  study  the  comets'  tails  at  these 
great  distances.  The  position  angle  of  the 
projection  of  the  comet  tail  on  the  sky  was 
measured  on  each  plate;  the  reductions 
show  that  this  angle  is  not  at  all  strongly 
correlated  with  the  position  angle  of  the 


projection  of  the  line  from  the  sun  to  the 
comet,  but  is  strongly  correlated  with  the 
position  angle  of  the  projection  of  the 
comet  orbit  behind  the  comet.  The  reduc- 
tions further  show  that,  on  the  reasonable 
assumption  that  the  comet  tail  is  in  the 
orbital  plane  of  the  comet,  it  lies  approxi- 
mately halfway  between  the  line  from  the 
sun  through  the  comet  and  the  line  along 
the  orbit  behind  the  comet.  This  indicates 
that,  unlike  most  of  the  well  known  bright 
comets  observed  close  to  the  sun,  in  which 
radiation  pressure  dominates  the  direction 
of  the  tail,  in  these  more  distant  comets 


44 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


the  pressure  of  the  interplanetary  matter 
is  roughly  as  important  as  radiation  pres- 
sure in  its  effects  on  the  tail.  As  the  density 
of  interplanetary  material  is  not  believed  to 
be  particularly  high  at  great  distances  from 
the  sun,  presumably  the  material  in  the 


tails  of  these  distant  comets  is  relatively 
ineffective  in  absorbing  solar  radiation. 

An  extensive  series  of  photographs  of 
comet  Arend-Roland  (1956h)  were  taken 
with  the  48-inch  schmidt  camera  by 
Nicholson,  Minkowski,  and  Schmidt. 


STELLAR  SPECTROSCOPY  AND  PHOTOMETRY 


Spectroscopic  observations  have  been 
regularly  carried  out  with  all  major  tele- 
scopes except  the  48-inch  schmidt  during 
the  moonlit  half  of  each  month.  Seven 
hundred  spectrograms  were  made  with  the 
200-inch  telescope,  827  with  the  100-inch, 
and  978  with  the  60-inch  during  the  year. 

White  Dwarfs  and  Subdwarfs 

The  survey  of  white-dwarf  spectra  by 
Greenstein  now  includes  about  60  objects. 
Hydrogen-line  profiles  were  obtained  for 
25  normal  objects  of  type  DA.  The  use  of 
the  prime-focus  spectrograph  of  the  Hale 
telescope  permits  spectra,  well  widened, 
to  be  obtained  at  the  dispersion  of  160 
A/mm  down  to  15.5  mag.  Fainter  stars 
seem  difficult  during  the  present  sunspot 
maximum  because  of  the  increased  bright- 
ness of  the  airglow,  whose  emission  lines 
are  now  easily  detectable  on  exposures 
longer  than  an  hour.  Various  groups  of 
peculiar  objects  have  been  discovered.  The 
star  HZ  29  has  extremely  shallow  lines 
of  He  I.  The  star  HZ  21  seems  to  be  one 
of  the  hottest  probable  white  dwarfs,  of 
spectral  type  dO.  It  shows  very  strong 
lines  of  He  I  and  He  II.  A  new  type  of 
yellowish  white  dwarf,  represented  by 
W  219  and  L  879-14,  has  been  found  to 
show  an  unidentified  broad  absorption 
near  A4670.  A  recurrent  nova,  WZ  Sagittae 
(1913,  1946),  has  broad  hydrogen  absorp- 
tion lines  similar  to  those  in  a  normal 
white  dwarf  underlying  its  broad  emission 
bands.  Its  luminosity  derived  from  proper 
motion  is  near  + 10,  so  that  it  seems  to  be 
the  expected  link  between  the  white  dwarf 
and  the  nova  stage  of  evolution. 

Most  old  novae  so  far  observed  have  rela- 
tively narrow  emission  lines,  presumably 


arising  from  post-nova  ejection  of  matter 
from  the  star.  Their  blue  continuous  spec- 
trum shows  no  distinct  sharp  or  broad  ab- 
sorption lines.  Nova  DQ  Herculis  has 
relatively  broad  emission  lines,  with  the 
higher  members  of  the  Balmer  series  varia- 
ble through  the  4-hour  cycle.  A  first  theo- 
retical analysis  of  the  observations  of  white- 
dwarf  spectra  has  been  made  by  Greenstein 
with  the  goal  of  obtaining  a  temperature 
scale  largely  based  on  colors  and  the  central 
depth  of  the  hydrogen  line.  The  colors 
should  be  very  reliable  for  the  white 
dwarfs  with  nearly  continuous  spectra. 
On  the  assumption  that  the  interior  com- 
position is  largely  helium  or  heavier  ele- 
ments, the  mean  radius  deduced  for  the 
white  dwarfs  is  0.01  solar  radius,  which 
corresponds  to  about  0.6  solar  mass.  The 
observations  of  the  dependence  of  line 
strength  on  color  demonstrate  clearly  that 
the  ratios  of  abundance  of  hydrogen  to 
helium  to  metals  are  variable  from  one 
type  of  white  dwarf  to  another.  At  ap- 
proximately the  same  color,  white  dwarfs 
can  be  found  with  Balmer  lines,  helium 
lines,  or  essentially  continuous  spectra. 
Possibly  another  opacity  source  exists  be- 
sides hydrogen;  otherwise  it  seems  difficult 
to  understand  the  hot  objects  with  continu- 
ous spectra.  A  method  of  observation  of 
broad  features  has  been  developed  which 
reliably  reveals  absorptions  of  5  per  cent 
or  less  in  depth,  over  a  wide  variety  of 
temperatures. 

A  method  of  analyzing  the  spectra  of 
O-type  subdwarfs  has  been  developed  and 
applied  by  Guido  Munch  to  some  of  the 
stars  discovered  earlier  by  him.  Essentially, 
it  is  based  on  the  fact  that,  over  a  relatively 
wide  range  of  effective  electron  pressure 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        45 


Pe  and  temperature  T,  for  a  given  H:He 
abundance  ratio,  the  intensity  ratios  be- 
tween lines  of  He  II  and  H,  and  between 
lines  of  N  III  and  N  II,  define  the  same 
curve  in  a  (Pe,  T  )  plane.  An  additional 
characteristic  in  this  plane  independent  of 
the  abundances,  as  is  the  Inglis-Teller  cri- 
terion, then  defines  both  Pe  and  T.  The 
analysis  of  the  stars  HZ  44  and  BD  +25° 
4655  gives  a  number  abundance  ratio  H  :He 
=  1:4,  while  the  relative  number  abun- 
dances of  the  heavy  elements  represented 
in  the  spectra  with  measurable  intensi- 
ties are  N:C:O:Ne:Si  =  100:0.5:6:20:6. 
The  effective  temperature  is  found  to  be 
35,000°  K,  and  the  surface  gravity  around 
106-8.  No  direct  information  is  available 
regarding  the  absolute  magnitudes  of  these 
objects,  but  for  assumed  masses  between 
1  O  and  15  O,  the  corresponding  visual 
absolute  magnitudes  range  from  +6.0  to 
+  3.0,  respectively.  The  observational  ma- 
terial available  on  the  six  stars  of  this  type 
known  at  present  is  now  being  analyzed. 

The  subdwarf  nature  of  the  blue  star 
BD  +25°2534,  found  by  Dr.  A.  Slettebak 
on  objective-prism  plates  taken  at  Ham- 
burg-Bergedorf,  has  been  verified  by  G. 
Munch  on  18  A/mm  plates  taken  at  Palo- 
mar.  Although  the  star  had  been  observed 
before  by  Munch  and  Greenstein,  it  had 
not  been  noticed  that,  besides  the  wide  and 
strong  Balmer  lines,  sharp  He  I  lines  and 
a  shallow  diffuse  line  of  He  II  at  A4686 
also  appear.  This  observation  points  to 
the  existence  of  a  pseudophotosphere  with 
temperature  not  as  high  as  would  be  indi- 
cated by  the  color,  where  the  Balmer  lines 
originate,  and  of  an  underlying  hot  core, 
where  the  high-temperature  color  and 
spectral  characteristics  arise.  Such  a  model 
was  suggested  in  the  last  annual  report  by 
G.  Munch  to  explain  the  spectrum  and 
color  of  the  blue  stars  below  the  horizontal 
branch  of  the  H-R  diagram  of  globular 
clusters. 

Feige  has  completed  the  project  for  the 
discovery  of  faint  blue  stars  on  the  Na- 
tional Geographic  Society-Palomar  Ob- 
servatory Sky  Survey  plates  near  the  south 


galactic  pole,  and  most  of  the  area  of  the 
north  galactic  pole.  Thus  far  a  total  of  180 
faint  blue  stars  between  11  and  16  mag. 
have  been  found.  Some  spectra  show  that 
a  considerable  number  of  these  are  the 
so-called  "halo"  blue  stars.  Others,  how- 
ever, are  helium-rich  subdwarfs,  and  three 
definite  new  white  dwarfs  are  included. 

Code  has  developed  a  photoelectric  scan- 
ning spectrograph  that  has  been  adapted 
for  both  the  100-inch  and  200-inch  tele- 
scopes and  has  been  used  for  a  detailed 
study  of  the  energy  distribution  in  the 
spectra  of  several  subdwarfs.  All  the 
energy  distributions  in  the  infrared  of  the 
subdwarfs  HD  19455,  HD  140283,  and  HD 
201891  correspond  to  lower  temperatures 
than  the  temperature  inferred  from  the 
spectral  type  or  the  B  — V  color.  These 
results  are  to  be  understood  in  terms  of 
weak  lines  presumably  resulting  from  a 
low  metal  abundance.  The  infrared,  where 
line  blanketing  is  very  small,  provides  a 
more  significant  measure  of  the  surface 
temperature.  Relative  to  normal  main- 
sequence  stars,  the  smaller  line  blanketing 
in  the  subdwarfs  leads  to  a  moderate  ex- 
cess in  the  B  — V  color  and  to  the  larger 
well  known  U  — B  excess.  Specifically, 
HD  19455  has  a  B  — V  color  corresponding 
to  an  F6  dwarf  and  an  assigned  spectral 
type  of  sdF7,  while  the  spectral  distribution 
in  the  infrared  is  that  of  a  GO  dwarf.  The 
subdwarf  HD  140283  is  similar  but  some- 
what more  extreme — a  result  consistent 
with  the  slightly  weaker  lines  as  measured 
in  its  spectrum. 

In  order  to  extend  the  results  obtained  to 
a  larger  sample  of  stars  a  photometer 
utilizing  a  red-sensitive  photomultiplier 
was  adapted  by  Code  for  use  on  the  100- 
inch  reflector.  Several  wavelength  regions 
were  isolated  by  means  of  glass  filters  and 
with  interference  filters.  It  was  found  that 
for  stars  with  the  same  infrared  color  index 
the  weak-line  objects  averaged  about  0.1 
mag.  bluer  in  the  B  — V  index  and  0.25 
mag.  bluer  in  the  U  — B  index. 

These  results  have  two  important  rami- 
fications.  First,  apparently  a  subdwarf  is 


46        CARNEGIE  INSTITUTION  OF  WASHINGTON 


not  as  underluminous  as  was  previously  year  or  more,  and  the  velocity  amplitudes 

thought;   second,  any  interpretation  of  a  rather  small,  the  spectrograms  now  at  hand 

color-magnitude  array  must  be  made  with  do  not  allow  any  conclusions.  On  the  pos- 

due    regard    for   the    influence    that   line  sibility  that  H3  and  K3  are  produced  in 

blanketing  may  have  upon  the  color  index,  circumstellar  envelopes  in  G  and  K  giants 

as  well,  a  few  of  these  stars  in  binary  sys- 

Late-Type  Stars  terns    are    also    being    observed    on    this 

Code  has  applied  his  photoelectric  scan-  program, 
ning  spectrograph  to  the  study  of  the  Coude  spectra  of  the  M2  +  Ia+  super- 
energy  distribution  of  the  high-velocity  giant  VV  Cephei,  made  during  the  total 
giant  Arcturus  and  of  two  red  giants  in  eclipse  of  its  B-type  companion,  have  re- 
M  92.  The  differences  between  the  ob-  vealed  both  circumstellar  and  interstellar 
served  energy  distribution  and  that  of  nor-  absorption  lines  at  H  and  K.  The  inter- 
mal  giants  may  be  interpreted  in  the  same  stellar  lines  have  a  velocity  and  strength 
manner  as  the  subdwarf  results  reported  appropriate  to  a  distance  of  about  0.8 
in  the  preceding  section.  kiloparsec,  in  good  agreement  with  Kee- 

In  the  spectra  of  most  M-type  giants  and  nan's  recent  luminosity  classification.  The 

supergiants,  the  H  and  K  lines  of  Ca  II  circumstellar  lines  are  somewhat  weaker 

show  deep  absorption  reversals  (H3  and  than  was  expected  by  analogy  with  other 

K3)   superposed  on  emission  components  equally  luminous  M  stars.   Possibly  the  B 

(H2  and  K2).  The  velocity  from  H3  and  star  has  an  effect  on  the  envelope  that 

K3  always  indicates  that  the  absorption  gas  persists,  in  some  degree,  even  during  total 

is  expanding  from  the  star.  Depending  on  eclipse. 

the  height  at  which  the  lines  are  formed,  The  system  of  Mira  is  similar  in  some 

the  observed  expansion  velocity  may  ex-  respects.  The  spectrum  of  the  long-period 

ceed  the  velocity  of  escape,  and  the  matter  variable  shows  a  sharp  absorption  core  at 

will  be  ejected  into  the  interstellar  medium.  K,  with  a  strength  about  one-third  that 

This  is  true  for  the  M5  II  star  a  Herculis;  of  K3  in  a  Herculis  A.  This  feature  indi- 

it  and  all  other  M-type  supergiants  are  cates  a  variable  velocity,  which  correlates 

losing  mass  at  a  rate  comparable  with  their  with  the  velocity  of  the  reversing  layer  but 

evolutionary    time    scale.     The    question  is  generally  about  2.5  km/sec  less.   A  still 

arises  whether  H3  and  K3  in  all  M  giants  weaker   absorption   core   at   K   has   been 

arise  in  envelopes  so  distended  that  the  noted  by  Joy  in  the  spectrum  of  Mira  B. 

observed  velocities  will  suffice  for  escape.  Its  velocity,  which  appears  to  be  constant, 

If  so,  as  it  was  shown  last  year  by  Deutsch,  is  only  slightly  less  than  that  of  the  sharp 

the  observed  number  of  white  dwarfs  can  core  in  the  M  star.   If  both  K  cores  are 

be  accounted  for  as  the  remnants  of  the  produced  in  a  common  envelope,  then  the 

massive  stars  that  have  condensed  into  the  radius   of   the   envelope   must   exceed   25 

main  sequence  during  the  last  5  billion  astronomical  units, 

years.  The  spectrum  of  the  long-period  variable 

To  investigate  the  dimensions  of  the  re-  Mira  has  been  found  to  exhibit  a  number 

gions  responsible  for  H3  and  K3  in  ordi-  of  remarkable  changes  from  cycle  to  cycle, 

nary  M  giants,  a  number  of  spectroscopic  As  compared  with  the  spectra  of  ordinary 

binaries  have  been  observed  at  10  A/mm.  M  giants,  the  absorption  features  in  Mira 

If  the  gas  that  produces  H3  and  K3  is  really  tend  to  be  the  most  nearly  normal  at  bright 

circumstellar,  and  escaping  from  the  sys-  maxima.  At  most  faint  maxima,  however, 

tern,  it  cannot  follow  the  orbital  motion  of  the  atomic  absorption  lines  are  strongly 

the  M  star;  in  this  event,  H3  and  K3  should  suppressed,  especially  in  the  region  of  the 

be  stationary,  or  nearly  so.  The  periods  of  TiO  bands.  As  the  star  fades,  the  intensi- 

M-giant  binaries  being  of  the  order  of  a  ties   of   many   of   these   lines   change   in 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        47 


opposite  directions  after  maxima  of  these  a  theoretical  derivation  of  the  width- 
two  kinds.  The  effects  are  extremely  com-  luminosity  relationship  can  be  obtained, 
plicated,  but  often  very  large.  Presumably  So  far,  additional  spectrograms  of  the  four 
they  are  principally  stratification  effects,  Hyades  stars  combined  with  the  previous 
but  as  yet  they  are  not  well  understood.  ones  yield   an  average  deviation  for   the 

An  attempt  will  be  made  by  Deutsch  method  of  0.3  mag.  Spectrograms,  though 

this  summer  to  observe  the  rapid  spectro-  not  of  first  quality,  of  the  yellow  giants  in 

scopic  changes  in  Mira  B  found  at  recent  Praesepe  give  an  average  deviation  of  0.5 

minima  of  the  long-period  variable.   The  mag.  Further  observations  of  both  clusters 

companion  has  been  observed  visually  at  should  provide  information  on  measuring 

each  of  the  last  three  minima,  in  roughly  error,    intrinsic    scatter    among    stars    of 

the  same  configuration  as  at  all  other  re-  closely  similar  luminosities,  and  the  mean 

liable    observations     (p  =  0'.'5,    0  =  130°).  line  width  for  these  eight  stars  of  known 

These  observations  require  the  abandon-  brightness.    Even   though  the  calibration 

ment  of  a  period  near  14  years,  as  had  of  the  K-line  method  is  still  incomplete, 

been   suggested   by   Parenago.    Evidently  it  appears  already  to  be  adequate  to  pro- 

the  motion  is  very  slow,  and  the  mass  of  vide  improved  information  on  the  yellow 

the  system  very  low.  Another  long-period  and  red  giants  in  the  solar  neighborhood, 

variable   with   a   visual  companion   is   X  Under  consideration  are  observations  in- 

Ophiuchi.    Recent    spectrograms    of    this  tended  to  extend  knowledge  of  luminosity 

companion  confirm  that  it  is  a  subgiant  functions,  color-magnitude  diagrams,  and 

which  is  much  less  luminous  than  normal  masses    (through    the   derivation   of   im- 

K  giants.  These  two  systems  suggest  that  proved  parallaxes  of  binaries  and  physical 

long-period  variables  are  likely  to  be  ex-  pairs), 

tremely  old  stars.  Under    the    second    category,    the    first 

Wilson  and  M.  K.  Vainu  Bappu  have  problem  is  to  decide  on  the  nature  of  the 

completed  the  measurements  of  the  line  emitting  layers.  Wilson  favors  the  view 

width  of  the  H  and  K  emission  lines  in  that  they  are  probably  optically  thin  be- 

185  late-type  stars.    As  mentioned  in  the  cause  of  intensity  differences  between  K 

last  report,  the  main  result  is  that  a  plot  of  and  H  which  can  be  seen  in  many  stars, 

the  logarithms  of  the  corrected  line  widths  This  evidence  is  not  conclusive,  however; 

against  visual  absolute  magnitudes  is  linear  the  layers  may  be  optically  thick.   In  any 

over  a  15-mag.  range.  Another  finding  is  event,  if  the  layers  are  optically  thin,  then 

that  neither  surface  temperature  nor  sur-  the  lines  are  widened  purely  by  Doppler 

face  gravity  can  play  much  of  a  role  in  this  effect,  the  measured  widths  are  approxi- 

functional  relationship,  which  appears  to  mately  equal  to  the  Doppler  widths,  AAd, 

be   a   relation   between   a   chromospheric  and  the  turbulence  is  large.   Under  these 

phenomenon  and  the  total  energy  produc-  circumstances,  AAd  a  LVq,  and  the  only  re- 

tion  deep  within  the  star.  striction  on  N  (particles  per  square  centi- 

A    number    of    important    possibilities  meter)  is  that  it  is  never  so  large  that  the 

opened  by  these  observations  can  be  di-  optical  thickness  in  the  line  center  exceeds 

vided  into  two  categories:  use  of  the  rela-  approximately  1. 

tionship  as  a  tool  for  the  measurement  of  Dr.  L.  Goldberg,  of  the  University  of 

absolute  magnitude,  and  information  that  Michigan,  has  pointed  out  that,  with  op- 

they   provide   in   regard   to   the   physical  tically    thick    layers,    AA,    the    measured 

processes  operating  in  the  atmospheres  of  width,  is   approximately   three   times   the 

these  stars.  Doppler  width,  AAd.  Thus  the  real  turbu- 

In   considering   the   first   category,   the  lence  is  only  about  one-third  as  large  as 

major  problem  is  to  refine  the  calibration,  for   thin    layers.    In    this    case,   however, 

which  is  a  purely  empirical  matter  unless  calculation  (unpublished)  shows  that  both 


48        CARNEGIE  INSTITUTION  OF  WASHINGTON 


AAd  and  N  must  vary  with  luminosity  in  cepheids  in  globular  clusters  and  in  the 
a  prescribed  fashion  in  order  to  agree  with  galactic  field.  The  line  emission,  and  its 
the  observations.  Thick  layers  are  thus  variations,  resembles  that  in  W  Virginis. 
more  restrictive  on  any  physical  theory  In  certain  globular-cluster  cepheids  the 
seeking  to  explain  the  width-luminosity  absorption  lines  double,  but  in  others  they 
correlation.  merely  broaden  at  phases  in  which  W  Vir 
Emission  at  He  was  first  noted  by  Wil-  showed  line  doubling.  This  material  is  at 
son  in  the  spectrum  of  Arcturus  in  1938.  present  under  discussion  for  the  deter- 
It  appears  on  many  spectrograms  of  the  mination  of  the  radius  changes,  spectral- 
late-type  stars  used  for  the  foregoing  H  type  variations,  and  anomalous  spectral 
and  K  investigation.  All  these  plates  were  behavior  of  the  Population  II  cepheids. 
carefully  compared  with  one  of  Arcturus  The  R  Coronae  Borealis  variable,  RY 
in  order  to  make  a  preliminary  study  of  Sagittarii,  was  found  by  Greenstein  to 
the  intensity  of  the  He  emission  as  related  show  variable  absorption-line  doubling 
to  K  emission  strength,  to  spectral  type,  during  small  light-variations  near  its  maxi- 
and  to  absolute  magnitude.  The  chief  mum,  with  displaced  components  up  to 
results  are  that  He  intensity  increases  on  —150  km/sec.  Studies  by  Greenstein  and 
the  average  in  the  direction  G— »K— >M,  Merrill  of  the  infrared  spectrum  of  R 
and  that  there  seems  to  be  a  statistical  cor-  Andromedae  showed  that  this  S  star  had  a 
relation  between  emission  strengths  of  K  circumstellar  envelope,  visible  in  certain 
and  of  He.  There  is  not  a  one-to-one  corre-  lines,  with  about  —  20  km/sec  relative 
lation  between  He  and  K,  since  some  stars  velocity. 

with  strong  K  intensity  show  no  emission  Zwicky  continued  to  co-ordinate  the 
at  He.  Presumably  both  the  Ca  II  and  search  for  and  the  investigation  of  super- 
hydrogen  emission  are  of  chromospheric  novae  conducted  at  the  Lick,  Steward, 
origin,  and  they  may  well  supply  clues  to  Berne  (Switzerland),  and  Palomar  Ob- 
physical  properties  of  the  stellar  chroma-  servatories  with  the  aid  of  funds  from  the 
spheres.  National  Science  Foundation  and  the 
Variable  Stars  Swiss  Government.   During  the  year  two 

_    ..  .      .     .  bright  supernovae  were  discovered,  one  in 

Radial-velocity  measurements  were  com-  NGC  2m  .     g^-^,  ;Q  Berne>  and  the 

pleted  on  spectrograms  of  the  cluster-type  othef  b  M  g4  fe    Gates  a£  palomar>  M 

variable  stars  SW  Andromedae,  DX  Del-  '    ,          u                       n 

.  .  .  _T7  TT  ..  .  '_  _  .  recent  supernovae  nave  been  continually 
phini,  DY  Herculis,  and  DH  Pegasi,  ,  i  i  i  rj  .  i  Vi_  ^i_  aq  •  L 
r  ,  •  ,  i  t  i  i  .  •  ,  -m  a  /m?  u  photographed  by  Zwicky  with  the  4o-incn 
which  had  been  obtained  with  the  6U-incn  r  .  *  .r  ,  , }  .J  r  , 
telescope  during  1955  and  1956  by  TifiEt  an^OO-inch  telescopes  in  four  color  ranges 
and  Bonsack.  Radial-velocity  and  radius-  (ultraviolet,  blue,  green-yellow  and  red) 
variation  curves  were  obtained.  The  with  a  vietw  to  securing  four  light-curves 
velocity  curves  of  DY  Her  and  DH  Peg  corresponding  to  these  ranges.  Efforts  by 
cannot  be  described  as  mirror  images  of  ZwickY  to  investigate  theoretically  simple 
the  published  light-curves  for  these  stars,  models  of  supernova  outbursts  have  led  to 
but  the  mirror-image  relationship  does  results  giving  promise  that  both  the  light- 
hold  for  SW  And  and  DX  Del.  curves  and  the  sequences  of  the  spectra  in 
Tifft  and  H.  J.  Smith,  of  Yale,  have  supernovae  of  types  I  and  II  may  become 
completed  a  study  of  the  three-color  light-  understandable  in  the  near  future, 
variation  and  radial-velocity  variation  for  The  supernova  in  M  84  was  observed 
the  star  T  Sextantis,  an  RR  Lyrae  star  of  photoelectrically  by  Baum  at  the  200-inch 
subclass  c.  telescope.  On  May  24  its  photovisual  mag- 
Wallerstein  has  completed  his  study  nitude  was  13.32,  and  its  B— V  index  was 
of  the  velocity   curves   of  Population   II  +0.80.  Multicolor  observations  were  also 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        49 


obtained  in  order  to  determine  the  general 
character  of  its  spectral-energy  distribution. 

Magnetic  Stars 

The  results  of  an  11-year  program  de- 
voted to  the  observation  of  stellar  mag- 
netic fields  have  been  summed  up  in  a 
catalogue  of  magnetic  stars  by  Horace  W. 
Babcock.  Table  1  of  this  catalogue  is  a 
compilation  of  results  for  84  stars  for  which 
magnetic  fields  have  been  observed  by 
means  of  the  Zeeman  effect.  Notes  are 
given  on  the  spectra,  line  widths,  abnormal 
line  intensities,  and  magnetic  variations. 
Table  2  lists  55  stars  that  probably  but  not 
definitely  have  magnetic  fields.  Table  3  is 
a  list  of  55  stars  having  sharp  lines  that 
give  little  or  no  evidence  of  the  Zeeman 
effect;  Table  4  is  a  collection  of  111  stars 
having  lines  too  broad  for  magnetic  meas- 
urements. 

The  analysis  and  discussion  of  the  nu- 
merous results  now  available  on  magnetic 
stars  lead  to  the  following  preliminary 
conclusions.  Of  the  magnetic  stars  in 
Table  1  of  the  catalogue,  1  is  a  cluster-type 
variable,  1  is  a  subdwarf,  2  are  of  type  S, 
3  are  M-type  giants,  7  are  "metallic-line" 
stars,  and  64  are  sharp-line  A-type  stars. 
This  variety  shows  that  stellar  magnetic 
fields  are  in  all  probability  ubiquitous, 
particularly  when  it  is  recalled  that  only 
strong  coherent  fields  in  sharp-line  stars  are 
susceptible  of  measurement  by  available 
methods.  Another  significant  result  is  that 
all  stellar  fields  appear  to  be  variable,  and 
the  great  majority  show  irregular  varia- 
tions. Stellar  magnetic  phenomena,  like 
those  of  the  sun,  are  evidently  not  simple; 
rather,  the  observations  reflect  complex 
hydromagnetic  fluctuations  of  the  photo- 
spheric  material.  It  is  legitimate  to  think 
of  hydromagnetic  turbulence  in  which  the 
energy  of  the  magnetic  field  is  of  the  same 
order  as  the  kinetic  energy  of  motion  of 
the  gas  masses.  The  statistics  of  line 
widths  among  the  rapidly  rotating  stars 
of  type  A  are  in  accord  with  the  supposi- 
tion that  nearly  all  the  sharp-line  magnetic 


A-type  stars  are  rapid  rotators  viewed 
pole-on.  As  a  working  hypothesis,  it  can 
be  maintained  that  the  prevalence  of  rapid 
axial  rotation  plus  hydrogen  convective 
zones  is  responsible,  through  a  dynamo 
process,  for  the  strong  fields  of  the  A-type 
stars. 

Of  the  magnetic  stars  found  in  the 
course  of  this  survey,  many  have  peculiar 
and  variable  line  profiles,  several  are  spec- 
trum variables,  and  six  are  new  spectro- 
scopic binaries.  Secular  variations  in  line 
intensities  and  in  amplitude  of  magnetic 
variation  have  been  found  in  certain  mag- 
netic stars.  The  variety  of  significant  yet 
unexplained  phenomena  observed  is  con- 
siderable, and  this  field  deserves  increased 
attention  in  the  future.  The  interpretation 
of  the  stellar  magnetic  results  will  un- 
doubtedly be  facilitated  by  the  increased 
understanding  of  solar  magnetic  phenom- 
ena, and  particularly  the  solar  magnetic 
cycle,  that  is  accruing  from  current  studies. 

The  star  HD  125248  reverses  its  mag- 
netic field  with  a  period  of  9.3  days,  and 
shows  synchronous  changes  in  line 
strength,  line  width,  and  radial  velocity. 
By  a  kind  of  harmonic  analysis,  Deutsch 
has  shown  that  it  is  possible  to  derive  a 
rigidly  rotating  configuration  which  satis- 
fies the  observations  in  any  one  cycle  rea- 
sonably well.  Superposed  on  the  9.3-day 
cycle,  however,  is  another,  much  slower, 
variation  in  radial  velocity,  which  has  here- 
tofore prevented  the  compilation  of  ob- 
served velocities  to  form  mean  curves. 

From  coude  observations  accumulated 
over  a  10-year  interval,  by  Deutsch  and 
H.  W.  Babcock,  it  has  now  been  found 
that  the  secondary  velocity  variation  has  a 
period  of  about  1670  days.  The  amplitude 
of  this  long  cycle  is  about  7  km/sec,  or 
more  than  twice  that  of  the  9.3-day  cycle. 
The  long  cycle  is  probably  due  to  Kepler 
motion  in  an  eccentric  orbit  about  an  in- 
visible companion. 

When  the  orbital  velocity  variation  is 
removed,  the  observations  may  be  com- 
bined to  yield  mean  velocity  curves  which 
represent  the  motions  due  to  rigid  rotation. 


50        CARNEGIE  INSTITUTION  OF  WASHINGTON 


One  such  curve  is  required  for  the  lines 
of  Eu  II,  Gd  II,  and  Ce  II;  a  second  for 
the  lines  of  Cr  I  and  II;  and  a  third  for 
the  lines  of  Fe  I,  Fe  II,  and  Ti  II.  Since 
these  mean  curves  make  use  of  many  more 
observations,  they  are  much  better  deter- 
mined than  the  velocity  curves  previously 
used  for  the  harmonic  analysis.  Accord- 
ingly, the  harmonic  analysis  will  be  re- 
peated by  Deutsch  in  an  attempt  to  im- 
prove the  fidelity  of  the  map  that  has 
been  derived. 

Spectrograms  were  obtained  by  Bonsack 
with  the  60-inch  telescope  of  the  spectrum 
variable  56  Arietis.  They  were  measured 
to  determine  the  radial  velocities  of  the 
individual  lines  as  a  test  of  the  rigid  mag- 
netic rotator  model  for  this  star.  Analysis 
of  the  wavelength  and  intensity  variations 
of  the  lines  showed  that  the  star  can  be 
represented  as  a  rigid  rotator  of  period 
0.73  day. 

Because  of  the  unusually  strong  Si  II 
lines,  21  Aquilae  is  placed  in  the  group  of 
"silicon-helium"  peculiar  A  stars  although 
it  is  classified  as  B8  from  the  He  I  lines 
in  its  spectrum.  Its  spectrum  lines  are  un- 
usually narrow,  so  that  wavelengths  can 
be  measured  with  good  accuracy.  Com- 
bining Miss  Burd's  measurements  of  plates 
taken  by  H.  W.  Babcock  with  data  from 
a  plate  taken  at  the  McDonald  Observa- 
tory, G.  R.  and  E.  M.  Burbidge  have  ob- 
tained evidence  for  a  systematic  shift  be- 
tween the  singlet  and  triplet  lines  of  He  I. 
Although  some  part  of  this  may  be  due 
to  Stark  effect,  comparison  with  the  labora- 
tory measures  of  isotope  shifts  between 
lines  of  He3  and  He4  suggests  that  there 
is  a  reasonable  probability  that  the  major 
part  of  the  shift  may  be  due  to  the  pres- 
ence of  He3  in  the  star's  atmosphere  in  an 
amount  comparable  with  that  of  He4. 

The  presence  of  He3  may  be  explained 
by  a  theoretical  treatment,  carried  out  by 
G.  R.  Burbidge  and  by  W.  A.  Fowler 
and  E.  M.  Burbidge,  of  the  Kellogg  Radia- 
tion Laboratory,  of  nuclear  reactions  on 
the  surfaces  of  magnetic  stars.  It  appears 
that  a  flux  of  neutrons  will  be  produced  by 


reactions  between  accelerated  protons  and 
light  nuclei,  and  will  be  captured  by  cool 
hydrogen  to  form  deuterium.  Reactions 
between  deuterons  and  protons  will  either 
build  He3,  or  free  the  neutrons  again,  so 
that  eventually  they  may  be  captured  by 
elements  in  the  iron  group  to  build  heavy 
nuclei. 

Globular  and  Galactic  Clusters  and 
Stellar  Evolution 

Schmidt  has  started  an  investigation  of 
the  color-magnitude  diagram  for  the  galac- 
tic cluster  NGC  6939.  The  cluster  appears 
to  be  relatively  old  and  has  an  incipient 
Hertzsprung  gap.  More  photoelectric 
standards  are  being  obtained. 

Photographic  material  has  been  obtained 
for  the  galactic  clusters  NGC  2269,  2309, 
2311,  2367,  2401,  2453,  and  6834.  Poor  ob- 
serving conditions  in  the  winter  prevented 
the  establishment  of  photoelectric  stand- 
ards in  these  clusters. 

Schmidt  carried  out  photographic,  photo- 
electric, and  spectroscopic  observations  on 
a  small  condensation  of  stars  at  R.A.  19h 
14m  35s,  Dec.  +15°  137.  The  diameter  is 
l'x2',  and  the  tenth-brightest  star  is 
mpg=l65. 

Study  of  color-magnitude  diagrams  for 
a  number  of  star  clusters  was  continued 
by  Sandage  during  the  report  year  in  con- 
nection with  the  problem  of  stellar  evolu- 
tion. Because  of  the  importance  of  the 
ultraviolet  excess  shown  by  stars  with 
B  —  V— 0.5  in  the  globular  clusters  M3  and 
NGC  4147  (reported  last  year),  Sandage 
and  Walker  did  three-color  photometry  on 
the  UBV  system  for  200  of  the  brighter 
stars  in  M  92.  Photoelectric  observations 
were  made  on  8  nights  with  the  60-inch 
telescope,  and  a  special  series  of  photo- 
graphic plates  were  taken  with  the  100- 
inch.  The  measurements,  which  have  been 
completed,  indicate  that  the  giant  stars  in 
M  92  also  show  the  A(U  — B)  excess  of 
about  0.3  mag.  in  agreement  with  the  value 
found  for  stars  in  M  3  and  NGC  4147. 
Stars  on  the  horizontal  branch,  however, 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        51 


show  an  ultraviolet  deficiency  of  nearly 
A(U-B)=0.15,  again  like  stars  in  M  3, 
M  13,  and  NGC  4147.  It  is  therefore  be- 
coming clear  that  the  energy-distribution 
curves  for  globular-cluster  stars  differ  in  a 
fundamental  way  from  curves  for  stars  in 
the  solar  neighborhood,  and  the  difference, 
which  shows  up  in  the  three-color  pho- 
tometry, provides  an  easy  means  to  search 
for  globular-cluster-like  stars  in  the  gen- 
eral field.  The  differences  in  the  U,  B,  V 
values  between  globular-cluster  stars  and 
normal  field  stars  are  believed  to  be  due 
to  differences  in  chemical  composition  and 
the  resulting  blanketing  of  the  continuum 
by  the  absorption  lines  in  the  blue  and 
ultraviolet  region  of  the  spectrum.  A  spe- 
cial study  of  the  blanketing  effect  was 
begun  by  E.  M.  Burbidge,  G.  R.  Burbidge, 
and  Sandage  with  the  globular-cluster 
problem  in  mind.  The  study  is  reported 
in  more  detail  in  another  section  of  this 
report. 

The  globular  cluster  NGC  5897  was 
placed  on  the  three-color  program  because 
a  spectrogram  by  Deutsch  showed  that  this 
cluster  had  very  weak  absorption  lines  and 
therefore  is  expected  to  have  a  large  ultra- 
violet excess.  Photoelectric  observations 
with  the  100-inch  and  photographic  plates 
with  the  200-inch  were  obtained  for  this 
cluster  by  Sandage.  Schmidt  is  reducing 
the  photographic  material,  but  the  results 
are  not  yet  available.  Other  clusters  on  the 
current  program  include  NGC  6356,  which 
is  one  of  the  W.  W.  Morgan  strong-line 
globular  clusters  near  the  galactic  nucleus; 
NGC  6712,  a  globular  cluster  situated  in 
the  Scutum  star  cloud;  NGC  7789,  an  old 
galactic  cluster  probably  of  the  M  67  type; 
NGC  7788,  which  has  the  three  classical 
cepheids  CF  Cassiopeiae,  CE  a  Cas,  CE  b 
Cas  associated  with  it;  and  NGC  7790, 
which  forms  a  double  cluster  with  7788. 
Sandage  has  obtained  photoelectric  calibra- 
tions and  photographic  plates  for  all  these 
clusters  with  either  the  60-inch  or  the  100- 
inch  telescopes.  The  measurements  are 
almost  complete  for  most  of  the  clusters, 


The  work  on  NGC  7789  is  a  joint  project 
with  E.  M.  Burbidge. 

The  cluster  NGC  1866  in  the  Large 
Magellanic  Cloud  is  under  study  by  Arp 
and  Sandage  in  collaboration  with  Dr. 
A.  D.  Thackeray,  of  the  Radcliffe  Observa- 
tory, Pretoria,  South  Africa.  This  cluster 
is  globular  in  appearance  but  has  a  color- 
magnitude  diagram  that  seems  at  this  stage 
of  the  investigation  to  resemble  that  of 
M  11.  Its  importance  lies  in  the  fact  that 
9  cepheids  with  periods  ranging  from  2.64 
to  3.52  days  are  associated  with  the  cluster. 
All  these  cepheids  have  the  same  apparent 
magnitude  and  therefore  are  at  the  same 
place  in  their  evolutionary  history.  The 
details  of  the  connection  of  the  cepheids 
with  the  nonvariable  stars  in  NGC  1866 
promise  to  clarify  our  ideas  of  how  cepheid 
variables  fit  into  the  evolutionary  picture. 
Photoelectric  calibration  to  V  =  19.0  was 
completed  by  Arp  while  he  was  in  South 
Africa;  Thackeray  has  obtained  an  exten- 
sive series  of  plates  with  the  74-inch  Rad- 
cliffe reflector;  Sandage  has  started  meas- 
urement of  the  plate  material.  At  the 
present  writing,  NGC  1866  appears  to  be 
one  of  the  most  important  clusters  in  the 
sky  for  the  evolutionary  problem. 

Several  years  ago,  E.  E.  Salpeter,  of  Cor- 
nell, derived  a  theoretical  luminosity  func- 
tion giving  the  distribution  of  stars  along 
the  main  sequence  at  the  time  of  their 
formation.  This  creation  function  is  of 
interest  because  with  it  can  be  predicted 
the  number  of  stars  at  any  given  lumi- 
nosity which  have  been  formed  in  the  life- 
time of  the  Galaxy.  Because  of  its  signifi- 
cance, observational  checks  on  the  Salpeter 
function  are  necessary.  Sandage  showed 
that  the  luminosity  functions  in  each  of  the 
open  clusters  h  Persei,  Pleiades,  Coma 
Berenices,  Hyades,  and  Praesepe  agree  well 
with  the  Salpeter  creation  function,  and 
this  agreement  supports  the  argument  that 
the  peculiar  form  of  the  van  Rhijn  lumi- 
nosity function  for  stars  in  the  general  field 
brighter  than  Mv—  +3.5  is  due  to  stellar 
evolution. 

Sandage  derived  a  new  luminosity  func- 


52        CARNEGIE  INSTITUTION  OF  WASHINGTON 


tion  for  M  3  which  predicts  a  total  mass 
for  M  3  of  2.45 X  105  MO,  a  total  number 
of  stars  of  5.9  X 105,  and  a  total  number  of 
white  dwarfs  of  4.8  X  104.  By  means  of  the 
Salpeter  creation  function  it  was  estimated 
that  the  stars  which  are  now  white  dwarfs 
in  M  3  have  shed  a  mass  equal  to  1.1  X  105 
MO  in  the  form  of  gas  as  they  evolved 
from  the  main  sequence  to  the  white-dwarf 
stage.  This  mass  has  escaped  from  the 
cluster  into  the  interstellar  medium.  Simi- 
lar considerations  for  E  galaxies  show  that 
the  gas  formed  by  the  shedding  process  has 
probably  not  escaped  and  makes  up  about 
1/200  of  the  total  mass  of  the  E  galaxy. 
Osterbrock  has  suggested  that  this  mass 
may  be  the  origin  of  the  A3727  [O  II] 
emission  from  the  E  systems. 

Semiempirical  evolutionary  tracks  were 
computed  by  Sandage  for  the  stars  in  M  3 
and  M  67.  M  3  and  M  67  are  clusters  of 
about  the  same  age  (^5xl09  years),  but 
the  stars  in  each  cluster  follow  very  differ- 
ent tracks  of  evolution  in  the  giant  region 
even  though  they  are  of  about  the  same 
mass.  Presumably  the  track  differences  are 
due  to  differences  in  the  chemical  com- 
position of  the  two  clusters.  The  method 
of  obtaining  the  tracks  of  evolution  for 
individual  stars  utilizes  the  information 
contained  in  the  observed  luminosity  func- 
tions and  color-magnitude  diagrams  of 
clusters.  The  evolutionary  tracks,  the  time 
scale  for  evolution  along  these  tracks,  and 
the  fraction  of  the  total  mass  exhausted  of 
hydrogen  at  each  evolutionary  stage  are 
determined.  These  semiempirical  results 
were  compared  with  the  predictions  of  the 
Hoyle-Schwarzschild  (HS)  theoretical 
evolving  models,  and  Sandage  showed  that 
the  time  scale  of  the  HS  models  gives 
nearly  the  correct  luminosity  function  for 
M  3  except  at  the  top  of  the  giant  branch, 
where  the  HS  time  scale  is  too  fast  by  a 
factor  of  3.  The  lifetime  of  the  RR  Lyrae 
stars  is  estimated  to  be  8  X 107  years.  This 
figure  gives  an  expected  rate  of  change  of 
period  for  these  variables  due  to  evolution 
of  A*//=2.40X10-11,  which  is  0.1  second 
of  time  per  century.  The  final  result  of  the 


study  shows  that  stars  in  M  3  completely 
exhaust  their  energy  store  of  1.60  XlO52 
ergs  in  their  lifetime  as  they  evolve  from 
the  main  sequence,  through  the  giant  stage, 
and  finally  to  the  white  dwarfs.  But  stars 
in  M  67  exhaust  only  37  per  cent  of  their 
energy  store.  Since  there  can  be  no  internal 
energy  reservoir  in  the  white  dwarfs,  this 
result  suggests  that  mass  loss  must  occur 
from  stars  like  those  in  M  67  before  they 
become  white  dwarfs.  This  conclusion  is 
supported  empirically  by  Deutsch's  study 
of  the  giant  a  Herculis  reported  last  year. 

Chemical  Composition  of  Stellar 
Atmospheres 

Under  the  sponsorship  of  the  Physics 
Division  of  the  U.  S.  Air  Force,  Office  of 
Scientific  Research,  a  project  entitled 
"Stellar  Composition  and  Related  Nuclear 
Processes"  has  been  established  at  the 
Mount  Wilson  and  Palomar  Observatories 
under  the  direction  of  Greenstein.  The 
goal  is  to  increase  the  astronomical  data 
relevant  to  theories  of  the  origin  of  the 
elements,  as  well  as  to  bring  together  a 
group  of  nuclear  physicists  and  theoretical 
astrophysicists  interested  in  aspects  of  this 
fundamental  question.  It  is  generally  ac- 
cepted now  that  certain  stars  show  evi- 
dence for  the  current  formation  of  ele- 
ments, for  example  most  obviously  the  ele- 
ment technetium  in  S  stars,  originally  dis- 
covered by  Merrill.  In  addition,  the 
thermonuclear  conversion  of  hydrogen  to 
helium,  and  the  burning  of  helium  to  car- 
bon, in  stars  has  been  definitely  established. 
These  processes  occur  in  certain  parts  of 
the  evolution  of  stars,  and  should  be  corre- 
lated with  studies  of  stellar-interior  theory. 
The  group  under  Air  Force  sponsorship 
will  apply  more  advanced  theoretical  tech- 
niques to  the  determination  of  the  abun- 
dances in  normal  and  peculiar  stars,  with 
the  hope  of  correlating  these  results  with 
nuclear  data  and  theory.  The  general  ques- 
tion of  the  possible  evolutionary  trend  in 
the  abundance  of  heavy  elements  with  time 
in  our  own  Galaxy  will  also  be  studied. 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        53 


Abundance  analyses  for  such  elements  in 
carbon-rich  stars,  S  stars,  stars  with  abun- 
dant rare  earths,  very  old  and  very  young 
main-sequence  and  giant  stars,  and  young 
and  old  subgiants  will  be  among  the  goals 
of  this  research.  It  is  hoped  that  the  study 
will  be  continued  for  several  years. 

The  two-lined  spectroscopic  binary 
-f74°493,  a  high-velocity  dwarf,  has  been 
studied  by  Greenstein  in  collaboration  with 
Drs.  Margherita  Hack  and  Otto  Struve, 
of  the  University  of  California.  The 
masses  seem  to  be  close  to  those  of  nor- 
mal main-sequence  G  dwarfs;  in  other 
words,  high  velocity  does  not  necessarily 
mean  in  the  dwarfs  a  deviation  from  the 
mass-luminosity  relation.  A  spectrophoto- 
metric  analysis  showed  that  the  lines  may 
be  slightly  weaker  than  normal  for  similar 
Population  I  dwarfs,  indicating  a  slight 
underabundance  of  the  metals. 

A  detailed  study  of  line  intensities  of  the 
metals,  CN,  and  CH  has  been  made  by 
Greenstein  and  Dr.  Philip  C.  Keenan,  of 
the  Perkins  Observatory.  Fourteen  giants 
near  spectral  type  G8  of  both  high  and  low 
velocities  have  been  studied.  The  deduced 
reduction  in  the  number  of  metallic  atoms 
in  high-velocity  stars  is  by  a  factor  of  about 
0.4  to  0.6;  the  effective  number  of  CN 
molecules  is  reduced  to  about  0.06  normal, 
and  CH  is  hardly  affected.  Two  new  ap- 
parently carbon-poor  stars  have  been 
found.  One  of  the  high-velocity  stars,  u2 
Cancri,  is  shown  to  be  of  normal  composi- 
tion; it  is  therefore  a  runaway  evolved 
Population  I  star. 

Further  spectra  of  the  brightest  stars  in 
the  globular  clusters  M  13  and  M  92  have 
been  obtained  by  Greenstein  at  18  A/mm 
with  exposures  running  from  two  to  three 
nights.  The  M  13  spectra  resemble  those 
of  high-velocity  stars  in  the  solar  neighbor- 
hood; the  M  92  spectra  show  very  weak 
but  numerous  metallic  lines  corresponding 
to  a  quite  low  excitation  temperature.  A 
quantitative  analysis  of  these  stars  is 
planned. 

A  survey  of  early  R  stars  at  dispersion 
4  and  7  A/mm  is  being  carried  out  by 


Greenstein  for  the  study  of  the  atomic-line 
differences  between  the  hydrogen-rich  and 
hydrogen-poor  carbon  stars. 

Work  was  begun  by  Bonsack  on  an  ex- 
tensive program  to  survey  a  variety  of  stars 
of  type  K  to  determine  the  possible  varia- 
tions in  the  abundance  of  lithium,  and  a 
number  of  stars  of  type  A  to  study 
beryllium. 

The  comparison  of  the  spectrum  of  the 
Ba  II  star  HD  46407  with  that  of  the  stand- 
ard G8  III  star  k  Geminorum  has  been  con- 
tinued by  G.  R.  and  E.  M.  Burbidge.  The 
theoretical  curves  of  growth  used  were 
those  by  Wrubel  for  a  Milne-Eddington 
atmosphere.  Conditions  in  the  standard 
star  k  Gem  and  in  HD  46407  were  found 
to  be  very  similar,  as  had  been  anticipated. 
There  were  no  detectable  differences  be- 
tween the  two  stars  in  Texc,  in  the  degree 
of  ionization,  or  in  the  total  velocity  (ther- 
mal and  turbulent).  From  a  preliminary 
comparison  with  the  sun,  Texc  was  found 
to  be  3900°  C;  with  log  Pe=-03,  Tion 
was  found  to  be  4200°  C;  the  velocity 
parameter  was  4  km/sec. 

Relative  abundances  of  the  following 
elements  were  determined:  sodium,  mag- 
nesium, aluminum,  silicon,  calcium,  scan- 
dium, titanium,  vanadium,  chromium, 
manganese,  iron,  cobalt,  nickel,  strontium, 
yttrium,  zirconium,  barium,  lanthanum, 
cerium,  praseodymium,  neodymium,  and 
samarium;  also  less  certain  values  were 
found  for  copper,  zinc,  germanium,  nio- 
bium, molybdenum,  ruthenium,  europium, 
gadolinium,  ytterbium,  and  tungsten.  Car- 
bon has  a  slightly  greater  than  normal 
abundance  in  HD  46407.  The  elements 
from  sodium  through  germanium  were 
found  to  have  the  same  abundances  in  the 
Ba  II  stars  and  in  k  Gem,  apart  from  barely 
significant  slightly  increased  abundances 
of  aluminum  and  scandium  in  HD  46407. 
Most  of  the  heavier  elements,  from  stron- 
tium onwards,  however,  were  found  to 
have  abundances  of  the  order  of  10  times 
those  in  the  standard  star. 

The  results  have  been  discussed  in  the 
context  of  a  theory  of  the  stellar  origin  of 


54        CARNEGIE  INSTITUTION  OF  WASHINGTON 


the  elements  in  the  universe;  they  are 
found  to  give  good  support  for  it.  On  this 
theory  certain  isotopes  of  the  elements 
heavier  than  iron  are  built  by  a  slow  neu- 
tron-capture process  in  the  interiors  of  red 
giant  stars.  Abundance  peaks  are  produced 
at  nuclei  having  a  magic  number  of  neu- 
trons, e.g.  strontium,  yttrium,  zirconium, 
barium,  lanthanum,  cerium,  praseodym- 
ium, and  neodymium,  all  of  which  are 
overabundant  in  HD  46407.  Europium,  so 
prominent  in  peculiar  A  stars  with  mag- 
netic fields,  is  not  built  predominantly  by 
neutron  capture  on  the  time  scale  supposed 
to  occur  in  red  giant  stars,  and  its  abun- 
dance in  HD  46407  is  no  larger  than  in 
k  Gem. 

Coude  spectrograms  have  been  obtained 
by  G.  R.  Burbidge  with  the  100-inch  tele- 
scope for  a  continuation  of  the  program 
for  the  determination  of  heavy-element 
abundances  in  cool  stars.  The  identifica- 
tion by  Merrill  of  Tc  I  in  a  carbon  star 
indicates  that  element  synthesis  through  a 
slow  neutron-capture  chain  occurs  in  these 
stars  as  well  as  in  S  and  Ba  II  stars.  A 
number  of  carbon  stars  have  been  ob- 
served, including  "normal"  stars  with  C13 
bands,  hydrogen-poor  stars  with  no  C13, 
and  CH  stars. 

Sandage  and  G.  R.  and  E.  M.  Burbidge 
have  started  a  program  for  the  measure- 
ment of  the  blanketing  effect  in  a  number 
of  standard  stars  in  the  range  F7  to  G2, 
and  in  the  Population  II  star  HD  19445. 
The  latter  has  a  low  abundance  of  most 
elements,  relative  to  hydrogen,  and  conse- 
quently weak  spectral  lines.  In  a  two-color 
plot  of  U  — B  against  B  — V,  this  star  has 
an  ultraviolet  excess.  It  lies  close  to  the  line 
on  which  H.  L.  Johnson  and  Sandage  have 
shown  the  stars  in  M  3  to  lie.  The  pro- 
gram is  to  see  whether  the  difference  in 
blanketing  between  HD  19445  and  a  nor- 
mal star  of  the  same  effective  temperature 
would  move  the  star  in  the  U  — B,  B  — V 
plane  so  as  to  account  for  the  ultraviolet 
excess.  It  will  certainly  account  for  part 
of  it,  but  whether  there  is  a  remainder 
needing  some  other  explanation  must  be 


determined.  If  blanketing  can  account  for 
the  whole  effect,  then  we  shall  be  able,  in 
principle,  to  use  two-color  measures  to  de- 
duce whether  the  elements  calcium,  iron, 
etc.,  in  a  distant  group  of  stars  are  under- 
abundant,  relative  to  hydrogen,  and  by 
how  much.  All  the  observations,  consist- 
ing of  10  A/mm  spectrograms  covering  the 
range  A3300  to  A6300,  have  been  obtained 
with  the  100-inch  telescope.  Almost  all  the 
tracings  have  now  been  completed,  with 
the  Babcock  microphotometer,  and  their 
measurement  with  a  planimeter  is  now 
under  way. 

Nuclear  Reactions  in  Stars 

G.  R.  Burbidge  and  F.  Hoyle,  and  Drs. 
W.  A.  Fowler  and  E.  M.  Burbidge,  of  the 
Kellogg  Radiation  Laboratory  of  the  Cali- 
fornia Institute,  have  continued  their  work 
on  the  synthesis  of  the  chemical  elements 
in  the  stars.  They  find  that  eight  processes, 
as  follows,  are  necessary  to  account  for  the 
abundances  of  all  the  327  isotopes  found  in 
the  solar  system:  (1)  Hydrogen  burning 
is  responsible  for  the  majority  of  the  en- 
ergy production  in  stars.  This  process 
synthesizes  helium,  and,  when  it  occurs 
in  a  mixture  of  hydrogen  with  other  ele- 
ments, it  builds  all  those  isotopes  of  carbon, 
nitrogen,  oxygen,  fluorine,  neon,  and  so- 
dium that  are  not  built  by  process  2.  It 
occurs  in  main-sequence  stars  and  in  shells 
around  the  cores  of  giants.  Its  results  may 
be  seen  in  hydrogen-exhausted  hot  stars, 
some  carbon  stars,  WN  and  other  nitrogen- 
rich  hot  stars,  and  some  white  dwarfs. 

(2)  Helium  burning  builds  C12  from  he- 
lium and,  by  further  a-particle  addition, 
O16,  Ne20,  and  perhaps  Mg24.  Its  onset  oc- 
curs in  the  cores  of  red  giant  stars,  and  it 
presumably  continues  in  stars  in  later  evo- 
lutionary stages.  Its  results  may  be  visible 
in  some  carbon  stars  and  in  WC  stars. 

(3)  The  a  process  builds,  through  charged- 
particle  interactions,  the  rest  of  the  four- 
structure  nuclei  Mg24,  Si28,  S32,  A  36,  Ca40, 
and  probably  Ca44  and  Ti48.  (4)  The  e 
process  builds  the  elements  comprising  the 
iron  peak  in  the  abundance  curve  (vana- 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        55 


dium  through  nickel).  It  occurs  at  very 
high  temperatures  and  densities,  when  con- 
ditions of  statistical  equilibrium  are  set  up. 
Both  it  and  the  a  process  are  thought  to 
occur  shortly  before  a  star  explodes  as  a 
supernova.  (5)  The  s  process  is  a  slow 
neutron-capture  chain  which  builds  many 
of  the  isotopes  in  the  ranges  23<^4<46 
and  63<A<209.  It  is  thought  to  take 
place  in  the  interiors  of  red  giant  stars, 
when  neutrons  are  produced,  and  to  be 
responsible  for  the  observed  anomalies  in 
S  stars,  Ba  II  stars,  etc.  (6)  The  r  process 
is  a  rapid  neutron-capture  chain,  occurring 
on  a  very  short  time  scale,  and  is  thought 
to  take  place  in  supernovae.  It  will  pro- 
duce a  large  number  of  isotopes  in  the 
range  70<A<209,  and  uranium  and  tho- 
rium. It  may  also  build  a  few  lighter  iso- 
topes not  built  by  other  processes,  e.g.  S36, 
Ca46,  Ca48.  The  decay  of  radioactive  Cf254, 
built  by  this  process,  is  thought  to  be  re- 
sponsible for  the  exponential  light-curve 
of  some  Type  I  supernovae.    (7)  The  p 


process  is  a  proton-capture  or  photoneu- 
tron  process,  also  thought  to  occur  in  some 
supernovae.  It  builds  the  remaining  iso- 
topes in  the  range  63<A<209  which  are 
proton-rich,  have  abundances  0.01  to  0.001 
times  the  near-by  normal  and  neutron-rich 
isotopes,  and  cannot  be  built  by  either  the 
s  or  the  r  process.  (8)  The  x  process,  not 
properly  worked  out  yet,  must  be  respon- 
sible for  building  deuterium,  lithium, 
beryllium,  and  boron,  which  are  unstable 
in  hydrogen  burning  in  stellar  interiors. 
There  may  be  some  production  in  stellar 
atmospheres  in  magnetic  stars  (including 
all  stars  with  flare  activity),  and  deuterium 
may  be  made  in  some  supernovae  when  a 
large  flux  of  neutrons  impinges  on  an  ex- 
panding, relatively  cool  envelope  in  which 
hydrogen  has  not  been  exhausted. 

Further  work  on  the  x  process  is  going 
on  at  present.  Observations  have  been 
made  with  Dr.  Philip  C.  Keenan,  of  the 
Perkins  Observatory,  and  theoretical  work 
is  under  way  with  W.  A.  Fowler. 


GASEOUS  NEBULAE 


Internal  Motions  and  Radial  Velocities 

In  past  years,  Guido  Munch  and  Wilson 
have  reported  on  an  extensive  series  of  ob- 
servations of  the  internal  motions  in  the 
Orion  nebula  using  a  multislit  on  the  72- 
inch  camera  of  the  200-inch  coude  spectro- 
graph. During  the  current  year  they  have 
extended  these  observations  to  fainter  re- 
gions of  the  nebula  by  using  the  multislit 
with  the  36-inch  camera. 

All  plates  have  now  been  measured  and 
reduced  by  Miss  Flather  and  Mrs.  Coffeen 
for  radial  velocities  of  the  [O  II],  H,  and 
[O  III]  lines.  A  large  number  of  line  pro- 
files have  also  been  determined,  and  the 
material  is  being  analyzed.  The  aspect  of 
the  problem  related  to  the  verification  in 
the  nebula  of  the  predictions  of  the  equilib- 
rium theory  of  turbulence  at  high  Reynolds 
numbers  has  been  studied.  In  good  agree- 
ment with  results  derived  by  Dr.  S.  von 
Horner  from  radial  velocities  determined 
at  the  Lick  Observatory,  Munch  and  Wil- 


son find  that  the  mean  square  difference 
between  two  points  in  the  nebula  separated 
by  a  distance  d  varies  nearly  as  d^,  for 
values  of  d  between  1"  and  60".  At  vari- 
ance with  von  Horner's  conclusions,  how- 
ever, they  find  that  this  statistical  relation 
cannot  be  taken  as  a  proof  that  the  Kol- 
mogoroff  law  is  satisfied  in  the  nebula,  for, 
if  it  were,  the  line  widths  predicted  would 
be  3  times  smaller  than  those  observed.  If 
KolmogorofTs  law  were  satisfied,  the  aver- 
aging effect  along  the  line  of  sight  involved 
in  the  observations  should  be  negligible, 
and  the  nebula  would  be  required  to  have 
the  shape  of  a  thin  sheet  of  matter  in  the 
plane  of  the  sky.  They  find  such  a  con- 
figuration inadmissible  in  the  light  of  di- 
rect observational  evidence,  such  as  the  ap- 
pearance of  the  line  23S-33P  of  He  I  in 
absorption  in  the  spectra  of  the  illuminat- 
ing stars  and  also  the  reddening  of  the 
Trapezium  cluster.  The  failure  of  the 
Kolmogoroff  law  to  describe  the  state  of 


56        CARNEGIE  INSTITUTION  OF  WASHINGTON 


motion  of  the  nebula  is  due  to  the  com-  supports  Oort's  suggestion  that  the  Cygnus 

pressibility  effects.  The  spectra  show  many  loop  is  a  shell  originally  ejected  at  a  high 

areas  in  the  nebula  where  the  lines  appear  velocity  and  decelerated  by  collisions  with 

distinctly   as    double,    suggesting   the   ex-  interstellar  clouds.    In  order  to  form  an 

istence  of  discontinuities  in  the  flow,  pro-  object  like  the  Cygnus  loop  in  a  region  of 

duced  by  shock  waves.  Munch  and  Wilson  average  interstellar  density   (A/h  =  0.01  to 

visualize  these  shock  waves  as  a  result  of  1),  the  shell  must  have  a  momentum  of  the 

the   interaction   of   the   expanding   H    II  order  of  1043  cm.  g.  sec-1.  This  value  is  too 

region  with  the  surrounding  cold  material,  high  for  shells  ejected  by  ordinary  novae 

An  investigation  of  the  radial  velocities  and  even  by  supernovae  of  Type  I,  such  as 

in  the  Cygnus  loop  has  been  completed  by  the  Crab  Nebula,  but  it  appears  possible 

Minkowski.  The  average  picture  found  is  that  such  a  value  pertains  to  the  shells  of 

that   of   an   expanding   incomplete   thick  supernovae  of  Type  II.  The  Cygnus  loop 

shell.    The   velocity    of   expansion    is    65  and  other  objects  of  this  type  thus  may  be 

km/sec  at  the  inner  boundary  with  a  di-  the  hitherto  unobserved  remnants  of  these 

ameter  of  about  80'  and  115  km/sec  at  the  supernovae. 

outer  boundary  with  a  diameter  of  about  A  preliminary  discussion  of  the  observa- 

170'.  This  picture  resembles  in  many  ways  tions  of  the  radial  velocities  of  the  bright 

the  appearance  of  IC  443,  which  is  obvi-  filaments  in  the  Crab  Nebula  has  been  pre- 

ously  an  object  of  the  same  type  as  the  pared  by  G.  Munch.    It  was  found  that 

Cygnus  loop.  If  the  velocity  of  expansion  many   of   those    filaments    that   by    their 

at  the  outer  border  is  combined  with  the  radial  velocities  can  be  considered  as  a  unit 

outward  motion  of  0703  per  year  found  by  are  oriented  at  right  angles  to  the  direction 

Hubble,  a  distance  of  770  parsecs  is  ob-  of  the  magnetic  field,  as  determined  by 

tained.  The  diameter  of  the  main  part  of  Hiltner  from  polarization  observations  of 

the  nebula  is  then  40  parsecs;  faint  matter  the  synchrotron  radiation.    This  observa- 

in  the  south  extends  to  a  distance  of  35  tion  suggests  that  the  filaments  move  in  a 

parsecs  from  the  center.  "force-free"   field,   in   which    the   electric 

The  absence  of  an  exciting  star  suggests  currents  are  parallel  to  the  magnetic  field, 
that  the  excitation  of  the  emission  spec-  The  radial  velocities  of  the  brighter  central 
trum  in  the  Cygnus  loop  is  collisional.  The  filaments  also  show  that  their  motion  is 
observational  decision  on  the  type  of  exci-  not  one  of  uniform  expansion  from  the 
tation  depends  essentially  on  the  ratio  of  star  supposed  to  be  the  remnant  of  the 
the  intensities  of  Ha  relative  to  H3  for  supernova.  Study  of  the  large-scale  geom- 
which  conflicting  results  had  been  obtained  etry  of  the  filamentary  mass  disclosed  that 
by  various  observers.  New  measures  by  the  direction  of  the  major  axis  of  the 
Minkowski  confirm  the  result  by  Pikelner  nearly  elliptical  outer  boundary  is  that  of 
that  the  average  ratio  (Ha+[N  II])  :H|3  the  galactic  equator,  to  the  degree  of  pre- 
has  the  value  6.1.  The  [N  II]  lines,  how-  cision  with  which  such  major  axis  can  be 
ever,  have  considerable  strength,  and  the  determined.  The  importance  of  the  role 
average  value  of  the  ratio  Ha:H(3  is  3.4,  that  the  prevalent  galactic  magnetic  field 
with  local  variations  up  to  5.4.  These  values  plays  in  determining  the  present  structure 
are  consistent  with  the  interpretation  that  of  the  shell  thus  becomes  apparent.  The 
the  excitation  is  collisional.  The  lower  outer  galactic  magnetic  field  being  re- 
values of  the  ratio  conform  to  electron  tern-  sponsible  for  the  ellipticity  of  the  shell,  it 
peratures  of  the  order  of  100,000°,  which  follows  that  the  expansion  velocity  of  the 
is  in  general  agreement  with  the  tempera-  shell  at  present  may  have  values  along  the 
tures  found  from  the  relative  intensities  of  lines  of  force  differing  from  values  at  right 
the  [O  III]  lines  A4363  and  A5007/4959.  angles  to  them.  The  distance  of  the  Crab 

The  fact  that  the  excitation  is  collisional  Nebula,  determined  on  the  assumption  of 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        57 


the  equality  of  the  cross  motions  with  the 
radial  velocities,  may  have  to  be  revised 
and  increased  upward.  Further  observa- 
tions of  the  fainter  filaments  are  being 
planned  to  elucidate  this  point. 

Because  of  the  renewed  interest  in  the 
intensity  changes  in  the  continuum  of  the 
Crab  Nebula,  the  continuum  was  regularly 
photographed  by  Baade  in  the  range  A5300 
to  A6400.  No  moving  wisps  were  observed 
during  the  fall  of  1956. 

In  continuation  of  observations  going 
back  to  the  late  1930's,  the  shells  of  Nova 
T  Aurigae  (1891),  Nova  Cygni  (1920), 
and  Nova  Herculis  (1936)  were  photo- 
graphed by  Baade  at  the  prime  focus  of 
the  200-inch.  The  progressive  expansion  of 
all  three  shells  is  very  conspicuous  in  the 
blink  comparator. 

Radial  velocities  of  101  faint  planetary 
nebulae  have  been  determined  by  Minkow- 
ski; almost  all  of  them  are  for  objects 
which  are  within  10°  from  the  position  of 
the  galactic  center.  In  this  region  the 
velocities  range  between  about  —300  and 
+  300  km/sec,  showing  the  presence  of  a 
large  velocity  dispersion  in  the  central  part 
of  the  Galaxy.  The  observations  are  still 
being  continued,  but  the  available  results 
are  already  adequate  for  a  general  discus- 
sion of  the  motions  of  planetaries,  which 
Schmidt  has  started. 

Densities  of  Nebulae 

Osterbroek  continued  measurements  of 
the  intensity  ratio  of  the  two  components 
of  the  [O  II]  A3727  doublet  in  order  to 
determine  the  electron  densities  in  gaseous 
nebulae.  Measurements  of  this  ratio  show 
that  the  density  in  the  brightest  filaments 
of  the  Crab  Nebula  is  of  the  order  of  1000 
electrons/cm3.  The  total  volume  of  such 
filaments,  estimated  from  Baade's  direct 
plates  of  the  nebula,  is  approximately 
8  X  1051  cm3,  and  the  resulting  mass  of  the 
system  of  brightest  filaments  is  about  0.02 
solar  mass.  Rough  estimates  of  the  densi- 
ties and  volumes  of  the  fainter  filaments 
can  also  be  made,  leading  to  a  total  mass 
of  the  whole  filamentary   system  of  the 


Crab  Nebula  in  the  range  0.05  to  0.1  solar 
mass. 

Plates  were  also  obtained  for  measure- 
ment of  the  A3727  intensity  ratio  in  a 
number  of  planetary  nebulae,  particularly 
IC  418,  NGC  6720,  and  NGC  7293.  These 
observations  were  planned  to  study  the 
spatial-density  variation  in  the  various 
planetaries,  for  the  electron  density  gives 
a  good  measure  of  the  mass  density  in 
these  objects.  Reductions  of  the  NGC  6720 
observations  show  that  in  this  well  known 
ring  planetary  all  the  regions  that  emit 
A3727  have  essentially  the  same  density, 
about  1000  electrons  (or  hydrogen  ions) 
per  cm3.  Additional  observations  of  the 
A3727  ratio  in  the  Orion  nebula  were  ob- 
tained, to  complete  the  study  of  the  large- 
scale  structure  of  this  object. 

Several  diffuse  nebulae  in  which  a  dark 
cloud  is  ionized  by  an  O  star  outside  the 
cloud  were  studied  by  Osterbroek.  The 
ionized  material,  seen  in  emission,  lies 
mostly  between  the  star  and  the  dark 
cloud,  and  is  sharply  bounded  on  the  side 
toward  the  cloud  by  a  bright  rim,  while 
on  the  other  side  it  fades  out  gradually. 
In  each  of  these  nebulae,  long-exposure 
schmidt  photographs  taken  in  Ha  show 
that  there  is  parallel  filamentary  structure, 
approximately  perpendicular  to  the  bright 
rim,  in  the  emission  nebulosity  (these  stri- 
ations  were  observed  some  years  ago  in 
IC  434,  the  brightest  member  of  this  group, 
by  Duncan,  with  the  100-inch  telescope). 
These  parallel  bright  filaments  must  result 
from  regions  of  high  density  in  the  origi- 
nal cloud,  which  are  drawn  out  by  expan- 
sion without  being  mixed  appreciably. 
There  are  two  possible  interpretations  for 
the  fact  that  the  filaments  are  long  but 
remain  unmixed:  either  there  is  a  mag- 
netic field  that  prevents  motions  perpen- 
dicular to  its  own  direction  in  all  these 
objects,  or  else  the  mechanism  that  gen- 
erates turbulence  in  most  diffuse  nebulae 
cannot  operate  in  these  objects,  perhaps 
because  they  are  expanding  into  regions 
of  very  low  density. 


58        CARNEGIE  INSTITUTION  OF  WASHINGTON 


GALAXIES 

The  Andromeda  Galaxy  (Messier  31)  and  photovisual  measurements  for  the  color- 

Other  Members  of  the  Local  Group  magnitude  diagram  of  this  system.    The 

During  the  past  year  the  photovisual  ob-  results  can  bf  Pref nted  in  final  £orm  as 

servations  of  the  cepheids  in  the  outer  field  soon  as  thf  Photoelectric  sequence  in  Mes- 

of  the  Andromeda  galaxy,  96'  south  pre-  sier  13>  fhlch  has  been  measured  by  Dr. 

ceding   the   nucleus,   were   concluded   by  HL.  Johnson,  of  the  Lowell  Observatory, 

Baade.  Combined  with  the  earlier  photo-  and   whlch  has,  been   transferred  to  the 

graphic  series  of  plates  they  should  furnish  Drac°   system,   becomes   available.    Since 

the  necessary  data  about  color  excesses  and  enouSh  Plates  rhave  been,  obtained  for  the 

absorption  in  this  field.  Still  under  way  is  investigation  of  the  variables  in  the  Leo  II 

a  survey  of  this  same  field  for  faint  red  system>  only  the  Ursa  Minor  and  Leo  I 

variables  which  were  below  the  plate  limit  systems  remain  under  observation, 

of  the  30-minute  photographic  series  at  the  The  studY  o£  the  stellar  contents  of  M  33, 

200-inch  but  show  up  in  remarkably  large  reported  last  year,  has  continued.  Huma- 

numbers  on  photovisual  and  red  plates  of  son  and  Sandage  began  a  search  for  the 

long  exposures.  These  faint  red  variables  red  supergiants  which  are  expected  from 

are  clearly  members  of  the  Population  II  evolutionary  considerations  to  accompany 

which  pervades   the   whole   disk   of  the  the  blue  O  and  B  type  stars  in  the  spiral 

Andromeda  galaxy  (the  "interarm"  popu-  arms-    °ver    100°   red    supergiants   were 

lation).  They  deserve  further  investigation  found  in  M  33  by  Humason  by  blinking 

because  they  should  throw  much  needed  Pairs  of  blue  (103a-O  +  GG  13)  and  yellow 

light  on  the  characteristics  of  the  interarm  (103a-D  +  GG  11)   plates  taken  with  the 

population  of  our  own  Galaxy.  200-inch.   A  special  field  south  preceding 

Most  of  Baade's  observing  time  during  the  nucleus  was  chosen  to  study  these  stars, 
the  past  year  was  devoted  to  the  dwarf  E  and  Plates  taken  sporadically  during  the 
galaxies  of  the  local  group  which  as  typical  season  indicated  that  many  of  these  red 
representatives  of  the  pure  Population  II  stars  are  irregular  variables.  They  may  be 
are  of  special  interest.  Four  of  them  (the  the  extragalactic  analogues  of  the  M  super- 
Sculptor,  Ursa  Minor,  Draco,  and  Leo  II  Siants  found  in  h  and  X  Persei,  for  exam- 
systems)  are  close  enough  to  reach  the  Ple*  Photometric  measurements  on  the 
cluster-type  variables  with  the  large  mod-  UBV  sYstem  are  in  progress  with  a  stand- 
ern  telescopes.  Although  all  four  are  E  ard  photoelectric  sequence  set  up  by  Dr. 
galaxies  of  very  low  luminosity,  the  cluster-  H-  L-  Johnson  in  M  33  several  years  ago. 
type  variables  appear  in  them  in  large  plates  in  blue  and  yellow  wavelengths 
numbers  (on  the  average  more  than  200  for  a  number  of  other  galaxies  (NGC 
cluster-type  variables  per  system).  Type  II  6822,  Sextans  Dwarf,  Leo  Dwarf,  W-L-M 
cepheids  with  periods  longer  than  a  day  Dwarf,  NGC  2403,  M  101)  have  been  ob- 
are  rare  in  these  dwarf  systems.  The  Draco  tained  for  a  similar  study  of  red  super- 
system,  for  instance,  contains  only  two,  giants.  Blink  surveys  show  that  the  red 
and  the  same  number  was  found  by  the  supergiants  are  indeed  present  in  these 
Pretoria  observers  in  the  Sculptor  system,  galaxies  as  well  as  in  M  33. 
But  with  increasing  stellar  content  their  Schmidt  has  computed  a  model  of  the 
number  increases  rapidly;  examples  are  the  distribution  of  mass  in  M  31.  It  is  based 
Fornax  system  and  the  Leo  I  system  north  on  recent  results  obtained  by  Dutch  ob- 
of  Regulus.  servers  from  observations  at  21-cm  wave- 
Miss  Swope  has  finished  the  investigation  length,  and  gives  a  total  mass  of  3.4  X 1011 
of  the  variables  in  the  Draco  system.  She  solar  masses.  About  50  per  cent  of  the  mass 
also    completed    the    photographic    and  has  a  mass-luminosity  ratio  of  around  27; 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        59 


the  ratio  for  the  whole  system  has  about 
the  same  value. 

Studies  of  Individual  Galaxies 

Osterbrock  began  obtaining  spectra  at  a 
dispersion  of  66  A/mm  of  those  elliptical 
galaxies  already  known  from  the  observa- 
tions of  Humason  to  have  [O  II]  A3727  in 
emission.  Only  a  few  galaxies  have  been 
observed  to  date,  but  several  interesting 
preliminary  results  have  appeared.  In  all 
the  galaxies  studied,  except  a  single  EO,  the 
material  emitting  A3727  is  in  rapid  rotation. 
One  EO  and  one  El,  both  very  nearly 
round  objects,  as  well  as  several  more- 
elongated  objects,  show  this  rotation  of 
the  interstellar  matter  quite  definitely. 
That  the  A3727  lines  are  resolved  into  two 
components  in  only  one  object  indicates 
quite  high  turbulent  velocities  as  well  as 
systematic  rotational  velocities  for  the  in- 
terstellar matter  near  the  nuclei  of  these 
elliptical  galaxies.  Among  the  ellipticals 
known  to  have  A3727  in  emission,  there  are 
wide  variations  in  the  strength  of  the  line, 
but  it  is  invariably  so  strong  at  the  66 
A/mm  dispersion  that  possibly  all  ellipti- 
cals will  have  detectable  A3727  at  this  dis- 
persion. 

The  blue  galaxies  recently  discovered  at 
Tonantzintla  by  Dr.  G.  Haro  are  being 
observed  both  spectroscopically  and  directly 
by  Guido  Munch.  Among  those  already 
observed,  an  appreciable  fraction  have  been 
found  to  have  regular  geometry,  resem- 
bling that  of  early  and  intermediate  spirals. 
When  spiral  arms  can  be  seen,  as  in  NGC 
263  and  NGC  2415,  they  appear  thicker 
and  with  brighter  condensations  than  in 
typical  spirals.  Their  spectra  show  the 
emission  lines  characteristic  of  planetary 
nebulae,  superposed  on  a  continuum  corre- 
sponding to  an  early  spectral  type.  Strong 
Balmer  lines  in  absorption  are  prominent, 
and  in  one  case  the  line  He  A4471  has  been 
measured  in  absorption.  The  emission 
lines  and  early-type  spectrum  extend 
through  the  entire  body  of  the  systems, 
with  increased  relative  strengths  of  the 
emission  lines  in  the  nuclei  and  in  the  con- 


densations. The  components  of  the  [O  II] 
doublet  are  clearly  resolved,  indicating 
that,  unlike  the  condition  in  the  normal 
ellipticals,  the  random  motions  of  the  gas 
producing  them  are  small.  The  relative 
intensities  of  the  [O  II]  lines  indicate  num- 
ber densities  of  free  electrons  of  the  order 
of  103  cm"3. 

Code  has  made  scans  of  several  elliptical 
galaxies  in  the  Virgo  cluster  with  his 
photoelectric  scanning  spectrograph.  His 
curves  should  provide  further  information 
on  the  energy  distribution  in  the  spectrum 
of  elliptical  galaxies  and  on  their  possible 
stellar  content. 

TifTt  has  begun  the  photoelectric  pho- 
tometry of  the  brighter  galaxies  in  four 
colors  in  the  range  A3400  to  A6000  A.  This 
work  will  be  extended  to  the  red  and 
infrared  this  coming  year.  Field  galaxies 
of  nearly  all  types,  with  special  emphasis 
on  those  for  which  W.  W.  Morgan  has  de- 
rived spectral  types,  are  being  obtained. 
The  Coma  and  Virgo  clusters  are  included 
for  comparison.  The  hope  is  that  the 
photometric  system  will  be  calibrated  in 
absolute  energy  units.  The  goal  is  a  study 
of  the  variations  of  color  between  galaxies 
and  within  galaxies,  as  well  as  an  attempt 
to  synthesize  the  observed  colors  in  terms 
of  the  stellar  populations  present. 

Zwicky  has  continued  the  investigation 
of  pairs  and  groups  of  galaxies  that  are  in- 
terconnected by  luminous  intergalactic  fila- 
ments. All  types  of  galaxies  have  been 
found  to  be  thus  linked  by  luminous  mat- 
ter, usually  blue,  suggesting  clouds  of  sub- 
luminous  blue  stars  whose  absolute  photo- 
graphic magnitude  is  greater  than  Mp  =  0. 
Most  of  the  double  nebulae  photographed 
originally  by  Pease  with  the  60-inch  reflec- 
tor were  rephotographed  and  found  to 
show  faint  countertides  on  one  or  on  both 
components.  The  absence  of  countertides 
would  lead  the  investigator  to  suspect 
strongly  that  he  was  dealing  with  optical 
doubles  whose  differences  in  radial  veloci- 
ties should  not  be  used  for  a  determination 
of  the  masses  involved. 


60 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


Catalogues  and  Statistics  of  Galaxies 

Work  on  the  catalogue  of  galaxies 
brighter  than  the  apparent  photographic 
magnitude  +15.5  has  been  continued  by 
Herzog  and  Zwicky  with  a  grant  from  the 
Office  of  Naval  Research.  Charts  are  being 
prepared  for  publication  of  all  results  in 
the  strip  from  a  =  7h  to  17h  between 
h—  —10°  and  +20°  with  all  the  measured 
galaxies  indicated  by  various  symbols  giv- 
ing the  photographic  magnitudes  in  ranges 
of  1  mag.  Each  chart  is  on  the  scale  of  the 
48-inch  photograph,  and  for  the  conveni- 
ence of  the  users  is  centered  near  the  center 
of  a  48-inch  Sky  Survey  chart,  1950  co- 
ordinates being  used.  The  catalogue,  when 
completed,  is  expected  to  give  the  magni- 
tudes and  positions  as  well  as  certain  other 
data  for  35,000  galaxies. 

In  preparation  for  a  study  of  the  statistics 
of  galaxies  and  clusters  of  galaxies  the  strip 
between  a  =  12h  and  14h  40m  from  8=  +5° 
to  +15°  was  completely  covered  by  Zwicky 
with  27  fields  at  the  48-inch,  each  field  hav- 
ing been  photographed  on  103a-O  with 
exposures  of  3.5  and  10  minutes  and  on 
103a-D  behind  yellow  Plexiglass  filter  with 
exposures  of  5  and  15  minutes.  Extensive 
counts  covering  large  numbers  of  galaxies 
in  a  large  cap  around  the  north  galactic 
pole  have  confirmed  the  previous  result 
that  fields  containing  many  near-by  galax- 
ies (large  near-by  clusters)  contain  rela- 
tively few  distant  galaxies.  If  m  is  the 
number  of  galaxies  brighter  than  + 15.5  on 
one  of  the  charts  of  36  square  degrees  of 
our  new  catalogue,  and  n/  is  the  number 
of  galaxies  in  the  approximate  range  from 
+  15.5  to  +19.0  counted  on  good  red  48- 
inch  schmidt  plates,  we  have  approxi- 
mately mXnf  =  B.  The  value  of  B  de- 
creases rapidly  when  we  come  near  the 
belt  of  interstellar  obscuration,  but  B  is  ap- 
proximately a  constant  =5x  106  in  a  large 
cap  of  40°  radius  around  the  north  galactic 
pole.  The  lowest  values  of  «/  are  obtained 
near  the  centers  of  the  near-by  clusters  in 
Virgo  and  Coma,  suggesting  that  inter- 
galactic  dust  producing  obscuration  to  the 


amount  of  0.25  to  0.5  mag.  is  locally  con- 
centrated in  the  central  regions  of  these 
clusters. 

The  nonuniformities  in  the  distribution 
of  galaxies  are  exceedingly  pronounced, 
both  locally  and  integrally.  Zwicky  be- 
lieves that  this  can  be  understood  only  on 
the  basis  of  the  assumption  that  clustering 
of  galaxies  is  a  universal  phenomenon  and 
that  the  apparent  distribution  of  galaxies 
is  affected  in  an  intricate  way  by  the  effects 
of  both  interstellar  and  intergalactic  ob- 
scuration. These  circumstances  make  it 
difficult  to  arrive  at  any  definite  conclu- 
sions regarding  the  real  distribution  of 
galaxies  throughout  cosmic  space. 

Clusters  of  Galaxies 

About  two  dozen  rich  globular  clusters 
of  galaxies  were  chosen  by  Zwicky  for  fur- 
ther detailed  investigation  concerning  total 
population,  radial  distribution,  structural 
index  and  distribution  index,  distance, 
symbolic  velocity  of  recession,  and  internal 
velocity  dispersion. 

The  faintest  among  these  clusters,  barely 
recognizable  on  red  48-inch  schmidt  plates, 
are  expected  to  have  a  symbolic  velocity 
of  recession  Vs  =  cX  AA/A  of  approximately 
150,000  km/sec.  Each  cluster  is  photo- 
graphed with  the  200-inch  three  times  on 
103a-O  plates  (exposures  3,  9,  27  minutes) 
and  three  times  on  103a-D  behind  GG  11 
filter  (exposures  5,  15,  45  minutes).  The 
main  results  obtained  so  far  are:  (1)  The 
total  population  of  these  clusters  in  the  first 
three  magnitude  ranges  mmax  to  Wmax  +  3 
is  very  closely  the  same  regardless  of  the 
value  of  ramax.  (2)  The  structural  indices 
and  the  distribution  indices  are  closely  the 
same  for  clusters  at  all  distances.  (3)  The 
segregation  of  bright  and  of  faint  galaxies 
within  the  clusters  is  the  same  regardless 
of  their  distance.  (4)  The  total  population 
of  the  clusters  in  a  first  approximation  is 
proportional  to  y  —  Yo,  where  y  is  the  angu- 
lar diameter,  and  y0  is  a  constant.  (5)  The 
number  nc  of  member  galaxies  per  limiting 
square  degree  in  the  center  of  the  clusters 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES 


61 


in  a  first  approximation  is  inversely  propor- 
tional to  the  angular  diameter  y>  provided 
that  no  interstellar  or  intergalactic  absorp- 
tion interferes.  These  results  allow  a  dis- 
tance determination  from  counts  of  cluster 
galaxies  alone,  the  distance  being  inversely 
proportional  to  the  apparent  structural 
index. 

During  the  summer  of  1956,  Abell  com- 
pleted the  compilation  of  a  catalogue  of 
2712  rich  clusters  of  galaxies  discovered  on 
the  National  Geographic  Society-Palomar 
Observatory  Sky  Survey.  From  these  he 
selected  a  homogeneous  sample  of  1682 
clusters  each  of  which  contained  at  least 
50  members  within  2  magnitudes  of  the 
third  brightest  member.  A  statistical  analy- 
sis of  this  sample  indicates:  (1)  The  dis- 
tribution function  of  clusters  according  to 
richness  increases  rapidly  as  the  population 
per  cluster  decreases.  (2)  The  data  allow 
no  significant  decision  that  the  spatial 
density  of  cluster  centers  varies  with  dis- 
tance. (3)  Galactic  obscuration  of  the 
order  of  a  few  tenths  of  a  magnitude 
(photo-red)  exists  at  high  northern  galac- 
tic latitudes  around  longitude  300°.  (4) 
There  is  a  highly  significant  nonrandom 
distribution  of  clusters  in  direction  in  the 
sky,  both  when  clusters  at  all  distances  and 
when  clusters  at  various  distances  are 
considered. 

In  conjunction  with  the  new  catalogue 
of  galaxies,  a  catalogue  of  the  richest  clus- 
ters of  galaxies  is  being  constructed  by 
Zwicky,  including  the  1950  positions  of  the 
centers,  the  populations,  characters,  ap- 
parent diameters,  and  estimated  distances 
of  all  clusters.  Contours  of  all  clusters,  that 
is  isopleths  for  which  the  population  per 
square  degree  is  about  twice  that  found  in 
the  surrounding  field,  are  plotted  on  the 
same  charts  containing  the  galaxies  of  the 
catalogue  mentioned. 

Clusters  of  galaxies  are  the  only  objects 
that  can  be  used  for  distance  indicators  or 
for  the  study  of  such  problems  as  the 
velocity-distance  relation  out  to  the  extreme 
range  of  the  large  telescopes.  Because  of 
the  importance  of  locating  as  distant  clus- 


ters as  possible,  Baum  made  a  series  of 
experimental  exposures  with  the  48-inch 
telescope  in  a  study  of  the  most  effective 
techniques  for  locating  clusters  at  the  ex- 
treme limit  of  the  instrument.  Experi- 
ments were  made  with  Eastman  103-U 
plates  in  combination  with  a  Chance  OR-1 
filter  to  obtain  a  range  of  response  from 
roughly  6500  to  7500  A.  This  range  was 
selected  for  two  reasons:  it  lies  within  a 
spectral  region  unusually  free  of  radiation 
from  the  night  airglow;  it  particularly 
favors  galaxies  of  the  type  sought,  namely, 
those  having  redshifts  equivalent  to  about 
half  the  velocity  of  light.  Although  the  ad- 
vantage over  the  red-sensitive  plates  ordi- 
narily used  amounts  to  only  a  fraction  of 
a  magnitude  in  threshold  detection,  about 
a  dozen  suspected  clusters  were  observed 
in  this  manner,  and  four  of  them  were 
rephotographed  with  the  200-inch  tele- 
scope. Since  all  these  clusters  were  found 
to  have  relatively  small  membership,  it 
will  be  worth  some  further  searching, 
possibly  with  the  additional  aid  of  finer- 
grained  emulsions. 

Velocities  and  Distances  of  Galaxies 

During  the  past  three  years,  observations 
have  been  made  by  Humason  at  the  prime 
focus  of  the  200-inch  for  the  purpose  of 
obtaining  larger  redshifts  than  had  hereto- 
fore been  measured.  The  results  of  this 
investigation  have  been  negative  in  that  it 
has  not  been  possible  to  identify  known 
spectral  features  with  the  certainty  re- 
quired for  the  measurement  of  redshifts. 
Inability  to  obtain  usable  spectra  is  due  to 
the  following  reasons.  As  the  present  sun- 
spot  maximum  develops,  intensity  of  the 
airglow  spectrum  has  increased  to  the  point 
where  it  almost  obliterates  the  spectrum  of 
a  faint  galaxy.  Magnitudes  of  the  brightest 
members  in  the  clusters  observed  are 
fainter  than  20.0.  The  spectra  are  ex- 
tremely narrow  because  the  diameters  of 
distant  galaxies  are  small.  Redshifts  of 
very  distant  clusters  are  large  enough  to 
displace  such  well  known  features  as  the 


62        CARNEGIE  INSTITUTION  OF  WASHINGTON 


G  band,  H  and  K,  and  the  emission  at 
A3727,  beyond  the  long-wavelength  limit 
of  fast  blue  emulsions.  All  this  has  necessi- 
tated the  use  of  slower  panchromatic  emul- 
sions, which  increases  the  exposure  times 
by  a  factor  of  10  or  more. 

The  negative  results  obtained  for  this 
particular  investigation  are  reported  on 
here  both  because  the  observations  have 
consumed  much  valuable  200-inch  time 
and  because  the  data  given  below  will  lo- 
cate and  identify  the  clusters  for  other  ob- 
servers who  may  intend  to  continue  this 
type  of  research.  All  the  clusters  listed  in 
table  3  were  first  found  on  plates  of  the 
National  Geographic  Society-Palomar  Ob- 
servatory Sky  Survey  and  later  rephoto- 
graphed  by  Sandage  with  the  200-inch. 

TABLE  3.    Clusters 


(1950) 

R.A 

Dec 

1. 

Possible 

Redshif  t 

0h  24m 

0s 

+  16° 

53' 

103,000  < 

Dr  167,000 

10 

44 

11 

+  9 

20 

63,000 

13 

32 

10 

+  28 

28 

74,000 

14 

47 

33 

+  26 

22 

118,000 

Co-ordinates  are  for  1950,  and  refer  to  the 
center  of  each  cluster.  In  the  last  column 
appear  possible  values  of  the  red  displace- 
ments. It  should  be  stated  that  they  are 
unmeasured,  and  their  reality  is  uncer- 
tain. They  were  obtained  from  one  or 
more  spectral  features  which  seemed  to 
be  dimly  visible  but  could  not  be  positively 
identified. 

Two  uncertain  displacements  are  given 
for  the  first  cluster.  If  either  is  real  it  is 
most  probably  the  smaller  value.  The  most 
certain  value  is  that  for  the  second  cluster 
in  the  list,  +63,000  km/sec. 

During  the  report  year,  Baum  has  con- 
tinued the  photoelectric  program  for  de- 
termining both  the  redshifts  and  the  mag- 
nitudes of  remote  galaxies  by  multicolor 
photometry.  It  consists  in  measuring  their 
relative  luminosities  in  a  number  of  differ- 
ent colors  ranging  from  3800  A  in  the 
ultraviolet  to  10,000  A  in  the  infrared.  The 
data  for  each  object  yield  a  curve  of  radi- 
ated energy  E  as  a  function  of  wavelength 


A.  For  a  galaxy  that  is  shifted  to  the  red, 
the  whole  E(X)  curve  is  displaced  toward 
longer  wavelengths,  and  the  amount  of  the 
displacement  yields  the  "velocity"  of  re- 
cession. The  result  is  the  same  as  a  spec- 
trographic  measurement  of  the  amount  by 
which  individual  spectrum  lines  are  dis- 
placed, but  multicolor  photometry  has  the 
advantage  of  being  able  to  reach  galaxies 
considerably  fainter  and  more  distant  than 
those  within  spectrographic  reach.  The 
E(X)  curves  also  provide  bolometric  mag- 
nitudes directly  without  the  need  for  K 
conditions. 

This  multicolor  photoelectric  procedure 
rests  on  two  conditions:  the  E(X)  curves 
must  be  on  a  true  scale  of  energy  per  unit 
wavelength;  the  galaxies  of  one  cluster 
being  compared  with  those  of  another 
cluster  must  be  intrinsically  similar,  that 
is  the  differences  between  their  E(X) 
curves  must  be  due  largely  to  their  red- 
shifts  and  not  to  other  effects.  Although 
this  second  condition  cannot  be  guaranteed 
for  unlimited  distances,  neither  Whitford 
nor  Baum  now  finds  any  clear  evidence 
for  other  reddening  effects  within  the 
range  of  distances  reachable  spectroscopi- 
cally.  There  is,  however,  the  possibility 
that  effects  due  to  evolution  or  obscuration 
may  influence  the  magnitudes  more 
strongly  than  the  E(X)  redshifts.  This  pos- 
sibility can  be  checked  by  comparing  mag- 
nitudes with  apparent  angular  diameters 
estimated  from  photoelectrically  measured 
brightness  profiles,  and  efforts  were  con- 
tinued during  the  report  year  to  obtain  the 
profile  observations  required. 

The  photoelectric  redshift-magnitude 
data  are  being  accumulated  as  rapidly  as 
telescope  time  permits,  and  some  interest- 
ing results  are  beginning  to  emerge.  Ob- 
servations obtained  thus  far  extend  from 
the  near-by  cluster  of  galaxies  in  Virgo 
(about  10  megaparsecs  distant)  to  one  of 
the  remotest  clusters  of  galaxies  detectable 
on  the  48-inch  Sky  Survey  plates.  The 
E(X)  redshif t  of  this  latter  cluster  was 
found  to  be  of  the  order  of  120,000  km/sec 
(or  OAc),  which  is  roughly  twice  that  of 
the  present  spectroscopic  limit. 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        63 


RADIO  SOURCES 

Identification  of  Radio  Sources  able  that  most  radio  sources  are  distant 
In  a  sample  area  between  0b  and  6h,  gala*ies  fainter  than  18th  magnitude. 
-9°  to  +3°,  a  detailed  study  is  now  being  Two  regions,  previously  found  by  Mat- 
carried  out  by  Minkowski  of  those  objects  thews  t0  have  an  excess  of  21-cm  radiation, 
that  may  be  of  interest  in  connection  with  have  been  identified  by  him  with  features 
the  problems  of  the  identification  of  radio  appearing  on  the  48-inch  survey.  The  first 
sources.  For  this  area  the  records  and  re-  o£  these  regions  is  in  the  OB  aggregate  I 
suits  by  Mills  and  the  results  of  the  Cam-  Camelopardalis,  where  the  schmidt  plates 
bridge  Survey  were  compared  with  the  show  a  region  of  very  high  absorption 
prints  of  the  National  Geographic  Society-  about  4°  across  with  a  few  spots  of  weak 
Palomar  Observatory  Sky  Survey  during  Ha  emission  around  the  edges.  About 
Minkowski's  stay  at  the  Division  of  Radio-  three-quarters  of  the  stars  in  the  OB  aggre- 
physics  of  the  Commonwealth  Scientific  gate  are  located  less  than  1°5  from  the  ab- 
and  Research  Organization,  Sydney,  Aus-  sorbing  region.  Their  proximity,  together 
tralia.  The  aim  of  the  study  is  not  pri-  with  the  observed  21-cm  radial  velocity  of 
marily  to  identify  a  few  more  radio  sources,  the  feature,  suggest  that  the  distance  to  the 
but  to  obtain  a  clear  picture  of  the  limita-  absorbing  cloud  is  1  kiloparsec. 
tions  to  which  attempts  at  identification  The  21-cm  observations  show  that  the 
are  subjected,  in  particular  for  extragalactic  feature  is  6°  across,  which  gives  a  diameter 
sources.  Since  the  intrinsic  strength  of  of  105  parsecs.  The  total  mass  of  neutral 
sources  has  a  very  large  dispersion,  the  hydrogen  in  the  region  is  7.8  X 104  times 
situation  differs  for  strong  and  for  weak  the  mass  of  the  sun,  giving  a  mean  density 
sources.  Intrinsically  very  strong  extra-  of  5.5  H  atoms/cm3.  This  mass  is  the  same 
galactic  sources  are  expected  to  be  optically  as  the  mass  of  neutral  hydrogen  in  the 
of  low  apparent  brightness,  since  Cygnus  Orion  region  given  by  T.  K.  Menon.  The 
A,  the  prototype  of  this  class,  is  already  of  21-cm  profiles  show  that  the  expansion  of 
18th  magnitude.  The  accuracy  of  the  posi-  the  region,  if  any,  is  less  than  3  km/sec. 
tions  in  the  present  radio  surveys  does  not  Photoelectric  measures  of  selected  stars  in 
permit  the  identification  of  objects  fainter  the  OB  aggregate  and  in  an  open  cluster 
than  this,  and  additional  identifications  of  situated  within  the  area  of  the  absorbing 
intrinsically  strong  radio  sources  will  be  cloud  are  in  progress, 
possible  only  when  more  precise  positions  The  second  region  under  study  is  at 
become  available.  Intrinsically  weak  extra-  galactic  longitude  100°,  latitude  +11°. 
galactic  sources  may  be  optically  relatively  The  48-inch  survey  shows  some  absorbing 
bright,  such  as  NGC  5128  or  NGC  1275.  clouds  to  be  present.  Deep  Ha  photo- 
Such  objects  can  easily  be  photographed  graphs,  taken  with  the  48-inch  schmidt, 
and  recognized  as  peculiar  at  distances  at  show  the  presence  of  faint  Ha  emission  in 
which  they  are  beyond  the  sensitivity  limit  the  same  region  that  has  the  excess  21-cm 
of  present  radio  telescopes.  At  present,  radiation.  No  star  or  stars,  down  to  the 
only  radio  sources  of  intermediate  intrinsic  10th  magnitude,  are  known  either  within 
intensity  can  be  expected  to  be  identifiable,  the  region  or  near  by  which  could  provide 
The  results  obtained  in  the  still-incom-  the  ionizing  radiation  to  produce  the  Ha 
pleted  study  show  already  that  at  the  pres-  emission.  Thus  collisional  excitation  is 
ent  stage  of  technical  development  not  probably  present.  Further  observations  are 
more  than  a  small  percentage  of  all  sources  in  progress,  and  calculations  will  be  made 
can  be  identified  with  galaxies.  Since  the  to  check  this  hypothesis, 
available  evidence  suggests  strongly  that  The  32-foot-diameter  radio  telescope  on 
stars  are  not  radio  sources,  it  seems  prob-  Palomar  Mountain  is  being  used  by  Mat- 


64        CARNEGIE  INSTITUTION  OF  WASHINGTON 


thews  to  make  a  21-cm  survey  of  the  Milky 
Way  region  between  galactic  longitudes 
190°  and  250°.  The  coverage  in  galactic 
latitude  extends  up  to  16°  from  the  plane 
of  the  Galaxy.  Preliminary  results  on  the 
distribution  of  neutral  hydrogen  in  the 
galactic  plane  show  a  good  agreement  with 
the  Dutch  and  Australian  results.  The 
hydrogen  belonging  to  the  Orion  arms 
shows  the  presence  of  systematic  velocities 
in  varying  amounts  up  to  10  km/sec  be- 
tween longitudes  200°  and  240°.  A  survey 
of  the  hydrogen  distribution  near  selected 
galactic  radio  sources  is  also  in  progress. 
In  order  to  provide  independent  evidence 
on  the  distance  of  the  Cassiopeia  radio 
source,  a  search  for  faint  B  stars  in  that 
field  was  made  by  Luis  Munch  on  Ha 
plates  taken  with  the  Tonantzintla  pris- 
matic camera  and  a  red  filter.  Three  stars 
tentatively  classified  as  B  stars  were  found 
at  distances  of  1'6,  2'2,  and  53  from  the 


center  of  the  source  as  given  by  Baade  and 
Minkowski.  Photoelectric  colors  in  the 
UBV  system  of  these  three  stars,  deter- 
mined by  Luis  and  Guido  Munch  at  the 
60-inch  telescope,  have  shown  that  indeed 
these  stars  are  of  type  B,  with  color  ex- 
cesses E(B  —  V)  around  1.0  mag.  Al- 
though no  structure  in  the  interstellar  lines 
of  one  of  these  stars  has  been  observed, 
the  measured  K-line  radial  velocity  sug- 
gests that  the  star  is  in  the  Perseus  spiral 
arm.  Since  the  reddening  of  the  source 
estimated  by  Baade  and  Minkowski  is 
larger  than  that  of  this  star,  it  would  seem 
that  the  distance  of  the  source  is  larger 
than  2  kiloparsecs,  in  agreement  with  the 
distance  determination  from  the  21-cm  ab- 
sorption lines.  Spectroscopic  observations 
are  planned  for  the  two  other  fainter  stars, 
which  are  at  closer  distance  to  the  center 
of  the  source,  in  order  to  make  the  evi- 
dence somewhat  stronger. 


INSTRUMENTATION 


The  idea  of  the  pneumatic  mirror, 
formed  by  stretching  a  thin  solid  film  over 
an  optically  finished  ring,  and  aluminizing 
it,  has  been  developed  by  Horace  W.  Bab- 
cock,  and  experimental  work  on  such  a 
mirror  up  to  10  inches  in  size  is  being 
carried  out  in  the  laboratory.  Such  a  mir- 
ror, when  provided  with  a  backing  plate 
a  short  distance  behind  the  film,  has  pneu- 
matic stiffness  against  fluctuations  in  at- 
mospheric pressure.  It  also  has  the  inter- 
esting property  that,  in  the  flat  form,  its 
optical  figure  is  independent  of  the  tem- 
perature of  the  film.  The  film  can  readily 
be  cooled  from  behind,  as  is  desirable  for 
mirrors  of  solar  telescopes.  In  principle,  if 
a  differential  pressure  is  applied  to  the 
opposite  sides  of  a  uniform  film,  a  parabo- 
loidal  figure  is  obtained. 

Swanson  has  ruled  12  large  gratings  dur- 


ing the  year,  and  has  devoted  much  time 
to  tests  and  improvements  of  various  parts 
of  the  ruling  machine.  The  most  notable 
accomplishment  was  the  ruling  of  an  ex- 
cellent grating  having  the  exceptional 
width  of  10  inches  and  a  groove  length  of 
6  inches.  It  is  not  only  the  largest  high- 
precision  grating  ruled  here,  but  it  is  fully 
the  equal  in  quality  with  any  of  the  earlier 
and  smaller  gratings.  Its  resolving  power, 
though  not  yet  quantitatively  measured,  is 
distinctly  the  best  yet  seen,  showing  the 
anticipated  improvement  over  8-inch  grat- 
ings. This  accomplishment  proves  that  the 
ruling  engine  is  completely  successful  up 
to  the  limits  of  its  dimensional  capacity, 
and  that  a  ruling  diamond  can,  on  occa- 
sion, produce  more  than  14  miles  of  uni- 
form precision  grooves  on  a  single  plate 
without  appreciable  wear. 


GUEST  INVESTIGATORS 

The  Observatories  have  invited  a  num-  required  by  the  programs  of  the  regular 
ber  of  guest  investigators  to  make  use  of  staff.  The  following  studies  have  been 
such   observational  facilities  as  were  not      carried  out  by  these  investigators. 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        65 


Dr.  George  O.  Abell,  of  the  Department 
of  Astronomy  at  the  University  of  Cali- 
fornia at  Los  Angeles,  investigated  the 
bright  end  of  the  luminosity  function  of 
galaxies  in  rich  clusters  with  the  48-inch 
schmidt  telescope.  For  the  investigation 
about  30  clusters  have  been  chosen  from 
the  catalogue  of  clusters  compiled  from  the 
National  Geographic  Society-Palomar  Ob- 
servatory Sky  Survey  photographs.  Magni- 
tudes of  galaxies  (to  within  about  0.1 
mag.)  are  obtained  by  extrafocal  photo- 
graphic photometry,  extrafocal  images  of 
galaxies  being  compared  with  extrafocal 
images  of  stars  which  are  calibrated  with 
photographic  transfers  from  Selected 
Areas.  In  addition  to  the  luminosity  func- 
tion, information  is  obtained  about  the 
spatial  distribution  within  clusters  of  gal- 
axies of  various  luminosities  and  (pre- 
sumably) masses.  The  observational  phase 
of  the  program  is  now  about  30  per  cent 
complete. 

Observations  of  26  planetary  nebulae 
have  been  secured  with  a  photoelectric 
scanner  attached  to  the  60-  and  100-inch 
telescopes  by  Dr.  Lawrence  H.  Aller  and 
Dr.  William  Liller,  of  the  University  of 
Michigan.  Disperson  is  provided  by  a  600 
line/mm  reflection  grating,  with  identical 
//5  Newtonian  systems  used  as  the  colli- 
mating  and  focusing  units.  The  spectrum 
is  scanned  with  either  a  blue-sensitive  or 
a  red-  and  infrared-sensitive  photomulti- 
plier  permitting  a  study  of  the  spectrum 
from  A3200  to  A12,000  A.  The  total  nebular 
brightnesses  were  measured  photoelectri- 
cally  at  Mount  Wilson  in  1954.  By  com- 
bining both  the  direct  and  spectral  observa- 
tions with  previously  obtained  photo- 
graphic data  for  the  fainter  lines  and  the 
isophotic  contours,  Drs.  Aller  and  Liller 
expect  to  obtain  a  better  assessment  of 
stratification  effects  together  with  im- 
proved ionic  concentrations  and  electron 
temperatures.  The  variability  of  the  spec- 
trum of  IC  4997  has  been  established. 

Dr.  Dinsmore  Alter,  of  the  Griffith  Ob- 
servatory, has  continued  his  photographic 
observations  of  the  moon  with  the  60-inch 


telescope  on  11  nights  of  above-average 
seeing.  Photographs  were  taken  in  blue- 
violet  and  in  infrared  light,  special  atten- 
tion being  given  to  the  regions  of  Ptole- 
maeus,  Alphonsus,  Arzachel,  and  Atlas 
under  a  low  setting  sun  in  an  attempt  to 
obtain  evidence  for  scattering  by  traces  of 
escaping  gas. 

Dr.  James  Cuffey,  of  Indiana  University, 
obtained  photoelectric  measures  of  colors 
and  magnitudes  of  faint  stars  in  the  globu- 
lar clusters  M  53  and  NGC  5466  with  the 
60-  and  100-inch  reflectors  in  April  1957. 
The  photoelectric  standards  are  being  used 
to  calibrate  photographic  observations  of 
the  color-magnitude  relations  as  faint  as 
the  19th  magnitude. 

The  solar  furnace  located  on  the  roof  of 
Robinson  Hall  at  the  California  Institute 
has  been  reconditioned  and  used  for  high- 
temperature  materials  studies  by  the  Stan- 
ford Research  Institute  in  collaboration 
with  Dr.  Paul  Duwez,  of  the  Department 
of  Engineering  of  the  California  Institute. 
The  great  advantage  of  a  solar  furnace  in 
materials  research  is  the  high  concentra- 
tion of  radiant  heat  over  a  small  area  (l/2 
inch  in  diameter  in  the  present  apparatus) . 
Because  of  this  highly  localized  heat  flux, 
melting  of  a  portion  of  a  solid  sample  may 
be  achieved  so  that  the  material  under 
study  serves  as  its  own  crucible.  Refrac- 
tory substances  that  react  with  any  known 
crucible  can  therefore  be  melted  without 
being  contaminated.  Compounds  involv- 
ing two  of  the  most  refractory  oxides, 
namely,  thorium  oxide  (3200°  C±100°  C) 
and  zirconium  oxide  (2750°  C),  were  suc- 
cessfully melted  in  the  furnace.  The  struc- 
ture of  these  compounds  was  investigated 
by  X-ray  diffraction  methods,  and  the  re- 
sults of  these  studies  led  to  a  better  under- 
standing of  one  of  the  most  heat-resisting 
solid  materials  of  engineering  interest.  At 
present,  the  solar  furnace  is  being  used  for 
the  study  of  compounds  of  uranium  di- 
oxide and  zirconium  dioxide,  which  are  of 
great  potential  interest  in  the  development 
of  fuel  elements  for  high-temperature  nu- 
clear reactors. 


66        CARNEGIE  INSTITUTION  OF  WASHINGTON 


Dr.  Carlos  Jaschek,  of  the  Observatorio  cases  are  found  it  will  be  possible  to  apply 

Astronomic©  de  la  Universidad  Nacional  the  usual  methods,   involving  intensities 

de  La  Plata,  obtained  an  extensive  series  of  and  displacements  of  the  interstellar  lines, 

spectra  of  metallic-line  stars  in  order  to  to  derive  mean  luminosities, 
ascertain  the  existence  of  families  among         Studies  of  the  air  currents  and  "seeing" 

these  stars  in  analogy  to  the  existing  fami-  at  the  60-foot  solar  tower  have  been  carried 

lies  among  peculiar  stars.    Spectra  of  35  out  by  Dr.  R.  B.  Leighton,  of  the  Physics 

stars  of  this  type  were  taken  with  the  60-  Department   of   the    California   Institute, 

inch  telescope  at  a  dispersion  of  21  A/mm.  These  investigations  have  shown  that  it  is 

Five  spectra  of  peculiar  A-type  stars  were  possible    to    reduce    the    effects    of    local 

taken  with  the  100-inch  coude  spectrograph  thermal  air  currents  by  appropriate  treat- 

for  a  detailed  analysis  of  the  atmospheres  ment  of  exposed  surfaces  near  the  optical 

of  these  objects.  path  through  the  tower,  and  there  appears 

Spectrograms  of  T  Coronae  Borealis  at  to  be  considerable  hope  of  prolonging  the 

10  A/mm  were  obtained  by  Dr.  Robert  P.  period  of  early-morning  good  seeing  to  an 

Kraft,  of  Indiana  University,  in  an  attempt  hour  or  more. 

to  classify  the  motions  of  the  components         Three  hundred  feet  of  16-mm  Koda- 

of  this  binary  star.  Dr.  Kraft  also  observed  chrome  film  were  exposed  by  Dr.  Leighton 

the  spectra  of  several  of  the  fainter  mem-  in  a  photographic  study  of  Mars  during 

bers  of  the  open  cluster  NGC  6664  in  order  the  period  August  6  to  October  15,  1956. 

to    obtain   radial    velocities    and    spectral  Many    photographs    of   excellent    quality 

types.  were  obtained.  Study  of  these  photographs 

Spectrograms  of  39  long-period  variable  is  still  in  progress, 
stars  with  types  MO  to  M5  were  taken  with  Visual  observations  of  double  stars  were 
the  4-inch  camera  on  the  X  spectrograph  made  with  the  60-inch  reflector  at  the 
of  the  60-inch  by  Dr.  Philip  C.  Keenan,  of  Cassegrain  focus  on  portions  of  the  nights 
the  Perkins  Observatory.  This  group  of  of  August  16  to  19  and  all  night  at  the 
variables  was  selected  because  they  are  Newtonian  focus  on  August  20-21  by  Dr. 
made  up,  at  least  in  part,  of  Population  II  William  Markowitz,  of  the  U.  S.  Naval 
stars  which  include  some  with  luminosity  Observatory.  The  seeing  was  good  enough 
high  enough  to  make  them  valuable  as  on  all  nights  to  permit  measurement  of 
distance  indicators  for  moderately  distant  close  doubles.  The  Airy  disks  were  seen 
stellar  systems.  The  spectra  give  evidence  on  all  nights.  The  powers  generally  used 
of  a  considerable  spread  in  luminosity  were  1300  at  the  Cassegrain  and,  with  a 
within  the  group.  RT  Cygni  and  Z  Ophiu-  Barlow  lens,  2000  at  the  Newtonian, 
chi,  for  example,  are  probably  supergiants  Images  obtained  in  the  second  manner 
at  least  as  bright  as  a  Ononis,  while  the  were  superior  to  those  obtained  at  the 
least  luminous  stars  in  the  group  are  more  Cassegrain  without  a  Barlow  lens.  Thirty- 
comparable  to  ordinary  red  giants.  More  one  measures  of  23  pairs  were  made.  Most 
data  will  be  needed  to  fix  the  scale  of  of  the  pairs  had  separations  from  0'.'09  to 
absolute  magnitudes  of  these  variables,  but  0'.'19.  L726-8  was  measured.  The  results 
one  means  of  doing  that  was  found  when  of  these  tests  indicate  that  the  60-inch  may 
two  of  the  stars,  R  Trianguli  and  X  Mono-  be  used  to  a  limited  extent  for  the  meas- 
cerotis,  were  photographed  in  the  red  urement  of  very  close  pairs  and  in  search- 
region  with  the  100-inch  coude  spectro-  ing  for  duplicity  in  suspected  faint  stars, 
graph.  The  large  velocity  shifts  in  these  The  co-operative  program  with  the  Mc- 
spectra  made  it  possible  to  see  interstellar  Math-Hulbert  Observatory  was  continued 
components  of  the  sodium  D  line,  and  throughout  the  year  as  in  the  past  6  years, 
these  components  turned  out  to  be  quite  The  observer  for  the  project  stationed  on 
strong  in  both  stars.    When  more  such  Mount  Wilson  was  Mr.  Thomas  K.  Jones. 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES 


67 


Dr.  Robert  R.  McMath  spent  a  number  of 
days  in  February  inspecting  the  Snow 
telescope  instrument  and  reviewing  the 
various  aspects  of  the  program.  The  pro- 
gram for  the  Snow  telescope  for  the  cur- 
rent report  year  has  been  the  following: 
(1)  continuation  of  the  systematic  obser- 
vation of  the  infrared  helium  line  (10830 
A)  at  the  limbs  of  the  sun  and  in  the  plage 
regions;  (2)  systematic  observation  of  the 
central  structure  of  the  K  line  (3934  A) 
at  the  limbs  of  the  sun  and  in  plage  re- 
gions; (3)  observations  of  a  number  of  se- 
lected lines  in  the  region  7500  to  12000  A 
that  should  be  good  indicators  of  physical 
conditions  on  the  sun;  (4)  observations  of 
a  number  of  lines  that  are  badly  blended 
with  water-vapor  lines  (such  as  Hot)  for 
comparison  with  McMath-Hulbert  tracings 
made  under  conditions  of  high  water- 
vapor  content  in  the  earth's  atmosphere; 
(5)  continuation  of  infrared-sunspot  trac- 
ings as  suitable  spots  have  developed  on 
the  solar  disk;  (6)  repetition  of  tracings 
for  wavelength  measurement  in  the  3  to 
5  u  region  with  the  Lallemand  PbTe  cell. 

Observations  were  made  on  120  days; 
760  tracings  were  produced.  These  totals 
are  considerably  less  than  in  previous  years 
because  instrumental  troubles  with  the 
spectrometer  made  necessary  an  almost 
complete  overhaul  with  considerable  re- 
building of  worn  parts  of  the  mechanism. 

The  observations  on  dry  days  on  Mount 
Wilson  are  proving  to  be  very  valuable  for 
eliminating  the  effect  of  water-vapor  lines 
from  tracings  made  with  higher  dispersion 
at  the  McMath-Hulbert  Observatory  with 
the  McMath-Hulbert  vacuum  spectro- 
graph. 

The  programs  of  observation  of  the  Ca+ 
K  lines  and  the  10830  A  line  of  helium  are 
now  approaching  a  critical  stage  as  the  sun- 
spot  activity  increases.  The  continuation 
of  the  recording  throughout  the  present 
maximum  will  complete  the  observational 
history  of  the  variation  of  these  lines 
throughout  a  sunspot  cycle. 

With  the  present  Babcock  gratings  and 
the  reconditioned  spectrometer,  measure- 


ments of  improved  precision  are  being 
made  in  the  3  to  5  |j  region.  The  new 
measurements  are  being  made  on  tracings 
obtained  with  a  Lallemand  PbTe  cell, 
whose  increased  sensitivity  with  respect  to 
earlier  cells  also  makes  increased  accuracy 
possible. 

Spectroscopic  observations  of  the  eclips- 
ing systems  RZ  Scuti  and  U  Cephei  were 
made  by  Dr.  D.  H.  McNamara,  of  Brig- 
ham  Young  University.  The  Ha  line  in 
the  spectrum  of  RZ  Set  is  of  great  interest. 
The  absorption  line  is  bordered  by  emis- 
sion that  is  particularly  pronounced  during 
eclipse  but  is  also  faintly  present  outside  of 
eclipse.  The  Ha  absorption  line  undergoes 
a  change  in  width  as  well  as  in  intensity 
during  the  primary  eclipse.  When  the 
brighter  component  emerges  from  eclipse, 
the  line  is  1.3  times  wider  than  at  other 
phases.  Asymmetries  can  be  detected  in 
the  Ha  line  several  days  before  and  after 
eclipse.  For  U  Cephei  a  new  velocity 
curve  has  been  derived  from  plates  taken 
with  the  60-inch  telescope.  Of  particular 
interest  is  the  discovery  of  a  new  distortion 
in  the  velocity  curve  in  the  form  of  a  rapid 
rise  and  decline  in  the  velocity  of  the  order 
of  25  km/sec  occurring  near  phase  0.8  day. 

Dr.  \Y.  W.  Morgan,  of  the  Yerkes  Ob- 
servatory, continued  his  work  on  the  spec- 
tral classification  of  galaxies  which  he  had 
started  earlier  in  collaboration  with  Dr. 
N.  U.  Mayall,  of  the  Lick  Observatory. 
While  at  the  Mount  Wilson  and  Palomar 
Observatories  he  studied  the  files  of  spec- 
trograms obtained  by  Humason  and  the 
direct  photographs  of  Hubble,  Humason, 
Sandage,  and  Baade.  A  period  of  five 
nights  with  the  100-inch  nebular  spectro- 
graph was  used  to  obtain  new  spectra  of 
several  elliptical  galaxies;  these  made  possi- 
ble the  determination  of  spectral  types  of 
the  systems  in  the  ultraviolet.  A  discussion 
of  the  above  material,  together  with  spec- 
trograms obtained  by  Mayall  at  Lick,  has 
led  to  the  following  conclusions:  The 
great  majority  of  the  galaxies  can  be  classi- 
fied by  their  spectra  into  about  five  classes; 
if  these  are  denoted  by  the  spectral  types 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


as  determined  in  the  region  of  4000  A,  the 
spectroscopic  groups  range  from  A  to  K. 
There  is  a  marked  correlation  between 
the  degree  of  central  condensation  and  the 
spectral  type  of  the  system  as  a  whole; 
those  of  type  A  show  little  or  no  central 
condensation;  on  the  other  hand,  those  of 
type  K  consist  of  the  ellipticals  and  the 
Sa  and  Sb  systems  having  pronounced 
central  condensations. 

From  a  study  of  objective-prism  plates 
taken  with  the  schmidt  camera  of  the 
Tonantzintla  Observatory  a  number  of 
hitherto  unclassified  OB  stars  in  longitude 
82°  to  92°  have  been  selected  in  order  to 
determine  to  what  extent  the  OB  associa- 
tions I,  II,  and  III  Cassiopeiae  are  separated 
from  one  another  in  space.  Fifty  stars  have 
been  observed  with  the  4-inch  camera  of 
the  X  spectrograph  of  the  60-inch  telescope, 
and  their  spectral  types  on  the  Yerkes  sys- 
tem have  been  determined  by  Luis  Munch, 
of  the  Tonantzintla  Observatory.  It  is 
planned  to  reobserve  spectroscopically  as 
many  of  these  as  possible  to  derive  radial 
velocities.  The  photoelectric  colors  and 
magnitudes  of  these  stars  are  also  being 
measured  to  obtain  spectroscopic  parallaxes. 

A  number  of  stars  classified  on  objective- 
prism  plates  as  peculiar  A  stars  have  been 
observed  with  the  X  spectrograph  in  order 
to  relate  the  criteria  of  peculiarity  with 
those  established  in  the  Yerkes  system. 
The  stars  BD  -4°1644,  -1°1414,  and 
—  3°  1665  were  also  found  to  be  spectrum 
variables,  and  their  variations  are  being 
studied.  A  period  of  4.1  days  has  been  de- 
rived for  the  variation  of  Ca  II  K  in  the 
spectrum  of  BD  +46°  1913.  Photoelectric 
observations  of  these  same  objects  are  being 
carried  out  with  the  20-inch  telescope  of 
Palomar  Mountain. 

The  radial  velocities  of  the  most  distant 
early-type  stars  known  in  galactic  longi- 
tudes 325°  to  10°  are  being  determined 
from  plates  taken  with  the  8-inch  camera 
of  the  X  spectrograph  by  Luis  Munch  in 
collaboration  with  Guido  Munch.  The 
purpose  of  this  program  is  to  reanalyze 
the  problem  of  the  discrepancy  between 


the  rotational  velocity  of  the  inner  parts  of 
the  galactic  system  as  determined  from 
stellar  radial  velocities  and  21-cm-line  radio 
observations. 

Dr.  L.  Plaut,  of  the  Kapteyn  Astronomi- 
cal Observatory,  Groningen,  has  completed 
the  observational  part  of  his  investigation 
of  the  large-scale  structures  of  the  halo  of 
the  galactic  system.  Nearly  500  plates  were 
taken  with  the  48-inch  schmidt  camera. 
They  are  now  being  searched  in  Gronin- 
gen for  variable  stars.  Four  areas  are  being 
investigated,  centered  at  the  following  ga- 
lactic co-ordinates:  /=327°5,  £=+28°; 
l  =  327°5,  £=-12°;  /=331?0,  £=+12°; 
and/=147°5,  £=+15°. 

Dr.  Daniel  M.  Popper,  of  the  University 
of  California  at  Los  Angeles,  has  continued 
his  investigation  of  the  orbits  and  masses 
of  eclipsing  binaries.  He  has  recently  re- 
discussed  the  eclipsing  binary  Z  Vulpeculae 
on  the  basis  of  new  photoelectric  observa- 
tions at  Palomar  as  well  as  of  spectroscopic 
observations.  The  principal  interest  in  Z 
Vul  is  that  it  contains  an  A-type  star  of 
luminosity  class  III,  the  first  star  of  this 
type  to  have  reliable  determinations  of 
mass  and  radius.  During  the  current  re- 
port year,  one  star,  V  477  Cygni,  has  been 
added  to  the  list  of  systems  in  need  of  re- 
vision of  masses  and  radii,  and  two  stars, 
RY  Persei  and  RS  Vulpeculae,  have  been 
added  to  the  list  of  systems  with  com- 
ponents above  the  main  sequence  for 
which  masses  will  eventually  be  deter- 
mined. Observations  on  RX  Herculis  and 
RS  Canum  Venaticorum  have  been  nearly 
completed.  The  mass  of  the  former  system 
is  found  to  be  30  per  cent  larger,  that  of 
the  latter  about  40  per  cent  smaller,  than 
the  previously  published  values.  Clearly, 
higher  dispersion  than  heretofore  must  be 
applied  to  many  systems.  Fair  progress 
has  been  made  on  the  difficult  problem  of 
determining  the  masses  of  £  Aurigae  from 
spectrograms.  Although  final  results  are 
not  available,  the  published  value  for  the 
mass  of  the  cool  supergiant  appears  to  need 
serious  revision  downward. 

Drs.  Otto  Struve  and  Jorge  Sahade,  of 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        69 


the  University  of  California  at  Berkeley, 
have  continued  their  spectroscopic  observa- 
tions throughout  the  year.  Among  the  re- 
sults obtained  from  these  observations  are : 

1.  Emission  lines  (strong  at  Ha)  were 
discovered  in  the  spectrum  of  Algol.  The 
emission  is  observed  at  quadratures,  and  is 
different  in  character  from  the  emission 
previously  observed  in  eclipsing  systems. 

2.  Ha  emission  was  also  discovered  in 
3  Cephei,  U  Coronae  Borealis,  and  HD 
47129. 

3.  Individual  cycles  were  found  to  differ 
in  velocity  amplitude  in  h  Delphini,  the 
total  range  varying  from  1-2  km/sec  to 
4-5  km/sec. 

4.  Extensive  studies  were  made  of  the 
spectrum  of  e  Aurigae,  which  emerged 
from  its  last  eclipse  in  May  1957.  All  the 
radial  velocities  have  been  measured,  and 
the  results  indicate  large  changes  of  an  ir- 
regular nature  which  are  not  caused  by 
the  geometrical  properties  of  the  double- 
star  system.  A  spectrophotometric  study  of 
the  best  plates  during  and  outside  of 
eclipse,  made  in  Berkeley  with  the  co- 
operation of  Dr.  Margherita  Hack,  has 
indicated  that  the  general  character  of  the 
eclipsing  body  is  very  much  like  that  previ- 
ously described  by  Struve.  The  invisible 
nucleus  in  the  center  of  the  large  eclipsing 
shell  may  be  a  subluminous  B-type  star. 

5.  The  spectrograms  of  3  Lyrae  have 
been  enlarged  and  assembled  in  the  form 
of  an  atlas.  The  radial  velocities  of  3 
Lyrae  have  been  used  to  determine  the 
orbital  elements  with  the  help  of  the  IBM 
701  in  Berkeley.  The  precision  of  this  orbit 
is  of  a  high  order,  and  will  form  the  basis 
for  future  studies  of  the  perturbations  in 
the  system. 

6.  Observations  have  been  made  of  the 
following  additional  stars:  W  Serpentis, 
AZ  Cassiopeiae,  h  Capricorni,  12  Lacertae, 
and  17  Leporis. 

Professor  A.  Unsold,  of  the  University 
of  Kiel,  obtained  a  series  of  spectrograms 
for  a  detailed  study  of  the  atmospheres  of 
several  stellar  types.  They  included  spectra 
of  medium-type  subdwarfs,  red  and  infra- 


red spectra  of  normal  bright  stars,  spectra 
of  later-type  main-sequence  stars,  and  spec- 
tra of  M  dwarfs  of  emission  and  nonemis- 
sion  types. 

Photoelectric  observations  of  the  short- 
period  eclipsing  binary  Nova  DQ  Herculis 
(1934)  were  obtained  on  five  nights  during 
July  and  August  with  the  100-inch  reflector 
by  Dr.  Merle  Walker,  of  the  Warner  and 
Swasey  Observatory.  From  these  observa- 
tions, the  following  improved  elements 
have  been  derived: 

Min  =  Hel  JD  2434954.94475 + 0<?19362060E 

An  analysis  shows  that  the  form  of  the 
eclipse  curve  has  changed  since  1954,  pre- 
sumably owing  to  the  presence  of  gas 
streams  or  of  detached  material  in  the  sys- 
tem. It  is  not  possible  to  obtain  reliable 
photometric  elements  from  the  1956  obser- 
vations, and  the  change  in  the  light-curve 
throws  considerable  doubt  on  the  validity 
of  the  photometric  elements  derived  from 
the  1954  observations.  The  observations 
were  made  in  yellow  light  to  avoid  the 
effect  of  the  nebulosity  surrounding  the 
system.  A  more  detailed  study  of  the  1- 
minute  periodic  variations  has  been  made 
from  the  1956  observations.  It  has  been 
possible  to  derive  the  period  of  these  varia- 
tions over  a  2-day  interval.  The  elements 
are 

Max  =  Hel  JD  2435660.71 13  +  0<?000822528E 

for  the  observations  made  in  July;  for  those 
in  August,  the  epoch  is 

Hel  JD  2435695.7499 

The  change  in  the  visibility  and  amplitude 
of  these  oscillations  with  the  phase  in  the 
4-hour  period  suggests  that  they  originate 
on  the  hemisphere  of  the  Nova  facing  the 
secondary  star.  There  are  complications, 
however. 

Simultaneous  photometric  and  spectro- 
scopic observations  were  obtained  of  AE 
Aquarii  by  Dr.  Walker  in  collaboration 
with  Deutsch.  The  photometric  observa- 
tions, made  with  the  60-inch  reflector,  were 
used  to  direct  the  spectroscopic  observer  at 


70        CARNEGIE  INSTITUTION  OF  WASHINGTON 


the  100-inch  to  place  the  star  in  one  of  two 
regions  of  the  slit,  depending  upon  whether 
it  was  momentarily  bright  or  faint.  In 
this  way  two  spectra  were  eventually  built 
up,  corresponding  to  the  maxima  and 
minima  of  the  rapid  variations  in  light 
displayed  by  the  star.  In  the  red,  the 
equivalent  widths  of  all  absorption  and 
emission  lines,  including  Hoc,  appear  to  be 
the  same  in  the  two  spectra.  In  the  photo- 
graphic region,  the  continuous  spectrum 
is  much  bluer  at  maximum  light,  and  all 
emission  and  absorption  lines  have  de- 
cidedly smaller  equivalent  widths,  includ- 
ing the  Balmer  lines. 

The  infrared  spectra  of  bright  stars  were 
examined  by  Dr.  A.  E.  Whitford,  of  Wash- 
burn Observatory,  University  of  Wiscon- 
sin, using  a  germanium  photodiode  at  the 
exit  slit  of  the  scanning  spectrograph.  The 
new  detector  shows  considerable  promise 
in  the  range  from  10000  to  16000  A,  having 
a  detection  limit  about  100  times  better 


than  lead  sulfide  photoconductive  cells.  An 
exit  slit  20  A  wide  gave  a  resolving  power 
6  to  10  times  better  than  had  previously 
been  achieved  on  stars  beyond  the  photo- 
graphic limit.  This  resolution  was  ade- 
quate to  show  the  stronger  atomic  absorp- 
tion lines,  such  as  the  Paschen  series  of 
hydrogen,  and  molecular  absorption  bands. 
The  detector  sensitivity  would  permit  go- 
ing to  a  resolution  of  2  to  4  A,  which 
would  bring  out  subordinate  metallic  lines; 
a  different  optical  arrangement  would  be 
necessary,  however. 

Over  the  more  conventional  photomulti- 
plier  range  of  3400  to  10000  A,  Dr.  Whit- 
ford scanned  the  spectrum  of  NGC  4374, 
one  of  the  bright  elliptical  galaxies  in  the 
Virgo  cluster,  in  order  to  compare  its  spec- 
tral energy  distribution  with  that  previ- 
ously found  for  M  32  by  Code.  Selected 
pairs  of  reddened  and  unreddened  stars 
were  also  observed  with  the  scanner  as  a 
test  of  the  law  of  reddening. 


STAFF  AND  ORGANIZATION 


Dr.  Milton  L.  Humason  and  Dr.  Seth  B. 
Nicholson  retired  from  the  staff  of  the 
Observatories  on  June  30, 1957.  Dr.  Huma- 
son joined  the  Mount  Wilson  Observatory 
in  1917,  first  as  janitor  and  then  as  night 
assistant.  In  the  latter  position  he  displayed 
such  skill  as  an  observer  that  he  was  made 
a  member  of  the  Staff  of  Investigators  in 
1922.  He  first  assisted  Dr.  Merrill  in  a 
survey  for  early-type  stars  with  bright 
hydrogen  lines.  Later  he  collaborated  with 
Drs.  Adams  and  Joy  and  Miss  Brayton  in 
their  very  extensive  study  of  stellar  abso- 
lute magnitudes  and  spectroscopic  paral- 
laxes, which  resulted  in  the  publication  of 
the  magnitudes  and  parallaxes  of  4179  stars 
in  1935. 

In  the  course  of  these  studies  Humason 
developed  a  very  unusual  proficiency  in  the 
photography  of  spectra  of  very  faint  ob- 
jects. After  the  discovery  by  Hubble  in  the 
1920's  of  the  major  role  played  by  the 
galaxies  in  the  structure  of  the  universe, 
Humason  turned  his  attention  to  the  spec- 
tra of  these  objects  and  soon  accumulated 


spectra  of  a  substantial  number  of  these 
galaxies  spread  over  a  wide  range  of  dis- 
tances. A  study  of  the  relationship  be- 
tween the  velocities  as  measured  on  these 
spectrograms  and  the  distances  of  these 
galaxies  led  Hubble  to  the  concept  of  the 
expanding  universe.  For  the  next  quarter 
century  Humason  devoted  most  of  his  at- 
tention to  this  problem.  The  introduction 
of  extremely  fast  photographic  plates,  the 
development  of  new  and  very  rapid  spec- 
trographs, and  the  completion  of  the  200- 
inch  Hale  telescope  enabled  Humason  to 
push  his  observations  to  fainter  and  fainter 
and  therefore  more  and  more  distant 
galaxies.  These  techniques  now  permit 
photographing  the  spectra  of  galaxies  far 
too  faint  to  be  seen  visually  with  the  tele- 
scope used  to  collect  the  light.  Humason 
therefore  had  to  develop  elaborate  offset 
procedures  that  ensure  locating  invisible 
images  accurately  on  the  slit  of  the  spectro- 
graph and  holding  them  there  during  long 
exposures.  His  studies  culminated  in  the 
publication  in  1956,  in  collaboration  with 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        71 


Dr.  N.  Mayall,  of  the  Lick  Observatory, 
and  with  Dr.  Sandage,  of  the  velocities  of 
over  900  galaxies.  Some  of  these  velocities 
are  as  high  as  one-fifth  that  of  light. 

In  1948  Dr.  Humason  was  appointed 
Secretary  of  the  Observatories.  As  Secre- 
tary he  has  ably  handled  the  correspond- 
ence and  public  relations  as  well  as  many 
of  the  other  administrative  problems  of  the 
Observatories. 

Dr.  Nicholson  joined  the  staff  of  the 
Mount  Wilson  Observatory  in  1915.  Dur- 
ing the  first  few  years  he  investigated  the 
orbits  of  several  of  Jupiter's  satellites,  the 
ninth  of  which  he  had  discovered  at  Lick 
Observatory  in  1914.  In  collaboration  with 
Dr.  Pettit  he  developed  a  very  sensitive 
vacuum  thermocouple.  This  they  used  to 
measure  the  total  radiation  and  surface 
temperature  of  stars,  the  planets,  and  the 
moon.  Their  data  on  the  cool  long-period 
variables  were  of  special  value.  Studies  of 
the  rates  of  cooling  of  the  moon's  surface 
during  an  eclipse  gave  a  measure  of  the 
thermal  conductivity  of  the  surface  rocks 
and  provided  information  on  their  physical 
characteristics.  In  the  late  1930's  and  again 
in  the  early  1950's  Dr.  Nicholson  returned 
to  the  observation  of  Jupiter's  satellites, 
discovering  the  tenth,  eleventh,  and  twelfth 
of  these  objects  and  determining  the  posi- 
tions necessary  to  fix  their  orbits. 

Throughout  Dr.  Nicholson's  42  years  at 
the  Observatories  a  large  part  of  his  efforts 
has  been  devoted  to  solar  observations,  at 
first  in  collaboration  with  Dr.  Hale.  He 
has  developed  an  extraordinarily  detailed 
knowledge  of  the  complex  phenomena  of 
the  sun's  visible  surface.  He  has  supervised 
the  systematic  collection  of  data  on  sun- 
spots,  including  the  polarity  and  strength 
of  their  magnetic  fields.  In  collaboration 
with  Dr.  Oliver  Wulf,  of  the  U.  S. 
Weather  Bureau,  he  has  made  detailed  in- 
vestigations of  the  correlation  between 
solar  and  terrestrial  phenomena. 

Mr.  Edgar  C.  Nichols  retired  as  Chief 
Designer  and  Superintendent  of  the  Instru- 
ment Shop  on  February  28,  1957,  after  46 
years  of  service  at  the  Observatories.  Many 


of  the  instruments  on  Mount  Wilson  owe 
much  of  their  efficiency  and  ease  of  opera- 
tion to  Mr.  Nichols'  skill  as  a  designer. 

Dr.  Horace  W.  Babcock  was  appointed 
Assistant  Director  of  the  Observatories 
effective  January  1,  1957.  Dr.  Arthur  D. 
Code  became  a  member  of  the  Staff  of  the 
Observatories  on  September  1,  1956,  and 
Dr.  Halton  C.  Arp  on  July  1,  1957. 

Research  Division 
Staff  Members 

Halton  C.  Arp 
Walter  Baade 

Horace  W.  Babcock,  Assistant  Director 
William  A.  Baum 
Ira  S.  Bo  wen,  Director 
Arthur  D.  Code 
Armin  J.  Deutsch 
Jesse  L.  Greenstein 

Milton  L.  Humason,  Secretary  of  the  Ob- 
servatory * 
Rudolph  L.  Minkowski 
Guido  Munch 
Seth  B.  Nicholson  x 
Donald  E.  Osterbrock 
Robert  S.  Richardson 
Allan  R.  Sandage 
Olin  C.  Wilson 
Fritz  Zwicky 

Carnegie  Research  Fellows 
Geoffrey  R.  Burbidge 
Thomas  A.  Matthews 
Maarten  Schmidt 

Research  Assistants 

Sylvia  Burd 
Mary  F.  Coffeen 
Thomas  A.  Cragg 
Dorothy  S.  Deutsch 
Edith  Flather 
Emil  Herzog 
Joseph  O.  Hickox 
A.  Louise  Lowen 
Mildred  Matthews 
Carol  Nordquist 
Henrietta  H.  Swope 

Student  Observers 
George  O.  Abell 
Walter  K.  Bonsack 
Jacques  Feige 

1  Retired  June  30,  1957. 


72        CARNEGIE  INSTITUTION  OF  WASHINGTON 


William  G.  Tifift 
Dale  Vrabec 
George  Wallerstein 

Editor  and  Librarian 
Alexander  Pogo 

Photographer 

William  C.  Miller 

Instrument  Design  and  Construction 

Lawrence  E.  Blakee,  Electronic  Technician 

Floyd  E.  Day,  Optician 

Kenneth  E.  DeHuff,  Machinist 

Robert  D.  Georgen,  Machinist 

Don  O.  Hendrix,  Superintendent,  Optical 

Shop 
Melvin  W.  Johnson,  Optician 
Edgar    C.    Nichols,    Chief   Designer,   and 

Superintendent,  Instrument  Shop  2 
Bruce  Rule,  Project  Engineer 
Oscar  Swanson,  Instrument  Maker 

Maintenance  and  Operation 

Mount  Wilson  Observatory  and  Offices 
Audrey  A.  Acrea,  Stewardess 
Paul  F.  Barnhart,  Truck  Driver 
Ashel  N.   Beebe,   Superintendent  of  Con- 
struction 

2  Retired  February  28,  1957. 


Wilma  J.  Berkebile,  Secretary 
Ernest  V.  Cherry,  Janitor 
Hugh  T.  Couch,  Carpenter 
Eugene  L.  Hancock,  Night  Assistant 
Emerson  W.  Hartong,  Truck  Driver 
Anne  McConnell,  Administrative  Assistant 
Leah  M.  Mutschler,  Stenographer  and  Tele- 
phone Operator 
Bula  H.  Nation,  Stewardess 
Alfred  H.  Olmstead,  Night  Assistant 
Arnold  T.  Ratzlaff,  Night  Assistant 
Clyde  Sanger,  Gardener 
John  E.  Shirey,  Janitor  and  Relief  Engineer 
Benjamin  B.  Traxler,  Superintendent 

Palomar  Observatory  and  Robinson  Labora- 
tory 

Fred  Anderson,  Machinist 

Dorothea  Davis,  Secretary 

Eleanor  G.  Ellison,  Secretary  and  Librarian 

Ferd  Feryan,  Mechanic 

Arlis  Grant,  Stewardess 

Leslie  S.  Grant,  Relief  Night  Assistant  and 
Mechanic 

Byron  Hill,  Superintendent 

Charles  E.  Kearns,  Night  Assistant 

Harley  C.  Marshall,  Office  Manager 

George  W.  Pettit,  Janitor 

Robert  E.  Sears,  Night  Assistant 

William  C.  Van  Hook,  Electrician  and  As- 
sistant Superintendent 

Gus  Weber,  Assistant  Mechanic 


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Munch,  Guido.  The  mass  of  M  81.  Read  at 
1956  Berkeley  meeting  of  Am.  Astron.  Soc; 
(abstract)  Astron.  ].,  62,  28  (1957). 

Munch,  Guido,  and  Edith  Flather.  The  radial 
velocity  of  53  Arietis.  Pubs.  Astron.  Soc. 
Pacific,  69,  142-146  (1957). 


Nicholson,  Seth  B.  A  sunspot  group  in  excep- 
tionally high  latitude.  Pubs.  Astron.  Soc. 
Pacific,  69,  80-82  (1957). 

Nicholson,  Seth  B.  Solar  observations.  Eng. 
and  Sci.,  20  (no.  9),  14-15  (1957). 

Nicholson,  Seth  B.  Comets  of  recent  years. 
Astron.  Soc.  Pacific  Leaflet  338,  8  pp.  (1957). 

Nicholson,  Seth  B.  Review  of  Vistas  in  astron- 
omy, 1,  ed.  by  A.  Beer.  Pubs.  Astron  Soc. 
Pacific,  69,  188  (1957). 

Nicholson,  Seth  B.,  and  others.  Summary  of 
Mount  Wilson  magnetic  observations  of  sun- 
spots  for  March,  1956,  to  February,  1957. 
Pubs.  Astron.  Soc.  Pacific,  68,  365-368,  460- 
463,  550-552  (1956);  69,  86-90,  180-183, 
270-273  (1957). 

Osterbrock,  Donald  E.  Comet-tail  structures  in 
emission  nebulae.  Astrophys.  J.,  125,  622— 
635  (1957). 

Osterbrock,  Donald  E.  Electron  densities  in  the 
filaments  of  the  Crab  Nebula.  Pubs.  Astron. 
Soc.  Pacific,  69,  227-230  (1957). 

Osterbrock,  Donald  E.    See  also  Seaton,  M.  J. 

Parker,  James  M.  Line  contours  and  wave 
lengths  in  the  flash  spectrum  without  eclipse. 
Read  at  1956  Berkeley  meeting  of  Am. 
Astron.  Soc;  (abstract)  Astron.  ].,  62,  29 
(1957). 

Pettit,  Edison.  The  achromatic  refractor.  As- 
tron. Soc.  Pacific  Leaflet  330,  8  pp.  (1956). 

Pettit,  Edison.  The  reflector.  Astron.  Soc.  Pacific 
Leaflet  331,  8  pp.  (1956). 

Reaves,  Gibson.    See  Walker,  Merle  F. 

Richardson,  Robert  S.  Preliminary  report  on 
observations  of  Mars  made  at  Mount  Wilson 
in  1956.  Read  at  1956  New  York  meeting 
of  Am.  Astron.  Soc;  Pubs.  Astron.  Soc.  Pa- 
cific, 69,  23-30  (1957). 

Richardson,  Robert  S.  Some  observations  of 
Mars  made  at  Mount  Wilson  in  1956.  As- 
tron. Soc.  Pacific  Leaflet  333,  8  pp.  (1957). 

Rogerson,  John  B.,  Jr.  Photoelectric  observations 
of  solar-line  profiles.  Astrophys.  J.,  125, 
275-284  (1957). 

Sandage,  Allan  R.  The  systematics  of  color- 
magnitude  diagrams  and  stellar  evolution. 
Read  at  1956  Berkeley  meeting  of  Am. 
Astron.  Soc;  (abstract)  Pubs.  Astron.  Soc. 
Pacific,  68,  498-500  (1956). 

Sandage,  Allan  R.  The  red-shift.  Sci.  Ameri- 
can, 195  (no.  3),  171-182  (1956);  (no.  5), 
14-16  (1956). 

Sandage,  Allan  R.  Observational  approach  to 
evolution.  I.  Luminosity  functions.  As- 
trophys. ].,  125,  422-434  (1957). 

Sandage,  Allan  R.  Observational  approach  to 
evolution.  II.  A  computed  luminosity  func- 
tion for  K0-K2  stars  from  Mv  =  +5  to  Mv 
=  —4.5.    Astrophys.  J.,  125,  435-444  (1957) . 

Sandage,  Allan  R.  The  birth  and  death  of  a 
star.  Eng.  and  Sci.,  20  (no.  4),  17-21  (1957). 


MOUNT  WILSON  AND  PALOMAR  OBSERVATORIES        75 


Sandage,  Allan  R.  See  also  Hoyle,  Fred;  John- 
son, H.  L. 

Sanford,  Roscoe  F.,  and  J.  L.  Greenstein.  The 
absolute  magnitude  of  Nova  Puppis  1942. 
Pubs.  Astron.  Soc.  Pacific,  69,  75-77  (1957). 

Savedoff,  Malcolm  P.  A  photographic  color- 
magnitude  array  of  the  globular  cluster 
M  13.    Astron.  ].,  61,  254-261   (1956). 

Schmidt,  Maarten.  Exploring  our  Galaxy  with 
21-centimeter  radio  waves.  Astron.  Soc.  Pa- 
cific Leaflet  335,  8  pp.  (1957);  Danish 
versions:  Nordisl^  Astron.  Tidsshjift,  no.  2, 
pp.  51-56  (1957),  and  Urania,  14,  41-45 
(1957). 

Seaton,  M.  J.,  and  D.  E.  Osterbrock.  Relative 
[O  II]  intensities  in  gaseous  nebulae.  As- 
trophys.  ].,  125,  66-83  (1957). 

Tifft,  W.  G.  See  Bonsack,  Walter  K. 

Wahlquist,  H.  D.  See  Bonsack,  Walter  K.; 
Johnson,  H.  L. 

Walker,  Merle  F.  Studies  of  extremely  young 
clusters.  I.  NGC  2264.  Astrophys.  J.,  Suppl. 
Ser.,  2,  365-387  (1956). 

Walker,  Merle  F.,  and  G.  Reaves.  Photoelectric 
photometry  of  the  lunar  eclipse  of  July  26, 
1953.  Pubs.  Astron.  Soc.  Pacific,  69,  153- 
157  (1957). 

Walker,  Merle  F.     See  also  Wilson,  O.  C. 

Wallerstein,  George.  The  absolute  magnitude 
of  U  Sagittarii  and  its  membership  in  M  25. 
Pubs.  Astron. Soc. Pacific, 69,  172-175  (1957). 


Wallerstein,  George.  See  also  Arp,  Halton  C.; 
Bonsack,  Walter  K. 

Wilson,  O.  C.  The  new  Cassegrain  spectro- 
graph for  the  Mount  Wilson  60-inch  tele- 
scope. Pubs.  Astron.  Soc.  Pacific,  68,  346— 
350  (1956). 

Wilson,  O.  C.  The  analysis  of  the  chromosphere 
of  Zeta  Aurigae.  /.  Roy.  Astron  Soc.  Can., 
51,  70-74  (1957). 

Wilson,  O.  C.,  and  M.  F.  Walker.  Simultaneous 
spectrographic  and  photometric  observations 
of  the  short-period  variables  SX  Phoenicis 
and  CC  Andromedae.  Astrophys.  ].,  124, 
325-341   (1956). 

Wilson,  O.  C.,  and  M.  K.  Vainu  Bappu.  H  and 
K  emission  in  late-type  stars:  dependence 
of  line  width  on  luminosity  and  related 
topics.    Astrophys.  J.,  125,  661-683   (1957). 

Zwicky,  F.  Relative  populations  of  rich  spheri- 
cal clusters  of  galaxies.  Pubs.  Astron.  Soc. 
Pacific,  68,  331-338  (1956). 

Zwicky,  F.  Statistics  of  clusters  of  galaxies. 
Proc.  3d  Berkeley  Symposium  Math.  Statis- 
tics and  Probability,  3,  113-144  (1956). 

Zwicky,  F.  Morphologic  Industrielle  Organi- 
sation, 25,  425-428  (1956). 

Zwicky,  F.  Morphological  astronomy.  299  pp. 
Berlin-Gottingen-Heidelberg,  Springer- Ver- 
lag,  1957. 


COMMITTEE    ON     IMAGE     TUBES 
FOR    TELESCOPES 

Mount   Wilson   and  Talomar   Observatories,   Department   of    Terrestrial   Magnetism, 
National  Bureau    of  Standards,   United  States    Naval    Observatory,    and    California 

Institute  of  Technology 

W.  A.  BAUM,  Mount  Wilson  and  Palomar  Observatories 

JOHN  S.  HALL,  United  States  Naval  Observatory 

L.  L.  MARTON,  National  Bureau  of  Standards 

MERLE  A.  TUVE,  Chairman 


Carnegie  Institution  of  Washington  Year  Boo\  56,  1956-1957 


During  the  past  year  the  Committee  has 
continued  to  encourage  or  foster  several 
exploratory  projects  for  the  development 
of  image  tubes  useful  for  increasing  the 
range  of  telescopes.  Several  of  these  proj- 
ects were  outlined  in  the  last  report. 

Although  the  secondary-emission  image- 
multiplier  tube  still  appears  to  offer  the 
most  attractive  over-all  solution  to  the 
image-tube  problem,  serious  difficulties 
were  encountered  in  attempts  to  make  a 
pilot  model. 

Work  both  here  and  abroad  has  been 
carried  on  in  an  effort  to  make  an  image 
converter  containing  one  or  more  stages 
of  image  intensification.  Each  stage  con- 
sists of  a  very  thin  membrane  with  a 
phosphorescent  screen  on  one  side  and  a 
photocathode  on  the  other.  A  gain  of  10 
or  more  per  stage  has  been  reported.  These 
projects  have  thus  far  had  very  limited 
success,  because  of  technical  difficulties, 
dark  emission,  and  loss  of  resolution. 

During  the  past  year  no  important  ad- 
vance, useful  to  astronomers,  which  has 
to  do  with  the  development  of  an  elec- 
tronic storage  tube  with  a  built-in  electri- 
cal read-off  system,  has  come  to  the  atten- 
tion of  the  Committee. 

The  main  effort  of  the  Committee  was 
directed  toward  the  development  of  thin- 
film  image  converters.  Dr.  W.  Kent  Ford, 
Jr.,  continued  his  important  work,  with 
the  help  of  Committee  funds,  on  the  prob- 
lem of  making  suitable  thin  metal  films 
at  the  University  of  Virginia.  The  films 
transmit  electrons  but  protect  the  photo- 
cathodes  of  the  tubes  from  the  molecules 
exuded  from  the  emulsions  of  the  nuclear- 
track  plates  which  record  the  images  of 
stars.  The  manufacturer  mounted  the  films 
in  place  of  the  phosphorescent  screens 
used  in  commercial  tubes  for  viewing 
images  directly.  A  special  glass  envelope 
was  also  attached  to  the  rear  end  of  the 
tube  by  the  manufacturer  to  protect  the 


film  from  rupture  as  the  tube  was  evacu- 
ated and  sensitized.  After  the  finished 
tube  is  installed  in  a  special  chamber 
mounted  on  the  tail  end  of  the  telescope 
and  a  suitable  vacuum  around  the  glass 
cap  is  achieved,  the  cap  is  removed  by 
cracking  the  glass  along  a  circular  groove 
by  means  of  an  electrically  heated  wire. 
The  plate  is  next  admitted  through  an 
air  lock,  and  its  emulsion  is  placed  about 
0.3  mm  behind  the  thin  film.  Exposures 
are  made  by  application  of  high  voltages 
to  the  converter. 

Dr.  Ford's  most  successful  films  consist 
of  an  aluminum  coating  on  Formvar  and 
have  a  total  thickness  of  about  0.15  of  a 
wavelength  of  visible  light.  A  large  per- 
centage of  these  films,  mounted  on  Kovar 
rings,  withstand  baking  for  several  hours 
at  300°  C  and  are  strong  enough  to  be 
shipped  through  the  mails. 

One  highly  sensitive  converter,  having 
a  thin  film  made  by  Ford  and  an  Sll 
photocathode,  was  tested  on  the  Naval  Ob- 
servatory's 40-inch  telescope  at  Flagstaff, 
Arizona,  by  Drs.  W.  A.  Baum  and  J.  S. 
Hall.  Unfortunately,  the  thin  film  was 
broken  as  the  glass  cap  was  removed  just 
a  few  seconds  before  the  first  exposure 
was  made.  The  contamination  of  the 
cathode  was  so  rapid  that  no  stellar  image 
appeared.  This  rupture  of  the  thin  film 
was  doubtless  caused  by  gas  pressure  gen- 
erated in  the  cap  just  as  the  glass  was 
heated  by  the  wire  during  the  breakoff 
procedure.  This  phenomenon  was  not 
experienced  during  a  test  reported  a  year 
ago;  in  that  test,  however,  the  thin  film 
contained  pinholes,  and  only  one  useful 
exposure  could  be  made. 

In  August  1957,  after  the  close  of  this 
report  period,  a  tube  of  low  sensitivity  was 
successfully  used  to  record  the  images  of 
several  bright  stars  with  the  40-inch  tele- 
scope at  the  United  States  Naval  Ob- 
servatory. 


79 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 

Washington,  District  of  Columbia  MERLE  A.  TUVE,  Director 

RICHARD  B.  ROBERTS,  Acting  Director,  July-November  1956 


CONTENTS 


page 

Introduction    83 

Experimental  Geophysics 86 

Radio  astronomy   86 

Radio  emission  from  the  sun 86 

Absolute  intensity  measurements  of 

discrete  radio  sources 87 

Precise  position  apparatus 89 

Radio  emission  from  Jupiter 90 

Search  for  Venus 90 

Radio  hydrogen  91 

The  upper  atmosphere 93 

Winds  and  radio  star  scintillations .  .  93 

The  earth's  crust 94 

Seismic  studies  94 

Rock  magnetism   97 

Mineral  age  measurements 100 

Theoretical  and  Statistical  Geophysics .  .  108 

Equatorial  electrojet 108 

Variability  of  geomagnetic  diurnal 
variation  and  of  ionospheric 

winds   109 

Cosmic-ray  investigations 110 


page 

Laboratory  Physics Ill 

Nuclear  physics   Ill 

Coulomb  excitation  studies Ill 

Investigation  of  the  mechanism   of 

nuclear  reactions    114 

Biophysics    118 

Amino  acid  pools  in  E.  coli 119 

Amino  acid  pools  in  yeast 125 

Protoplasts 131 

Fractionation  of  cell  juices  on  ion- 
exchange  columns  133 

Incorporation   of    amino    acid    ana- 
logues into  proteins 136 

Particles  138 

Protein  synthesis  in  mouse  tissues.  .    142 

Visitors    142 

Operations  and  Staff 143 

Co-operative  work  of  the  Department.    143 

Administration  and  operation 144 

Bibliography  144 

Personnel 146 

Plates  2-5,  following  page  148 


Carnegie  Institution  of  Washington  Year  Boo\  56,  1956-1957 


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INTRODUCTION 


Basic  research  is  usually  described  as 
simply  the  active  expression  of  a  curious 
or  inquiring  mind,  whereas  applied  re- 
search is  goal-directed  and  motivated  by 
the  hope  of  useful  (and  profitable)  ap- 
plication. 

There  is  a  considerable  area  of  overlap, 
however,  as  much  of  the  activity  of  an  in- 
vestigator in  "pure  science"  is  goal-directed 
and  practical  to  a  high  degree.  This  is 
because  his  deep  interest  in  certain  prob- 
lems, or  his  "love  for  a  subject,"  drives  the 
investigator  to  find  usable  solutions  to  dif- 
ficulties which  he  discovers  must  be  over- 
come before  he  can  examine  or  understand 
certain  processes  or  conditions  he  has  en- 
countered in  his  studies.  His  actual  work 
is  nearly  always  "goal-directed,"  but  its 
usefulness  he  measures  in  terms  of  the 
extent  to  which  it  enlarges  his  understand- 
ing and  sharpens  his  concepts,  and  the 
profit  lies  in  the  corresponding  enrichment 
of  his  own  enjoyment  of  his  subject.  The 
subtle  effect  of  his  free-ranging  curiosity 
and  his  corresponding  willingness  to  be 
deflected  from  his  immediate  aims  for  a 
time,  in  order  to  inquire  into  some  un- 
expected feature  which  he  observes  in  the 
course  of  his  systematic  efforts,  is  another 
facet  of  difference  between  the  man  in 
basic  research  and  his  former  classmate  in 
the  applied  field.  The  principal  distinc- 
tion, however,  probably  lies  in  the  different 
motivation  of  the  individual  and  in  the 
scale  of  values  applied  by  the  man  and  by 
his  colleagues  to  the  different  types  of  con- 
tributions each  man  makes  as  time  goes  on. 

This  special  kind  of  motivation  of  the 
individual  investigator  in  "pure  science" 
is  of  course  strongly  reflected  in  the  char- 
acter of  the  encouragement  and  support 
which  the  members  of  such  a  research 
staff  are  given.  No  fully  effective  research 
man  is  ever  "dispassionate,  detached,  and 
disinterested" — on  the  contrary,  he  is  pas- 
sionately interested  and  very  much  im- 
mersed in  his  work.  His  intense  emotional 


investment  simply  makes  greater  demands 
on  the  homely  qualities  of  honesty  and  in- 
tegrity which  are  always  so  indispensable. 
This  report  illustrates  some  of  the  "goal- 
directed"  activities  of  a  group  of  physicists 
who  have  been  encouraged  for  some  years 
to  study  and  investigate  those  problems 
which  have  seemed  to  them  of  the  most 
compelling  interest,  and  each  man  has  thus 
been  invited  to  expand  and  deepen  his 
love  for  his  subject.  The  detailed  problems 
range  from  hydrogen  clouds  among  the 
stars  to  biochemical  complexes,  but  this 
whole  range  of  continually  shared  enthusi- 
asms in  the  group  finally  adds  up  to  a 
vigorous  expression  of  the  scope  of 
"natural  philosophy"  and  the  creative  use 
of  experimental  laboratory  methods  under 
intelligently  analytical  scrutiny. 

In  our  studies  of  the  radio  waves  ar- 
riving from  outside  the  earth's  atmosphere 
it  is  becoming  increasingly  apparent  that 
optical  identifications  of  the  radio  sources 
are  necessary  for  progress  in  understanding 
just  how  large  clouds  of  gas  can  radiate 
in  the  radio  region.  Even  in  studying  that 
relatively  near-by  object,  the  sun,  it  seems 
that  the  position  and  intensity  of  the  radio 
emission  must  be  related  to  optically  ob- 
served features  on  the  sun  before  a  satis- 
factory theory  can  be  evolved.  We  have 
been  led  by  this  necessity  to  build,  for 
scanning  the  sun,  an  antenna  with  angular 
resolution  sufficient  to  separate  two  sources 
one-sixth  of  a  solar  diameter  apart.  This 
antenna  takes  the  form  of  a  line,  2000  feet 
long,  of  helical  receiving  elements,  all  con- 
nected in  phase.  With  this  antenna,  and  a 
receiver  recording  the  power  received  at 
335  mc/sec,  the  sun  is  slowly  scanned  by 
its  own  motion  several  times  each  day  near 
local  noon. 

Observations  of  radio  sources  with  test 
arrays  at  400  mc/sec  and  with  the  300 
mc/sec  helix  array  this  year  have  provided 
interesting  information  on  the  possibility 


83 


84        CARNEGIE  INSTITUTION  OF  WASHINGTON 


of  constructing  relatively  simple  arrays 
capable  of  resolution  of  the  order  of  one 
or  two  minutes  of  arc.  Such  accuracy  is 
required  to  aid  in  the  important  problem 
of  reliably  identifying  radio  sources  with 
optical  objects. 

In  the  last  annual  report,  a  discussion 
was  given  of  some  evidence  suggesting 
that  directed  stresses  occurring  in  the  crust 
might  have  a  profound  influence  on  the 
magnetizations  of  various  rocks.  This  pos- 
sibility was  examined  by  direct  experiment 
this  year  with  new  equipment  constructed 
specifically  for  the  purpose;  the  results  in- 
dicate that  many  conclusions  that  have 
been  offered  by  various  authors  in  recent 
scientific  journals  on  the  basis  of  rock  mag- 
netism data,  relating  to  polar  wandering, 
continental  drift,  secular  variation  and  re- 
versal of  the  earth's  magnetic  field,  are 
subject  to  serious  doubt  because  of  the 
demonstrable  sensitivity  to  stress  of  the 
magnetizations  of  many  rocks. 

By  a  combination  of  the  rubidium-stron- 
tium, potassium-argon  age  methods  it  is 
now  possible  to  date  reliably  the  time  of 
crystallization  of  igneous  rocks  and  the 
time  of  formation  of  metamorphic  rocks. 
As  a  result  of  such  measurements  made 
here  and  by  workers  elsewhere,  it  has  been 
found  that  within  geographically  large 
regions  all  the  igneous  and  metamorphic 
rocks  were  formed  about  the  same  time. 
In  the  Grenville  subprovince  of  Ontario 
the  almost  uniform  occurrence  of  rocks 
approximately  1000  million  years  old  has 
been  known  for  some  time.  Similarly, 
in  the  Appalachians  all  the  rocks  that  have 
been  measured  give  an  age  of  300  ±100 
million  years.  Data  obtained  here  and  by 
workers  in  other  institutions  show  the 
presence  of  a  large  belt  of  2500-million- 
year-old  rocks  extending  from  Wyoming 
through  Montana,  Minnesota,  Manitoba, 
Ontario,  and  Quebec.  In  addition,  a  large 
region  of  1350-million-year-old  igneous  and 
metamorphic  rocks  has  been  found  in 
southwestern  United  States  as  a  result  of 
measurements    made    in    this    laboratory. 


Similarly,  areas  of  1000-  and  2600-million- 
year-old-rocks  have  been  found  in  Africa, 
and  a  group  of  2700-million-year-old  rocks 
has  been  found  in  Western  Australia. 

These  measurements  support  the  older 
idea  that  earth  history  is  characterized  by 
orogenic  episodes  during  which  a  large 
belt  of  the  earth's  crust  is  deformed,  up- 
lifted, intruded  by  igneous  magmas,  and 
subjected  to  regional  metamorphism.  An 
investigation  is  being  made  in  order  to  see 
whether  there  are  any  regularities  in  the 
geographic  distribution  of  successive  oro- 
genic belts  of  this  kind.  Measurements 
are  also  being  made  to  find  out  whether 
these  orogenic  episodes  of  approximately 
200  million  years'  duration  consist  of  a 
series  of  short  episodes  or  whether  the 
formation  of  igneous  metamorphic  rocks 
is  essentially  continuous. 

Soon  after  the  Huancayo  Magnetic  Ob- 
servatory was  established  by  the  Depart- 
ment, in  1922,  the  records  of  geomagnetic 
variations  obtained  there  showed  that  the 
amplitude  of  the  quiet-day  diurnal  varia- 
tion, Sq,  in  the  horizontal  magnetic  com- 
ponent, H,  is  abnormally  large.  This  ab- 
normally large  diurnal  variation  in  H  is 
due  to  the  existence,  during  midday,  of  a 
band  of  concentrated  electric  current  flow- 
ing eastward  in  the  ionosphere  over  Huan- 
cayo. This  current,  known  as  the  equa- 
torial electrojet,  is  superposed  on  the  cur- 
rent system  responsible  for  the  normal 
quiet-day  diurnal  variation,  Sq. 

To  determine  the  height,  intensity,  and 
the  pattern  of  the  current  flow  into  and 
out  of  the  electrojet  it  is  necessary  to  de- 
termine the  variation,  with  latitude,  near 
the  magnetic  equator,  of  the  amplitude 
of  the  diurnal  variation  in  the  three  com- 
ponents of  the  geomagnetic  field.  As  its 
contribution  to  the  U.  S.  International 
Geophysical  Year  effort,  the  Department 
carried  out,  from  March  to  May  1957,  with 
the  co-operation  of  the  Instituto  Geofisico 
de  Huancayo,  a  survey  on  the  west  coast 
of  Peru,  to  obtain  data  for  answering  these 
Questions.     In    addition,    locations    were 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


85 


chosen  for  recording  continuously  the  geo- 
magnetic variations  during  the  IGY.  These 
data  will  indicate  whether  the  same,  Sq, 
electro  jet  is  responsible  for  the  large  lu- 
nar diurnal  variations  at  Huancayo,  and 
whether  "electro jet"  effects  exist  for  the 
"sudden  commencements"  of  magnetic 
storms  and  for  other  magnetic  variations. 

In  nuclear  physics  a  study  has  been 
made  of  the  angular  correlation  between 
the  directions  of  emission  of  the  proton 
and  y  ray  in  an  a-particle-induced  reaction 
on  fluorine.  The  results  show  that  there 
is  indeed  a  definite  correlation,  that  some- 
how the  residual  neon  nucleus  remembers 
the  direction  in  which  the  proton  was 
emitted,  for  a  sufficiently  long  time  to 
allow  the  y  ray  to  be  emitted  in  a  definite 
direction  with  respect  to  the  proton  di- 
rection even  though  the  natural  period  of 
nucleon  motion  within  a  nucleus  is  very 
much  shorter  than  the  decay  time  for  the 
Y  ray.  The  actual  form  of  the  correlation 
shows  in  several  cases  a  surprising  agree- 
ment with  the  predictions  of  a  simple  di- 
rect or  surface  interaction  mechanism. 

In  the  work  of  the  biophysics  section  it 
is  increasingly  apparent  that  it  is  now 
timely  to  attempt  to  interpret  the  chemical 
activities  of  the  cells  in  terms  of  cellular 
structures.  Kinetic  models  of  the  bacterial 
cell  which  take  into  account  the  known 
structures  of  the  cell  have  been  considered 
in  detail.  One  model  which  fits  the  present 
data  suggests  that  there  may  be  a  kinetic 
relationship  among  the  various  classes  of 
particles  found  in  bacterial  cells,  that  one 
type  of  particle  grows  and  becomes  a  dif- 
ferent type.  Experiments  to  test  this  hy- 
pothesis have  been  started.  The  data  have 
not  yet  had  sufficient  refinement  to  test 
the  detailed  predictions  of  the  model,  but 


they  do  show  marked  differences  in  the 
rates  at  which  radioactive  materials  appear 
in  different  cellular  structures.  Another 
feature  of  one  of  the  models  is  the  assump- 
tion that  the  particles  are  arranged  within 
the  cell  in  a  definite  spatial  array.  Al- 
though this  feature  is  difficult  to  test  ex- 
perimentally it  has  received  some  support 
from  an  unexpected  direction.  Clear  solu- 
tions of  bacterial  juices  were  observed  to 
give  rise  to  cell-like  bodies  containing  pro- 
tein and  nucleic  acid.  Those  forms  that 
"reconstitute"  from  the  much  smaller  par- 
ticles of  the  fluid  may  quite  possibly  be  a 
different  expression  of  the  forces  that  or- 
ganize the  material  of  the  cells. 

That  the  mechanism  which  inserts 
amino  acids  into  the  peptide  chains  of 
protein  operates  with  a  high  degree  of 
accuracy  is  shown  by  studies  of  amino 
acid  sequences.  Recent  work  at  the  In- 
stitut  Pasteur  showed,  however,  that  the 
mechanism  was  not  perfect,  and  that  cer- 
tain analogues  of  amino  acids  could  be 
incorporated.  The  resulting  proteins  were 
sufficiently  altered  so  that  normal  growth 
was  not  possible.  During  the  year,  studies 
carried  out  here  in  collaboration  with 
Dr.  G.  N.  Cohen,  of  the  Institut  Pasteur, 
showed  that  methionine  could  be  com- 
pletely replaced  by  its  selenium  analogue. 
In  this  case  the  resulting  altered  proteins 
still  have  a  sufficient  enzymic  activity  to 
permit  continued  growth.  These  results 
show  that  some  errors  in  the  formation  of 
proteins  are  acceptable,  and  the  mechanism 
of  amino  acid  selection  does  not  have  to 
be  perfect.  Studies  along  these  lines  are 
being  continued  to  determine  whether  the 
degree  of  substitution  is  the  same  in  all 
proteins  or  whether  it  varies  from  one  pro- 
tein to  another. 


86        CARNEGIE  INSTITUTION  OF  WASHINGTON 


EXPERIMENTAL  GEOPHYSICS 

RADIO  ASTRONOMY  tion  and  the  behavior  of  localized  bright 

B.  F.  Bur\e,  W.  C.  Ericsson,  /.  W.  Firor,  H.  L.  areas  on  the  sun  is  different  from  the  prob- 

Heljer,  H.  E.  Tatel,  M.  A.  Tuve,  and  lem  of  preparing  to  search  for  new  radio 

T  T          TT7          Tjr        7  7  1~                L                             CD 

n.  w .  weus  stars  or  to  measure  accurately  the  position 

RADIO  emission  FROM  THE  SUN  Gr  intensity  of  radio  stars.  When  searching 

It   has   been   the  expectation   that   our  for  stars  the  investigator  must  be  able  to 

understanding    of    the    solar    atmosphere  scan  large  parts  of  the  sky  to  see  many 

will  be  increased  by  a  search  for  relation-  sources,  to  detect  weak  ones,  and  to  give  a 

ships  between  the  radio  emission  from  the  single  position  in  the  sky   for  each.    In 

sun  and  features  of  the  sun  observed  op-  the  solar  case  a  single  strong  object  is  being 

tically.    Almost   always   the   attempt  has  studied,  and  arrangements  to  make  meas- 

involved  measurements  of  one  feature  of  urements  on  this  one  object  continuously, 

the  radio  emission  and  some  selected  fea-  or  at  least  repeatedly,  during  the  day  are 

ture  of  the  optical  observations:    for  ex-  necessary.   On  the  other  hand,  advantage 

ample,  measurements  of  the  total  emission  may  be  taken  of  the  fact  that  there  is  only 

from  the  whole  sun  at  one  radio  frequency  one  source  like  the  sun  in  the  sky,  and  the 

and  the  sunspot  number  or  the  sunspot  antenna   pattern    may   have   considerable 

area  or  some  weighted  average  of  the  two.  positional    ambiguity— the    measurements 

Although  the  relation  between  the  spots  may   be   consistent   with   many    different 

and  the  radio  emission  was  never  found  to  positions  in  the  sky  as  long  as  only  one 

be  close,  the  matter  has  been  pursued  to  of  them  falls  near  the  known  position  of 

the  point  of  trying  to  determine,  statis-  tne  sun- 

tically,  from  which  spot  on  the  disk  the  An  antenna  designed  especially  for  solar 

radio  emission  comes  or,  by  extrapolation  studies  was  used  by  Christiansen  in  Sydney 

of  statistical  data,  what  would  be  the  level  for  several  years  to  determine  the  bright- 

of  radiation  in  the  absence  of  spots.  Most  ness   distribution   of  the   quiet  sun.    His 

of  the  conclusions  reached  in  this  manner  arrangement  was    an   array   of  32   small 

have  later  been  found  to  be  incorrect;  and,  paraboloids  in  a  line  1000  wavelengths  long 

further  hindsight  shows,  many  mistakes  and  operated  at  a  wavelength  of  about 

would  have  been  avoided  by  having  in  20  cm.   All  the  elements  were  connected 

hand  a  more  complete  radio  description  together   in   phase.    The  resulting  recep- 

of  the  phenomenon  before  the  optical  con-  tivity  pattern  in  the  sky  was  a  number  of 

nection  was  attempted.    In  the  examples  narrow  parallel  lobes,  about  3'  of  arc  wide 

mentioned,  a  measurement  of  the  position  and  spaced  about  2°.    These  fan-shaped 

on  the  solar  disk  of  the  source  of  radio  beams  remained  fixed  in  the  sky,  and  the 

radiation  would  have  guarded  against  the  sun,  moving  across  the  sky  in  its  diurnal 

incorrect  conclusions.  path,  was  scanned  by  each  beam   (lobe) 

Although    many    characteristics   of   the  in  turn.  As  used  by  the  Australian  group, 

solar  radio  emission  that  could  be  measured  this  antenna  permitted  bright  areas  on  the 

would  add  to  the  radio  description  of  the  sun  to  be  recognized  and  allowed  for  in 

sun,  the  measurement  of  the  positions  on  trying  to  deduce  the  distribution  of  bright- 

the  disk  of  the  sources  of  the  radiation,  or  ness  of  the  quiet  sun. 

in  other  words  the  distribution  of  bright-  Such  an  antenna  arrangement  can  clearly 

ness  on  the  solar  disk,  seemed  to  us  to  be  be  utilized  for  studying  bright  areas   as 

the  one  that  would  lead  most  directly  to  well   as   for   eliminating   their   influence, 

fruitful  optical  comparisons.  Each  scan  of  the  sun  by  one  of  the  fan 

The  problem  of  designing  an  antenna  beams  gives  a  position  line  across  the  sun 

for  studying  the  solar  brightness  distribu-  for  any  bright  areas  as  well  as  the  inten- 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


87 


sity  of  the  region.  Later  scans  then  reveal 
changes  in  position  or  intensity. 

The  selection  of  the  wavelength  depends 
on  the  end  in  view.  For  studying  the 
quiet-sun  radiation,  almost  any  wavelength 
in  the  radio-astronomy  range  is  of  interest, 
for  only  when  the  results  from  a  wide 
range  of  wavelengths  are  available  will  it 
be  possible  to  derive  a  radio  picture  of 
the  chromosphere  and  the  corona.  A  sim- 
ilar statement  could  be  made  for  the  ac- 
tive radiation  from  the  sun — the  localized 
bright  areas  and  the  bursts.  The  active 
radiation  is  very  complex,  however,  not 
only  in  its  variation  with  wavelength,  but 
also  in  its  polarization,  variation  with  time, 
and  change  in  position,  so  that  it  is  advan- 
tageous to  have  a  number  of  different  types 
of  measurements  made  on  a  single  active 
event  at  similar  wavelengths.  For  this 
reason  a  wavelength  near  to  that  used  by 
other  solar  investigators  in  the  same  hemi- 
sphere is  desirable. 

An  antenna  meeting  most  of  these  re- 
quirements has  been  built  at  our  River 
Road  site  near  Seneca,  Maryland.  The 
array  is  modeled  after  the  Australian  one, 
but  employs  a  longer  wavelength  (90  cm; 
328  mc/sec)  and  different  receiving  ele- 
ments. The  individual  elements  are  pairs 
of  10-turn  helices  mounted  on  a  common 
ground  screen.  One  helix  is  mounted  with 
a  half-turn  rotation  with  respect  to  the 
other  and  so  is  out  of  phase.  The  two 
helices  can  thus  be  connected  to  the  two 
sides  of  a  balanced  transmission  line.  (See 
fig.  1,  pi.  2,  facing  p.  148.) 

At  present  the  array  has  30  of  these 
elements  and  is  a  little  over  600  wave- 
lengths long.  The  measured  beamwidth 
of  one  of  the  fan  beams  is  4.8'  of  arc  to 
half-power  points,  and  the  fans  are  spaced 
2J/2°«  A  comparison-type  receiver  com- 
pares the  power  received  by  the  antenna 
with  that  from  a  room-temperature  re- 
sistor at  a  1000-cycle  rate. 

Four  scans  of  the  sun  taken  near  noon 
on  successive  days  are  shown  in  figure  2. 
Two  bright  regions  can  be  seen  moving 
across  the  disk  as  the  sun  rotates.  One  of 


them  is  variable  in  time — changes  take 
place  during  the  few  seconds  required  for 
the  beam  to  scan  it.  The  other  region  is 
not  only  steady  during  the  scan  but  also 
is  much  the  same  day  after  day.  For  the 
steady  regions  the  apparent  motion  of  the 
source  across  the  solar  disk  can  be  derived 
from  a  series  of  these  scans,  and  a  height 
above  the  photosphere  can  be  found  for 
the  source.  For  the  more  changeable  re- 
gions, connections  will  be  sought  with  the 


Fig.  2.  Scans  of  the  sun  on  four  successive 
days  taken  with  the  helix  array.  Two  regions 
of  enhanced  radiation  are  seen  which  move  from 
left  to  right  as  the  sun  rotates.  One  of  the 
regions  (near  the  center)  is  relatively  stable;  the 
other  (near  the  right,  or  west,  limb)  changes  in 
intensity  in  the  few  seconds  required  by  the  nar- 
row antenna  beam  to  scan  it. 

optically  observed  features  near  the  correct 
position  line  given  by  the  scan.  (/.  W.  F., 
W.  C.  E.,  B.  F.  B.)  ' 

ABSOLUTE  INTENSITY  MEASUREMENTS  OF 
DISCRETE  RADIO  SOURCES 

The  report  for  1955-1956  described  pre- 
liminary results  of  intensity  or  flux  meas- 
urements on  radio  stars  at  frequencies  be- 
low 30  mc.  Greatly  increased  solar  activity 
of  the  past  year  has  resulted  in  an  iono- 
sphere  which    usually    is    not   sufficiently 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


transparent  for  additional  radio  star  meas- 
urements at  the  lower  frequencies.  In  all 
probability,  it  will  be  impossible  to  repeat 
our  observations  in  the  12  to  15  mc  range 
until  perhaps  1963-1965. 

A  review  of  intensity  measurements  of 
discrete  stars  in  the  available  radio  spec- 
trum has  emphasized  the  very  unsatis- 
factory and  inadequate  nature  of  measure- 
ments in  this  important  area  of  radio  as- 
tronomy. As  yet,  there  is  not  one  accepted 
standard  of  reference  at  any  frequency. 
Even  in  measuring  the  same  star  in  the 
same  frequency  range  there  is  very  little 
agreement  among  different  investigators. 
Few  have  reported  any  flux  measurements 
at  more  than  some  isolated  frequencies, 
and  those  may  lack  consistent  observa- 
tional procedures.  No  one  has  assumed 
the  task  of  making  a  careful,  systematic 
series  of  "absolute"  measurements  over  a 
wide  range  of  frequencies. 

Accordingly,  one  of  our  objectives  in 
radio  astronomy  has  evolved  into  a  pro- 
gram of  flux  measurements  on  a  few  of 
the  intense  radio  stars  over  a  wide  band  of 
the  useful  spectrum.  For  the  purpose  of 
minimizing  all  errors,  both  relative  and 
absolute,  we  are  undertaking  a  series  of 
measurements  by  systematic  and  consistent 
procedures  over  the  frequency  range.  In 
theory  a  flux  measurement  is  simple.  The 
intensity,  S,  is  obtained  from 

S  =  \T/A 

where  S  is  in  watts  per  square  meter  per 
cycle  per  second,  T  is  the  equivalent  tem- 
perature of  the  signal  at  the  antenna,  \ 
is  Boltzmann's  constant,  and  A  is  the 
effective  area  of  the  antenna  in  square 
meters.  In  practice,  however,  there  are 
several  potential  sources  of  error.  T  de- 
pends on  (1)  precise  knowledge  of  all 
transmission  line  losses  between  antenna 
and  receiver,  (2)  accuracy  of  the  calibrat- 
ing system,  and  (3)  the  precision  of  the 
record  scalings.  The  effective  antenna  area, 
A,  is  calculated  from  knowledge  of  its 
polar  diagram,  the  efficiency  of  the  ground 
screen  being  taken  into  account.    Experi- 


ence indicates  that  the  most  likely  sources 
of  error  may  lie  in  the  calibration  method 
and  in  the  determination  of  antenna  aper- 
ture. Such  errors  are  now  minimized  by 
calibrating  noise  sources  against  heated 
resistors  at  each  frequency,  applying  cali- 
bration signals  while  antennas  are  also 
connected  to  the  receiver,  and  using  the 
simplest  of  antennas  (dipoles)  for  all  pri- 
mary observations. 

The  use  of  dipole  antennas  limits  the 
primary  observations  that  can  be  made  at 
this  latitude  to  one  or  two  relatively  iso- 
lated radio  sources.  Even  with  one  primary 
measurement  at  any  frequency,  however, 
higher  gain  arrays  with  adequate  resolu- 
tion are  then  employed  to  obtain  relative 
intensity  measurements  from  which  an 
accurate  flux  may  be  determined  for  other 
radio  stars. 

At  frequencies  below  approximately  100 
mc  we  have  made  dipole  (primary)  meas- 
urements of  both  Cassiopeia  A  and  Virgo 
A.  We  plan  to  continue  dipole  measure- 
ments to  the  limit  of  sensitivity,  which 
may  be  several  hundred  megacycles.  For 
observations  at  higher  frequencies  it  will 
be  necessary  to  standardize  other  antennas 
of  larger  aperture — perhaps  horns — against 
dipoles  at  the  transition  frequency  and  to 
use  scaled  versions  of  the  large  antenna  in 
subsequent  operations.  In  this  manner,  no 
difficulty  is  anticipated  in  extending  the 
series  of  absolute  measurements  to  1000 
mc  or  more. 

The  present  series  of  measurements  in- 
cludes 18.5,  27,  50,  87,  and  108  mc.  The 
sources  of  principal  interest  are  Cassiopeia 
A,  Cygnus  A,  Taurus  A,  and  Virgo  A. 
Some  of  the  final  primary  observations  on 
Cassiopeia  at  87  and  108  mc  are  scheduled 
for  July  1957,  at  which  time  the  source 
will  be  transiting  just  before  sunrise.  The 
next  recording  frequency  is  207  mc.  Ad- 
vance preparations  are  nearing  completion, 
and  observations  are  scheduled  to  start  in 
late  June  or  early  July  1957.  The  next  step 
will  be  to  about  300  mc  or  higher,  depend- 
ing on  the  207-mc  results. 

When  our  measurements  are  combined 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        89 


with  all  other  known  values,  several  in-  of  the  gas  or  matter  emitting  the   radio 

teresting  characteristics  promptly  become  waves  are  known.  Some  sources  have  steep 

apparent:   (1)  there  appears  to  be  a  "knee"  density  gradients  to  high  pressures,  as  in 

or  change  in  slope  of  Cassiopeia  A  below  the    solar   atmosphere;    others   appear   to 

50  mc;    (2)   there  is  so  much  scatter  of  be  extremely   tenuous  and   extended  gas 

points  in  the  range  200  to  600  mc  that  clouds;   some  are  relatively  much  cooler 

earlier  curves  showing  a  "flat"  spectrum  than  others;  all  appear  to  be  highly  turbu- 

may  be  seriously  questioned;   (3)   at  fre-  lent.    Until  much  larger  numbers  of  the 

quencies  up  to  approximately  1000  mc  the  various  types  are  known  and  studied  by 

ratio  of  Cassiopeia  A  to  Cygnus  A  is  de-  optical  methods  we  can  hardly  consider 

creasing  (Cygnus  A  is  getting  relatively  radio    observations    to    have    contributed 

stronger  at  the  higher  frequencies),  but  much  to  astronomical  knowledge.    More- 

the  ratio  of  Virgo  A  to  Cygnus  A  is  essen-  over,    faint    but    easily    observable    radio 

tially  unchanging  over  the  same  range.  In  sources  may  lie  beyond  the  radius  of  the 

connection  with  the  ratio  measurements  it  optically  observable   universe.    Therefore, 

is  perhaps  significant  to  note  that  the  ratio  the  statistics   of  faint  radio  sources  may 

of  two  extragalactic  sources  (Virgo  A  and  yield    information    about    the    large-scale 

Cygnus  A)  is  steady  but  the  ratio  of  Cas-  structure  of  the  universe, 

siopeia  A,  which  is  a  galactic  source,  to  In  order  to  extend  the  list  of  optical 

Cygnus  A  is  changing  in  a  manner  to  identifications,  precision  position  determi- 

indicate  that  the   very  distant  source  in  nations  for  a  large  number  of  radio  sources 

Cygnus  A  is  getting  relatively  weaker  at  must  be  made.  The  few  identifications  so 

the  lower  frequencies.  Absorption  in  inter-  far  have  proved  to  be  interesting  objects, 

stellar   space — a   rough   distance   scale — is  but  if  meaningful  identification  with  ob- 

one  of  several  possible  explanations  of  the  jects  as  faint  as  18th  magnitude  are  to  be 

trend.   (H.  W.  W.)  made,  radio  positions  should  be  measured 

to  the  order  of  several  square  minutes  of 

precise  position  apparatus  arc?  a  precision  attained  so  far  only  for 

The   optical    radiation   from   an   astro-  the  most  intense   sources.    The   strongly 

nomical  radio  source  is  capable  of  yielding  felt  need  for  a  greater  number  of  precise 

a  great  wealth   of  information   that  the  positions  has  led  us,  therefore,  to  investi- 

radio  radiation  cannot  give.  Therefore,  to  gate  the  problem.  An  antenna  constructed 

obtain  detailed  knowledge  of  the  nature  for  precise   position   measurements   must 

of  radio  sources,  optical  identification  must  possess  not  only  the  necessary  mechanical 

be  made.  Up  to  this  time,  however,  a  dis-  and  electrical  stability  but  also  sufficient 

couragingly  small  number  of  radio  sources  angular  resolution  to  guarantee  that  most 

have  been  unequivocally   identified  with  of  the  sources  measured  are  truly  discrete, 

optically  observed  objects.    These  sources  not  simply  blends  of  several  sources  (often 

represent  a  great  variety  of  objects,  rang-  referred  to  as  "confusion"), 

ing  from  the  sun   and  planets,  through  A  long  array,  to  give  a  narrow  "line  of 

supernova  remnants,  and  peculiar  galactic  position"  in  the  sky,  or  an  interferometer 

emission  nebulosities,  to  external  galaxies,  composed  of  a  pair  of  long  arrays  along 

Only  a  few  objects  of  each  class  have  been  one  line,  appears  promising,  particularly 

identified.    Before    definitive    conclusions  in  view  of  the  success  of  the  328  mc/sec 

about  the  general  nature  of  radio  sources  helix  array  we  have  in  use  on  the  sun. 

can  be  drawn,  many  sources  of  each  class  The   arrays  must  be  oriented  in  several 

must  be  identified.  It  is  impossible  to  carry  different  azimuths,  since  a  single  orienta- 

out  any  extensive  astrophysical  studies  us-  tion  gives  high  precision  for  only  one  co- 

ing  radio  information  unless  the  state  of  ordinate.   At  least  three  different  orienta- 

aggregation  and  other  physical  properties  tions   of  the  arrays  appear   desirable,   in 


90 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


order  to  overdetermine  the  position  and 
guard  against  confusion  errors. 

Several  small  arrays  and  a  receiver  were 
constructed  for  use  at  400  mc/sec  to  aid 
in  design  of  the  large  arrays  with  the  aim 
of  achieving  position  accuracy  within  4 
square  minutes  of  arc.  These  arrays  are 
expected  to  be  made  in  small  sections,  each 
about  10  feet  long  to  facilitate  remounting 
along  different  lines  of  azimuth.  The  most 
suitable  element  investigated  so  far  is  a 
60°  V  reflector  excited  by  a  line  of  full- 
wave  dipoles.  The  test  arrays  used  open- 
wire  feeder  lines  which  can  be  constructed 
to  give  low  losses  and  good  phase  stabil- 
ity. Trial  interferometric  measurements  of 
right  ascension  were  made  with  small  ar- 
rays and  a  short  baseline  (50  meters)  on 
the  strong  sources  in  Cygnus  and  Cassi- 
opeia, the  results  agreeing  with  the  known 
positions  to  within  a  minute  of  arc.  Prep- 
arations have  been  completed,  and  the 
construction  of  a  large  array  is  in  prog- 
ress.  (B.  F.  B.,  /.  W.  F.,  W.  C.  E.) 

RADIO  EMISSION  FROM  JUPITER 

Regular  observations  of  the  planet  Jupi- 
ter were  not  continued,  but  data  taken  in 
previous  years  at  this  laboratory  were  re- 
examined in  the  course  of  preparing  a  sum- 
mary of  the  present  status  of  this  phase  of 
radio  astronomy.  In  the  previous  report 
it  was  mentioned  that  the  region  of  the 
planet  which  appeared  to  be  the  most  per- 
sistent source  of  noise  during  1955-1956 
was  certainly  not  the  same  as  that  reported 
by  Australian  workers  from  their  predis- 
covery  records  taken  from  August  to  Sep- 
tember 1951.  An  analysis  of  the  time  de- 
pendence of  all  obtainable  observations, 
including  the  Australian  observations  in 
late  1950  and  early  1951,  the  August-Sep- 
tember 1951  Australian  series,  the  pre- 
discovery  observations  at  this  laboratory 
during  June  1954,  the  Mills  Cross  series 
from  January  to  May  1955,  and  the  1955- 
1956  Carnegie  observations,  revealed  that 
the  most  active  region  could  always  be 
reconciled  with  a  single  center  of  activity 


on  the  planet,  having  an  approximately 
uniform  rotational  period  of  9h  55m  28.5s. 
Interestingly,  none  of  the  visual  observa- 
tions report  any  surface  features  exhibit- 
ing this  rotational  period;  the  source  of 
radio  radiation  therefore  probably  lies  be- 
low the  cloud  level,  and  might  well  be 
associated  with  the  surface  of  the  planet 
itself.   (B.  F.  B.) 

SEARCH  FOR  VENUS 

During  the  fall  of  1956,  when  Venus 
was  at  elongation,  two  interferometers 
were  placed  in  operation  to  check  on  the 
validity  of  the  reported  low-frequency  non- 
thermal radiation  from  this  planet.  These 
interferometers  operated  at  frequencies  of 
22  and  26.75  mc/sec.  The  22  mc/sec  array 
consisted  of  two  elements,  each  contain- 
ing eight  half-wave  dipoles,  which  were 
phased  in  such  a  direction  that  Venus  rose 
through  the  beam  about  2  hours  before 
sunrise  each  morning.  Each  element  of 
the  26.75  mc/sec  array  consisted  of  four 
half-wave  dipoles  phased  in  a  similar  man- 
ner. The  observations  were  attempted  be- 
fore sunrise,  since  after  sunrise  strong  in- 
terfering signals  of  terrestrial  origin  make 
identification  far  more  difficult.  Observa- 
tions were  made  continuously  from  Sep- 
tember 19  to  October  25,  1956,  but  no  ra- 
diation of  Venusian  origin  was  found. 
If  during  this  period  Venus  had  been  a 
source  of  equal  intensity  to  the  Crab  Neb- 
ula, it  would  have  easily  been  observed. 

During  these  observations,  one  interest- 
ing effect  was  noted.  Approximately  30 
minutes  before  sunrise,  just  as  the  inter- 
fering signal  strengths  were  rising,  a  few 
lobes  of  an  interference  pattern  were  often 
found  at  both  frequencies.  They  could  not 
be  associated  with  radiation  originating  at 
Venus,  since  they  disagreed  both  in  phase 
and  in  period  with  radiation  coming  from 
the  direction  of  that  planet.  The  effect 
may  be  due  to  the  build-up  and  movement 
of  ionized  regions  in  the  atmosphere  as 
they  are  illuminated  by  sunlight,  some  of 
these  regions  being  responsible  for  the  re- 
flection of  the  interfering  radiation,  which 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        91 


may  be  of  terrestrial  or  solar  origin,  to  the 
observing  site.   (B.  F.  B.,  W.  C.  E.) 

Other  interferometer  records  of  the  sum- 
mer of  1956  using  simple  dipoles  at  18.5 
and  26.75  mc  were  scanned  in  the  search 
for  Venus.  No  events  at  either  frequency 
could  be  uniquely  identified  as  having 
origin  in  Venus,  although  several  interest- 
ing borderline  occurrences  were  noted  on 
the  18.5-mc  instrument.  These  tests  indi- 
cate that  no  pronounced  signals  from  Ve- 
nus were  received,  but  do  not  conclusively 
prove  the  absence  of  some  weak  emissions 
at  random  intervals.   (H.  W.  W.) 

RADIO  HYDROGEN 

During  the  past  year  a  large  part  of  our 
effort  in  the  21-cm  hydrogen-line  program 
has  been  devoted  to  the  improvement  of 
our  observing  equipment.  We  have  de- 
signed an  equatorial  telescope  mount  suit- 
able for  large  dishes,  installed  a  multi- 
channel spectrometer,  and  improved  the 
over-all  stability  of  our  recording  equip- 
ment. In  addition  to  this  emphasis  on  in- 
strument improvement,  however,  we  have 
continued  our  measurements  at  a  modest 
rate.  Several  more  meridian  galactic  sur- 
veys have  been  finished,  and  a  thorough 
survey  of  the  Pleiades  and  the  II  Persei 
clusters  is  nearing  completion.  One  find- 
ing is  that  a  large  region  of  the  sky  in  the 
direction  of  these  clusters  is  covered  by  a 
homogeneous  hydrogen  gas  cloud.  Pre- 
liminary examination  of  the  Doppler-shift 
cross  section  of  this  cloud  indicates  that  a 
Gaussian  velocity  distribution  represents 
the  major  portion  of  the  observed  inten- 
sity. The  velocity  distribution  parameter 
is  5  km/sec,  corresponding  to  600°  K, 
whereas  the  "spin  temperature"  is  assumed 
to  be  about  150°  K.  It  should  be  noted 
that  the  optical  absorption  of  interstellar 
lines  indicates  that  this  mass  of  gas  is 
probably  150  to  350  parsecs  distant. 

The  general  problem  of  the  design  of 
large  parabolic  antennas  was  resolved  into 
two  principles:  astronomical  uses  make  it 
desirable  to  have  an  equatorial  mount; 
and  the  structure  should  be  designed  with 


rigidity  commensurate  with  the  precision 
of  the  reflector.  Hence  the  main  drive 
gears  and  major  structural  units  should  be 
large,  so  that  machining  tolerances  can 
also  be  large.  Numerical  studies  of  our 
resulting  initial  design  showed  it  to  be 
adequate  and  economical  for  supporting 
reflectors  as  large  as  85  feet.  The  National 
Science  Foundation  is  planning  to  build  a 
large  "national  facility  for  radio  astron- 
omy" at  Greenbank,  West  Virginia.  Hence 
we  carried  out  some  careful  studies  of  the 
features  required  for  larger  parabolic  re- 
flectors and  mounts.  A  200-foot  bar  of 
steel  first  compressed  and  then  stretched 
by  its  own  weight  will  elongate  about  0.4 
cm.  Since  any  major  structural  unit  must 
support  more  than  its  own  weight,  its 
elongation  will  be  greater.  If  it  supports 
2l/z  times  its  own  weight  the  elongation 
is  1  cm.  In  a  reflector  the  depth  is  much 
less  than  the  breadth,  so  that  major  struc- 
tures have  even  larger  loads  than  simple 
trusses  of  equal  width  and  breadth — per- 
haps twice  as  much.  If  the  deflection  be- 
comes 5  cm  it  reaches  (exceeds)  the  limit 
for  a  reflector  intended  for  21-cm  waves. 
This  very  rough  calculation,  which  neg- 
lects some  features  such  as  "hoop  strength," 
indicates  that  a  simple  cantilever  structure 
of  steel  cannot  be  expected  to  be  useful  as 
a  steerable  astronomical  instrument  if  it 
is  much  longer  than  about  200  feet.  For 
larger  structures  other  features  of  design 
must  be  devised  to  surmount  the  problem 
of  the  elasticity  of  steel.  The  economic 
problem  is  also  considerable.  Devices  of 
this  magnitude  constructed  with  present 
techniques  are  expected  to  have  costs  in 
the  range  of  perhaps  10  million  dollars. 
Our  hydrogen-line  radiometer  has  been 
converted  to  a  multichannel  device.  It  is 
now  used  to  record  in  54  channels  10 
km/sec  wide,  spaced  at  frequencies  equiva- 
lent to  a  Doppler  shift  of  4  km/sec  between 
channels.  The  basic  system  is  a  Dicke- 
Ewen  comparison  receiver  with  two  local 
oscillators  alternately  switched  on  and  off. 
The  oscillators  are  tuned  separately,  so  that 
the   two   receiving  frequencies  and   their 


92 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


differences  can  be  adjusted  with  precision. 
The  received  signal,  detected  in  a  crystal, 
is  doubly  converted  to  a  band  extending 
from  1.5  to  2.5  mc/sec,  at  an  output  level 
of  2  to  3  volts  rms.  A  common  output 
amplifier  drives  54  separately  tuned  fil- 
ters. At  the  output  of  each  filter  is  an  in- 
dividual amplifier  with  ample  feedback 
stabilization. 

The  signal  detected  at  the  output  of 
each  of  these  radio-frequency  amplifiers 
contains  the  switching  frequency  (about 
450  cps).  It  is  amplified  in  a  feedback- 
stabilized  audio  amplifier  and  detected  in 
a  phase-sensitive  (450  cps)  detector.  The 
output  of  the  final  amplifier  on  each  chan- 
nel is  2  volts  rms.  Between  this  output 
and  the  final  detector  is  a  potentiometer 
gain  control  for  each  individual  channel. 
The  phase  detectors  charge  l-|jf  condensers 
through  400  or  4000  megohms,  depending 
on  the  desired  output  time  constant.  The 
voltage  on  the  storage  condensers  is  read 
out  by  means  of  an  electrometer  tube  and 
recording  potentiometer.  Read-out  time  is 
2  minutes  for  the  54  channels.  This  sys- 
tem has  very  great  advantages  over  the 
single  channel  unit  with  frequency  scan, 
but  there  are  several  features  that  we  wish 
to  modify.  The  output  diodes  have  a  sta- 
bility of  about  l/2  millivolt  per  day,  which 
is  equivalent  to  a  signal  of  1°  K  at  the 
antenna,  so  that  the  diodes  need  adjust- 
ment every  two  or  three  days.  We  there- 
fore expect  later  to  increase  the  audio  gain 
by  about  a  factor  of  8.  The  gains  of  the 
feedback  amplifiers  are  difficult  to  moni- 
tor; we  calibrate  the  over-all  system  with 
a  modulated  noise  diode  at  the  input,  and 
statistical  fluctuations  during  the  calibra- 
tions are  important.  Our  wide-band  ampli- 
fier (1.5  to  2.5  mc/sec)  does  not  have  a 
sufficiently  low  impedance  to  drive  the 
high  capacity  of  the  existing  cables  feed- 
ing the  54  filters,  so  that  we  are  forced  to 
operate  at  a  low  output  diode  level.  These 
cables  must  be  replaced  by  a  low-capacity 
feed. 

The  whole  system  is  flexible  enough  to 
use  in  many  problems.  The  oscillators  can 


be  tuned  over  a  wide  range.  Channels 
can  be  connected  in  parallel  so  as  to  have 
greater  bandwidth  and  smaller  fluctua- 
tions. We  are  now  in  the  process  of  de- 
veloping the  observing  procedures  for  the 
best  use  of  this  powerfully  analytical  in- 
strument. 

Another  problem  of  great  difficulty  and 
even  greater  importance  is  the  zero  sta- 
bility of  the  detection  system.  Many  in- 
teresting problems  require  the  detection  of 
minute  signals  of  the  order  of  1°  K  an- 
tenna temperature,  or  less.  Such  measure- 
ments require  a  system  with  zero  drifts 
and  changes  not  exceeding  0.5°  or  03°  K 
over  periods  of  several  hours.  Our  detec- 
tion system  last  year  had  a  variable  stability 
with  occasional  fluctuations  even  as  high 
as  10°  K  over  a  run  of  several  hours.  After 
much  testing  and  many  changes,  including 
the  physical  separation  of  the  local  oscil- 
lators from  the  receiver  units  and  im- 
provement in  the  shielding  of  transmission 
cables,  we  have  been  able  to  reduce  the 
zero  changes  to  a  drift  of  less  than  1°  K 
per  week  on  the  dummy  antenna.  On  the 
sky  antenna  the  system  is  not  as  free  of 
drifts;  at  times  it  may  shift  as  much  as 
±1°  K  in  several  hours.  For  the  narrow- 
band short  time  constant  (7  minutes)  this 
amount  of  drift  is  not  important,  but  in 
looking  for  signals  of  a  few  tenths  of  a 
degree  Kelvin  it  is  still  a  limiting  factor. 

Using  this  new  multichannel  recording 
instrument  we  have  in  progress  a  repeti- 
tion and  extension  of  our  survey  of  the 
hydrogen  clouds  within  ±20°  of  the  galac- 
tic plane,  for  a  great  many  points  spaced 
from  2°  to  10°  apart  along  the  galactic 
equator  as  visible  in  Washington.  Resid- 
ual hydrogen  is  also  found  at  all  points 
examined  to  date  at  higher  galactic  lati- 
tudes. (H.  L.  H.,  H.  E.  T.,  M.  A.  T.) 

Tidal  distortion  of  the  galaxy.  The 
Leiden  and  Australian  groups  have  shown 
that,  if  the  Lund  galactic  pole  is  shifted, 
the  major  concentration  of  galactic  hydro- 
gen lies  close  to  the  plane,  with  small 
deviations.  The  deviation  for  the  outer- 
most spiral  structure  is  noticeably  greater, 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM         93 


and  the  21-cm  meridional  surveys  taken  at  45°.  Such  large-scale  drifts  are  predomi- 
this  laboratory  were  examined  to  see  nantly  downward  and  into  the  east.  Often 
whether  the  effect  was  systematic.  Sur-  there  is  no  significant  change  either  in 
veys  were  available  here,  at  galactic  longi-  velocity  or  in  direction  as  the  disturbance 
tudes  50°,  60°,  80°,  90°,  110°,  180°,  200°,  progresses  downward  through  the  outer 
and  210°,  which  showed  that  in  general  atmosphere.  Effects  such  as  described  could 
the  center  of  mass  of  the  outermost  hydro-  be  caused  by  an  inclined  wave  front  mov- 
gen  lay  consistently  below  the  plane  on  the  ing  horizontally,  an  inclined  wave  front 
side  closest  to  the  Large  Magellanic  Cloud  moving  vertically,  or  combinations  of  both 
(LMC),  but  above  the  plane  on  the  more  motions.  Predominant  velocities  are  be- 
distant  side,  except  for  longitude  110°.  Al-  tween  100  and  200  m/sec. 
though  the  effect  is  qualitatively  in  the  In  another  review  of  ionospheric  winds 
proper  direction  to  be  due  to  tidal  effects  from  other  radio  methods  of  measurement, 
of  the  LMC,  the  observed  deviation  ap-  an  intercomparison  was  made  of  results 
pears  to  be  much  too  large  if  conventional  from  the  "meteor-Doppler"  and  the  "fad- 
values  for  the  masses  and  distance  scales  of  ing"  techniques.  The  outcome  was  the 
the  galaxy  and  LMC  are  assumed.  At  interesting  fact  that  the  two  methods  inde- 
1=210°,  the  deviation  is  about  300  parsecs,  pendently  establish  similar  characteristics 
which  is  approximately  20  times  larger  of  EAaycr  winds.  The  outstanding  features 
than  would  be  expected  from  gravitational  are  (1)  velocities  in  the  range  50  to  100 
effects,  if  Schmidt's  galactic  model  is  used,  m/sec,  (2)  large  semidiurnal  components 
together  with  a  mass  of  4  X  109  solar  masses  with  clockwise  rotation  of  wind  directions 
for  the  LMC.  The  effect  is  sensitive  to  the  in  the  northern  hemisphere,  and  (3)  coun- 
assumed  force  perpendicular  to  the  galactic  terclockwise  rotation  in  the  southern 
plane,  but  it  appears  that  both  a  larger  hemisphere. 

mass  for  the  LMC  and  a  larger  distance  Radio  star  scintillations  have  been  ob- 
scale  for  our  galaxy  are  required  if  the  served  at  all  operating  frequencies  between 
effect  is  to  be  explained  using  gravitational  18.5  and  108  mc.  Although  the  scintilla- 
forces  only.    (B.  F.  B.)  tions  at  108  mc,  which  is  the  IGY  satellite 

frequency,  are  not  a  normal  occurrence,  it 

THE  UPPER  ATMOSPHERE  [s  c}ear  ^at  varying  refraction  in  the  iono- 

H.  W.  Wells  sphere  causes  the  apparent  "radio"  position 
WINDS  AND  RADIO  STAR  SCINTILLATIONS  of  an  object  to  change  by  significant 
A  paper,  "Large  scale  movements  of  the  amounts.  At  50  mc,  scintillations  were 
layers,"  was  presented  to  the  AGARD  prevalent  during  the  period  of  observation. 
(Advisory  Group  for  Aeronautical  Re-  At  27  mc,  preparations  have  been  made 
search  and  Development)  at  Oslo,  Nor-  for  the  operation  of  a  three-station  network 
way,  in  July  1956.  The  activities  of  this  to  measure  the  drift  characteristics  of  the 
Department  and  others  were  reviewed  in  ionized  clouds  producing  the  scintillations, 
the  light  of  additional  analyses.  Sweep-  To  explore  the  possibility  of  long- 
frequency  observations  of  the  ionosphere  at  distance  propagation  of  electromagnetic 
networks  of  stations  spaced  20  to  200  miles  waves  from  power  lines  some  brief  experi- 
reveal  the  nature  of  apparent  large-scale  ments  were  conducted  at  the  Derwood 
movements  and  permit  a  three-dimen-  Field  Station.  It  was  assumed  that  any 
sional  interpretation.  Analyses  clearly  peak  in  radiation  at  50  cycles  would  indi- 
show  for  the  first  time  that  traveling  dis-  cate  foreign  origin.  Filters  were  incorpo- 
turbances  have  vertical  as  well  as  hori-  rated  so  that  the  strong  60-cycle  radiation 
zontal  components  of  motion.  The  dis-  from  domestic  sources  would  not  interfere, 
turbance  wave  front  is  often  inclined  about  The  recordings  showed   the  presence  of 


94        CARNEGIE  INSTITUTION  OF  WASHINGTON 


very  substantial  energy  between  45  and  55 
cycles  without  any  peak  in  the  50-cycle 
region.  Random  atmospheric  noise  and 
other  disturbances  left  a  high  residual  noise 
level,  however.  A  few  isolated  cases  of  ac- 
tivity during  thunderstorms  clearly  estab- 
lished the  fact  that  electromagnetic  radia- 
tion of  these  extremely  long  wavelengths  is 
generated  at  such  times. 

Preparations  for  the  Xllth  General  As- 
sembly of  the  International  Scientific 
Radio  Union  at  Boulder  in  August-Sep- 
tember 1957,  and  attention  to  many  fea- 
tures of  the  program  of  the  International 
Geophysical  Year,  especially  in  the  areas 
of  ionospheric  physics,  have  occupied  some 
members  of  the  DTM  staff  during  a  con- 
siderable part  of  the  current  report  year. 

THE  EARTH'S  CRUST 

L.  T.  Aldrich,  J.  W.  Graham,  H.  E.  Tatel, 
M.  A.  Tuve,  and  G.  W.  Wetherill 

The  exploration  of  the  earth's  crust  con- 
tinues to  present  us  with  problems  of  great 
interest.  Our  general  goal,  of  course,  is  a 
clear  recognition  and  understanding  of  the 
many  large-scale  physical  processes  that, 
operating  during  the  long  periods  of  geo- 
logical time,  have  resulted  in  the  present 
conspicuous  features  of  the  earth,  such  as 
the  continents  and  the  ocean  depths,  moun- 
tain ranges  and  high  plateaus,  and  the  dis- 
tribution of  land  and  ocean  areas.  We  are 
also  interested  in  other  matters  like  the 
equatorial  bulge,  the  stability  with  time  of 
the  position  of  the  geographical  poles,  and 
the  time  scale  of  geological  uplift  and  ero- 
sion. Perhaps  we  may  some  day  have 
better  notions  about  the  remote  and  the 
immediate  "causes"  of  such  processes  as 
mountain  building  and  the  cyclical  immer- 
sion of  large  continental  areas  under  shal- 
low seas,  but  clearly  the  first  necessity  is 
a  comprehensive  and  quantitative  descrip- 
tion of  the  earth  as  it  is  today.  In  particu- 
lar, we  need  data  on  relatively  inaccessible 
matters,  like  the  horizontal  and  vertical 
density  distribution  of  the  rocks  under  the 
continents  and  under  the  oceans.  We  have 
directed  our  efforts  toward  such  questions 


in  the  seismic  program  with  explosion 
waves.  Our  work  on  isotopes  in  rocks  aims 
at  establishing  bench  marks  for  a  time 
scale  in  Precambrian  geology. 

SEISMIC  STUDIES 

The  mathematical  picture,  for  gravity 
and  seismic  computations,  of  an  earth's 
crust  comprised  of  a  series  of  horizontal 
rock  layers,  each  several  kilometers  thick 
and  of  successively  increasing  density,  has 
given  way  in  very  recent  years  to  a  much 
less  specific  picture,  namely,  a  crust  with 
horizontal  and  vertical  inhomogeneities, 
and  with  average  characteristics  that  do  not 
change  by  large  amounts  over  short  hori- 
zontal distances. 

In  Alaska  we  find  a  crust  that  has  a 
mean  seismic  velocity  uniform  with  depth 
to  the  mantle.  It  is  easy  to  imagine,  then, 
as  appears  to  be  increasingly  acceptable 
among  students  of  earth  structure,  that 
the  change  in  velocity  is  the  result  of  a 
"phase  transition,"  a  change  of  chemical 
crystal  lattice  relations  and  resulting 
change  in  density  without  change  of 
chemical  composition.  But  if  this  is  ac- 
tually true,  why  is  the  transition  only  11 
km  under  the  ocean  surface  and  30  km 
under  the  continental  surface  ?  The  puzzle 
is  even  more  perplexing  in  view  of  the 
recent  heat-flow  measurements  through  the 
ocean  bottom  in  the  Atlantic  and  the  Pa- 
cific. The  oceanographers  find,  contrary 
to  expectation,  that  ocean  and  continental 
heat  flows  upward  through  the  rocks  of 
the  crust  are  almost  the  same.  This  being 
so,  it  can  hardly  be  an  equilibrium  tem- 
perature and  pressure  distribution  that  de- 
termines the  depth  of  the  velocity  discon- 
tinuity, and  hence  it  seems  improbable  that 
this  abrupt  change  from  crustal  to  "outer 
mantle"  rocks  can  be  a  phase  transition, 
unless  the  present  heat  flow  is  in  part  an 
indicator  of  changing  heat  flow  and  chang- 
ing temperature  distribution. 

Velocity  versus  Depth 

We  have  tried  to  fit  the  crustal  data  ob- 
tained from  our  measurements  on  the  seis- 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        95 


mic  waves  from  explosions  during  the  past  the   critical   reflection,   calculated   on   the 

decade  to  various  types  of  possible  crustal  basis   of   SnelPs   law   and   the   measured 

structures,  treating  the  problem  as  one  in  velocities,  is  appreciably  (10  or  15  per  cent) 

geometric   optics   in    which    the   velocity  less   than    the   observed    distance    to   the 

varies  in  different  specific  ways  with  depth,  abrupt  appearance  of  the  critical  reflection 

Our  conclusion  has  been  that  the  compres-  of  the  compressional  wave.    This  is  just 

sional  velocity  does  increase  with  depth  in  what  we  observe  in  field  work,  but  in  the 

some  manner,  probably  at  an  increasing  laboratory  experiment  we  know  that  the 

rate,  from  a  mean  surface  value  of  about  "crustal"   velocity   did   not  increase  with 

6  km/sec  to  a  value  of  about  7  km/sec  at  depth. 

a  depth  of,  say,  30  km,  and,  just  below  this,         There  is  at  present  no  theory  describing 

abruptly  to  about  8  km/sec,  the  compres-  the  nature  of  a  critical  reflection  of  a  com- 

sional  velocity  of  sound  waves  in  the  outer  pressional  pulse  in  such  a  medium  as  the 

mantle.     These    conclusions    were    based  earth.  As  a  rough  approximation,  the  criti- 

upon  the  geometrical  optics  approximation  cal  reflection  pattern  could  be  equated  to 

for  sound  waves,  which  has  been  the  only  that  obtained  by  the  masking  of  a  point 

complete  theory  available.    We  have  al-  source  by  a  large  disk,  the  apparent  source 

ways  noticed,   however,   that  certain  ex-  being  the  mirror  image  of  the  true  source 

pected   arrivals  have  not  been  observed,  at  the  surface.   The  solution  to  even  this 

for  example  the  refracted  wave  expected  problem  does  not  exist  for  light  waves, 

between  100  and  180  km.  This  failure  has  Since  the  source  and  image  are  not  a  great 

been  excused  on  the  hypothesis  that  the  many  wavelengths   apart  in  our   seismic 

"reverberation"  level,  due  to  interconver-  work  and  also  in  the  laboratory  model,  it 

sion  of  wave  types  at  topographic  and  sub-  might  be  imagined  that  there  would  be  a 

terranean    boundaries,    is     unfortunately  kind  of  Fresnel  interference  at  the  edge  of 

enough  to  obscure  these  arrivals.  This  may  the  excluded  disk   (due  to  compressional 

still  be  so.  waves  entering  the  mantle  within  the  cir- 

The  Alaskan  measurements  (Year  Book  cle  defined  by  SnelPs  law) .  Such  an  inter- 
54,  1954-1955)  are  one  of  our  more  precise  ference  pattern,  strongly  dependent  on 
sets  of  data.  They  show  well  developed  frequency,  would  predict  an  intensity  that 
total  reflection  from  80  to  200  km  and  only  begins  to  rise  at  the  geometrical 
strong  refracted  waves  from  160  km  out.  shadow  edge  (that  is,  at  the  critical  reflec- 
These  values  are  well  fitted  by  a  simple  tion  distance  defined  by  Snell's  law),  and 
crust  of  a  single  layer  of  rock  in  which  increases  to  a  maximum  at  a  distance  well 
the  velocity  is  constant  with  depth  down  beyond  this.  The  lateral  extent  of  this 
to  31  km,  at  which  point  it  jumps  abruptly  interference  zone  can  be  estimated  as  fol- 
from  6.1  to  8.1  km/sec.  With  this  simple  lows:  The  minimum  length  of  the  ob- 
structure  the  critical  reflection  should  have  served  critical  reflection  pulse  in  seismic 
been  observed  at  70  to  72  km;  in  actual  field  work  is  0.15  to  0.25  second,  and  the 
fact  it  was  observed  strongly  at  88  km  and  pulse  consists  of  three  undulations,  up- 
weakly  at  80  km  from  the  shot.  down-up.   If  there  is  interference,  it  must 

A  model  experiment  carried  out  in  the  occur  between  at  least  two  Fresnel  half- 
laboratory  using  impulses  of  microsecond  wave  zones  generating,  say,  two  of  these 
duration  on  a  two-layered  medium  of  brass  undulations  0.12  second  apart.  For  these, 
and  iron  showed  the  same  effect;  namely,  the  distance  R  from  source  (mirror  image) 
no  refracted  wave  was  visible  above  the  to  surface  must  differ  by  l/2X  (A  =  wave- 
reverberation  level  at  distances  beyond  the  length) .  That  there  is  complete  interfer- 
critical  reflection  where  it  would  be  ex-  ence  at  a  point  means  a  lesser  degree  of 
pected  (though  perhaps  weak) .  interference  along  the  surface  for  a  distance 

The  distance  from  the  impulse  point  to  of,  say,  h.    By  simple  geometry,  the  dis- 


96        CARNEGIE  INSTITUTION  OF  WASHINGTON 


tance,  perpendicular  to  a   (slanting)    ray 
path,  is  V^RA,  and  along  the  earth's  surface 

h  is  about  1.5 V~RX. 

Typical  values  obtained  in  Alaska  give 
£~90  km,  A  =  0.12X6  (km/sec)  =0.7  km, 
leading  to  a  value  of  h  of  about  12  km. 
Thus  the  spread  of  the  interference  pattern 
along  the  earth's  surface  would  be  expected 
to  be  in  the  neighborhood  of  12  km.  In 
this  interval  the  amplitude  of  the  "critical 
reflection"  would  be  expected  to  increase 
with  distance  from  the  source  from  a  low 
to  a  high  value.  The  reflected  pulse  is 
therefore  expected  to  be  weak  at  the  critical 
distance  calculated  from  the  ratio  of  veloci- 
ties by  Snell's  law  and  could  be  obscured 
by  the  reverberation  background.  Thus 
the  total  reflection  might  not  be  observable 
until  well  beyond  the  critical  distance  pre- 
dicted on  a  simpler  basis  without  the  inter- 
ference effect.  Though  the  estimate  is 
crude,  it  is  based  upon  well  known  princi- 
ples and  probably  gives  the  correct  order 
of  magnitude  of  the  interference  effect. 
The  difference  between  70  km  as  calcu- 
lated for  the  critical  reflection  distance  by 
Snell's  law  from  the  observed  upper  and 
lower  velocities  and  the  observed  distance 
of  88  km  when  the  strong  reflections  first 
appeared  is  close  to  the  added  distance 
estimated  by  this  crude  approximation. 

Hence,  the  system  of  reflection  observed 
on  our  Alaskan  expedition  is  indeed  that 
which  must  be  expected  from  the  sim- 
plest form  of  a  single  layer  of  crustal  rock 
overlying  the  mantle,  a  crustal  layer  having 
a  constant  velocity,  that  is,  no  change  of 
velocity  with  depth.  The  conclusions  pre- 
viously reached  about  the  velocity  distri- 
butions in  other  regions  will  have  to  be 
re-examined,  as  we  have  previously  ac- 
cepted the  first  appearance  of  the  critical 
reflection  at  distances  beyond  where  it  was 
expected,  on  the  basis  of  Snell's  law,  as 
evidence  of  moderate  increase  of  velocity 
with  depth.  In  general,  the  increases  in 
velocity  with  depth  that  we  have  previously 
deduced  will  be  diminished.  They  have 
not  been  large,  and  this  new  interfer- 
ence prediction  may  wipe  them  out,  leav- 


ing velocity  constant  with  depth  in  the 
crust,  at  least  in  most  places.  (H.  E.  T., 
M.  A.  T.) 

Gravity  and  the  Earth's  Crust 

The  literature  contains  about  two  thou- 
sand measurements  of  gravity  whose  iso- 
static  corrections  have  been  calculated. 
These  serve  as  the  basis  of  the  general 
belief  in  Airy's  hypothesis  that  high  moun- 
tains are  supported  in  hydrodynamic  equi- 
librium by  a  thicker  crust  floating  in  the 
outer  mantle  of  heavier  rocks.  Our  seismic 
measurements  on  the  Colorado  Plateau 
and  in  Alaska  (Year  Book  52,  1952-1953; 
Year  Book  54, 1954-1955)  have  shown  that 
high  land  areas  and  thick  crustal  regions 
do  not  necessarily  go  together.  The  ques- 
tion then  arises  whether  or  not  there  is 
disagreement  between  the  two  sets  of 
measurements,  gravity  and  seismic. 

An  analysis  of  the  gravity  data  shows 
that  the  data  are  much  too  few  to  give  de- 
tailed crustal  information.  If  all  the  uncer- 
tainties are  taken  into  account,  and  all  the 
data  averaged  together  to  obtain  a  mean 
world-wide  crustal  depth  with  minimum 
apparent  statistical  error,  the  depth  turns 
out  to  be  30  ±20  km.  This  can  hardly  be 
considered  an  accurate  specification  of  the 
depth  to  the  mantle.  For  any  smaller  por- 
tion of  the  earth's  surface,  the  statistical 
situation  is  even  worse.  The  reasons  for 
this  inaccuracy  in  the  specification  of  man- 
tle depth  from  gravity  measurements  do 
not  seem  to  be  widely  recognized.  There 
are  two:  the  data  are  few;  gravity  values 
are  not  sensitive  to  the  "depth  of  compensa- 
tion" (the  depth  at  which  the  excess  weight 
of  the  mountains  is  exactly  balanced  by 
the  defect  of  weight  due  to  flotation  in  the 
heavier  rocks  below). 

The  gravity  measurements  show  wide- 
scale  isostatic  and  free  air  residuals  of  the 
same  size.  Some  of  these  regions  have 
dimensions  of  a  few  hundred  kilometers. 
The  origin  of  the  residuals  is  not  specifi- 
cally known.  They  indicate  wide-scale 
crustal  inhomogeneities,  or  perhaps  a  hori- 
zontal distribution  of  inhomogeneities  in 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        97 


density  in  the  upper  mantle  rocks.  Further 
measurements  of  gravity  may  give  us  some 
better  basis  for  judgment  about  the  nature 
or  cause  of  the  residuals,  and  possibly  some 
indications  concerning  outer  earth  struc- 
tures. (H.  E.  T.) 

International  Geophysical  Year 

In  co-operation  with  the  U.  S.  National 
Committee  for  the  International  Geophysi- 
cal Year  we  are  organizing  a  seismic  expe- 
dition to  South  America.  Using  the  waves 
from  the  large  explosions  regularly  set  off 
in  the  copper  mines  there,  we  will  en- 
deavor to  explore  the  crustal  structure  and 
measure  the  crustal  depths  under  the  high 
Andes  and  the  coastal  plains.  The  mean 
heights  are  about  10,000  feet  near  the  large 
copper  mines  of  southern  Peru  and  north- 
ern Chile.  We  therefore  hope  to  be  able 
to  make  crustal  measurements  under  re- 
gions of  great  topographic  heights,  per- 
mitting a  more  definitive  study  of  the 
effect  of  topographic  height  on  crustal 
depth  than  we  were  able  to  achieve  in  our 
efforts  on  the  Colorado  Plateau  and  in 
Alaska. 

Much  effort  has  been  expended  on  the 
complex  arrangements  necessary  for  an  ex- 
pedition of  this  nature.  Outfitting  six 
vehicles  for  three  months  of  measurements, 
many  of  them  in  locations  without  roads, 
is  an  arduous  and  time-consuming  task. 

Instrumental  development.  The  seismic 
instruments  we  have  designed  and  made 
have  proved  rugged  and  dependable.  They 
are  in  general  sufficiently  sensitive  and 
fairly  portable.  In  some  places,  however, 
the  ground  unrest  is  small  enough  so  that 
amplifier  input  provides  the  limiting  sensi- 
tivity. In  others  there  are  special  oppor- 
tunities to  observe  which  we  miss  because 
of  the  bulk  of  the  equipment  we  must 
carry.  We  have  therefore  constructed  new 
seismometers  and  prototype  transistor 
amplifiers  for  increased  sensitivity  and  de- 
creased bulk. 

The  new  seismometer  has  a  pendulum 
mass  100  times  the  older  seismometer  (the 
total  weight  of  this  new  unit  is  14  pounds) . 


With  this  instrument  the  input  noise  volt- 
age of  the  amplifiers  (usually  1  to  2  micro- 
volts) will  be  one-fifth  to  one-tenth  the 
voltage  produced  by  ground  unrest  in  the 
quietest  spots  of  quiet  regions. 

The  new  transistor  amplifiers  (devel- 
oped by  E.  T.  Ecklund,  of  our  staff)  are 
small,  compact,  and  rugged.  The  circuits 
are  stabilized  by  degeneration  so  that  the 
power  gain  (1,000,000)  is  largely  independ- 
ent of  temperature  and  battery  voltages. 
The  input  fluctuation  voltage  is  compara- 
ble with  but  not  quite  so  good  as  that  of 
a  vacuum-tube  system.  The  combination 
of  the  new  seismometer  and  transistor 
amplifier,  however,  is  far  more  advan- 
tageous in  signal  noise  and  weight  than 
the  system  we  have  been  using  to  date. 
(H.  E.  T.,  M.  A.  T.) 

ROCK  MAGNETISM 
/.  W.  Graham 

Within  the  past  few  years  the  challenges 
presented  by  the  subject  of  rock  magnetism 
have  been  taken  up  vigorously  by  approxi- 
mately a  dozen  research  groups  in  many 
countries  of  the  world.  It  is  not  yet  certain 
what  rewards  will  accrue  from  the  efforts. 
Briefly,  the  subject  has  become  subdivided 
into  two  schools :  one  maintaining  that  the 
rock-magnetism  data  already  at  hand  pro- 
vide justification  for  believing  that  it  is 
now  possible  to  talk  with  considerable  as- 
surance about  large-scale  geophysical  phe- 
nomena like  continental  drift  and  polar 
wandering,  while  the  other  group  holds 
that  the  subject  is  intrinsically  so  complex 
that  no  such  important  conclusions  can  be 
justified  in  our  present  state  of  very  limited 
knowledge.  Each  school  has  been  able  to 
make  a  strong,  but  not  convincing,  case 
for  its  stand. 

The  efforts  at  the  Department  during 
the  past  year  have  centered  on  the  ques- 
tion of  the  possible  influence  of  stress  on 
the  directions  of  magnetization  of  rocks. 
It  is  at  once  clear  that,  in  rocks  which  have 
been  stressed  beyond  the  limit  from  which 
they  can  recover  mechanically  on  being 
relieved,  some  changes  of  magnetic  prop- 


98 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


erties  are  to  be  expected.  Such  rocks,  in 
general,  are  thought  to  have  been  ade- 
quately excluded  from  rock-magnetism 
studies  aimed  at  questions  like  continental 
drift  and  polar  wandering.  But  a  more 
subtle  problem  demands  serious  attention: 
if  a  rock  is  in  a  state  of  nonhydrostatic 
stress  at  the  time  it  is  magnetized  (a  condi- 
tion that  most  certainly  has  frequently 
occurred — for  example,  in  sediments  mag- 
netized after  deposition,  and  in  intrusive 
igneous  rocks),  and  then  the  stress  is  re- 
lieved, the  magnetic  moment  of  the  sample 
may  change  to  another  value,  at  the  time 
of  unloading,  by  virtue  of  the  property 
known  as  magnetostriction.  If  the  mag- 
netization of  rocks  in  general  should  prove 
to  be  particularly  stress-sensitive,  many  of 
the  data  supposedly  bearing  on  the  prob- 
lems of  continental  drift  and  polar  wan- 
dering would  become  immediately  suspect, 
simply  on  the  basis  that  our  knowledge  of 
the  physical  conditions  prevailing  during 
the  time  the  rocks  were  magnetized,  and 
subsequently,  is  woefully  inadequate. 

The  basic  question  of  the  stress  sensi- 
tivity, at  room  temperature  and  atmos- 
pheric pressure,  of  the  magnetization  of 
rocks  is  being  investigated  experimentally 
with  new  equipment  constructed  for  the 
purpose.  The  direction  and  intensity  of 
magnetization  are  measured  with  an  astatic 
magnetometer  while  the  sample  is  held 
under  compressive  stress  of  about  2500  psi 
by  a  simple  nonmagnetic  mechanical  "nut- 
cracker." This  stress  is  about  the  same  as 
would  be  acting  at  the  base  of  a  column  of 
rock  1800  feet  high.  Although  the  ultimate 
stability  and  sensitivity  of  this  particular 
magnetometer  have  not  been  achieved 
(thus  precluding  studies  of  weakly  mag- 
netized sediments,  for  example),  and  the 
force  that  can  be  applied  is  well  below  the 
limit  where  fracture  and  flow  would  begin, 
nevertheless  the  observations  to  date  are  of 
sufficient  importance  and  interest  to  war- 
rant further  elaboration.  They  are  being 
made  in  collaboration  with  J.  R.  Balsley, 
of  the  U.  S.  Geological  Survey,  and  Pro- 
fessor   A.   F.   Buddington,    of   Princeton 


University,  utilizing  the  extensive  suite  o£ 
rocks  on  which  detailed  mineralogical, 
chemical,  and  magnetic  analyses  have  al- 
ready been  performed. 

In  this  laboratory  reconnaissance  it  has 
been  found  that  the  greatest  stress  sensi- 
tivity is  displayed  by  rocks  that  contain 
magnetite  as  the  principal  magnetic  con- 
stituent. If  the  original  natural  magnetiza- 
tion of  the  sample  is  expressed  as  an  in- 
tensity-direction vector,  and  then  the  mag- 
netic vector  of  the  stressed  sample  is  ob- 
served, a  vector  resulting  from  the  stress 
can  be  inferred.  Most,  but  not  all,  samples 
return  reversibly  to  their  original  condition 
when  the  stress  is  released.  For  nearly  pure 
magnetite  (96  per  cent),  the  length  of  the 
stress-induced  vector  may  be  as  much  as 
40  per  cent  of  the  original  vector  for  a 
stress  of  only  2500  psi.  In  contrast,  rocks 
whose  ferromagnetic  minerals  have  com- 
positions between  the  extremes  of  ilmenite 
and  hematite  are  quite  insensitive,  e.g., 
intensity  change  of  1  per  cent  or  less  for  a 
compressive  stress  of  2500  psi.  (See  figs.  3 
and  4.)  No  general  rules  covering  all  rocks 
can  be  formulated  for  the  orientation  or 
sense  of  the  added  vector  relative  to  the 
stress  direction  or  the  original  direction  of 
magnetization.  The  inference  is  that  the 
various  magnetic  components  present  in 
rocks  are  of  both  positive  and  negative 
magnetostrictive  signs,  and  that  there  can 
be  interaction  of  the  magnetostrictive  mo- 
ments with  the  natural  moment  of  the 
sample. 

It  is  worth  while  to  make  an  estimate  of 
some  of  the  ways  in  which  these  findings 
can  be  related  to  what  is  known  of  the 
magnetization  mechanism  of  rocks.  The 
various  ferromagnetic  minerals  that  have 
been  recognized  in  rocks  are  known  to 
cover  a  considerable  spread  in  the  numeri- 
cal values  that  can  be  assigned  to  such 
measurable  properties  as  Curie  point, 
saturation  magnetization,  susceptibility, 
and  variation  of  various  properties  with 
temperature.  It  is  rare  that  in  any  given 
rock  a  single  magnetic  species  occurs; 
usually  two  or  more  coexist,  and  they  may 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        99 


be  intimately  intermingled  or  remotely 
separated  as  discrete  units.  Depending  on 
the  state  of  aggregation,  there  may  be  con- 


25 


50  75 

Percent    of   original   intensity 


100 


Fig.  3.  Figure  3  summarizes  the  magnetic 
changes  that  were  produced  by  increasing  the 
axial  compressive  stress  from  350  to  2650  psi. 
The  results  are  plotted  as  vectors:  the  original 
intensity  at  350  psi  is  taken  as  100  per  cent,  and 
its  angle  relative  to  the  direction  of  compression 
is  plotted.  The  arrow  end  of  the  vector  indicates 
the  intensity  and  direction  of  magnetization  of 
the  stressed  sample. 


FeTiO, 


Fe304 


Fig.   4.    Composition  of  the  rock  samples. 

siderable,  or  little,  magnetic  interaction  of 
the  different  species  on  one  another.  At  the 
time  of  formation,  some  ferromagnetic 
minerals  may  appear  as  metastable  single 


phases  which  slowly  during  geologic  time 
break  down  into  a  mosaic  of  two  or  more 
mineral  species.  Some  ferromagnetic  min- 
erals are  prone  to  marked  alteration  by  the 
simple  process  of  oxidation.  It  is  known 
that  all  these  features  are  important  in  rock 
magnetism. 

To  this  already  complicated  picture  we 
now  add  the  question  of  the  effect  of  stress. 
Reconnaissance  measurements  indicate  that 
stresses,  which  geologically  speaking  are 
almost  trivial,  can  have  a  marked  influence 
on  magnetization.  The  response  of  the 
magnetizations  to  stress  is  such  as  to  indi- 
cate that  different  species  present  are  mak- 
ing different  types  of  contributions  to  the 
change  of  the  magnetization.  It  probably 
would  be  possible  to  describe  the  relative 
magnetostrictive  contributions  of  the  dif- 
ferent ferromagnetic  species  in  a  given 
sample,  but  such  knowledge  gained  today 
would  not  necessarily  have  any  meaning 
to  the  more  interesting  problem  that  we 
have  had  in  view,  namely,  attempting  to 
infer  the  past  directions,  not  to  mention 
intensity,  of  the  earth's  magnetic  field. 
This  is  so  for  two  simple  reasons :  that  we 
can  give  an  accurate  account  neither  of  the 
stress  history  of  the  rock  nor  of  the  chemi- 
cal and  physical  evolution  of  the  magnetic 
species.  It  is  of  course  clear  that,  the  older 
the  rock,  the  greater  will  be  the  uncer- 
tainty. The  only  obvious  way  out  of  these 
difficulties  is  to  have  so  many  field  observa- 
tions from  so  many  rocks  of  so  many  types 
in  so  many  settings  that  the  insidious  in- 
fluence of  magnetostriction,  taken  either 
alone  or  in  conjunction  with  time-depend- 
ent parameters,  is  eliminated.  The  prospect 
is  hardly  encouraging. 

The  ultimate  geophysical  implications  of 
these  observations  are  not  yet  known,  but 
they  certainly  do  not  foster  the  hope  that 
has  prevailed  for  decades  that  by  way  of 
the  techniques  of  rock  magnetism  it  will 
be  possible  to  deal  effectively  with  such 
major  geophysical  questions  as  continental 
drift  and  polar  wandering.  The  present 
observations  do  not  assure  that  such  hopes 
are  beyond  reach;  they  do  call  for  great 


100        CARNEGIE  INSTITUTION  OF  WASHINGTON 


caution,  however,  in  accepting  rock-mag- 
netism data,  of  the  sort  usually  presented, 
as  evidence  bearing  satisfactorily  on  major 
geophysical  phenomena. 

MINERAL  AGE  MEASUREMENTS 

L.  T.  Aldrich,  G.  W.  Wetherill,  G.  L.  Davis,1 
and  G.  R.  Tilton  1 

About  ten  years  ago,  improvements  in 
mass-spectrometric  techniques  and  the  de- 
velopment of  chemical  analysis  by  isotope 
dilution  made  it  possible  to  measure  the 
small  quantities  of  radiogenic  daughter 
products  in  ordinary  rock-forming  min- 
erals. It  thus  appeared  possible  to  extend 
greatly  the  scope  of  mineral  age  measure- 
ments, which  had  previously  been  limited 
to  rocks  containing  uranium  and  thorium. 
Accordingly  work  was  initiated  in  a  num- 
ber of  laboratories  with  particular  attention 
to  the  measurement  of  radiogenic  argon  in 
potassium  minerals,  and  radiogenic  lead 
in  minerals  like  zircon  that  contain  only 
small  quantities  of  uranium. 

In  1950  a  mineral  age  program  was 
started  in  this  laboratory.  The  emphasis 
during  the  first  few  years  was  on  the  de- 
velopment and  quantitative  field  testing 
of  a  mineral  age  method  based  on  the 
decay  of  rubidium  into  strontium  as  well 
as  the  extension  of  the  earlier  work  with 
zircons.  In  1954  potassium-argon  measure- 
ments began. 

Until  the  last  year  workers  in  this  field 
have  been  primarily  concerned  with  the 
following  three  problems:  the  develop- 
ment of  satisfactory  chemical  techniques 
for  analysis  of  microgram  quantities  of  the 
parent  and  daughter  elements;  investiga- 
tions of  the  extent  to  which  minerals  have 
formed  closed  chemical  systems  with  re- 
spect to  the  parent  and  daughter  elements; 
the  accurate  determination  of  the  decay 
constants  for  the  decay  of  the  parent  into 
the  daughter  isotopes.  Contributions  made 
by  this  group  on  these  problems  are  sum- 
marized in  previous  annual  reports. 

1  Geophysical  Laboratory,  Carnegie  Institution 
of  Washington. 


Advances  toward  their  solution  have 
been  substantial  during  the  past  several 
years,  and  although  many  questions  re- 
main unanswered,  emphasis  has  now 
shifted  to  the  application  of  the  techniques 
to  problems  of  geology.  The  shift  in  em- 
phasis is  reflected  in  the  present  report. 
Whereas  in  previous  years  most  of  the  dis- 
cussion has  concerned  the  problems  enu- 
merated above,  a  large  part  of  this  report 
is  devoted  to  actual  geological  applications. 
On  the  other  hand,  concern  with  the  re- 
liability of  the  techniques  has  not  ended. 
As  was  stated  last  year,  agreement  of  the 


0.6      0.7 


0.8      09       |.'0        l.'l         1.2        1.3 
Rb-Sr  AGE/  K-A    AGE  OF  MICAS 


Fig.  5.  Histogram  showing  ratio  of  K-A  age 
to  Rb-Sr  age  of  all  the  mica  samples  for  which 
this  comparison  has  been  made. 

rubidium-strontium  and  potassium-argon 
ages  for  a  sample  of  mica  is  a  good  indica- 
tion that  the  mineral  has  formed  a  closed 
system.  Therefore  an  age  measurement  is 
not  considered  satisfactory  unless  such 
agreement  is  found.  The  results  of  further 
comparisons  of  K-A  and  Rb-Sr  ages  of 
mica  are  shown  in  figure  5.  Agreement 
between  these  two  ages  is  most  common, 
although  not  invariable.  Attention  is  being 
given  to  those  cases  in  which  agreement  is 
not  found  in  order  to  see  whether  the  lack 
of  agreement  is  related  to  the  condition  or 
type  of  rock  or  to  the  history  of  a  particular 
geographical  region. 

It  was  reported  last  year  that  satisfactory 
agreement  between  K-A  ages  of  mica  and 
concordant  U-Pb  ages  of  uraninite  could 
be  obtained  if  the  specific  gamma  activity 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        101 


of  potassium  were  taken  to  be  3.2  y/g/sec.  is  a  long  band  of  approximately  2600- 
During  the  past  year,  an  absolute  counting  million-year-old  rocks  extending  from  Wy- 
experiment  has  been  carried  out  here  oming  through  Montana,  Minnesota, 
which  indicates  that  the  specific  gamma  Manitoba,  and  Ontario  into  Quebec.  Simi- 
activity  is  slightly  higher  than  this,  3.39  ±  lar  areas  of  very  ancient  rocks  have  been 
0.12  y/g/sec.  Thus  even  the  best  micas  found  in  Africa  and  Australia.  Less  corn- 
may  lose  about  5  per  cent  of  their  argon,  plete  data  indicate  similar  regional  epi- 
The  experimental  errors  are  such,  however,  sodes  elsewhere. 

that  the  specific  activities  determined  by  the  These  results  will  be  discussed  in  more 

counting  experiment  and  by  the  geological  detail  in  the  following  sections, 
comparisons  are  not  in  disagreement. 

The  number  of  important  geological  T/ie  specific  Gamma  Activity  of  Natural 
problems  that  are  amenable  to  study  by  Potassium 
these  techniques  is  overwhelming,  and  Until  recently  one  of  the  principal  diffi- 
workers  in  other  laboratories  as  well  as  culties  in  the  determination  of  K-A  ages 
here  have  now  turned  their  attention  to-  has  been  the  lack  of  an  accurate  value  for 
ward  them.  During  the  past  year  our  the  decay  constant  of  K40  for  electron  cap- 
group  has  begun  an  investigation  of  re-  ture  to  A40,  or  its  equivalent,  the  specific 
gional  regularities  in  the  ages  of  the  Pre-  gamma  activity  of  potassium.  In  last  year's 
cambrian  rock  exposures.  That  such  regu-  annual  report  it  was  shown  that  good 
larities  probably  exist  was  suggested  by  the  agreement  was  obtained  between  K-A  ages 
remarkable  agreement  found  between  ages  of  mica  and  concordant  U-Pb  ages  of 
of  rocks  from  various  parts  of  the  Grenville  uraninite  if  a  specific  gamma  activity  of 
subprovince  of  the  Canadian  Shield.  Early  3.2  y/g/sec  were  used.  It  was  pointed  out, 
work  by  Ellsworth  and  subsequent  work  however,  that  probably  the  true  specific 
by  other  investigators  has  demonstrated  gamma  activity  was  slightly  higher  than 
that  over  this  area  of  approximately  10,000  this  and  that  a  few  per  cent  of  the  radio- 
square  miles  all  the  rocks  have  an  age  of  genie  argon  has  been  lost  by  the  mica.  To 
1000  ±100  million  years.  Similarly  in  the  resolve  this  question  an  absolute  counting 
Appalachian  system  almost  all  the  igneous  experiment  has  been  carried  out  which 
and  metamorphic  rocks  had  been  found  to  eliminates  several  of  the  uncertainties  pres- 
have  an  age  of  300  ±100  million  years,  ent  in  earlier  measurements. 
These  results  suggest  the  hypothesis  that  With  the  exception  of  the  recent  experi- 
throughout  earth  history  there  have  been  ment  of  McNair,  Glover,  and  Wilson 
periods  of  a  few  hundred  million  years'  {Phil.  Mag.,  1,  199  [1956]),  all  previous 
duration  in  which  extensive  igneous  and  determinations  of  the  specific  gamma  ac- 
metamorphic  activity  took  place  in  a  given  tivity  have  made  use  of  counting  tech- 
area.  The  techniques  of  age  measurement  niques  that  did  not  distinguish  between  the 
should  make  it  possible  to  discover  the  ionization  produced  by  the  particular 
time  and  places  of  these  orogenic  events  gamma  ray  being  studied  and  other  gam- 
and  to  see  whether  any  regularities  can  be  mas  or  sources  of  ionizing  radiation.  The 
found  in  their  occurrence.  As  an  early  re-  difficulty  is  not  serious  for  K40  because  of 
suit  of  this  investigation  it  has  been  found  the  simplicity  of  its  gamma  spectrum.  But 
that,^  over  a  large  part  of  Arizona,  New  to  know  the  efficiency  of  the  counter  for 
Mexico,  Colorado,  and  Wyoming,  rocks  gamma  rays  of  this  energy  (1.46  Mev)  re- 
were  formed  1350  ±  100  million  years  ago,  quires  calibration  of  the  counter  with  gam- 
and  that  in  Ontario  there  is  a  large  group  mas  from  sources  of  known  specific  ac- 
of  rocks  2600  million  years  of  age.  Com-  tivity.  Unfortunately,  all  the  standard 
bination  of  these  results  with  those  found  sources  for  this  energy  region  either  have 
in  other  laboratories  indicates  that  there  more  than  one  gamma  ray  in  their  spec- 


102 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


trum  or  have  a  serious  uncertainty  in  the 
fraction  of  the  disintegrations  that  involve 
the  emission  of  the  standard  gamma  ray. 
These  difficulties  are  sufficiently  great  to 
account  easily  for  the  wide  spread  in  the 
results  of  earlier  experiments. 

In  the  measurement  of  McNair,  Glover, 
and  Wilson,  referred  to  above,  some  of  the 
difficulties  were  eliminated  by  means  of 
a  Nal  (Tl)  scintillation  spectrometer  which 
enabled  them  to  use  Na24  as  a  standard 
since  they  could  single  out  those  counts 
due  to  the  1.38-Mev  gamma  ray  and  reject 
those  due  to  the  2.75-Mev  gamma  ray. 
In  this  way  they  obtained  a  value  of  3.33 
y/g/sec  for  the  specific  gamma  activity. 
Although  this  experiment  is  superior  to  the 
earlier  ones  that  did  not  make  use  of  a 
scintillation  spectrometer,  two  objections 
can  be  raised  against  it:  the  uncertainty 
in  guessing  the  difference  in  the  efficiencies 
of  the  counter  at  1.38  and  1.46  Mev;  and 
the  fact  that  their  experiment  was  designed 
to  determine  not  the  specific  gamma  ac- 
tivity but  the  (3-y  branching  ratio.  Since  it 
is  the  specific  gamma  activity  that  is  im- 
portant for  age  measurements,  their  value 
of  the  branching  ratio  must  be  multiplied 
by  the  specific  beta  activity,  thus  introduc- 
ing another  serious  probable  error. 

The  specific  gamma  activity  was  deter- 
mined here  with  a  scintillation  spectrom- 
eter; Co60  was  used  as  a  standard  as  well 
as  Na24,  the  efficiency  of  the  counter  being 
thus  determined  at  1.17, 1.33,  and  1.38  Mev. 
The  absolute  activities  of  the  standards 
were  known  as  a  result  of  absolute  beta 
measurements  made  at  the  National  Bu- 
reau of  Standards  by  H.  M.  Seliger. 

A  diagram  of  the  counting  apparatus  is 
shown  in  figure  6.  A  concentrated  solution 
of  potassium  acetate  was  placed  in  the 
counting  bottle  above  the  3  by  3  inch 
Nal(Tl)  crystal.  A  single-channel  pulse- 
height  analyzer  was  used  to  obtain  the 
spectrum  shown  in  figure  7.  The  peak  in 
the  spectrum,  known  as  the  "photopeak," 
represents  all  the  1.46-Mev  gamma  rays 
that  lose  all  their  energy  in  the  crystal. 
The  1.46-Mev  gamma  ray  was  counted  by 


setting  the  bias  of  the  pulse-height  analyzer 
so  that  all  pulses  of  higher  voltage  were 
counted.  The  background  was  determined 


6.3" 


5.4' 


JL 


500  ml   polyethylene  bottle 


Potossium  acetate 
solution 

Polystyrene  cylindrical 
shell 

3"x  3"   No  I  (Tl)  crystal 


Dumont  6363 
Photomultiplier 


JTTTfTJr      Scintillation  counter 


Fig.  6.     Scintillation  counter  for  the  measure- 
ment of  the  specific  gamma  activity  of  potassium. 


20  22  24  26  28  30  32  34  36  38  40  42  44 

Pulse  height- volts 

Fig.  7.  Gamma-ray  spectrum  of  K40.  The 
large  peak  on  the  right  is  the  photopeak  caused 
by  those  gamma  rays  that  have  lost  all  their 
energy  in  the  Nal  crystal. 

in  the  same  way  with  water  instead  of  po- 
tassium acetate  in  the  counting  bottle. 
The  efficiency  of  the  counter  was  meas- 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


103 


ured  by  mixing  standard  Na24  and  Co60  energy  region  from  35  to  40  volts  and  then 
sources  of  relatively  high  specific  activity  using  the  spectrum,  figure  8,  to  make 
in  with  the  potassium  acetate.  The  spectra      corrections  for  the  small  part  of  the  photo- 


30       32       34        36       38 
Pulse    height -volts 


Fig.  8.    Gamma-ray  spectrum  of  Na24  showing  the  photopeak  produced  by  the  1.38-Mev  gamma  ray. 


26 


28 


30 


38 


44 


32  34  36 

Pulse  height-volts 

Fig.  9.     Gamma-ray  spectrum  of  Co60  showing  the  photopeaks  produced  by  the  1.17-  and  1.33- 
Mev  gamma  rays. 

obtained  with  these  sources  are  shown  in  peak  that  does  not  occur  in  this  interval, 

figures  8  and  9.  The  photoefficiency  of  the  It  should  be  emphasized  that  the  photoeffi- 

1.38-Mev  gamma  ray  from  Na24  was  de-  ciency  does  not  depend  in  first  order  on  the 

termined  by  counting  all  the  pulses  in  the  accuracy  of  the  gamma-ray  spectrum,  but 


104        CARNEGIE  INSTITUTION  OF  WASHINGTON 


on  the  counting  rate  for  the  35  to  40  volt 
interval.  Similar  measurements  were  made 
with  Co60.  The  two  photopeaks  were 
counted  by  counting  the  intervals  28  to  34 
and  34  to  40  volts,  respectively.  The  cor- 
rections were  greater  for  Co60  because  of 
the  incomplete  resolution  of  the  two  photo- 
peaks.  Corrections  were  made  for  the 
portion  of  the  1.33-Mev  peak  that  lay  below 
34  volts  by  assuming  that  the  1.33-Mev 
Co60  peak  has  the  same  shape  as  the  1.38- 
Mev  Na24  peak.  Subtracting  out  the  1.33- 
Mev  peak  corrected  in  this  way  from  the 
measured  Co60  spectrum  gives  the  1.17-Mev 
peak.  A  check  was  made  by  comparing 
the  calculated  1.17-Mev  peak  with  the 
photopeak  of  the  1.12-Mev  gamma  ray 
from  Zn65.  The  shape  of  the  two  peaks 
was  identical  within  experimental  error. 
Although  these  corrections  were  rather 
tedious,  the  accuracy  of  the  Co60  photo- 
efficiencies  is  comparable  to  that  of  the 
Na24  photoeffkiency.  For  both  Na24  and 
Co60,  small  additional  corrections  were 
made  for  coincidence  between  the  two 
gamma  rays. 

The  calculated  efficiencies  at  the  three 
energies  1.17, 1.33,  and  1.38  Mev  are  plotted 
in  figure  10.  The  curve  through  these 
three  points  is  extrapolated  to  1.46  Mev. 
The  efficiency  calculated  in  this  way  was 
then  combined  with  the  potassium  integral 
counting  data,  and  the  specific  gamma 
activity  was  found  to  be  3.39  ±0.12  y/g/sec. 
This  value  is  in  agreement  with  the  result 
of  McNair,  Glover,  and  Wilson  (3.33  ±0.15 
y/g/sec),  and  is  about  5  per  cent  higher 
than  that  given  last  year  from  measure- 
ments of  the  radiogenic  argon  content  of 
mica  samples  of  known  age. 

The  Retention  of  Argon  by  Minerals 

A  number  of  analyses  have  been  made 
of  potassium  minerals  whose  age  is  known 
from  concordant  U-Pb  ages  of  cogenetic 
minerals.  By  means  of  the  specific  gamma 
activity  of  3.39  y/g/sec,  the  ratio  of  A40 
to  K40  that  would  be  found  in  the  potas- 
sium mineral  if  all  the  radiogenic  argon 
had  been  retained  can  be  calculated.  Com- 
parison of  this  ratio  with  that  found  by 


analysis  of  the  potassium  mineral  indicates 
the  fraction  of  the  radiogenic  argon  re- 
tained by  the  mineral.  Previously  reported 
measurements  made  by  this  group  have 
been  combined  with  measurements  made 
at  the  University  of  Chicago  by  Wasser- 
burg  and  Hayden  to  calculate  the  retentivi- 
ties  shown  in  table  1.  Adequate  data  are 
available  only  for  mica  and  feldspar  at 
present. 

The  retentivity  of  mica  averages  about 
90  per  cent;  that  of  feldspar  is  consider- 
ably lower.  The  error  in  these  retentivity 


£  .7 

U 

| -6 
g.5 

|!  .4 

01 

A.3 

O 

0-.2 
.1 


1.00 


1.10 


1.20 


1.30 


J.40 


1.50 


E  Mev 


Fig.  10.  The  measured  efficiency  of  the  Nal 
crystal  as  a  function  of  energy.  The  curve  is 
extrapolated  to  1.46  Mev  to  determine  the  effi- 
ciency for  the  K40  gamma  ray. 

measurements  is  about  10  per  cent,  owing 
to  the  uncertainties  in  the  true  value  of  the 
specific  gamma  activity,  the  comparison 
U-Pb  ages,  and  the  analytic  determination 
of  potassium  and  argon.  Thus  it  is  difficult 
to  be  absolutely  certain  that  the  average 
mica  sample  loses  any  argon;  the  data  indi- 
cate, however,  that  micas  probably  lose  a 
small  fraction  of  their  radiogenic  argon 
whereas  feldspars  lose  about  25  per  cent. 
The  mica  ages  in  this  report  are  calculated 
using  a  specific  gamma  activity  of  3.24 
y/g/sec,  which  is  approximately  equivalent 
to  using  3.39  y/g/sec  with  a  5  per  cent 
correction  for  argon  loss. 

There  are  other  minerals  that  contain 
small  amounts  of  potassium,  and  with 
modern  analytical  techniques  it  should  be 
possible  to  measure  their  radiogenic  argon 
content  and  hence  their  retentivity.  It  may 
be  that  minerals  will  be  found  that  retain  a 
greater  fraction  of  their  argon  than  the 
micas. 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        105 


TABLE  1.    Retention  of  Argon  by  Minerals  as 

Indicated  by  Comparison  with  Concordant 

Uraninite  Ages 

Specific  gamma  activity  of  3.39  y/g/sec  and 
specific  beta  activity  of  27.6  (3/g/sec 

(Many  of  these  comparisons  are  obtained  from 

the  work  of  Wasserburg  and  Hayden, 

Geochim.  et  Cosmochim.  Acta,  7,  51 

[1954];  9,  153   [1956].) 


Sample  Location 


Concordant  Argon 

Uranium  Reten- 

Age,  mil-  tivity, 

lion  years  % 


A.  Micas 

1.  Portland,  Conn 267            0.95 

2.  Glastonbury,  Conn 255 

3.  Spruce  Pine,  N.  C 375 

4.  Branchville,  Conn 367 

5.  Parry  Sound,  Ont 994 

6.  Cardiff  Twp.,  Ont 1020 

7.  Wilberforce,  Ont 1030 

8.  Keystone,  S.  Dak.,  lepido- 

lite  1600 

9.  Keystone,  S.  Dak.,  musco- 

vite    1600 

10.  Viking  Lake,  Sask 1890 

11.  Bikita,  S.  Rhodesia   2650 

B.  Feldspars 

1.  Portland,  Conn 267 

2.  Glastonbury,  Conn 255 

3.  New  Bedford,  N.  Y 355 

4.  Branchville,  Conn 367  .75 

5.  Parry  Sound,  Ont.,  micro- 

cline  1  994  .72 

6.  Parry  Sound,  Ont.,  micro- 

cline  2 994  .78 

7.  Parry  Sound,  Ont.,  albite.  .     994  .60 

8.  Cardiff   Twp.,    Ont.,    sam- 

ple 1   1010  .81 

9.  Cardiff  Twp.,   Ont.,   sam- 

ple  2    1010  .76 

10.  Wilberforce,  Ont 1030  .77 

11.  Tory    Hill,    Ont.,    pegma- 

tite    1030  .68 

12.  Tory  Hill,  Ont,  granite...  1030  .68 

13.  Keystone,  S.  Dak 1600  .59 

14.  Viking  Lake,  Sask 1890  .79 

Ages  of  Roc\s  in  the  Canadian  Shield 

For  a  number  of  years  it  has  been  recog- 
nized that  the  pegmatites  intruding  the 
older  rocks  in  the  Grenville  subprovince 
are  approximately  1000  million  years  of 
age.  More  recently,  measurements  of  ages 


of  igneous  and  metamorphic  rocks  in  this 
area  have  shown  that  the  age  of  the 
igneous  intrusion  and  the  metamorphism 
is  likewise  1000  million  years.  Rocks  of 
this  age  have  also  been  found  south  of  the 
Grenville  region  in  New  York  State,  both 
in  the  Adirondacks  and  in  the  Catskill 
Mountains.  Measurements  of  "Grenville 
ages"  made  at  the  Carnegie  Institution  are 
shown  in  table  2,  and  the  location  of  the 
Canadian  samples  on  the  map  (fig.  11). 
Numerous  similar  results  have  been  found 
in  other  laboratories,  but  the  boundaries 

TABLE  2.    Rocks  of  Grenville  Age 


.97 

,88 

Sample  Location 

Age,  million  years 

.99 

K-A 

Rb-Sr 

U238- 

TJ235_ 

.93 

Pb206 

Pb207 

.92 

.87 

1. 

Wilberforce,  Ont. . 

975 

1000 

1040 

1050 

2. 

Cardiff  Twp., 

.81 

Ont 

1010 

1030 

1020 

1020 

3. 

Bancroft,  Ont.  .  .  . 

890 

990 

.95 

4. 

Wavy  Lake,  Ont. . 

1025 

1075 

.93 

5. 

Canada  Hill  gneiss, 

.80 

6. 

BearMt.,N.  Y.. 
Storm  King  gran- 
ite, Bear  Mt., 

930 

1030 

1020 

1060 

.77 
.81 
.77 

N.  Y 

900 

7. 

Natural  Bridge, 

N.  Y 

1025 

1065 

of  this  "Grenville  orogeny"  have  not  yet 
been  established. 

Farther  to  the  north  in  Ontario,  much 
more  ancient  rocks  have  been  found,  all 
approximately  2600  million  years  of  age, 
representing  the  oldest  rocks  that  have 
been  found  in  North  America.  The  data 
are  shown  in  table  3.  As  a  result  of  meas- 
urements made  here  and  elsewhere,  there 
appears  to  be  a  belt  of  these  very  old  rocks 
extending  from  Wyoming  through  Mon- 
tana, Minnesota,  Manitoba,  and  Ontario 
into  Quebec.  In  eastern  Ontario  near  the 
Quebec  border  these  rocks  appear  within 
about  150  miles  of  the  Grenville  rocks,  and 
later  measurements  of  the  rocks  around 
Lake  Timiskaming  in  Ontario  and  Quebec 
may  bring  these  rocks  of  such  different 
age  into  even  closer  contact. 

A  number  of  measurements  have  also 


106        CARNEGIE  INSTITUTION  OF  WASHINGTON 


been  made  on  rocks  lying  in  the  region 
between  these  two  areas.  Here  the  K-A 
and  Rb-Sr  ages  are  generally  in  disagree- 
ment, in  contrast  to  the  other  two  areas 
discussed,  and  also  in  contrast  to  our  previ- 
ous experience.  Some  of  the  discordance 
may  result  from  the  heating  and  partial 
recrystallization  of  the  2600-million-year- 
old  rocks  during  the  Grenville  orogeny, 


but  it  also  seems  probable  that  rocks  of 
intermediate  age  occur  in  this  region.  The 
results  of  these  measurements  are  found 
in  tables  4,  5,  and  6. 

The  Cutler  batholith  (table  4)  intrudes 
the  Sudbury  series,  and  thus  these  sedi- 
mentary rocks  are  older  than  1350  million 
years.  The  agreement  of  the  Rb-Sr  ages 
of  both  mica  and  feldspar  from  the  peg- 


Fig.  11.    Map  showing  the  location  of  samples  from  the  Canadian  Shield. 


TABLE  3.    Rocks  Approximately  2600  Million 
Years  of  Age 

Age,  mil- 
Location  and  Sample  lion  years 

Rb-Sr   K-A 

Hearst,  Ont.,  pegmatite 2605  2595 

Kirkland  Lake,  Ont.,  Round  Lake 

lamprophyre   2600  2450 

Kirkland  Lake,  Ont.,  Round  Lake 

granite    2640  2530 

Timmins,  Ont.,  granite 2470  2520 

Silver  Leaf  Mine,  S.  E.  Manitoba.  .  2640  2210 


matites  and  the  agreement  of  the  K-A  ages 
of  the  micas  and  the  Rb-Sr  age  of  the 
granite  suggest  that  the  batholith  was 
formed  about  1750  million  years  ago  and 
reheated  1350  million  years  ago.  The  data 
are  insufficient  to  establish  these  events, 
however. 

The  Copper  ClifT  (table  5)  rhyolite  is  a 
highly  metamorphosed  rock;  originally  it 
was  probably  an  intrusive  igneous  rock, 
although  some  workers  have  thought  it  to 
be  a  lava   or  a  sedimentary  rock.    The 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


107 


Rb-Sr  and  K-A  ages  are  the  most  dis- 
cordant ones  that  have  been  found.  In 
particular,  the  K-A  age  of  the  mica  is  much 
higher  than  the  Rb-Sr  age. 

Other  ages  found  in  this  region  are 
shown  in  table  6.  Here  are  two  additional 
K-A  ages  appreciably  higher  than  Rb-Sr 
ages.  The  Sudbury  breccia  contains  pieces 

TABLE  4.    Age  Determinations  on  the  Cutler 
Batholith 


Sample 


Age,  million  years 


Rb-Sr 


K-A 


Pegmatite  1     Muscovite 1750  1440 

Feldspar  1760  1165 

Pegmatite  2    Muscovite 1700  1420 

Granite  Biotite  1325  1380 


TABLE  5.    Age  Determinations  on  the  Copper 
Cliff  Rhyolite 


Sample 


Age,  million  years 


Rb-Sr 


K-A 


Muscovite 1730  1390 

Biotite 1220  2130 

Feldspar  2360  1400 

TABLE  6.    Other  Age  Determinations  in  the 
Sudbury  Area 


Location  and  Sample 


Age,  million  years 


Rb-Sr 


K-A 


Sudbury,  gabbro 1325  1830 

Sudbury,  breccia  (matrix) 1440  1870 

Levack,  norite 1830 

Cobalt,  Ont.,  lamprophyre 2050  2160 


of  the  Copper  Cliff  rhyolite  and  the  Mc- 
Kim  formation,  and  hence  these  rocks  are 
older  than  the  mica  in  the  matrix  of  the 
breccia.  Although  the  Rb-Sr  and  K-A  ages 
are  discordant  there  is  little  doubt  that  the 
breccia  is  older  than  1500  million  years, 
and  hence  the  rocks  found  in  the  breccia 
cannot  be  late  Precambrian.  The  Sudbury 
gabbro  intrudes  the  Missasagi  quartzite  at 
Sudbury.  As  a  result  of  the  age  measure- 
ment it  is  found  that  this  rock  is  older  than 


the  Grenville  rocks.  Thus  all  the  rocks 
in  this  region  appear  to  be  intermediate  in 
age  between  the  1000-million-year-old  rocks 
in  the  Grenville  subprovince  and  the  2600- 
million-year-old  rocks  farther  north,  but 
no  conclusions  can  yet  be  drawn  about 
their  exact  ages  and  relationships.  These 
results  illustrate  the  importance  of  meas- 
uring both  the  Rb-Sr  and  the  K-A  ages  of 
a  mica  sample. 

TABLE  7.    Potassium-Argon  and  Rubidium- 
Strontium  Ages  of  Rocks  from  Western 
United  States 

K-A  ages  are  calculated  from  decay  constants 
of  K40  of  Ac  =  0.557x  10-10  yr-1,  Xj3  =  4.72x  lO"10 
yr-1  or  a  total  half-life  of  K40  of  1.31  X  109  years. 
Rb-Sr  ages  are  calculated  using  a  half-life  for 
Rb87  of  50X109  years. 


Sample  Location 


Age,  mil- 
lion years 

K-A   Rb-Sr 


1.    Gneiss,  Zoroaster,  Grand  Can- 
yon, Ariz 1390    1370 

2a.  Lawler  Peak  granite,  Bagdad, 

Ariz 1410     1390 

2b.  Pegmatite  in  Lawler  Peak 

granite    1410     1500 

3.  Pegmatite,  Wickenberg,  Ariz..   1160     1300 

4.  Pidlite  Mine,  Mora  Co.,  N.  M. .   1330     1490 

5.  Granite,     Sandia    Mts.,    Albu- 

querque, N.  Mex 1350    1340 

6.  Harding  Mine,  Dixon,  N.  Mex. .   1300     1300 

7.  Uncompahgre  granite,  Mesa 

Co.,  Colo 1320    1320 

8.  Granite,  Doyleville,  Colo 1320     1310 

9.  Brown  Derby  pegmatite,  Ohio 

City,  Colo 1330    1420 

10.   Granite,  Sherman,  Wyo 1420     1410 

Another  group  of  granitic  rocks  from 
western  United  States  present  interesting 
analyses.  The  ages  of  micas  from  these 
rocks  are  given  in  table  7,  and  the  locations 
of  the  rocks  are  shown  in  figure  12.  The 
sample  numbers  in  the  table  correspond  to 
the  numbered  locations  on  the  map.  Four 
other  locations  are  also  shown  on  the  map. 
The  age  of  the  sample  from  each  of  these 
locations  is  indicated  by  letter,  A  corre- 
sponding to  2500,  B  to  1600,  and  C  to  1100 


108 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


million  years.  The  map  shows  all  the  Pre- 
cambrian  rocks  measured  at  this  laboratory 
from  these  states. 

The  agreement  of  the  ages  in  table  7 
shows  that  the  mica  in  all  these  rocks  was 
formed  close  to  1350  million  years  ago,  and, 
therefore,  that  there  was  widespread  crys- 
tallization of  granitic  rocks  at  that  time  in 


CHEYENNE 


Table  8  gives  the  ages  of  several  South 
African  micas  for  which  both  K-A  and 
Rb-Sr  ages  have  been  measured.  Samples 
from  Manano  and  Karema  were  provided 
by  Dr.  L.  Cahen,  of  the  Belgian  Congo 
Museum.  The  Muika  sample  was  part  of 
the  collection  analyzed  by  L.  O.  Nicolaysen 
several  years  ago  here  at  the  Carnegie  In- 
stitution. From  geologic  evidence  it  was 
thought  that  the  Karema  pegmatite  was 
formed  as  part  of  a  much  earlier  process 

TABLE  8.    Ages  of  African  Rocks 


Sample  Location 

Age,  mil- 
lion years 

K-A       Rb-Sr 

Muika,  Belgian  Congo 

Manano,  Belgian  Congo 

Karema,  Tanganyika  Territory. 

Bikita,  S.  Rhodesia 

Kubuta,  Swaziland  

950         950 

870         975 

980        1100 

2450       2680 

2730       2920 

FORT   o 
WORTH 


SCALE,  STATUTE   MILES 
100  200  300 


(S) 


Fig.  12.    Map  showing  the  location  of  samples 
from  western  United  States. 

this  area.  It  is  suggested  that  this  crystal- 
lization accompanied  a  period  of  regional 
rock  formation  comparable  to  the  period 
of  igneous  intrusion  and  metamorphism 
in  the  Grenville  subprovince.  It  is  also 
evident  that  these  mica  ages  have  been 
preserved  in  spite  of  subsequent  geologic 
events  in  western  United  States  such  as  the 
Laramide  orogeny. 


than  that  which  formed  the  Muika  and 
Manano  pegmatites.  These  measurements 
show  that,  if  this  inference  is  true,  the 
later  process  completely  removed  any  trace 
of  the  earlier  history  of  the  mica  from  the 
Karema  pegmatite.  The  analytical  data  on 
the  Muika  mica  concurred  with  those  ob- 
tained by  Nicolaysen  within  3  per  cent. 

The  Bikita  and  Kubuta  micas  were  also 
part  of  the  Nicolaysen  collection.  The 
Bikita  ages  have  been  presented  before, 
but  are  included  for  comparison  with  the 
Kubuta  ages.  The  Kubuta  ages  are  the 
greatest  obtained  in  our  laboratory  by 
either  the  Rb-Sr  or  the  K-A  method. 


THEORETICAL  AND  STATISTICAL  GEOPHYSICS 

S.  E.  Forbush 


EQUATORIAL  ELECTROJET 

Near  the  magnetic  equator  the  ampli- 
tude, Ah,  of  the  diurnal  variation  in  the 
horizontal  component,  H,  of  the  geomag- 
netic variations  is  unusually  large.  At 
Huancayo,  Peru,  the  abnormality  exceeds 
that  observed  elsewhere.  Along  the  west 
coast  of  South  America,  Ah  was  observed 


in  1949  at  fourteen  stations  by  A.  A. 
Giesecke,  Jr.,  Director  of  the  Instituto 
Geofisico  de  Huancayo.  These  stations  ex- 
tended from  geographic  latitude  3.4°  N 
to  16.2°  S.  The  observed  rapid  decrease  of 
Ah  with  distance  north  or  south  of  the 
magnetic  equator  indicated  a  concentrated 
narrow  band  of  electric  current  flowing 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        109 


eastward  in  the  upper  atmosphere  during  tion  and  of  the  vertical  field  had  not  been 

midday.  This  concentrated  current,  known  measured. 

as  the  equatorial  electrojet,  is  superposed  Continuous  operation  of  the  four  vario- 

on  the  more  diffuse  current  distribution  graphs   during   the   IGY   should   provide 

that   accounts   for   the   normal   quiet-day  data   from   which   to  determine   whether 

magnetic  diurnal  variation,  SQ.  electrojet  effects  occur  in  the  lunar  diurnal 

The  existence  of  the  equatorial  electrojet  variation,    magnetic    sudden    commence- 

effect  on  the  quiet-day  diurnal  variation  ments,  solar-flare  effects,  magnetic  storm 

near  the  magnetic  equator  is  thus  definitely  changes  (Dst) ,  etc.  If  it  turns  out  that  no 

established.  To  determine  whether  similar  electrojet  effects  are  found  for  changes  dur- 

electrojet  effects  occur  for  other  variations  ing  magnetic  storms,  then  the  records  of 

in  the  geomagnetic  field,  and  if  so  to  de-  vertical   intensity   from   the   two   stations 

termine  whether  the  same  electrojet  is  in-  nearest  the  magnetic  equator  promise  to 

volved,  a  chain  of  four  temporary  magnetic  provide  a  measure  for  the  amplitude  of  the 

recording  stations  is  now  being  established  quiet-day   diurnal  variation  and  its  vari- 

for  the  International  Geophysical  Year  on  ability,  which  should  be  free  of  the  effects 

the  west  coast  of  Peru,  to  operate  in  con-  of  magnetic  disturbance  that  often  spoils 

junction  with  the  John  A.  Fleming  Ob-  Bartels'  present  measure  (hw),  based  on 

servatory    of   the    Instituto    Geofisico    de  the  diurnal  variation  of  H  at  Huancayo. 
Huancayo.  At  each  of  the  four  temporary 

TOY    stations    a    nnrtihle    Askania    vario-  VARIABILITY    OF    GEOMAGNETIC   DIUR- 
IGY    stat  ons   a   portable   Askania   vario  ^^  VAJR1ATI0N  AND  0F  /olo- 
graph will  register  the  variations  in  dec-  SPHERIC  WINDS 

lination,  horizontal  intensity,  and  vertical  _               ,                 ,       .,     ,    ,             , 

«,            .        .     J     j            .,  ,  Last  year  s  report  described  the  results 

intensity.    The   proiect   is   made   possible  -          I    .    ,      r    .            ,       .       ,       , 

.          /                            i  t       1     A  or  a  statistical  experiment  showing  that  the 

through  grants  approved  by  the  Geomag-  .     ,       c    F        ,      a           °         , 

.    °    6,     ,  ,  r£T  n  T     ;        .       1n°  magnitude  or  the  solar  Hare,  or  crochet, 

netic  Panel  of  the  U.  S.  International  Geo-  ^    .r   ^   horizontal             etic   com„ 

physical  Year  and  through  the  co-operation  t  ^  Hu  a  was  dennitely  greater, 
of  the  U.  S.  Coast  and  Geodetic  Survey,  ^  ^  ayer  on^d  when  ^  iet_d 
which  has  lent  die  four^  variographs  to  the  ^^  variatioilj  Sqj  in  the  geomagrietic 
Department  of  Terrestrial  Magnetism,  and  fidd  was  greaten  Akhough  the  amplitude 
the  help  of  the  Instituto  Geofisico  de  of  Sq  [s  known  t0  increase  with  sunspot 
Huancayo,  which  has  co-operated  in  the  numDer,  the  size  of  crochets  was  found  to 
preliminary  survey  and  will  manage  the  ^e  independent  of  sunspot  number;  thus 
operation  of  the  five  stations.  the  above  relation  between  crochet  size 
The  preliminary  survey,  using  two  vario-  and  amplitude  of  Sq  was  not  due  to  a  solar 
graphs,  involved  two  or  three  days'  con-  activity  effect  common  to  both.  It  was  con- 
tinuous registration  of  the  variations  in  the  eluded  that  both  effects  could  be  ascribed 
geomagnetic  field  at  each  of  some  sixteen  to  variations  in  the  strength  of  the  wind 
stations.  This  survey  was  begun  in  March  system  that  drives  the  dynamo  responsible 
and  completed  in  May  1957.  The  results  for  Sq,  since  on  days  with  stronger  wind 
provided  a  necessary  guide  to  locate  the  systems  both  the  size  of  crochets  and  the 
final  stations,  and  indicated  an  electrojet  amplitude  of  Sq  would  be  larger, 
with  total  extension  of  roughly  500  miles  In  the  last  few  years  ionospheric  wind 
in  the  north-south  direction.  Moreover,  velocities  have  been  measured  from  the 
these  observations  also  provided  data  from  rate  of  drift  of  meteor  trails  by  Professor 
which  to  calculate  the  height  of  the  electro-  A.  C.  B.  Lovell  and  his  colleagues  at  Jodrell 
jet,  previously  undetermined  since,  near  Bank.  Their  results  showed  that  the  semi- 
the  magnetic  equator,  the  variation  with  diurnal  variation  of  wind  velocity,  in  the 
latitude  of  the  diurnal  variation  of  declina-  range  of  heights  where  it  was  measured, 


110        CARNEGIE  INSTITUTION  OF  WASHINGTON 


had  the  wrong  phase,  according  to  the  Zealand).  The  station  at  Cheltenham 
dynamo  theory,  to  explain  the  quiet-day  (Maryland,  U.  S.)  was  transferred  in  Oc- 
magnetic  variation.  The  results  obtained  tober  1956  to  the  Fredericksburg  Magnetic 
also  showed  large  variations  from  day  to  Observatory  at  Fredericksburg  (Virginia, 
day  in  the  amplitude  of  the  semidiurnal  U.  S.).  Tabulations  of  bihourly  means  of 
wind  components  (N-S  and  E-W)  and  in  ionization  corrected  for  bursts  and  baro- 
the  daily  average  wind  velocity  in  the  N-S  metric  pressure  for  Huancayo  from  1946 
and  E-W  directions.  Professor  Lovell  has  to  1955,  and  for  Cheltenham  from  1937  to 
made  available  to  us  the  amplitudes  of  the  1954,  as  well  as  summaries  for  Godhavn 
semidiurnal  wind  component  for  70  days  and  Christchurch  have  been  published  in 
together  with  the  daily  values  of  the  pre-  volume  XX  of  Carnegie  Institution  of 
vailing  wind  components.  Arrangements  Washington  Publication  175.  These  re- 
have  been  made  to  obtain  constants  for  suits,  compiled  in  collaboration  with  the 
recent  magnetograms  from  Huancayo  Instituto  Geofisico  de  Huancayo,  The  Dan- 
which  will  be  measured  with  a  recently  ish  Meteorological  Office,  The  Department 
constructed  rapid  scaling  device  to  furnish  of  Scientific  and  Industrial  Research,  New 
material  from  which  to  derive  the  ampli-  Zealand,  and  the  U.  S.  Coast  and  Geodetic 
tude  of  Sg.  It  will  then  be  possible  to  de-  Survey,  together  with  those  contained  in 
termine  statistically  whether  the  measured  earlier  volumes,  make  available  to  investi- 
variability  of  the  ionospheric  winds  is  cor-  gators  many  of  the  essential  data  obtained 
related  with  the  variability  of  the  ampli-  since  the  start  of  the  Department's  cosmic- 
tude  of  Sg.  ray  program. 

Large  ionization  chamber.    The  large 

COSMIC-RAY  INVESTIGATIONS  cosmic-ray  ionization  chamber  was  main- 

Twenty-seven-day  variation  in  cosmic-  tained  in  essentially  continuous  operation 

ray  intensity  and  in  the  geomagnetic  field,  at  Derwood  during  the  report  year.   No 

The  phase  and  amplitude  of  the  27-day  solar-flare  effects  have  been  observed  since 

waves  in  horizontal  magnetic  intensity,  H,  February  23,  1956. 

at  Huancayo  have  been  determined  for  Co-operation  in  operation  of  cosmic-ray 
about  155  solar  rotations.  Magnetic  results  meters.  The  successful  operation  of  Comp- 
are expected  shortly  from  Huancayo  for  ton-Bennett  cosmic-ray  meters  over  a  long 
some  of  the  years  after  1947;  these  will  be  period  at  so  many  stations  has  been  possi- 
analyzed  for  the  27-day  waves.  With  re-  ble  only  through  the  wholehearted  and  un- 
sults  already  at  hand  for  the  27-day  waves  selfish  co-operation  of  several  organizations 
in  cosmic-ray  intensity  for  250  solar  rota-  and  individuals.  We  wish  to  express  our 
tions  it  will  thus  be  possible  to  determine  appreciation  to  the  following  organizations 
rather  reliably  whether  there  is  any  signifi-  for  the  operation  and  maintenance  of 
cant  phase  difference  between  the  maxima  cosmic-ray  meters :  The  Danish  Meteoro- 
of  the  cosmic-ray  waves  and  the  minima  logical  Institute  and  the  staff  of  its  God- 
of  the  waves  in  H  at  Huancayo.  The  re-  havn  Magnetic  Observatory  at  Godhavn, 
suits  should  have  a  significant  bearing  on  Greenland;  the  U.  S.  Coast  and  Geodetic 
theories  for  explaining  decreases  in  cosmic-  Survey  and  the  staff  of  its  magnetic  ob- 
ray  intensity  associated  with  magnetic  servatory  at  Cheltenham,  Maryland  (at 
disturbance.  Fredericksburg,    Virginia,    since    October 

Old  cosmic-ray  program.  Compton-Ben-  1956);  the  High  Altitude  Observatory  of 

nett   meters   were   satisfactorily   operated  the  University  of  Colorado  and  its  staff  at 

throughout  the  report  year  at  Godhavn  Climax,  Colorado;  the  Instituto  Nacional 

(Greenland),  Climax  (Colorado,  U.  S.),  de  la  Investigation  Cientifica  and  the  Uni- 

Ciudad    Universitaria    (Mexico,    D.   F.),  versidad  de  Mexico,  Mexico,  D.  F.;  the 

Huancayo  (Peru),  and  Christchurch  (New  Government  of  Peru  and  the  staff  of  its 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        111 


Instituto  Geofisico  de  Huancayo  for  mak-  Scientific  and  Industrial  Research  and  the 
ing  available  the  Compton-Bennett  records  staff  of  its  Magnetic  Observatory  at  Christ- 
from  Huancayo;  and  the  Department  of      church,  New  Zealand. 

LABORATORY  PHYSICS 


NUCLEAR  PHYSICS 

N.   P.  Heydenburg,  G.  M.   Temmer,1  and 
G.  F.  Pieper 

During  the  past  year,  our  continuing 
Coulomb  excitation  studies  of  nuclear  en- 
ergy levels  included  an  investigation  of  the 
gamma  radiation  observed  in  krypton  with 
enriched  targets,  further  analysis  of  the 
gamma-ray  spectrum  of  Fe57,  and  a  study 
of  the  rotational  levels  of  the  dysprosium 
isotopes  with  enriched  targets.  In  addition 
to  the  Coulomb  excitation  work,  we  have 
been  engaged  in  an  experimental  study  of 
the  angular  distribution  and  angular  corre- 
lation of  the  protons  and  gamma  radiation 
emitted  when  fluorine  is  bombarded  by  6- 
to  6.5-Mev  alpha  particles.  The  interest 
here  is  to  determine,  if  possible,  whether 
the  reaction  proceeds  by  compound-nucleus 
formation  or  by  some  direct-interaction 
process. 

COULOMB  EXCITATION  STUDIES 

Krypton.  In  last  year's  annual  report, 
tentative  isotopic  assignments  were  given 
for  the  four  gamma  rays  observed  from 
natural  krypton  bombarded  by  6.4-Mev 
alpha  particles.  With  six  isotopes  present 
in  natural  krypton,  it  was  desirable  to  have 
these  assignments  checked  with  isotopically 
enriched  samples. 

During  the  year  two  gas  samples  of 
krypton  with  different  isotopic  enrich- 
ments were  made  available  to  us  from 
Yale.  In  co-operation  with  C.  E.  Anderson, 
as  a  Guest  Investigator  from  Yale,  these 
samples  have  been  bombarded  here  with 
6.1-  and  6.6-Mev  alpha  particles,  using  our 
high-voltage  equipment.  With  three  tar- 
gets having  different  isotopic  ratios  it  was 
possible  to  make  the  following  gamma-ray 

1  On  leave  of  absence,  1956-1957,  as  Guggen- 
heim Fellow,  Saclay  Laboratories,  Paris,  and 
Institute  for  Theoretical  Physics,  Copenhagen. 


energy  assignments  unambiguously :  Kr78, 
450  kev;  Kr80,  620  kev;  Kr82,  780  kev;  and 
Kr84,  880  kev.  No  gamma  rays  were  ob- 
served in  Kr83  and  Kr86.  One  of  the  tar- 
gets, enriched  30  fold  in  Kr78  (0.35  per 
cent  abundant  in  natural  krypton),  made 
it  possible  to  observe  the  gamma  ray  asso- 
ciated with  this  isotope. 

The  gamma  rays  from  these  even-charge, 
even-mass  isotopes  are  due  to  electric  quad- 
ruple excitation  of  the  first  spin  2+  level. 
The  energies  of  the  2+  states  increase  in  a 
systematic  way  with  increasing  mass  of  the 
krypton  isotope,  whereas  the  gamma-ray 
intensity  decreases.  According  to  nuclear 
shell  theory,  Kr86  has  a  closed  shell  system 
for  neutrons  (neutron  number  50).  Our 
results  for  the  first-excited  states  of  the 
krypton  isotopes  are  consistent  with  the 
now  well  established  trends  of  first-excited- 
state  energies,  which  have  much  lower 
values  for  nuclei  having  partially  filled 
shells  and  rise  to  quite  large  values  at  the 
closed  shells.  Similarly,  the  reduced  transi- 
tion probabilities  B(E2)  decrease  in  ap- 
proaching a  closed  shell.  Again  we  observe 
a  strong  excitation  for  Kr78  and  have  found 
no  evidence  of  a  gamma  ray  for  Kr86. 

Iron.  Natural  iron  has  a  high  abundance 
of  the  isotope  Fe56,  and  the  T  first-excited 
state  of  this  isotope  at  854  kev  is  readily 
excited  by  6-Mev  alpha  particles.  Gamma 
rays  at  123  kev  and  350  kev  are  also  seen; 
they  are  due  to  Fe57,  which  has  an  abun- 
dance of  only  2.2  per  cent  in  natural  iron. 
We  have  investigated  the  energy  levels  of 
Fe57  with  a  target  enriched  to  59  per  cent. 
The  gamma-ray  spectrum  observed  with 
an  alpha-particle  energy  of  4  Mev  is  shown 
in  figure  13.  In  the  present  study  we  have 
been  concerned  with  the  properties  of  the 
third-excited  level  in  Fe57,  since  earlier  in- 
vestigations both  here  and  by  a  group  at 
Oxford  had  established  the  level  scheme 


112        CARNEGIE  INSTITUTION  OF  WASHINGTON 


for  the  first  and  second  levels.  The  level 
scheme  and  associated  gamma-ray  transi- 
tions are  shown  in  figure  14.  We  have 
shown  that  the  350-kev  gamma  ray  is  due 
to  the  Coulomb  excitation  of  a  level  at 
365  kev  rather  than  at  350  kev,  by  observa- 
tions on  the  yield  of  this  gamma  ray  as  a 
function    of    the    alpha-particle    energy. 


15  20  25  30 

CHANNEL    NUMBER 

Fig.  13.  Gamma-ray  spectrum  from  the  Cou- 
lomb excitation  of  Fe57  by  4-Mev  alpha  particles. 
The  solid  line  connected  to  the  peak  at  350  kev 
is  the  shape  of  a  single  gamma  ray  of  that 
energy,  obtained  under  similar  conditions  from 
the  Coulomb  excitation  of  Ru104.  The  dashed 
parabolas  labeled  123  and  228  kev  represent 
the  photopeaks  of  gamma  rays  of  these  energies, 
after  allowance  has  been  made  for  higher-energy 
radiations  and  background.  The  "escape  peak" 
from  the  123-kev  gamma  ray  is  evident  at  about 
channel  9. 

These  results  are  shown  in  figure  15.  The 
theoretical  yield  curves  calculated  from 
Coulomb  excitation  theory  for  the  excita- 
tion of  a  350-kev  and  a  365-kev  level  have 
been  normalized  to  the  experimental  point 
at  4  Mev.  The  curve  for  AE  =  365  kev  is 
in  better  agreement  with  the  experimental 
data.  It  should  also  be  noticed  that  the 
230-kev  gamma-ray  yield  follows  the  curva- 
ture for  AE  =  365  kev.  That  the  230-kev 
gamma  ray  is  also  due  to  the  excitation  of 


the  365-kev  level  and  is  a  cascade  transition 
to  the  137-kev  level  was  shown  by  observ- 
ing coincidences  between  the  230-kev  and 
the  123-kev  gamma  rays. 

Since  the  ground-state  spin  of  Fe57  is  1/2, 
and  only  electric  quadrupole  (E2)  transi- 
tions are  induced  by  Coulomb  excitation, 
the  365-kev  level  can  have  spin  of  either 
3/2  or  5/2.   From  our  results,  5/2  seems 

Fe57(cc.,cc'r)    Fe57 


(5/2-) 


I       13 


J  , 


(5/2-) 


71 


10      I 


(3/2-)- 
(1/2-)- 


23 


YI4  \i 


137 


228 


365  KEV 


350 


137 


14 
0 


Fig.  14.    Proposed  level  scheme  for  Fe57. 

more  likely  for  the  following  reasons:  the 
observed  branching  ratio  for  the  350-kev 
and  the  230-kev  gamma  rays  is  in  much 
better  agreement  with  the  predicted  ratio 
for  spin  5/2  than  for  3/2;  if  the  spin  were 
3/2,  a  transition  to  the  ground  state  by 
magnetic  dipole  (Ml)  radiation  would  be 
more  probable  than  to  the  first-excited 
state,  whereas  for  5/2  spin  only  E2  radia- 
tion is  allowed  to  the  ground  state,  which 
should  be  much  weaker  than  Ml  radiation 
to  the  first-excited  state.  We  observe  the 
transition  predominantly  to  the  first-excited 
state;  a  gamma  ray  of  365  kev  cannot  be 
present  to  an  amount  greater  than  5  per 
cent  of  the  350-kev  gamma  ray. 

Angular  distributions  were  also  observed 
for  the  230-kev  and  350-kev  gamma  rays. 
The  theoretical  predictions  are  not  unique 
for  either  of  the  two  spin  choices,  since 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        113 


Ea   (Mev) 

Fig.  15.  Excitation  curves  for  the  Coulomb 
excitation  of  Fe57  by  alpha  particles.  The  points 
are  the  experimental  gamma-ray  yields.  The 
solid  and  dashed  curves  are  the  theoretical  thick 
target  E2  Coulomb  excitation  functions  for  the 
level  positions  indicated. 


the  Coulomb  excitation  of  enriched  iso- 
topes of  dysprosium,  recently  available 
from  Oak  Ridge.  In  each  of  the  two  even- 
even  isotopes  Dy162  and  Dy164  we  observed 
only  one  gamma  ray,  with  energies  82  kev 
and  75  kev,  respectively.  These  are  due 
to  the  excitation  of  the  first  of  the  rota- 
tional levels  in  the  sequence  having  spins 
2+,  4+,  6+  *  •  *  with  ground-state  spin  0+. 
By  E2  excitation  we  can  excite  only  the 
first  T  level. 

For  odd-A  nuclei  it  is  possible  to  excite 
two  of  the  rotational  levels  by  El  transi- 
tions since  the  levels  have  spins  70  +  l, 
7o+2,  7o  +  3,  *  *  *,  where  h  is  the  ground- 
state  spin.  These  levels,  according  to  the 
theory  of  Bohr  and  Mottelson,  should  have 
energies  given  by 

Z?=J[/(/+l)-/o(/o  +  l)] 

where  /  is  the  spin  of  the  level,  and  S  is 
the  effective  moment  of  inertia  of  the 
rotating  nucleus. 


TABLE  9.     Experimental  Results  from  the  Coulomb  Excitation  of  Fe57 

Column  1  gives  the  energies  of  the  levels  excited  in  Fe57.  Column  2  gives  the  reduced  upward 
transition  probability,  B(E2),  in  units  of  <?2Xl0~48  cm4.  Column  3  gives  F,  the  favored  factor, 
the  ratio  of  the  observed  B(E2)  to  that  expected  for  a  single  particle  transition.  Column  4  gives 
the  energies  of  the  observed  gamma  rays,  and  column  5  the  branching  ratios  of  the  levels  from 
which  they  originate.  Columns  6  and  7  give  S  and  S2,  where  S2  is  the  ratio  of  E2  to  Ml  compo- 
nents in  the  radiation. 


Fe57  Level, 
kev 


B(E2) 


Gamma-Ray 

Energies, 

kev 


Branching, 
per  cent 


E2 

Ml 


137 

0.050 

13 

123 

91 

+  0.19               0.04 

137 

9 

PureE2 

365 

0.033 

8.4 

228 

7 

-0.18                0.03 
+  2.6                 6.7 

350 

93 

+  0.28               0.08 
-90              8000 

another  parameter,  h2,  the  mixing  ratio  of 
E2  to  Ml  radiation,  is  involved  for  the 
downward  transitions.  Our  results  for 
Fe57  are  summarized  in  table  9. 

Dysprosium.  Continuing  our  investiga- 
tions of  the  rotational  bands  that  occur  in 
the  region  of  the  rare-earth  nuclei,  we  have 
observed  the  gamma  rays  resulting  from 


In  our  earlier  survey  of  the  rare-earth 
nuclei  we  had  observed  two  gamma  rays 
in  natural  dysprosium,  one  of  which  at  166 
kev  was  thought  to  be  due  to  the  second 
rotational  level  in  one  or  both  of  the  odd-A 
isotopes  Dy161  and  Dy163.  Targets  en- 
riched to  75  per  cent  were  available  for 
these  two  isotopes.  This  enrichment  proved 


114        CARNEGIE  INSTITUTION  OF  WASHINGTON 


to  be  satisfactory  for  Dy163.  The  166-kev 
gamma  ray  was  found  to  be  due  entirely 
to  this  isotope.  Another  gamma-ray  peak 
at  about  75  kev  was  found  to  be  due  in 
part  to  Dy163  and  in  part  to  the  neighbor- 
ing isotopes  Dy162  and  Dy164.  The  two 
gamma  rays  in  Dy163  at  75  kev  and  166 
kev  are  believed  to  be  due  to  excitation  of 
the  first  and  second  rotational  levels  (of 
the  ground-state  rotational  band).  The 
ratio  of  the  energy  of  the  second-excited 
level  to  that  of  the  first-excited  level  agrees 
within  our  experimental  errors  to  the  pre- 
dicted ratio  calculated  from  the  equation 
above  for  7o  =  5/2,  which  is  the  known 
ground-state  spin  of  Dy163.  A  much  weaker 
gamma  ray  at  about  93  kev  was  observed 
which  could  correspond  to  a  transition 
from  the  second-  to  the  first-excited  rota- 
tional levels.  This  interpretation  was  con- 
firmed by  observing  coincidences  between 
the  93-kev  and  75-kev  gamma  rays. 

The  situation  in  Dy161  was  not  so  simple, 
however;  at  first  sight  there  did  not  ap- 
pear to  be  any  gamma  rays  associated  with 
this  isotope,  but  a  careful  analysis  did 
reveal  a  weak  gamma  ray  at  about  103  kev. 
The  strong  gamma  ray  observed  at  82  kev 
was  accounted  for  by  the  presence  of  the 
neighboring  isotope  Dy162  in  the  sample. 
Further,  the  K  X-ray  peak  which  is  always 
excited  in  these  rare-earth  targets  appeared 
to  be  stronger  than  would  have  been  ex- 
pected from  observations  on  the  Dy162 
target.  It  is  known  that  the  K  X-ray  peak 
results  primarily  (for  excitation  by  alpha 
particles)  from  a  so-called  fluorescence 
process.  In  this  process,  for  example  in 
Dy162,  the  82-kev  transition  can  occur  both 
by  gamma  emission  and  by  conversion 
electron  emission.  In  the  latter  case,  for 
K  conversion,  a  K  electron  is  emitted,  leav- 
ing a  vacancy  in  the  K  shell  which  can  be 
filled  from  a  higher  shell  with  emission  of 
a  K  X-ray.  Hence  it  would  be  expected 
that  the  K  X-ray  peak  should  follow  the 
same  yield  as  a  function  of  alpha  energy 
as  the  82-kev  gamma.  This  was  found  to 
be  true  for  the  Dy162  target  but  not  for 


Dy161.  The  yield  of  the  peak,  having  about 
the  same  energy  as  the  K  X-ray  peak, 
varied  more  slowly  with  energy  than  in 
the  Dy162  target,  and  indeed  it  followed 
a  theoretical  yield  curve  for  the  excitation 
of  a  46-kev  gamma  ray.  Hence,  it  seems 
reasonable  to  believe  that  most  of  this  peak 
is  due  to  a  gamma  ray  of  about  46-kev 
energy.  We  have  suggested  that  this  ray 
is  due  to  the  excitation  of  the  first  rota- 
tional level  and  that  the  weak  gamma  ray 
at  103  kev  is  due  to  the  excitation  of  the 
second  rotational  level.  The  ratio  of  en- 
ergies is  again  in  agreement  with  the  pre- 
dicted ratio  for  the  ground-state  spin  of 
5/2  for  Dy161.  Recently  we  have  heard 
that  evidence  has  also  been  found  for  these 
two  levels  in  inelastic  proton  scattering  by 
Elbek  at  Copenhagen.  The  value  of  % 
the  effective  moment  of  inertia,  calculated 
from  the  energy-level  spacings  for  the  two 
isotopes  Dy161  and  Dy163,  is  quite  different 
— a  rather  striking  result,  since  both  have 
the  same  ground-state  spin. 

INVESTIGATION  OF  THE  MECHANISM  OF 
NUCLEAR  REACTIONS 

In  recent  years  it  has  been  reasonably 
well  established  that  nuclear  reactions 
other  than  elastic  scattering  proceed  by  a 
range  of  mechanisms  lying  between  the 
two  extremes  of  compound-nucleus  for- 
mation and  direct  interaction.  The  picture 
of  the  compound-nucleus  mechanism  is 
that  the  incoming  particle  is  quickly  amal- 
gamated by  the  target  nucleus  to  form  a 
highly  excited  compound  system,  the  en- 
ergy brought  in  by  the  incoming  particle 
being  rapidly  shared  by  all  the  nucleons 
in  the  system.  The  compound  nucleus  thus 
formed  lasts  a  long  enough  time  (perhaps 
10-15  sec)  to  "forget"  how  it  was  formed 
and  then  decays  by  particle  (or  quantum) 
emission  into  an  outgoing  particle  (or 
quantum)  and  a  residual  nucleus.  The 
residual  nucleus  may  be  left  in  an  excited 
state,  and  decay  to  its  ground  state  by 
further  particle  or  quantum  emission.  One 
possible  picture  of  the  direct-interaction 
mechanism  is  that  the  incoming  particle 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        115 


makes  a  two-body  collision  with  one  of 
the  surface  nucleons  of  the  nucleus,  caus- 
ing the  nucleon  to  be  ejected,  while  the 
incoming  particle  is  itself  then  captured 
by  the  remainder  of  the  nucleus. 

The  predictions  of  the  direct-interaction 
reaction  model  differ  from  those  of  the 
compound-nucleus  theory,  especially  with 
regard  to  the  angular  distributions  of 
emitted  particles  and  the  angular  corre- 
lations between  the  incoming  and  out- 
going particles  and  the  gamma  radiation 
which  usually  comes  from  the  residual 
nucleus  if  that  is  left  in  an  excited  state. 

We  have  investigated  the  angular  dis- 
tributions of  protons  and  the  angular  cor- 
relation of  protons  and  gamma  rays  in 
the  F19(a,  p)Ne22  reaction  in  order  to 
characterize,  at  least  to  some  extent,  the 
reaction  mechanism.  The  bombarding  en- 
ergies employed  (6.0  to  6.5  Mev)  are  in  a 
sense  putting  the  direct-interaction  mech- 
anism to  a  rather  severe  test,  since  such  a 
mechanism  is  expected  to  apply  better  at 
higher  bombarding  energies.  Our  results, 
however,  show  some  striking  agreements 
with  the  predictions  of  the  direct-inter- 
action model.  The  best  agreement  in  pro- 
ton angular  distribution,  shown  in  figure 
16,  occurred  for  the  ground-state  transition 
at  £"0  =  6.40  Mev.  By  itself,  the  close  fit  of 
the  experimental  data  to  the  predicted 
yield  based  on  the  direct-interaction  theory, 
[jo(QR)]2*  may  be  taken  as  evidence  for 
this  reaction  mechanism.  We  observed, 
however,  that  a  relatively  small  change  in 
bombarding  energy  alters  the  distribution 
rather  considerably.  Since  the  direct  mech- 
anism should  not  show  any  "resonant" 
behavior,  this  result  presumably  indicates 
a  contribution  to  the  yield  from  compound- 
nucleus  processes.  This  effect  is  shown  in 
figure  17,  in  which  five  proton  angular 
distributions  taken  at  closely  spaced  en- 
ergies are  presented.    Of  these  five,  only 

*  j0  is  the  zeroth-order  spherical  Bessel  func- 
tion; its  argument  is  QR,  where  Q=\  Ka  —  Kp|, 
the  K's  being  the  wave  vectors  of  the  incident 
alpha  particle  and  outgoing  proton,  respectively, 
and  R  being  the  interaction  distance. 


those  at  6.25-  and  6.40-Mev  bombarding 
energies  have  shapes  clearly  interpretable 
in  terms  of  a  direct  interaction.  The  dis- 
tributions at  6.00-  and  6.10-Mev  bom- 
barding energies  do  show  peaks  at  ap- 
proximately the  proper  places  for  the  di- 
rect mechanism,  although  their  shapes  dif- 
fer from  the  shape  characteristic  of  the 
direct  process.  This  difference  in  shape 
and,  even  more  striking,  the  completely 


Fl9(oc,p0)  Ne' 
Eoc  '6  40  Mev 


—     Experiment 
2 


Fig.  16.  Angular  distribution  of  protons  from 
the  ground-state  transition  in  F19(a,  p)Ne22  at 
an  alpha-particle  bombarding  energy  of  6.40 
Mev.  The  dashed  curve  shows  the  theoretical 
prediction  of  the  direct-interaction  reaction  mech- 
anism. 

different  nature  of  the  distribution  at  6.55- 
Mev  bombarding  energy  are  indications  of 
the  existence  of  a  process  additional  to  the 
direct  one  responsible  for  the  result  at 
6.40  Mev. 

The  same  change  of  distribution  shape 
with  bombarding  energy  was  observed  for 
the  protons  corresponding  to  the  first- 
excited-state  transition  in  F19(a,  p)Ne22, 
as  will  be  seen  in  figure  18.  Some  of  the 
data  of  the  figure  (e.g.,  the  distribution  at 
6.10-Mev  bombarding  energy)  can  be  fitted 
fairly  well  by  the  appropriate  direct-inter- 
action prediction  for  this  case,  [J2(QR)]2, 


116        CARNEGIE  INSTITUTION  OF  WASHINGTON 


but  certainly  not  all  the  results  can  be  so 
treated.  The  reason  for  this  rather  pecul- 
iar behavior  on  the  part  of  these  angular 
distributions  as  a  function  of  bombarding 
energy  is  at  present  not  understood  in 
detail. 

It  has  been  pointed  out  by  Butler,  how- 
ever, that  at  low  energies  contributions  to 
the  direct  reaction  from  the  interior  of  the 
nucleus  would  tend  to  alter  the  angular 


for  certain  direct  processes  has  been  de- 
veloped by  Satchler.  It  predicts  that  the 
gamma-ray  yield  should  be  observed  to  be 
azimuthally  symmetric  about  the  direction 
Q  =  Ka—  Kp,  and  also  symmetric  about  a 
plane  through  the  nucleus  perpendicular 
to  Q.  It  is  clear  that  the  direction  Q  is 
specified  by  the  momenta  of  the   alpha 


ANGULAR    DISTRIBUTIONS 


'(*.  P.)   Ne 


ANGULAR    DISTRIBUTIONS 
Fl9t«.P0)N«22 


Ew  -6  55  Mev 


E«  «6.40  Mev 


0         20       40        60       80       100      120       140      160      ISO 
Gp  -  cm  system 

Fig.  17.  Proton  angular  distributions  in  F19 
(a,  /?0)Ne22  as  a  function  of  bombarding  energy 
in  the  range  of  6.00  to  6.55  Mev.  The  insert 
shows  the  excitation  curve  at  9p  =  45°;  it  is  not 
particularly  representative  of  the  total  cross  sec- 
tion. 


distributions,  perhaps  markedly,  from  the 
expected  form,  and  that  under  such  con- 
ditions a  measurement  of  the  angular  cor- 
relation of  the  gamma  radiation  emitted 
in  the  decay  of  the  residual  nucleus  with 
respect  to  the  direction  of  momentum 
transfer,  Q,  would  provide  a  test  as  to 
whether  the  reaction  proceeds  directly  or 
via  compound-nucleus  formation.  We  have, 
for  this  reason,  begun  investigating  the 
correlations  in  the  reaction  F19(a,  /?i)Ne22a? 
(y)Ne22.    The   theory  of  the  correlation 


0         20       40        60       80       100      120      140      160       180 
6p  -  cm   system 

Fig.  18.  Proton  angular  distributions  in  F19 
(a,  /71)Ne22  as  a  function  of  bombarding  energy 
in  the  range  6.00  to  6.55  Mev.  The  insert  shows 
the  excitation  curve  at  0p  =  45°;  it  is  not  particu- 
larly representative  of  the  total  cross  section. 

particle  and  proton;  thus  experimentally 
one  measures  the  number  of  (pi,  y)  co- 
incidences as  a  function  of  the  position  of 
the  gamma-ray  detector,  while  selectively 
detecting  only  pi  protons  at  a  fixed  posi- 
tion. 

Our  first  correlation  was  done  at  Ea  = 
6.40  Mev  and  0P  =  4O°,  <pP  =  0°  (0P  and  4>p 
are  the  polar  and  azimuthal  angles  speci- 
fying the  proton  direction  with  respect  to 
the  beam  direction).  These  angles,  the 
bombarding  energy,  and  the  known  en- 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        117 


F19  (a,/»,  )   Ne22*  (y)  Ne22     Correlations 
Ea   •  6  40  Mev 


180  gy      90  0  90    b7     180 

£y«l80°  ♦y-O0 

Fig.  19.  F19(a,  p1)Ne22a;(Y)Ne22  angular  correlations  at  6.40-Mev  bombarding  energy,  for  pro- 
ton detection  angles  0p  of  0°,  40°,  90°,  and  140°.  The  solid  curve  in  each  correlation  represents  one 
particular  (not  unique)  prediction  of  the  direct-interaction  theory;  it  is  included  to  show  that  the 
results  at  0°,  40°,  and  140°  show  the  symmetries  with  respect  to  0^  (called  Qq  in  the  text)  predicted 
by  the  theory,  while  the  data  at  90°  do  not  show  these  symmetries.  The  inserts  are  the  p±  proton 
angular  distribution  at  6.40-Mev  bombarding  energy  and  a  diagram  of  the  directions  involved  in 
the  reaction. 


118        CARNEGIE  INSTITUTION  OF  WASHINGTON 


ergy  release  of  the  reaction  specify  Q  as 
having  the  direction  0q  =  28°,  <j>q  =  180°. 
The  gamma  counter  was  placed  at  several 
angles  07  for  <py  =  0°  and  4>T  =  180°. 

The  results  of  this  and  three  other  cor- 
relations done  at  6.40  Mev  for  different 
values  of  QP  are  shown  in  figure  19.  The 
symmetry  predictions  of  the  Satchler  the- 
ory are  seen  to  be  rather  strikingly  borne 
out  by  the  results  for  0P  values  of  0°,  40°, 
and  140°.  (The  solid  curve  shown  in  each 
correlation  has  to  do  with  the  details  of 
the  theory;  it  is  not  a  unique  prediction, 
and  somewhat  better  fits  [e.g.,  at  0P  =  40°] 
can  be  obtained  by  using  different  values 
of  the  parameters  in  the  theory.)  The 
failure  of  the  result  for  6P  =  90°  to  show 
the  proper  symmetries  is  equally  striking. 
It  is  possible  that  we  are  observing  one 
type  of  direct  interaction  in  the  forward 
direction  and  another  type  in  the  back- 
ward direction  (of  proton  emission)  while 
in  the  central  region  (0P  =  9OO)  interfer- 
ence effects  between  the  two  types  destroy 
the  correlation. 

In  any  event,  the  fact  that  a  relatively 
simple  theoretical  development,  based  on 
the  Born  approximation,  fits  many  of  the 
data  obtained  in  a  quite  complicated  ex- 
periment is  very  encouraging.  Further 
angular  correlation  experiments  on  this 
reaction  and  on  similar  ones,  especially 
as  a  function  of  bombarding  energy,  should 
throw  additional  light  on  the  actual  proc- 
esses involved  in  nuclear  reactions. 

BIOPHYSICS 

E.  T.  Bolton,  R.  J.  Britten,  D.  B.  Cowie, 

/.  /.  Leahy}  F.  T.  McClure,2 

and  R.  B.  Roberts 

For  ten  years  the  aim  of  our  studies  in 
biophysics  has  been  the  understanding  of 
the  processes  by  which  protein  and  nu- 
cleic acid  are  synthesized.  Although  this 
goal  has  been  constant,  the  activities  lead- 
ing toward  it  have  varied  greatly.  During 

1  Fellow,  CIW,  University  of  California. 

2  Visiting  Investigator.  Home  address:  Ap- 
plied Physics  Laboratory,  Johns  Hopkins  Uni- 
versity, Silver  Spring,  Maryland. 


the  first  years  our  efforts  were  confined 
to  observations  of  the  synthesis  of  rela- 
tively small  molecules.  Later  they  shifted 
to  studies  of  the  metabolic  pools  which 
are  the  precursors  of  the  macromolecules. 
It  is  not  sufficient,  however,  to  consider 
merely  the  gross  chemical  fractions  of  the 
cell,  the  protein,  nucleic  acid,  lipid,  and 
other  fractions;  it  is  equally  important 
to  distinguish  whether  a  specific  protein, 
for  example,  is  located  in  the  cell  wall  or 
in  the  cytoplasm.  For  many  problems  it 
may  also  be  necessary  to  consider  the  or- 
ganization of  the  cell  in  terms  of  some 
framework  larger  than  a  protein  molecule. 
We  have  directed  more  attention  this  year 
to  the  organization  of  the  cell. 

Various  approaches  to  the  problem  of 
cellular  organization  are  possible.  Studies 
of  the  metabolic  pools  show  that  they  are 
sensitive  to  osmotic  shock  and  must,  there- 
fore, be  held  in  some  osmotically  sensitive 
structure.  In  yeast,  two  types  of  pools  can 
be  distinguished,  of  which  one  is  an  im- 
mediate precursor  of  macromolecules  and 
the  other  is  exchangeable  with  outside 
material.  The  application  of  high  pressure 
causes  an  interconversion  of  the  pools,  pre- 
sumably by  alteration  of  cellular  structure. 

The  cellular  structure  as  a  whole  can  be 
altered  by  formation  of  protoplasts  which 
have  weakened  walls  and  lose  the  charac- 
teristic appearance  of  intact  cells.  These 
altered  forms  continue  to  synthesize  pro- 
tein and  nucleic  acid.  A  beginning  has 
been  made  in  the  study  of  the  "particles" 
of  the  cells  and  their  role  in  the  processes 
of  synthesis.  A  new  approach  has  been 
found  in  the  study  of  quite  large  particles 
that  form  spontaneously  from  disintegrated 
cellular  material.  Through  the  use  of 
amino  acid  analogues,  the  mechanism  that 
selects  amino  acids  for  protein  synthesis 
has  been  investigated  by  observing  the 
"mistakes"  a  cell  can  make  in  protein 
formation.  These  various  items,  reported 
in  detail  below,  have  each  contributed  to 
a  better  understanding  of  the  functional 
operation  of  the  cell. 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        119 


AMINO  ACID  POOLS  IN  Escherichia  coli 

Further  studies  have  been  carried  out 
on  the  amino  acid  pools  of  E.  coli  in  order 
to  understand  the  mechanisms  of  pool 
formation  and  maintenance.  The  work 
has  been  guided  by  the  general  idea  that 
a  detailed  understanding  of  the  first  step 
in  amino  acid  incorporation  by  the  cell 
will  supply  a  foundation  for  investigations 
of  the  later  steps  leading  to  macromolecule 
synthesis,  and  may  supply  clues  to  the 
mechanisms  involved  in  the  later  steps. 

Pool  formation  is  an  expression  of  the 
ability  of  the  cell  to  obtain  nutrients  pres- 
ent at  very  low  concentrations  in  the  en- 
vironment and  to  supply  them  to  the  syn- 
thetic machinery  at  high  concentrations. 
This,  perhaps,  allows  significant  simplifi- 
cation of  subsequent  problems  of  macro- 
molecular  synthesis. 

The  principal  question  is  whether  the 
internally  concentrated  substances  are  free 
in  solution  within  the  cell  or  held  in  a 
more  complex  fashion.  If  the  pool  is  simply 
a  concentrated  solution  that  pervades  the 
cell,  then  the  synthetically  active  structures 
within  the  cell  are  bathed  in  this  solution, 
which  is  thus  the  "medium"  in  which  syn- 
thesis occurs.  On  the  other  hand,  the  amino 
acids  of  the  pool  may  be  more  closely  as- 
sociated with  the  substructures  of  the  cell 
responsible  for  protein  synthesis.  They 
might  be  trapped  in  such  substructures 
(as  in  a  brush  heap)  or  be  bound  to  them 
by  labile  chemical  bonds.  In  the  latter  case 
it  would  be  highly  important  to  know  the 
nature  of  the  binding  sites  and  how  in- 
timately they  are  related  to  the  synthetic 
activities. 

The  experimental  work  described  below 
was  aimed  at  distinguishing  between  these 
alternatives.  Although  no  directly  conclu- 
sive experiments  were  devised,  the  totality 
of  the  experimental  evidence  obtained 
showed  that  various  simplified  models 
based  on  these  alternatives  were  inad- 
equate. The  elaboration  of  the  properties 
of  the  pool  obtained  by  these  studies  pro- 
vides a  list  of  critical  requirements  that 


must  be  met  in  the  formulation  of  any 
satisfactory  model. 

Studies  of  the  rate  of  formation,  ex- 
change, and  loss  from  the  pool.  Previous 
studies  have  shown  that  the  pool  formed 
by  growing  cells  is  proportional  to  the 
quantity  of  amino  acid  supplied,  until  the 
pool  approaches  its  saturation  value.  A 
typical  curve  from  which  the  pool  size  and 
rate  of  pool  formation  are  estimated  is 
shown  in  figure  20.  Of  more  direct  in- 
terest for  the  analysis  of  the  mechanism 
of  pool  formation  are  the  relationship  of 
the  pool  size  to  the  external  concentration 


Time  of  sampling,  minutes 


Fig.  20.  Typical  curve  for  the  uptake  of  C14 
proline  by  E.  coli  at  25°  C.  Initial  proline  con- 
centration 10-6  M;  cell  concentration  0.52  mg 
wet  cells/ml.  The  initial  total  rate  of  uptake  of 
proline  may  be  calculated  from  the  slope  of  the 
dashed  line.  The  steady-state  pool  size  and  the 
external  concentration  at  the  time  it  is  achieved 
are  determined  from  the  values  of  am  and  £m 
shown. 

present  at  the  time  a  steady-state  pool  is 
achieved,  and  the  initial  rate  of  pool  for- 
mation. For  the  purposes  of  this  discussion 
the  steady-state  pool  size  is  defined  as  the 
size  of  the  pool  at  the  time  its  rate  of 
change  is  zero.  A  large  number  of  experi- 
ments with  C14  proline  over  the  range  of 
concentrations  from  10~6  M  to  2  X  10~4  M 
have  been  analyzed  in  order  to  study  the 
variation  of  these  two  parameters  with 
external  concentration.  The  steady-state 
pool  size  varies  by  a  much  larger  factor 
than  the  initial  rate  of  pool  formation.  A 
mechanism  sufficient  to  explain  these  re- 
sults will  necessarily  be  much  more  com- 


120        CARNEGIE  INSTITUTION  OF  WASHINGTON 


plicated  than  the  "permease"  mechanism 
proposed  by  Monod  et  al.  (1956)  for  the 
concentration  of  galactosides  in  E.  coli. 

Studies  have  also  been  carried  out  on 
the  rate  of  loss  from  the  pool  when  the 
external  amino  acid  is  removed.  When 
samples  of  cells  at  25°  C  are  caught  on  a 
filter  and  washed  with  the  usual  growth 
medium  (but  no  glucose)  for  varying 
periods,  a  rapid  loss  of  about  20  per  cent 
of  the  pool  is  followed  by  a  very  slow  loss. 
These  experiments  are  complicated  by  the 
continuation  of  protein  synthesis,  and  as 


Exchange  is  observed  with  about  the  same 
time  constant  as  in  A.  For  experiment  C 
another  part  of  the  culture  was  diluted  by 
a  factor  of  30  and  correspondingly  large 
samples  were  taken.  There  is  loss  from 
the  pool  at  a  slower  rate  than  the  exchange 
process  shown  in  B.  Experiment  D  is 
similar  to  C  but  in  place  of  the  dilution 
the  samples  were  washed  on  the  filter  for 
varying  lengths  of  time  with  the  usual 
growth  medium  (with  glucose  omitted). 
The  time  constant  for  D  is  similar  to  that 
for  C. 


B,  add   C12  proline   to  I0"4  molar 
C,  dilute   by  factor  of  30 


Time,   hours 

Fig.  21.  Study  of  rate  of  exchange  and  loss  of  C14  proline  pool  in  E.  coli  at  0°  C.  Cell  concen- 
tration 1.0  mg  wet  cells/ml.  Suspension  incubated  at  25°  C  for  5  minutes  after  addition  of  10~5 
M  C12  proline  and  quickly  chilled  to  0°  C.  Cells  then  centrifuged  and  resuspended  in  unsupple- 
mented  medium  at  0°  C.  After  1  hour,  C14  proline  was  added  for  experiment  A.  In  experiment 
C,  a  part  is  diluted  by  a  factor  of  30  with  supplemented  medium.  For  curve  D  samples  were  washed 
on  the  filter  for  the  times  indicated  with  unsupplemented  medium. 


a  result  good  quantitative  measurements 
of  the  loss  at  25°  have  not  yet  been  ob- 
tained. The  rate  of  loss  after  removal  of 
the  external  amino  acid,  however,  is  very 
much  slower  than  the  initial  rate  of  uptake 
when  the  amino  acid  is  added. 

Similar  studies  have  been  carried  out  at 
0°  C  where  protein  synthesis  is  suppressed 
and  more  accurate  rate  measurements  can 
be  made.  Figure  21  shows  the  results  of 
an  experiment  performed  at  0°  C  in  which 
the  pool  was  labeled  by  exchange  A.  The 
culture  was  then  divided,  and  to  one  part, 
B,  carrier  C12  proline  (10~4  M)  was  added. 


In  another  experiment  (fig.  22)  the  rate 
of  pool  formation  was  measured  at  0°  C. 
It  will  be  observed  that  the  rate  of  forma- 
tion of  pool  (time  constant  4  hours)  is 
considerably  slower  than  the  rate  of  loss 
(time  constant  <1  hour,  fig.  21,  D). 

These  results  at  0°  C  contrast  sharply 
with  those  at  25  °  C,  where  pool  formation 
is  a  much  faster  process  than  loss.  In 
spite  of  this  inversion  of  the  relative  rates 
of  formation  and  loss,  the  pool  sizes  at 
25°  and  0°  C  are  the  same  within  a  fac- 
tor of  2.  It  appears  that  the  equilibrium 
pool  size  must  be  determined  by  other 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        121 


parameters  in  addition  to  the  relative  rates 
of  formation  and  loss,  as  measured  above. 

The  results  suggest  that  the  existence  of 
a  pool  suppresses  the  pool-formation  step, 
and  that  the  existence  of  an  appropriate 
external  concentration  suppresses  the  loss 
step.  Appropriate  temperature  coefficients 
of  the  four  processes  (pool  formation  and 
its  suppression,  pool  loss  and  suppression) 
might  account  for  the  observations. 

Results  reported  in  last  year's  annual 
report  have  demonstrated  that  exchange 
between  pool  and  external  amino  acid  is 
an  important  process  during  pool  forma- 
tion at  25°  C  with  an  energy  source  pres- 


-Total   C14  proline  present 


cur  either  through  reactions  that  are  an 
essential  part  of  the  over-all  mechanism 
of  pool  formation  or  through  reactions 
that  play  no  real  part  in  that  process.  In 
connection  with  the  latter  case,  it  should 
be  noted  that  a  reaction  of  the  type 

A*  +  R-A<^A*-  -R-  -A       A*-R  +  A 

where  R-A  is  some  complex  containing 
A,  would  be  observable  in  an  exchange 
study  but  would  not  necessarily  be  ob- 
servable in  the  process  of  pool  formation, 
since  the  reaction  causes  no  net  change 
in  the  amount  of  the  complex. 

TABLE  10.    Approximate   Rates    of    Formation 
and  Exchange 

The  values  are  expressed  in  millimicromoles 
of  proline  per  minute  per  milligram  wet  cells  at 
an  external  concentration  of  3.5  X  10~6  M  C14 
proline.  No  glucose  was  present  in  the  exchange 
experiments. 


Fig.  22.  Proline  pool  formation  at  0°  C,  1.1 
mg  wet  cells/ml  suspension;  3.4  XlO-6  M  C14 
proline.  Exponentially  growing  cells  chilled  to 
0°  C  for  45  minutes  before  C14  proline  was 
added. 

ent.  Exchange  was  found  to  continue  in 
the  absence  of  an  energy  source,  or  at  0°  C, 
conditions  that  strongly  suppressed  pool 
formation.  Current  studies  show  that  the 
exchange  rate  has  a  relatively  small  tem- 
perature coefficient  whereas  the  rate  of 
pool  formation  has  a  very  large  one  (at 
least,  at  low  temperature,  table  10). 

Table  10  lists  approximate  values  for  the 
initial  rates  of  pool  formation  and  ex- 
change at  25°  and  0°  C. 

Any  satisfactory  model  of  the  amino 
acid  pool  must  certainly  allow  for  the 
occurrence  of  exchange  in  the  absence  of 
an  energy  source  and  for  the  strikingly 
different  temperature  dependence  of  the 
exchange  process  and  the  process  of  pool 
formation.  The  exchange  process  may  oc- 


Tem- 

Rate of 

perature, 
°C 

Pool  Formation 

Exchange 

0 
25 

0.0074 
2.0 

0.18 
0.63 

Miscellaneous  properties  of  the  amino 
acid  pool.  As  mentioned  in  the  last  annual 
report,  cells  suspended  in  high-osmotic- 
strength  media  have  higher  saturation 
values  of  pool  size.  For  example,  when 
proline  (0.07  mg/ml)  is  supplied  to  cells 
suspended  in  1.3  osmolal  medium  (four 
times  the  strength  of  the  usual  growth 
medium),  a  pool  of  about  1000  uM/g  dry 
cells  is  observed.  When  20  mg/ml  of  ca- 
sein hydrolysate  is  supplied  in  the  same 
medium  (1.4  osmolal),  however,  the  total 
pool  for  all  the  amino  acids  is  only  about 
1000  uM/g  dry  cells.  Thus,  whereas  small 
amino  acid  pools  are  unaffected  by  the 
presence  of  other  amino  acids  (except  for 
certain  interactions  of  similar  amino  acids, 
such  as  valine,  leucine,  and  isoleucine)  the 
large  amino  acid  pools  interact  strongly, 
and  are  clearly  not  held  by  mechanisms 
specific  for  each  amino  acid. 


122        CARNEGIE  INSTITUTION  OF  WASHINGTON 


In  order  to  gain  insight  into  the  nature 
of  pool  binding,  experiments  were  carried 
out  to  determine  the  temperature  change 
in  a  thick  suspension  of  cells  when  a  large 
amino  acid  pool  was  released  by  osmotic 
shock.  The  results  indicated  that  very 
little  heat  was  released  or  absorbed  during 
the  process.  The  experimental  limit  was 
about  2  kcal/mole  of  amino  acid  pool. 

Some  exploratory  studies  have  been 
made  on  the  reaction  of  hydroxylamine 
with  the  pool  amino  acids  of  E.  colt.  Hy- 
droxylamine reacts  rapidly  with  acyl  phos- 
phates, anhydrides,  and  halides  to  form 
hydroxamic  acids;  the  corresponding  car- 
boxylates,  amides,  and  peptides  react  very 
slowly.  If  the  pool  amino  acids  were 
present  as  activated  forms  such  as  acyl 
phosphates,  a  fairly  efficient  conversion  to 
the  corresponding  amino  hydroxamic  acids 
would  be  expected  in  the  presence  of  high 
concentrations  of  hydroxylamine.  Experi- 
ments to  test  this  possibility  show  very 
small  yields  of  amino  hydroxamic  acids. 
In  the  two  cases  which  were  tested  with 
great  sensitivity,  identifiable  quantities  of 
leucine  and  tyrosine  hydroxamic  acids  have 
been  observed.  These  quantities,  however, 
correspond  to  a  very  small  fraction  of  the 
total  pool  of  these  amino  acids. 

In  "Mg-deficient"  media  the  ability  to 
form  amino  acid  pools  in  E.  coli  was 
markedly  reduced,  as  was  the  rate  of  incor- 
poration into  the  TCA-precipitable  frac- 
tion. Reductions  of  as  much  as  a  factor  of 
5  in  pool  size  have  been  observed,  but  the 
results  are  quite  variable,  presumably  as 
a  result  of  uncontrolled  traces  of  Mg 
present  in  the  "Mg-deficient"  media. 

When  E.  coli  cells  are  exposed  for  a  few 
minutes  to  a  hydrostatic  pressure  of  20,000 
psi,  a  large  part  of  the  amino  acid  pool 
is  released  to  the  medium.  Even  though 
growth  of  the  cells  is  inhibited  for  an  hour 
or  so  after  the  pressure  is  removed,  most 
of  the  released  pool  is  quickly  reincorpo- 
rated. The  sensitivity  of  the  pool  to  hydro- 
static pressure  presumably  results  from  the 
distortion  of  the  structures  holding  the 
amino  acid  pool,  and  is  probably  related 


to  the  sensitivity  of  the  pool  to  osmotic 
shock. 

Osmotic  effects.  Further  studies  have 
been  carried  out  on  the  effect  of  osmotic 
strength  on  the  amino  acid  pool  in  the 
hope  of  obtaining  insight  into  the  mech- 
anisms that  hold  the  pool. 

The  pool  size  at  low  amino  acid  con- 
centration is  independent  of  the  osmotic 
strength  of  the  medium.  When  a  sudden 
drop  in  osmotic  strength  occurs,  however, 
the  pool  is  partly  removed  and  after  a 
short  time  recovers  to  its  previous  value 
if  the  amino  acid  concentration  remains 
constant.  These  results  were  reported  in 
last  year's  annual  report  without  interpre- 
tation. In  combination  with  later  evidence, 
they  lead  to  the  following  picture  of  the 
process  of  osmotic  shock. 

The  cell  is  initially  in  osmotic  equilib- 
rium with  its  normal  medium.  When  the 
osmotic  strength  is  suddenly  reduced  there 
is  first  a  flow  of  water  into  the  osmotically 
sensitive  structures  along  with  a  slow  loss 
of  solute  from  the  cell.  The  consequent 
stretching  of  the  structures  due  to  the  in- 
ternal pressure  increases  the  permeability 
to  the  solute,  allowing  a  faster  rate  of  loss 
of  solute  molecules.  These  two  processes 
together  finally  lead  to  a  new  osmotic 
equilibrium.  The  dynamics  of  this  process 
are  such  that  the  cell  passes  through  a 
transient  state  in  which  the  structures  are 
distended.  The  loss  of  pool  is  associated 
with  this  loosening  up.  The  structures 
responsible  for  the  holding  of  the  pool  may 
be  either  the  cell  wall  or  membrane  or 
internal  constituents  normally  constrained 
by  the  cell  wall. 

Since  competing  rates  of  flow  of  water 
and  solute  are  involved,  this  picture  sug- 
gests that  a  slow  change  in  the  osmotic 
strength  might  be  less  effective  than  a 
rapid  shock.  Observation  bears  out  the  sug- 
gestion. In  an  experiment  with  a  large  pro- 
line pool  a  reduction  in  osmotic  strength 
of  a  factor  of  3  was  made  in  four  steps  of 
equal  concentration  ratio.  As  a  result,  70 
per  cent  of  the  pool  was  removed.  If  the 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        123 


same  final  osmotic  strength  was  achieved 
in  a  single  step,  90  per  cent  was  removed. 
Further,  when  the  same  final  strength  was 
achieved  through  a  concentration  change, 
graded  continuously  over  several  minutes, 
only  50  per  cent  of  the  pool  was  removed. 

Another  implication  of  this  description 
of  the  process  of  osmotic  shock  is  that 
molecules  which  do  not  ordinarily  enter 
the  osmotically  sensitive  structures  might 
be  able  to  diffuse  in  during  the  transient 
period  when  the  permeability  is  increased. 
In  our  laboratory  jargon  this  process  has 
been  called  "trick  or  treat,"  since  it  was 
suggested  just  after  Halloween  and  brings 
to  mind  the  children's  trick  of  throwing 
in  orange  peels  while  the  door  is  open. 

This  transient  permeability  was  tested 
experimentally  by  giving  a  thick  suspen- 
sion of  cells  at  0°  C  a  sudden  osmotic 
shock  in  the  presence  of  radioactive  S04" 
or  PC>4=.  The  suspension  was  then  diluted 
without  osmotic  shock  to  remove  diffusible 
label,  and  filtered.  A  small  amount  of 
SO/  or  P04=  was  taken  up,  corresponding 
to  about  5  per  cent  of  the  cell  volume  at 
the  external  concentration  of  SO/  or  PO/. 
Various  controls  showed  that  this  uptake 
was  indeed  due  to  the  sudden  downward 
change  in  osmotic  strength.  Upward  os- 
motic shocks  neither  remove  the  pool  nor 
cause  the  trick-or-treat  phenomenon. 

This  phenomenon  may  shed  some  light 
on  earlier  observations  of  the  paradoxical 
conditions  required  for  efficient  produc- 
tion of  mutations  with  Mn++,  as  described 
in  the  annual  report  of  1951-1952  (Year 
Book  51).  Effective  production  of  muta- 
tions occurred  when  cells  suspended  in 
saline  were  transferred  to  low-osmotic- 
strength  medium  containing  Mn++. 

Studies  have  been  made  of  the  osmotic 
effectiveness  of  various  solutes  for  protec- 
tion of  a  preformed  pool  or  its  removal  by 
osmotic  shock.  The  experiments  were  per- 
formed by  collecting  on  a  filter  cells  con- 
taining a  C14  proline  pool,  and  briefly 
washing  (5  seconds)  with  the  following 
types  of  solutions:  (A)   the  solute  at  the 


same  osmotic  strength  as  the  growth  me- 
dium (0.37  osmolal)  dissolved  in  growth 
medium;  (B)  the  solute  at  this  osmotic 
strength  dissolved  in  water;  and  (C)  solu- 
tion as  in  A,  followed  by  a  wash  with  the 
usual  growth  medium.   Table  11  summa- 

TABLE  11.     Osmotic  Effects  of  Various  Solutes 
on  E.  coli  Proline  Pool 


Solutes 


Percentage  of  Pool  Removed 


A, 
upshock 


Butanol 77 

Diethylene  glycol    .  .  30 

Ethyl  acetoacetate    .  .  50 

Methanol    20 

Ethanol 20 

Propanol    20 

Acetone    10 

Propionamide   10 

Succinimide 20 

Acetamide    20 

Dioxan   5 

Glycerol    5 

Urea    5 

NaCl  0 

NaAC  3 

Diethylamine  HC1  .  .  6 

Tris  HC1   8 

Glycine 1 

Alanine    3 

Valine 5 

Proline    5 

Glucosamine  HC1  ...  0 

Xylose 0 

Glucose 0 

Galactose    0 

Sucrose  0 


c, 

B, 

upshock 

protec- 

and 

tion 

down- 

shock 

100 

77 

70 

95 

90 

50 

100 

20 

100 

20 

100 

20 

100 

15 

100 

20 

100 

20 

100 

50 

95 

40 

99 

70 

97 

63 

38 

55 

60 

50 

35 

60 

35 

55 

16 

47 

12 

50 

12 

60 

30 

60 

5 

50 

10 

52 

10 

52 

10 

45 

5 

70 

A.  Washed   on  filter  with  solute  at  0.37  os- 
molal in  growth  medium. 

B.  Washed   on   filter  with   solute  at   0.37  os- 
molal in  H20. 

C.  As  in  A  followed  by  wash  with  growth 
medium. 

rizes  the  results.  Since,  in  general,  upward 
osmotic  shock  has  no  effect  on  the  pool,  A 
simply  measures  possible  chemical  or  de- 
structive effects  on  the  cells.  Compounds 
such  as  butanol  remove  most  of  the  pool. 
Washes  of  type  B  measure  the  effectiveness 


124        CARNEGIE  INSTITUTION  OF  WASHINGTON 


of  the  solute  as  an  osmotic  protector  for 
short  periods  of  time.  It  will  be  seen  that, 
in  general,  high-molecular-weight  com- 
pounds are  most  effective,  although  the 
zwitterion  glycine  (M.W.  75)  is  an  effec- 
tive protector  but  glycerol  (M.W.  92)  is 
not.  It  is  presumed  that  solutes  which 
do  not  act  as  protectors  are  able  to  enter 
the  osmotically  sensitive  structures  rapidly. 
The  resulting  excess  water  activity  outside 
causes  water  to  flow  in  until  the  distension 
allows  internal  osmotic  constituents  to  leak 
out,  re-establishing  equilibrium. 

Washes  of  type  C  measure  the  effect  of 
a  sudden  doubling  of  the  osmotic  strength 
followed  rapidly  by  a  return  to  the  usual 
medium.  Compounds  like  acetone  which 
enter  the  cell  rapidly  without  causing 
damage  (as  shown  by  the  figures  in  col- 
umns A  and  B)  do  not  cause  significant 
removal  by  downward  osmotic  shock.  On 
the  other  hand,  compounds  like  urea  and 
glycerol,  which  are  not  effective  protectors, 
are  capable  of  removing  the  pool  by  os- 
motic shock. 

A  sudden  increase  of  the  osmotic 
strength  of  the  medium  causes  a  quite 
different  effect  from  a  sudden  decrease. 
When  a  growing  cell  suspension  is  sud- 
denly mixed  with  an  equal  volume  of 
medium  containing  1  M  sucrose,  synthesis 
of  nucleic  acid  and  protein  stops.  After 
a  period  of  roughly  8  minutes,  the  syn- 
thetic activities  resume;  during  this  period 
the  metabolic  pool  materials  continue  to  be 
incorporated.  Similar  effects  are  observed 
with  glucose  and  sodium  chloride,  but 
proline  causes  no  major  effect. 

If  the  cells  are  washed  with  Tris  me- 
dium just  after  sucrose  is  added,  there  is 
no  loss  of  P32-labeled  pool  materials.  At 
the  end  of  8  minutes  a  Tris  wash  removes 
half  the  pool.  It  appears  that  the  sucrose 
penetrates  slowly  into  some  structure  of 
the  cell  associated  with  holding  the  P32- 
labeled  pool.  Before  the  sucrose  has  pen- 
etrated, the  structure  is  perhaps  dehy- 
drated, causing  the  cessation  of  synthesis. 
After  the  sucrose  has  penetrated,  the  struc- 


ture can  be  osmotically  shocked  by  wash- 
ing the  cells  with  Tris.  It  is  striking  that 
the  period  for  this  action  is  quite  different 
from  the  period  required  for  sucrose  to 
penetrate  the  cell  wall  of  lysozyme-treated 
cells  in  the  procedure  for  protoplast  for- 
mation. It  may  also  be  significant  that 
glucose  has  the  same  action,  whereas  it  is 
less  effective  in  the  protoplast  procedure 
(see  below). 

An  observation  of  considerable  interest 
from  the  point  of  view  both  of  the  osmotic 
properties  of  the  cell  and  of  the  mechanism 
of  pool  formation  is  that  different  types 
of  pools  appear  to  have  different  sensitivity 
to  osmotic  shock.  Both  amino  acid  pools 
and  P32-labeled  pools  are  completely  re- 
moved by  a  quick  water  wash  at  room 
temperature;  at  0°  C,  however,  while  the 
amino  acid  pools  are  still  completely  re- 
moved, only  half  of  the  P32-labeled  pool  is 
removed.  Osmotic  shocks  (at  room  tem- 
perature) that  remove  half  of  the  amino 
acid  pool  will  remove  considerably  less  of 
the  P32-labeled  pool.  It  also  appears  that 
when  very  large  amino  acid  pools,  formed 
at  high  osmotic  strength  with  casein  hy- 
drolysate,  are  partially  removed  by  osmotic 
shock,  the  amino  acid  distribution  is  con- 
siderably altered. 

These  observations  indicate  that  various 
pool  materials  are  organized  in  different 
ways  within  the  cell,  and  perhaps  are  asso- 
ciated with  different  substructures. 

Some  studies  have  been  made,  by  means 
of  freezing-point  measurements,  of  the  re- 
lease of  the  total  osmotically  active  material 
of  the  cell  by  osmotic  shock.  The  results 
are  broadly  similar  to  those  of  studies  of 
amino  acid  pools.  Water  washes  remove 
the  total  osmotically  active  constituents  al- 
most completely.  Boiling  of  the  cells  after 
water  washing  releases  only  traces  of  addi- 
tional material  effective  in  depressing  the 
freezing  point  of  water.  When  the  osmotic 
shock  is  performed  in  small  steps,  the  re- 
lease of  the  total  osmotically  active  material 
is  similar  to  the  release  of  amino  acid  pools, 
though  perhaps  a  somewhat  greater  per- 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


125 


centage  is  released  for  the  same  shock. 
The  total  released  from  the  cell  indicates 
that,  if  this  material  is  osmotically  active 
when  present  in  the  cell,  the  osmotic  pres- 
sure within  the  cell  is  slightly  greater  than 
that  of  the  medium  and  is  dependent  on 
the  osmotic  strength  of  the  medium.  If 
this  material  were  concentrated  in  regions 
smaller  than  the  whole  cell,  the  osmotic 
pressure  would  be  proportionately  higher. 

Unusual  behavior  is  exhibited  by  a  thick 
water  suspension  of  water-washed  cells.  If 
such  a  suspension  is  cooled  somewhat  be- 
low 0°  C  (in  a  vigorously  stirred  freezing- 
point  cell),  and  an  ice  crystal  is  added  to 
seed  the  crystallization,  the  temperature 
rises  initially  as  in  a  typical  freezing-point 
experiment.  The  temperature  rises  higher 
than  0°  C,  however,  and  continues  to  rise 
slowly  and  steadily  as  heat  is  extracted. 
When  the  temperature  reaches  about 
+  0.7°  C,  stirring  of  the  mixture  becomes 
difficult.  If  the  system  is  now  removed 
from  the  cooling  bath  and  allowed  to  stand 
(with  stirring)  in  the  air,  the  temperature 
falls.  The  fall  can  be  made  more  precipi- 
tous by  immersing  in  hot  water.  If  the 
system  is  returned  to  the  cold  bath  (—2° 
C),  the  temperature  rises.  This  anomalous 
behavior,  an  apparent  negative  heat  ca- 
pacity, is  reversible  provided  that  the  tem- 
perature is  kept  in  the  range  of  0  to  +0.7° 
C.  The  cause  of  this  apparent  negative 
heat  capacity  has  not  yet  been  determined. 

Summary  of  the  properties  of  the  met- 
abolic pool  in  E.  coli.  The  properties  of 
the  pool  that  must  be  incorporated  in  any 
model  may  be  summarized  as  follows. 

1.  Energy  is  required  for  formation  of 
the  pool  but  not  for  maintenance  of  a 
preformed  pool. 

2.  Pools  are  formed  very  slowly  at  0°  C, 
and  preformed  pools  are  maintained. 

3.  Exchange  occurs  independently  of  any 
energy  source.  The  temperature  coefficient 
of  the  exchange  process  is  small;  that  for 
formation  is  very  large. 

4.  Small  pools  are  not  influenced  by  the 
presence  of  other  amino  acids,  but  large 
pools  are  suppressed. 


5.  When  the  external  amino  acid  is  re- 
moved, the  pool  is  lost  at  a  much  slower 
rate  than  that  at  which  it  was  initially 
formed. 

6.  The  initial  rate  of  pool  formation  and 
the  pool  size  do  not  have  the  same  de- 
pendence on  amino  acid  concentration. 

7.  Pools  are  removed  by  osmotic  shock, 
but  not  all  pool  compounds  are  removed 
equally. 

8.  The  saturation  value  of  the  pool  is 
roughly  proportional  to  the  osmotic 
strength  of  the  medium. 

As  yet  no  model  incorporating  all  the 
features  necessary  to  provide  for  the  eight 
properties  listed  above  has  been  worked 
out  in  sufficiently  critical  detail  to  be  tested 
against  the  available  data. 

AMINO  ACID  POOLS  IN  YEAST 

Kinetic  studies  have  shown  that  in 
Candida  utilis  pool  formation  is  a  pre- 
liminary and  necessary  step  in  macro- 
molecule  formation.  For  nucleic  acid  syn- 
thesis two  chemically  distinct  and  func- 
tionally different  purine  pools  are  known. 
The  first,  a  concentrating  pool,  accumulates 
nucleic  acid  bases  within  the  cell  at  levels 
exceeding  their  external  concentrations. 
This  pool  is  evident  only  when  the  syn- 
thetic medium  is  supplemented  with  bases. 
The  pool  size  is  variable  and  dependent 
upon  external  concentration.  Once  concen- 
trated, these  bases  may  provide  material 
for  the  second,  a  nucleotide  pool,  which 
is  always  present  and  remains  constant  in 
size  during  exponential  growth.  Here  con- 
version of  one  nucleotide  to  another  oc- 
curs, furnishing  the  appropriate  molecules 
for  nucleic  acid  synthesis. 

Evidence  has  accumulated  indicating  the 
existence  of  two  functionally  distinct 
amino  acid  pools  (in  yeast)  analogous  to 
these  pools  of  purine  compounds. 

Kinetic  studies  of  pool  formation  from 
exogenous  amino  acids.  It  has  been  shown 
previously  that  during  exponential  growth 
in  media  containing  fructose  as  the  sole 
carbon  source  13  per  cent  of  the  cellular 
carbon  is  contained  in  an  amino  acid  pool. 


126        CARNEGIE  INSTITUTION  OF  WASHINGTON 


It  is  now  known  that  the  total  amount  of 
amino  acid  pooled  in  the  cell  can  be  in- 
creased by  the  addition  of  amino  acids  to 
the  growth  medium. 

Exogenous  amino  acids  are  quickly  in- 
corporated by  exponentially  growing  cells. 
Figure  23  shows  the  time  course  of  incor- 
poration of  trace  quantities  of  C14  glutamic 
acid.  The  tracer  "pulse"  appears  first  in 
the  cold  trichloroacetic  acid  (TCA) -soluble 
fraction,  and,  as  the  small  quantity  of 
exogenous  amino  acid  becomes  exhausted, 
the  transfer  of  pool  radiocarbon  (cold- 
TCA-soluble  fraction)  to  the  protein  frac- 
tion is  observed.    These  results  resemble 


Total 

3- 

• 

s 

Cold -TCA- preopitable  fraction 

£   2' 

1 

1 

1/ / 

><  i- 

,Cold-TCA-soluble  traction 

i 

§ 

Q: 

0- 

Fig.  23.  Time  course  of  incorporation  of  tracer 
quantities  of  C14  glutamic  acid.  At  time  =  0,  the 
exogenous  concentration  was  0.002  mg  glutamic 
acid/ml  medium. 

those  obtained  in  the  investigation  of  the 
kinetics  of  incorporation  of  exogenous 
purines,  and  demonstrate  that  the  incor- 
porated amino  acid  is  contained  in  a  met- 
abolic pool  which  may  supply  amino  acid 
carbon  for  protein  synthesis.  Similar  re- 
sults have  been  obtained  with  a  variety  of 
C14-labeled  amino  acids  supplied  to  C. 
utilis  growing  exponentially  in  C  medium. 
When  concentrations  of  exogenous 
amino  acids  are  higher,  the  quantity  of 
amino  acid  contained  in  the  cold-TCA- 
soluble  fraction  increases  and  exceeds  the 
external  concentration.  Table  12  shows  the 
accumulation  of  C14  threonine  in  the  cold- 
TCA-soluble  fraction  with  increasing  con- 
centrations of  exogenous  threonine.  For 
comparison,  table  13  shows  the  steady-state 
distribution  of  pool  amino  acid  and  protein 
amino  acid  found  in  cells  grown  in  C 


medium  when  fructose  was  the  sole  carbon 
source.  These  data  demonstrate  that  the 
size  of  the  pool  concentrated  from  exoge- 

TABLE  12.    Distribution  of  C14  Threonine 

Carbon  among  Pool  and  Protein 

Amino  Acids* 


C14 

Threonine, 

Concentration 
of  Exogenous 

[iM/g  dry  weight  cells  f 

C14  Threonine, 

Cold-TCA- 

Cold-TCA- 

(aM/ml  medium 

Soluble 

Precipitable 

Fraction 

Fraction 

50.0 

....   442 

520 

8.4 

....   354 

446 

6.7 

....   268 

328 

5.0 

....    190 

272 

3.4 

....   104 

149 

1.7 

....     32 

82 

0.8 

9 

41 

*  Cells  grown  from  light  inoculum  to  about 
2.8  mg  wet  weight  of  cells  per  ml  medium. 

t  Calculated  on   the  basis  that  all  the  radio- 
carbon incorporated  remained  C14  threonine. 

TABLE  13.     Steady-State  Distribution  of  Radio- 
carbon among  Pool  and  Protein  Amino  Acids* 

Pool  Protein 

Component         Quantity  rf   Quantity  of 

r  Compound,   Compound, 

uM/g  dry       uM/g  dry 

Isoleucine-leucine  117  785 

Lysine 24  625 

Glutamic  acid 290  640 

Aspartic  acid    9  762 

Valine 65  512 

Alanine 240  695 

Threonine    8  455 

Serine   8  600 

Proline   7  287 

Arginine    63  210 

Glycine  108  488 

Per  cent  accounted  for. .     87  85 

*  Data  obtained  from  cells  growing  exponen- 
tially in  C  medium  containing  C14  fructose. 

nous  amino  acids  depends  on  the  external 
concentration  and  may  greatly  exceed  the 
pool  formed  endogenously  from  fructose. 
Chromatographic  examination  of  hy- 
drolysates  of  the  cold-TCA-soluble   and 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        127 


precipitable  fractions  of  cells  grown  at  the 
highest  concentration  of  exogenous  thre- 
onine (50  uM/ml  medium)  showed  that 
more  than  90  per  cent  of  radiocarbon  in 
the  TCA-soluble  fraction  was  contained 
in  threonine,  with  the  remainder  in  iso- 
leucine.  In  the  protein  fraction,  however, 
the  ratio  of  radioactivity  in  these  two 
amino  acids  was  about  one-to-one. 

Amino  acid  pool  characteristics.  The 
size  of  pool  formed  from  fructose  carbon 
is  constant.  Furthermore,  the  addition  of 
high  concentrations  of  exogenous  amino 
acid  produces  no  immediate  dilution  or  ex- 
change with  the  existing  pool.  The  trans- 
fer to  protein  of  these  pool  amino  acids  is 
uninterrupted  by  the  addition  of  the  amino 
acid  supplements.  On  the  other  hand,  the 
exogenous  amino  acids  are  rapidly  incor- 
porated by  the  cell  (fig.  23)  and  accumu- 
lated to  levels  exceeding  their  external  con- 
centration. Thus,  there  are  two  pools  of 
amino  acids,  one  formed  from  fructose,  the 
other  from  exogenous  amino  acids;  for 
convenience,  they  will  be  called  the  in- 
ternal and  expandable  pools  of  amino 
acids,  respectively. 

The  amino  acids  of  the  internal  pool  are 
not  lost  to  the  medium  during  exponential 
growth,  nor  are  they  exchanged  with 
exogenous  amino  acids.  In  the  expandable 
pool,  however,  the  situation  is  quite  differ- 
ent, as  can  be  seen  from  the  results  of  ex- 
periments on  cells  grown  in  C  medium 
containing  fructose  and  supplemented  by 
a  high  concentration  of  C14-arginine  (1.0 
mg/ml  medium).  The  kinetics  of  incor- 
poration of  radiocarbon  into  pool  and 
protein,  followed  during  this  labeling 
growth  period,  showed  that  approximately 
two-thirds  of  the  protein  arginine  was  be- 
ing derived  from  fructose  carbon  and  one- 
third  from  the  amino  acid  supplement. 
After  3l/2  hours  of  growth  in  this  medium 
the  cells  were  harvested  and  washed  twice 
with  C  medium,  and  an  aliquot  was  trans- 
ferred to  C  medium  containing  nonradio- 
active arginine  (1.0  mg/ml,  culture  A). 
Since  the  quantity  of  amino  acid  incor- 
porated during  growth  in  the  labeled  me- 


dium was  quite  small  in  comparison  with 
the  total  quantity  present,  the  cells  were 
exposed  to  an  essentially  constant  environ- 
ment of  exogenous  arginine.  Another 
aliquot  was  added  to  C  medium  containing 
no  arginine  (culture  B).  At  the  time  of 
transfer,  57  per  cent  of  the  incorporated 
radiocarbon  was  contained  in  the  cold- 
TCA-soluble  fraction.  Optical-density 
measurements  indicated  that  growth  pro- 
ceeded after  the  transfer  with  no  delay  in 
the  unsupplemented  culture  (B)  and  with 


80  r 


60  80  100 

Time ,  minutes 

Fig.  24.  Upper  curves  =  loss  of  radioarginine 
from  cells  after  transfer  to  nonradioactive  C 
medium  containing  1.0  mg  C12  arginine/ml 
{A)  or  unsupplemented  C  medium  (B).  Lower 
curves  =  incorporation  of  radioarginine  carbon 
into  protein  fraction  of  C.  utilis  after  transfer 
of  labeled  cells  to  nonradioactive  C  medium 
(A  and  B  as  above). 

only  a  slight  delay  (10  min)  in  the  other 
(A). 

Both  groups  of  cells  lose  radiocarbon  to 
the  medium,  as  is  shown  in  figure  24,  but 
the  loss  in  B  (no  supplement)  is  less  rapid 
than  in  A.  In  B,  reincorporation  of  the 
undiluted  radioactivity  becomes  evident  in 
about  an  hour.  These  results  may  be  inter- 
preted as  follows.  Where  no  supplement 
was  added,  the  expandable  pool  decreases 
for  two  reasons :  there  is  a  continuous  flow 


128        CARNEGIE  INSTITUTION  OF  WASHINGTON 


into  the  internal  pool  and  thence  into  pro- 
tein, and  there  is  an  approach  to  a  new 
equilibrium  with  the  medium.  When  the 
expandable  pool  has  reached  a  small 
enough  value  through  these  two  processes, 
and  the  external  concentration  has  reached 
a  large  enough  value,  incorporation  of 
radiocarbon  into  protein  again  increases. 
In  experiment  A,  the  loss  of  expandable- 
pool  radiocarbon  is  due  to  transfer  through 
the  internal  pool  into  protein,  and  to  ex- 
change with  the  nonradioactive  arginine  in 
the  medium.  This  exchange  process  is 
faster  than  the  loss  of  pool  material  to  the 
medium  in  B.  These  results  are  similar  to 
those  obtained  with  E.  coli  discussed  ear- 
lier in  this  report.  The  continuous  and 
large  dilution  in  experiment  A  results  in  a 
steadily  decreasing  specific  radioactivity  of 
both  pools.  Consequently,  there  is  a  stead- 
ily decreasing  rate  of  radiocarbon  incor- 
poration into  the  protein.  The  protein- 
incorporation  curve  can  be  quantitatively 
predicted  on  the  assumption  that  the  cell 
processes  as  measured  in  the  S^-hour  pre- 
labeling  continued  (except  for  the  slight 
lag),  and  the  only  change  in  circumstances 
was  the  introduction  of  the  exchange  of 
radioactivity  between  the  pool  and  me- 
dium. 

The  rate  of  incorporation  of  radiocarbon 
into  protein  in  the  case  of  the  unsupple- 
mented  medium  (B)  is  not  immediately 
changed  by  the  transfer,  but  it  falls  as 
radiocarbon  from  the  expandable  pool  is 
lost  to  the  medium.  Apparently  the  pro- 
portion of  the  flow  of  arginine  carbon 
through  the  internal  pool,  which  is  derived 
from  the  expandable  pool  (as  contrasted  to 
that  derived  from  fructose),  is  a  function 
of  the  size  of  the  expandable  pool.  As  the 
flow  from  the  expandable  pool  decreases, 
the  specific  radioactivity  of  the  internal 
pool  also  decreases,  and  there  is  a  conse- 
quent reduction  in  the  rate  of  incorpora- 
tion of  radiocarbon  into  protein. 

In  figure  25  the  logarithms  of  the  radio- 
activity in  the  cold-TCA-soluble  fraction 
in  the  two  experiments  described  above  are 
plotted  against  the  time  after  the  transfer 


to  the  nonradioactive  medium.  In  both 
experiments  the  data  can  be  approximated 
by  a  pair  of  straight  lines.  In  A  the  early, 
fast  component  presumably  represents  the 
combined  effects  of  exchange  and  transfer 
to  protein  via  the  internal  pool,  whereas 
the  slow  component  reflects  the  decrease  in 
specific  radioactivity  of  the  internal  pool. 
Since  the  internal  pool  is  constant  in  size 
and  undergoes  no  exchange,  the  rate  of 
dilution  of  its  specific  radioactivity  is 
limited  by  the  rate  of  protein  synthesis. 
In  B,  the  slower  component  again  reflects 


50 1- 


Cold-TCA- soluble  fraction 


40         60  80  100 

Time,  minutes 


140 


Fig.  25.  Loss  of  pool  radioarginine  after 
transfer  of  labeled  cells  to  nonradioactive  C 
medium  {A  and  B  as  in  fig.  24) . 

the  transfer  of  internal  pool  carbon  to  pro- 
tein while  the  faster  component  includes 
the  approach  to  the  new  equilibrium  be- 
tween the  expandable  pool  and  the 
medium. 

Effect  of  hydrostatic  pressure.  Studies 
have  been  made  of  the  effect  of  pressure 
treatment  on  the  stability  of  the  amino 
acid  pools  in  yeast.  Exponentially  growing 
cells  were  labeled  by  a  2-minute  immer- 
sion in  C  medium  containing  carrier-free 
C14  fructose.  The  cells  were  washed  by 
centrifugation  in  nonradioactive  C  me- 
dium, and  then  resuspended  in  C  medium 
without  fructose.  These  cells  contained 
87  per  cent  of  the  incorporated  radiocarbon 
in  the  TCA-soluble  fraction. 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


129 


An  aliquot  of  these  cells  was  compressed 
in  a  pressure  cell  at  30,000  psi.  This  pres- 
sure was  rapidly  applied  and  released  10 
times  over  a  5-minute  interval.  C12  fructose 
was  added  to  the  treated  culture,  the  cells 
were  aerated  at  30°  C,  and  the  growth  and 
fate  of  the  labeled  pool  carbon  were  meas- 
ured. Figure  26  shows  that  64  per  cent 
of  the  incorporated  radiocarbon  was  lost 
from  the  cells  to  the  medium  during  the 
first  90  minutes  of  aeration.  The  remain- 


TIME    IN   MINUTES 

Fig.  26.  Loss  of  radiocarbon  from  cells  (up- 
per curve)  and  metabolic  pools  (lower  curve) 
after  cells  were  subjected  to  a  pressure  of  30,000 
psi. 

ing  pool  radiocarbon  was  transferred  to 
protein  or  nucleic  acid.  No  increase  in 
optical  density  was  observed  until  after 
100  minutes,  when  growth  resumed,  and 
the  cells  were  soon  growing  at  the  optimal 
rate. 

A  control  culture  of  these  labeled  cells 
not  subjected  to  pressure  continued  to  grow 
exponentially  upon  addition  of  fructose 
and  lost  only  a  few  per  cent  of  incorporated 
radiocarbon  to  the  medium  during  the  90- 
minute  interval. 

Simple  rupture  of  cellular  membranes 
cannot  be  responsible  for  the  release  of 


internal  pool  amino  acids  to  the  medium. 
No  loss  of  the  pool  is  observed  after  the 
pressure  treatment  unless  fructose  is  added 
to  the  culture.  Thus,  both  energy  and  time 
are  required  for  the  release  of  pool  ma- 
terials. Furthermore,  microscopic  examina- 
tion during  the  course  of  the  experiment 
showed  no  cell  fragments  or  visible  cellular 
alterations. 

One  explanation  of  the  observed  results 
is  that  the  pressure  treatment  disrupts  the 
pool  organization  and  reorganization  must 
occur  before  growth  resumes.  Evidence 
supporting  this  conclusion  was  obtained 


20  40  60  80  100  120  140  160 

TIME    IN   MINUTES 

Fig.  27.  Kinetics  of  incorporation  of  C14  fruc- 
tose in  C.  utilis  after  cells  were  subjected  to  a 
pressure  of  30,000  psi. 

in  another  experiment  by  following  the 
kinetics  of  C14  fructose  incorporation  im- 
mediately after  the  pressure  treatment. 
Figure  27  shows  that  rapid  incorporation 
of  fructose  carbon  occurs.  Initially  this  in- 
corporation is  due  to  pool  reconstruction, 
since  most  of  the  incorporated  radiocarbon 
appears  in  the  TCA-soluble  fraction.  The 
pool  appears  to  reach  saturation  in  90  min- 
utes, at  which  time  the  quantity  of  radio- 
carbon contained  in  the  TCA-soluble  frac- 
tion corresponded  to  two-thirds  of  the  nor- 
mal steady-state  value  of  the  internal  pool. 
This  incorporation  is  approximately  equal 
to  the  quantity  of  pool  material  lost  from 
the  cells  (fig.  26)  and  therefore  represents 
replenishment  of  the  pool.  No  increase  in 
the  optical  density  of  the  cells  was  ob- 
served until  120  minutes  after  the  addition 
of  the  fructose. 


130        CARNEGIE  INSTITUTION  OF  WASHINGTON 


The  effect  of  osmotic  shoc\.  The  in- 
ternal pool  of  amino  acids  is  relatively 
insensitive  to  osmotic  shock.  C14-fructose 
labeled  cells  lose  from  3  to  8  per  cent  of 
their  internal  pool  material  when  sus- 
pended for  half  an  hour  in  distilled  water. 
About  the  same  loss  is  observed  when 
these  labeled  cells  are  transferred  to  non- 
radioactive C  medium.  The  amino  acids 
in  the  expandable  pool,  on  the  other  hand, 
behave  quite  differently.  Cells  were  grown 
for  several  hours  in  medium  containing 
6  uM  C14  threonine/ml,  then  harvested 
and  washed  twice  in  unsupplemented  me- 
dium. An  aliquot  was  chemically  frac- 
tionated, and  the  quantity  of  C14-threonine 
carbon  found  in  the  TCA-soluble  fraction 


ably  due  to  a  distortion  of  the  structures 
binding  the  pool. 

Conclusions.  Two  functionally  distinct 
amino  acid  pools  exist  in  C.  utilis.  The 
major  characteristics  of  these  two  amino 
acid  pools  are  compared  in  table  14. 

The  fact  that  these  two  pools  display 
such  different  characteristics  and  do  not 
rapidly  equilibrate  with  each  other  in  the 
cell  indicates  that  they  are  physicochemi- 
cally  distinct.  It  seems  unlikely  that  phos- 
phorylated  forms  could  account  for  this 
difference,  since  there  is  insufficient  pool 
phosphorus  (300  uM/g  dry  weight  cells) 
available  even  for  the  1000  uM  of  amino 
acids  in  the  internal  pool.  The  expandable 
pool  can  be  even  larger  than  the  internal 


TABLE  14. 

Major  Characteristics  of  Amino  Acid  Pools  in  Candida  utilis 

Characteristic 

Expandable  Pool                                                   Internal  Pool 

Function  Concentrates  exogenously  supplied  ami- 

no acids. 

Size  Variable  and  dependent  upon  exoge- 

nous amino  acids  concentration. 

Stability  Sensitive  to  osmotic  shock.   Exchanges 

with  exogenous  amino  acids. 


Interconverts  and  selects  amino  acids 
for  protein  incorporation. 
Fixed. 

Insensitive  to  osmotic  shock.    Not  ex- 
changeable with  exogenous  amino  acids. 


corresponded  to  56  uM/g  dry  weight  of 
cells.  This  value  is  seven  times  the  con- 
centration found  for  threonine  in  the  in- 
ternal pool  (see  table  13).  When  another 
aliquot  of  these  labeled  cells  was  suspended 
in  water  the  cells  immediately  lost  50  per 
cent  of  the  total  pool  radiocarbon  to  the 
water. 

The  internal  pool  of  amino  acids  in  cells 
subjected  to  a  pressure  of  30,000  psi  be- 
comes very  sensitive  to  osmotic  shock. 
Cells  labeled  with  a  5-minute  immersion 
in  medium  containing  C14  fructose  were 
harvested  and  found  to  have  80  per  cent 
of  the  incorporated  carbon  in  the  TCA- 
soluble  fraction.  An  aliquot  of  these  cells 
after  the  pressure  treatment  lost  31  per  cent 
of  the  internal  pool  carbon  when  sus- 
pended in  distilled  water.  A  control  sus- 
pension (no  pressure)  lost  6  per  cent  to 
the  water  wash.  The  sensitivity  of  the  in- 
ternal pool  to  hydrostatic  pressure  is  prob- 


pool,  but  no  additional  incorporation  of 
P32  occurs  when  large  quantities  of  exoge- 
nous amino  acids  are  rapidly  accumulated 
in  the  expandable  pool.  Thus,  neither  the 
internal  nor  the  expandable  pool  can  be 
explained  on  the  basis  of  phosphorylation 
of  the  amino  acids.  Some  correlation  be- 
tween phosphorus  turnover  and  amino 
acid  accumulation  would  be  expected  if 
phosphorus  were  associated  with  these 
amino  acids. 

It  has  been  suggested  that  the  internal 
pool  is  complexed  with  macromolecular 
components  of  the  cell.  The  only  class  of 
substances  present  in  sufficient  quantity  to 
accommodate  the  internal  pool  amino  acids 
are  the  cellular  proteins.  A  one-to-one 
complex  between  protein  amino  acids  and 
pool  amino  acids  would  require  that  25 
per  cent  of  the  protein  be  so  involved. 

From  the  known  molar  distribution  of 
internal  pool  and  nucleic  acid  carbon  there 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


131 


would  be  3.3  times  too  many  amino  acids 
for  a  one-to-one  correlation  between  pool 
amino  acid  and  nucleotide  residues.  A 
mixture  of  protein  and  nucleic  acid  could, 
of  course,  serve  as  a  complexing  system. 

It  seems  likely  that  macromolecules,  most 
probably  the  proteins,  are  the  sites  of  asso- 
ciation for  the  internal  pool  amino  acids. 
These  amino  acids  are  on  the  main  line 
of  protein  synthesis,  and  are  more  tightly 
bound  than  those  in  the  expandable  pool. 
The  internal  pool  is  more  closely  linked  to 
the  mechanisms  of  final  protein  incorpora- 
tion, for  it  is  here  that  amino  acid  inter- 
conversions  and  selection  for  protein  incor- 
poration occur. 

In  the  expandable  pool  the  amino  acids 
accumulated  do  not  interconvert,  as  can  be 
seen  from  the  data  of  table  12.  The  thre- 
onine concentrated  by  the  cells  grown  on 
the  highest  exogenous  threonine  concentra- 
tion remained,  for  the  most  part,  as  pool 
threonine,  but  a  small  portion  was  con- 
verted to  pool  isoleucine.  This  isoleucine 
and  a  small  quantity  of  the  total  pool  thre- 
onine are  probably  components  of  the  in- 
ternal amino  acid  pool.  The  demonstration 
in  this  experiment  that  protein  threonine 
and  isoleucine  both  become  about  equally 
radioactive  even  though  there  is  a  large 
disparity  in  their  pool  concentrations  re- 
inforces this  conclusion.  Figure  28  is  a 
schematic  diagram  of  the  flow  of  carbon 
from  exogenous  amino  acids  and  from 
fructose,  via  the  metabolic  pools,  to  pro- 
teins as  interpreted  from  these  studies. 

These  kinetic  investigations  describing 
the  flow  of  exogenous  carbon  through 
metabolic  pools  and  hence  into  protein 
provide  a  more  definite  picture  of  some  of 
the  preliminary  steps  in  protein  formation. 
In  addition,  they  reveal  that  the  amino 
acid  composition  of  the  cell  may  vary, 
reflecting  the  kind  and  quantity  of  exoge- 
nous molecules.  This  altered  composition, 
in  turn,  affects  the  endogenous  flow  of 
fructose  carbon  which  alone,  in  the  ab- 
sence of  other  exogenous  organic  mole- 
cules, is  a  satisfactory  carbon  source.  Such 
studies  demonstrate  the  great  capacity  of 


some  living  cells  to  utilize  ever-changing 
environments  economically. 

PROTOPLASTS 

The  effects  of  lysozyme  on  the  structure 
and  function  of  E.  coli.  In  order  to  study 
the  macromolecular  composition  of  the 
bacterial  cell  by  physicochemical  methods, 
such  as  ion  exchange  and  ultracentrifuga- 
tion,  it  is  necessary  to  disrupt  the  cell  and 
release  its  contents.  The  use  of  the  enzyme 
lysozyme,  together  with  osmotic  shock, 
has  proved  an  efficient  way  of  breaking 


Exogenous  - 
threonine  «- 


Fructose  - 


Cold  -TCA-  soluble 
fraction 


Fig.  28.  Flow  of  threonine  carbon  through 
metabolic  pools  in  the  synthesis  of  protein. 

E.  coli.  The  conditions  for  lysis  and  physi- 
cal studies  of  the  lysates  are  described  be- 
low. Lysozyme  and  osmotic  shock  may 
also  be  used  to  inflict  controlled  damage 
upon  E.  coli  and  thus  provide  altered  cells, 
spherical  forms  which  are  usually  called 
"protoplasts."  Study  of  these  forms  should 
prove  helpful  in  evaluating  what  struc- 
tures of  the  cell  must  remain  intact  in 
order  for  macromolecule  synthesis  to  occur 
at  normal  rates.  Metabolic  studies  on  the 
spherical  forms  are  described  in  the  follow- 
ing paragraphs. 

Lysis  due  to  lysozyme  treatment  and 
osmotic  shoc\.  Cultures  of  E.  coli  growing 
or  resting  in  various  media  (C  medium, 
C  medium  diluted  with  9  volumes  of 
water,  or  C  medium  containing  18  per  cent 
sucrose)  show  no  response  to  added  lyso- 


132        CARNEGIE  INSTITUTION  OF  WASHINGTON 


zyme    (100    ug/ml).    They   neither    lyse,  complete  and  rapid  lysis.    On  the  other 

show  an  impaired  growth  rate  (15°,  23°,  hand,  when  the  osmotic  pressure  of  a  lyso- 

or    37°    C),    nor    exhibit    morphological  zyme-sucrose  suspension  of  cells  was  slowly 

change   visible   in    the    phase-contrast   or  lowered  by  the  dropwise  addition  of  dis- 

dark-field   microscopes.    When   such   cul-  tilled   water,  lysis  failed  to   occur.    Such 

tures  are  harvested,  washed  free  of  excess  "decompressed"  cells  were  morphologically 

lysozyme  by  centrifugation,  suspended  in  and  metabolically  indistinguishable  from 

0.5  M  sucrose,  and  suddenly  diluted  with  untreated  bacteria. 

10  volumes  of  distilled  water,  the  bacteria  From  these  results  it  was  evident  that 
continue  to  maintain  their  normal  rodlike  the  presence  of  lysozyme  and  a  consider- 
structure  and  upon  subculture  grow  as  well  able  osmotic  shoc\  were  necessary  to  cause 
as  the  corresponding  control  (lysozyme-  lysis.  Since  osmotic  shock  results  from  a 
omitted)  cultures.  It  appears  that  under  relatively  high  intracellular  concentration 
these  conditions  lysozyme  does  not  seri-  0f  solute,  the  opportunity  was  afforded  to 
ously  damage  E.  coli.  If,  however,  lyso-  test  the  rate  at  which  various  solutes  en- 
zyme is  injected  into  a  suspension  of  cells  tered  and  left  the  cell.  When  E.  coli  were 
in  0.5  M  sucrose  a  few  seconds  before  sud-  suspended  in  0.5  M  sucrose-lysozyme  solu- 
den  dilution  with  10  volumes  of  water,  tion  for  varying  lengths  of  time  and  sud- 
nearly  complete  lysis  occurs  and  a  highly  denly  diluted,  complete  lysis  occurred  only 
viscous  solution  containing  numerous  free  after  30  to  60  seconds'  equilibration  of  the 
cell  walls  results.  An  electron  micrograph  cells  with  the  suspending  medium.  Al- 
of  several  of  these  cells  walls  is  shown  in  ternatively,  when  bacteria  that  had  been 
figure  29,  plate  3.  Ultracentrifugal  analysis  equilibrated  with  a  0.5  M  sucrose  solution 
of  the  viscous  solution  shows  a  pattern  of  were  first  suddenly  diluted  and  then  lyso- 
sedimenting  components  typical  of  those  zyme  was  added  after  increasing  intervals, 
observed  in  cell  juices  of  E.  coli.  A  sedi-  lysis  occurred  only  in  those  cells  that  had 
mentation  diagram  is  shown  in  figure  30,  less  than  1  minute's  exposure  to  the  dilute 
plate  4.  medium.  Thus,  enough  sucrose  to  cause 
The  influence  of  molecular  size  of  the  osmotic  lysis  can  enter  or  leave  E.  coli 
solute  particle  on  the  ability  of  E.  coli  to  cells  in  about  a  minute, 
lyse  was  tested  by  suspending  cells  in  Amino  acid  utilization  by  E.  coli  proto- 
various  solutions  isotonic  with  0.5  M  plasts.  E.  coli  protoplasts  may  be  efficiently 
sucrose,  adding  lysozyme,  and  diluting  the  prepared  from  exponentially  growing  cul- 
suspensions  suddenly  with  10  volumes  of  tures  by  suspending  the  cells  in  0.5  M 
water.  The  degree  of  lysis  was  found  to  sucrose  in  C  or  Tris  medium,  adding  lyso- 
increase  with  increasing  molecular  weight  Zyme  (100  ug/ml),  and  suddenly  diluting 
of  the  solute  particle.  Thus,  inorganic  salts  the  suspension  with  an  equal  volume  of 
(NaCl,  Na2S04,  C  medium  salts)  and  water.  In  about  20  minutes  at  25°  C  (10 
low-molecular-weight  organic  compounds  min  at  37°  C)  the  suspension  consists  of 
(urea,  glycerol,  Tris,  sodium  succinate,  85  to  95  per  cent  protoplasts.  Under  these 
sodium  glutamate,  casamino  acids)  caused  conditions  protoplast  formation  requires 
no  change  in  the  suspension  of  cells.  With  considerable  time  and  is  a  temperature- 
glycine,  however,  lysis  occurred  slowly,  sensitive  process.  The  walls  of  these  forms 
Xylose,  sorbitol,  mannitol,  inositol,  and  enclose  volumes  from  2  to  50  times  those 
glucose  did  not  allow  lysis,  but  the  marked  of  the  rodlike  forms.  The  protoplasmic 
streaming  birefringence  of  the  suspensions  body  within  the  wall  may  occupy  the 
was  much  reduced,  and  observation  of  the  entire  volume  of  the  protoplast,  may  fre- 
bacteria  in  the  dark-field  microscope  re-  quently  be  observed  in  a  doubled  condition 
vealed  that  50  to  100  per  cent  of  the  cells  within  a  single  outer  wall,  or  may  adhere 
had  assumed  a  spherical  shape.  Lactose,  to  one  side  of  the  wall,  yielding  a  saucer- 
sucrose,    maltose,    and    raffinose    allowed  shaped  inner  structure.   Since  such  proto- 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


133 


plasts  are  morphologically  altered  E.  colt, 
it  was  pertinent  to  inquire  whether  the 
structural  changes  would  influence  the 
maintenance  and  formation  of  amino  acid 
pools  and  the  synthesis  of  protein. 

When  growing  E.  coli  were  allowed  to 
metabolize  C14  proline  in  the  presence  or 
absence  of  lysozyme,  no  differences  in  the 
utilization  of  the  amino  acid  could  be  de- 
tected. Equal  C14-proline  pools  were 
formed,  and  protein  synthesis  continued, 
as  shown  in  figure  31.   Lysozyme-treated 


•  r  Lysozyme  treated 

600- 

0=  No  Lysozyme 

Total -^__^        y. 

400- 

•/ 

- 

Or 

•TCA    Soluble 

• 

200- 

4* 

^ 

^O 

^TCA 

ppt. 

c 

1                1                1 

5              10             15            ; 

1 
>0 

1 

25 

1 

30 

Minutes    after  adding    C14- proline 


Fig.  31.  C14-proline  utilization  by  cells  grow- 
ing in  the  presence  of  100  ug/ml  lysozyme. 

cultures  grow  indefinitely  at  the  rate  char- 
acteristic for  E.  coli.  Thus,  lysozyme  treat- 
ment in  itself  had  no  apparent  effect  upon 
amino  acid  utilization  or  growth  of  E.  coli. 

Cells  that  had  previously  formed  a  C14- 
proline  pool  and  synthesized  protein  con- 
tinued to  maintain  a  large  fraction  of  the 
original  pool,  increased  the  size  of  the  pool, 
and  continued  to  synthesize  protein  at  a 
high  rate  even  though  they  were  undergo- 
ing the  morphological  change,  rod-to- 
sphere,  which  followed  lysozyme-sucrose 
osmotic-shock  treatment.  These  findings 
are  illustrated  in  figure  32. 

The  results  of  a  more  stringent  test  of 
the  capacity  of  E.  coli  protoplasts  to  form 
an  amino  acid  pool  and  to  synthesize  pro- 
tein are  shown  in  figure  33.  For  this  ex- 
periment a  protoplast  suspension  contain- 
ing 96  per  cent  spherical  forms  was 
prepared  and  allowed  to  utilize  C14  proline. 
It  is  evident  that  an  amino  acid  pool  is 
formed  and  that  protein  is  synthesized. 
It  was  also  found  that  washing  the  proto- 


plasts on  membrane  filters  with  isotonic 
media  removed  the  labeled  amino  acid  pool 
without  causing  lysis.  Thus  the  amino 
acid  pool  is  held  so  loosely  that  even  me- 
chanical mishandling  of  the  protoplasts 
causes  its  loss, 


•  =  Lysozyme  treated 
0=  Control 


10  20  30  40 

Minutes   after  osmotic   shock 


Fig.  32.  C14-proline  utilization  by  E.  coli  after 
osmotic  shock  in  the  presence  of  lysozyme  (solid 
circles).  Percentages  indicate  the  proportion  of 
cells  that  were  spherical  as  determined  by  direct 
observation  in  the  phase-contrast  microscope. 
Lysozyme  was  omitted  in  the  control  culture 
(open  circles) .  The  larger  pool  size  for  cells  that 
received  no  shock  or  lysozyme  treatment  is  shown 
by  the  dotted  line. 


Minutes  after  addmcj    C    -  proline 


Fig.  33.  C14-proline  utilization  by  a  suspen- 
sion of  cells  containing  96  per  cent  spherical 
forms  (solid  lines).  Washing  with  isotonic 
medium  removes  the  pool  but  does  not  lyse  the 
cells  (open  circles). 

FRACTIONATION    OF    CELL    JUICES    ON    ION- 
EXCHANGE  COLUMNS 

Proteins  and  nucleic  acids  of  E.  coli  have 
been  separated  and  characterized  by  means 
of  cellulose  ion  exchangers.1  Small  amounts 

1  For  preparation  of  the  exchangers  see  E.  A. 
Peterson  and  H.  A.  Sober,   /.  Am.  Chem.  Soc, 


134        CARNEGIE  INSTITUTION  OF  WASHINGTON 


of  TCA-soluble  bacterial  amino  acids,  glutamic  acid,  leucine,  and  isoleucine  for 
which  occur  in  apparent  association  with  the  purpose  of  (a)  tracing  the  behavior  of 
high-molecular-weight  components  of  cell  any  free  amino  acid  of  bacterial  origin,  and 
juice,  have  also  been  isolated  by  means  of  (b)  distinguishing  bacterial  amino  acids 
the  exchanger.  Various  proteins  having  that  were  not  free  to  equilibrate  with  the 
different  enzyme  activities  have  been  sepa-  C14-labeled  substances  under  these  condi- 
rated.  (3-Galactosidase  activity  has  been  tions.  This  radioactive  mixture  was  im- 
found  distributed  among  different  proteins  mediately  passed  into  a  column  of  the 
separated  by  the  exchanger.  Bacterial  anion  exchanger  DEAE  cellulose  (di- 
nucleic  acid  has  been  separated  from  bac-  ethylaminoethyl  cellulose), 
terial  protein,  and  the  nucleic  acid  has  been  Washing  the  column  with  several  col- 
further  fractionated.  umn  volumes  of  0.25  M  sucrose  in  Tris 

Association  of  bacterial  amino  acids  with  medium  completely   removes   the   C14-la- 

high-molecular-w  eight  components  of  E.  beled  amino  acids,  the  bulk  of  the  bacterial 

coli.   It  has  become  evident  from  studies  amino  acid,  and  a  small  fraction  of  the 

on  protoplasts  that  the  pool  holding  ca-  protein  and  nucleic  acid.  Elution  with  1  M 

pacity  of  the  E.  coli  cell  lies  beneath  the  NaCl  dissolved  in  the  sucrose-Tris  medium 

cell  wall.   Normal  pools  are  still  formed  releases  nearly  all  the  remaining  protein 

when  the  cell  wall  has  been  fundamentally  and  nucleic  acid  from  the  column.  When 

altered  by  lysozyme  and  osmotic  shock,  the  latter  substances  and  salts  are  removed 

Unfortunately,  the  inner  architecture  of  from  the  eluate  by  TCA  treatment  and  ion 

the  cell  is  only  crudely  known.   There  is  exchange,  amino  acids  can  be  recovered 

not  yet  completely  satisfying  evidence  of  and  identified  by  paper  chromatography 

the  physical  reality  of  a  plasma  membrane  (fig.  34) .    These  amino  acids  are  found 

or  of  a  nucleus.  On  the  other  hand,  it  is  to  be  nonradioactive.  Thus,  they  are  clearly 

clear  that  much  of  the  substance  of  the  cell  of  bacterial  origin  but  differ  in  their  be- 

is  organized  into  macromolecules  or  com-  havior  on  the  ion  exchanger  from  the  bulk 

plexes  of  macromolecules  such  as  the  20  S  of  the  TCA-soluble  bacterial  amino  acids 

and  40  S  ribonucleoprotein  particles;  see  and    also    from    the   admixed    C14-tracer 

figure  30.    An  attempt  was  made,  there-  amino  acids.  In  quantity  they  correspond 

fore,  to  learn  whether  pool  amino  acids  to  a  few  per  cent  of  the  pool  amino  acids 

could  be  found  in  association  with  macro-  originally  present  in  the  cells.   A  definite 

molecular  components.  tie   or   association   between   these   amino 

For  this  purpose  the  experimental  pro-  acids  and  macromolecules  seems  the  most 

cedure    was    as    follows.     Exponentially  probable  explanation  for  this  behavior, 

growing  E.  coli  were  suspended  in  0.5  M  Depending  on  the  criterion  employed, 

sucrose   dissolved   in   Tris   medium,   and  these  associated  amino  acids  resemble  or 

were  disintegrated  with  a  modified  French  differ  from  the  metabolic  pool  amino  acids 

pressure  cell.  The  resulting  suspension  was  0f  E.  coli.  For  example,  like  the  metabolic 

centrifuged,  the  pellet  was  discarded,  and  pool  amino  acids,  they  cannot  be  recovered 

the  supernatant  fluid  was  filtered  through  from    cells    that    have    been    osmotically 

collodion  membranes  to  yield  a  clear  am-  shocked  by  washing  with  distilled  water, 

ber  cell  juice.  This  juice  contains  all  the  Alternatively,  when  cell  juice  is  prepared 

material  of  the  original  suspension  except  in  0.5  M  sucrose  solution  lacking  salts,  and 

the  cell  walls  and  a  small  amount  of  un-  then  passed  over  the  ion  exchanger,  the 

broken  cells.    To  the  juice  was  added  a  free  neutral  amino  acids  pass  through  the 

solution  of  carrier-free  C14-labeled  alanine,  column.    The  anionic   amino   acids,  glu- 

^n  wi  /meA    \          7-     •            \                ~  tamic  and  aspartic  acids,  and  also  a  small 

78.751  (1956);  for  application  to  plasma  protein  r     L        t         .            -i       ri            •  i 

separations,  see  H.  A  Sober  et  al.,  /.  Am.Chem.  amount  of  neutral  amino  acids  of  bacterial 

Soc,  78,  756  (1956).  origin,  however,  remain  adsorbed.  These 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        135 


neutral  amino  acids  can  be  released  by 
washing  the  column  with  distilled  water 
and  be  identified  chromatographically 
(fig.  35) .  Proteins  and  nucleic  acids  are  not 
released  by  this  treatment.  Thus,  the  ion- 
exchanger-macromolecule  complex  holds 
the  associated  amino  acids  in  a  labile  fash- 
ion reminiscent  of  the  way  in  which  the 
metabolic  pool  amino  acids  are  held  in  the 
cell.  On  the  other  hand,  the  macromole- 
cule-associated  amino  acids  differed  in  that 
they  could  not  be  labeled  by  exchange  with 

Cell  juice  + 
Cl4-qlu,-ola,-L  +11 


cellulose  ion-exchange  columns.  Several 
examples  of  the  separation  of  E.  coli  pro- 
teins and  nucleic  acids  are  shown  below. 
Figure  36  illustrates  the  separation  of  S35- 
labeled  components  of  pressure  cell  juice 
prepared  from  cells  grown  to  a  high  den- 
sity from  a  small  inoculum  in  the  presence 
of  S3504=.  The  effluent  volume  is  given  on 
the  abscissa,  and  the  amount  of  radioac- 
tivity (upper  line)  or  amount  of  protein 
(lower  line,  chemically  determined  with 
the  Folin  phenol  reagent),  on  the  ordinate. 
It  is  evident  that  the  radioactivity  and  the 


DEAE—  Cellulose 
onion   exchanger 


/4  M    SUCROSE 
IN 
TRIS 


1 

1 

1/4M 

+  IM 

S-T 

NoCI 

Ao' 

OG 

J     O 

L+1L 

Fig.  34.  Ion-exchange  separation  of  bacterial 
amino  acids  from  admixed  C14  amino  acids. 
Solid  circles  indicate  the  location  of  labeled  amino 
acids  on  two-dimensional  paper  chromatograms ; 
open  circles  indicate  unlabeled  amino  acids. 
A  =  alanine,  G=glutamic  acid,  V  =  valine;  L-f-IL 
=  leucine,  isoleucine. 

C14  amino  acids,  by  using  either  cell  juices,, 
as  described  above,  or  undamaged  cells 
at  0°  C. 

It  is  not  yet  clear  what  role  the  macro- 
molecule-associated  amino  acids  play  in 
the  metabolism  of  the  cell.  Although  they 
constitute  only  a  few  per  cent  of  all  the 
TCA-soluble  amino  acids  in  the  cell,  they 
may  represent  a  transitional  phase  lying 
between  the  metabolic  pool  amino  acids 
and  the  protein  end  product. 

Protein  and  nucleic  acid  fractionation  on 


W'.'.'.W 


(*-SUC  ROSE -4*DISTILLED*|«- SUC  ROSE-*] 
WATER  +  TRIS 


•  o 
o  o 

•  o 


GLU 
ALA 
VAL 
L+IL 


=  Radiooctive 


O    -  Non  radioactive 


Fig.  35.  Separation  on  DEAE  cellulose  of  bac- 
terial amino  acids  from  C14-labeled  admixed 
amino  acids  by  means  of  distilled-water  wash- 
ing. The  amount  of  C14  eluted  is  plotted  against 
the  volume  of  eluent.  Fractions  shown  as  shaded 
areas  at  the  centers  of  each  region  were  chromato- 
graphed  on  paper  in  one  dimension.  The  result 
is  depicted  immediately  below  the  corresponding 
shaded  area. 

protein  of  the  cell  can  be  resolved  into 
several  components.  The  largest  S35  peak 
is  most  probably  due  to  the  peptide  gluta- 
thione; the  remaining  peaks  are  due  to 
jproteins.  Comparison  of  the  specific  radio- 
activities for  several  of  the  components  of 
the  diagram  demonstrates  that  the  com- 
ponents differ  in  the  amount  of  sulfur  that 
they  contain  relative  to  each  chemical  unit 
(principally  the  amino  acid  tyrosine) 
which    reacts    with    the   phenol    reagent. 


136        CARNEGIE  INSTITUTION  OF  WASHINGTON 


Thus,  different  proteins  are  separated.  Ion- 
exchange  separations  of  the  proteins  o£ 
cells  exposed  to  S3504=  for  only  a  few 
minutes  reveal  several  regions  of  even 
higher  and  several  regions  of  lower  specific 
radioactivity.  Such  a  finding  bears  the 
implication  that  the  sulfur  of  some  kinds 
of  proteins  passes  into  other  proteins.  The 
ion  exchanger,  thus,  provides  a  tool  for  the 
study  of  possible  generic  relationships 
among  the  bacterial  proteins. 


a  separation  is  shown  in  figure  39.  There 
is  little  correlation  between  the  nucleic 
acid  (ultraviolet  absorption  at  260  mu) 
distribution  and  the  protein  distribution 
(S35  content).  Since  ultracentrifuge  and 
electron-microscope  studies  have  shown 
that  much  of  the  ribonucleic  acid  is  found 
in  spherical  particles  of  about  1  million 
molecular  weight  it  appears  that  these 
cellulose  ion  exchangers,  as  we  have  em- 
ployed them,  destroy  the  original  nucleo- 


50 

Effluent  volume  (ml) 


Fig.  36.    Elution  diagram  of  S35-labeled  components  and  proteins  of  E.  coli.   One-milliliter  efflu- 
ent samples  were  analyzed  for  each  region.   The  elution  schedule  was  as  follows: 

a  =  05  M  sucrose 


b= 

a                       ( 

+  0.05  M  Tris- 

succinate 

pU  7.7 

c  = 

(< 

+  0.1 

M 

« 

(<     << 

d= 

(( 

+ 

< 

« 

pH  7.0 

e  = 

(( 

+ 

< 

<< 

«     <« 

+  0.05  M  NaCl 

f= 

«                       < 

+ 

< 

<< 

<<     n 

+  0.1    M      " 

ff= 

(<                        1 

+ 

< 

(< 

a         a 

+  0.2    M      " 

h  = 

u 

+ 

< 

M 

cc         (( 

+  0.4    M      " 

Figure  37  illustrates  the  separation  of 
two  enzyme  activities,  acetokinase  and 
(3-galactosidase. 

Higher  resolution  among  the  protein 
components  can  be  achieved  by  eluting  the 
column  with  a  smoothly  increasing  con- 
centration of  salt  as  shown  in  figure  38. 
In  this  run,  activity  corresponding  to  the 
adaptive  enzyme,  3-galactosidase,  was 
found  in  a  well  defined  region  of  120  to 
150  ml  effluent  volume. 

Nucleic  acids  may  also  be  separated 
from  one  another  and  from  protein  by 
means  of  cellulose  ion  exchangers.   Such 


protein  associations.  It  should  be  possible, 
therefore,  to  use  the  ion  exchangers  to  de- 
termine the  complexity  of  subcellular  par- 
ticulates such  as  the  microsomal  particles. 

INCORPORATION   OF  AMINO   ACID    ANA- 
LOGUES INTO  PROTEINS 

Through  collaboration  with  Dr.  Georges 
N.  Cohen,  of  the  Institut  Pasteur,  it  has 
been  shown  that  selenomethionine  can 
completely  replace  methionine  for  expo- 
nential growth  of  a  methionine-requiring 
mutant  of  E.  coli.  Active  (3-galactosidase 
is  found  under  this  condition.  Experiments 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM 


137 


are  in  progress  to  find  whether  this 
(3-galactosidase  has  the  same  specific  mo- 
lecular activity  as  the  normal  enzyme. 

The  demonstration  that  exponential 
growth  occurs  when  selenomethionine  re- 
places protein  methionine  reflects  the  syn- 
thesis of  all  the  essential  enzymes.  Work- 
ers at  the  Institut  Pasteur  have  found  that, 


20 
Effluent  volume  (ml) 


Fig.  37.  Ion-exchange  separation  of  acetoki- 
nase  (A)  and  (3-galactosidase  (B).  The  total 
protein  eluted  is  shown  as  a  continuous  line. 
The  elution  schedule  followed  was: 


with  other  structural  analogues  of  amino 
acids  (p-fluorophenylalanine,  (3-2-thienyl- 
alanine,  norleucine),  linear  growth,  instead 
of  exponential  growth,  always  occurred, 
accompanied  by  the  suppression  of  the  syn- 
thesis of  one  or  more  active  essential 
enzymes.  In  each  case  the  analogues  were 
incorporated  into  the  proteins,  replacing 
structurally  related  natural  amino  acids. 
These  results  and  the  selenomethionine 
data  demonstrate  that  the  amino  acid  com- 
position of  protein  can  be  altered  by  the 
presence  of  amino  acid  analogues  in  the 
medium.  Since  the  incorporation  of  amino 
acid  analogues  into  protein  results  either 
in  the  synthesis  of  fully  active  enzymes  or 
in  the  suppression  of  synthesis  of  some 
enzymes,  the  analogues  become  powerful 
tools  in  the  study  of  the  protein-forming 
mechanisms. 

Incorporation  of  selenium  into  proteins. 
While  selenomethionine  can  completely 
replace  methionine,  selenium  cannot  en- 
tirely replace  sulfur  for  growth  of  E.  coli; 
but,  when  the  cell  contains  glutathione, 
which  can  serve  as  an  internal  sulfur  reser- 
voir, or  when  traces  of  exogenous  sulfate 
added,    selenium    partially    replaces 


are 


a  =  0.02  MPO, 

b= 

c  = 

d= 

e  = 

f= 


+  0.005  M  cysteine  +  0.0  MNaCl 
0.1  M  " 
0.2  M  " 
0.3  M  " 
0.4  M  " 
0.6  M    " 


sulfur.  Hydrolysates  of  proteins  obtained 
from  cells  grown  in  media  containing 
radioactive  selenite  and  trace  quantities  of 
sulfate  are  found  to  contain  a  radioactive 
material  with  chromatographic  properties 
similar  to  those  of  cysteine.    The  incor- 


/3-Goloctosidase 
H  8      octivity 


80  100  120 

Effluent  volume,(ml) 


140 


160 


180 


200 


Fig.  38.  Elution  diagram  of  E.  coli  protein  on  DEAE-cellulose  column.  A  linear  salt  gradient 
was  used  as  shown  on  the  broken  line.  The  protein  pattern  (continuous  line)  is  very  complex, 
and  (3-galactosidase  (insert)  has  been  resolved  into  three  apparent  components. 


138 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


poration  of  selenium  is  proportional  to  the 
increase  in  bacterial  mass.  Selenium  is  also 
incorporated  into  the  alcohol-soluble  pro- 
teins, but,  unlike  the  sulfur  of  this  protein, 
cannot  be  transferred  from  it  to  the  resid- 
ual proteins  during  sulfur  starvation. 

A  possible  reason  for  the  inability  of 
selenium  to  totally  replace  sulfur  for  the 
synthesis  of  proteins  might  be  the  inability 
of  selenocysteine  to  form  Se-S  or  Se-Se 
bridges,  or  the  incompatibility  between 
proteins  containing  such  linkages  and  a 


diameter)  is  the  most  prominent.  A  sec- 
ond group,  which  is  sometimes  resolved 
into  two  groups,  has  roughly  one-half  this 
value. 

As  it  appeared  possible  that  one  group 
of  particles  might  be  the  product  of  the 
other,  an  attempt  was  made  to  observe 
kinetic  relationships  among  the  groups. 
Cells  were  labeled  with  S35  and  P32  during 
a  long  exposure  to  the  tracer  to  give  a 
steady-state  condition,  or  during  a  short 
exposure  to  place  the  tracer  materials  in 


200 


-  .6 


-  .4   c 


-  .2 


100 
Effluent  volume  (ml) 


200 


Fig.  39.  Elution  diagram  of  nucleic  acid  (O.D.  at  260  mu)  and  protein  (S35  radioactivity)  on  an 
Ecteola-cellulose  column.  A  linear  salt  concentration  gradient  was  used  for  elution.  The  occurrence 
of  (3-galactosidase  is  shown  by  the  shaded  area. 


normal  catalytic  activity.  It  is  also  possible 
that  the  responsible  enzymes  of  E.  coli  are 
incapable  of  transforming  selenocysteine 
to  selenomethionine.  This  possibility  is 
strengthened  by  the  finding  that  seleno- 
glutathione  is  not  formed  from  selenite. 
Perhaps  some  of  the  biosynthetic  enzymes 
might  thus  show  a  more  strict  specificity 
than  the  protein-synthesizing  mechanism. 

PARTICLES 

Various  lines  of  evidence  point  to  the 
importance  of  small  particles  in  the  syn- 
thetic activities  of  the  cell.  Sedimentation 
analysis  shows  several  groups  of  particles 
in  the  juice  of  E.  coli.  In  most  of  the  pub- 
lished work  a  group  having  a  sedimenta- 
tion constant  of  40  S  (corresponding  to  a 
molecular  weight  of  about  1  million,  200-A 


the  early  product  of  synthesis.  The  cells 
were  then  broken,  and  the  unbroken  cells 
and  cell  walls  were  centrifuged  out.  The 
supernatant  fluid  containing  the  small  par- 
ticles was  then  centrifuged  at  105,000g 
for  various  periods  of  time.  The  cellular 
material  was  separated  into  cell  walls, 
particles,  and  nonsedimentable  material, 
but  no  separation  of  the  groups  of  particles 
was  achieved.  Different  runs  gave  quite 
different  rates  of  sedimentation;  the  parti- 
cles seem  very  sensitive  to  the  composition 
of  the  suspending  fluid. 

It  did  appear  that,  when  the  tracer  was 
supplied  for  a  short  time  only,  the  specific 
radioactivity  of  the  fraction  containing  the 
particles  was  higher  than  that  of  the  other 
fractions.  Also,  chromatography  of  the 
particle  fraction  showed  that  a  small  but 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        139 


definite  portion  of  the  amino  acid  pool  is 
carried  down  with  the  particles.  Further 
work  is  planned  for  next  year  to  establish 
the  kinetic  relations  between  the  particles 
and  the  other  parts  of  the  cell. 

Model 

During  the  year  we  have  attempted  to 
arrange  the  information  about  the  activities 
of  the  cell  in  terms  of  definite  models. 
Even  if  they  are  completely  wrong,  models 
are  of  some  value,  as  they  suggest  numer- 
ous experiments.  The  models  attempt  to 
interpret  two  known  features  of  the  cell's 
operation :  the  role  of  particles  in  synthesis, 
and  the  role  of  organization  in  the  cell. 

A  large  fraction  of  the  cell  mass  is  found 
in  the  form  of  ribonucleoprotein  particles. 
Most  of  the  RNA  of  the  cell  and  a  con- 
siderable fraction  of  the  protein  can  be 
centrifuged  down;  indeed,  it  seems  quite 
possible  that  most  of  the  protein  and  RNA 
of  the  cell  is  associated  with  particles, 
some  of  the  protein  being  tightly  bound 
and  some  being  released  during  the  proc- 
ess of  disrupting  the  cell.  Accordingly, 
the  synthesis  of  a  new  cell  involves  as  a 
major  activity  the  synthesis  of  new  parti- 
cles. In  one  model  we  have  interpreted  the 
different  classes  of  particles  observed  in  the 
ultracentrifuge  (20,  26,  and  40  S)  as  stages 
in  a  process  wherein  small  particles  grow 
to  large  particles  which  then  disintegrate 
into  several  small  ones.  Such  a  model 
emphasizes  the  necessity  for  experiments 
to  determine  the  composition  and  kinetic 
relations  of  the  different  classes  of  particles. 


According  to  this  model,  each  particle 
would  synthesize  and  contain  only  one 
type  of  protein.  Therefore,  the  organiza- 
tion of  enzymes  must  result  from  a  spatial 
organization  of  the  particle  with  respect  to 
other  particles.  The  cell  wall  does  not  pro- 
vide enough  area  to  hold  the  particles. 
Consequently,  it  seems  reasonable  to  as- 


sume that  they  might  be  held  in  a  definite 
framework  by  the  deoxyribose  nucleic  acid. 
Calculation  shows  that  there  is  sufficient 
DNA  to  provide  a  framework  with  the 
DNA  arranged  in  coils  (300-A  diameter, 
200-A  pitch)  with  their  axes  parallel.  Such 
a  structure  could  account  for  the  relation- 
ship between  the  order  of  genes  and  the 
order  of  biochemical  events  which  was  re- 
ported last  year  by  the  Department  of 
Genetics  of  the  Institution.  It  also  appears 
possible  for  such  a  structure  to  duplicate 
all  its  individual  components  and  then  to 
divide  by  extrusion  into  two  identical 
structures. 

This  model  summarizes  our  present 
knowledge  of  the  cell.  It  shows  that  we  are 
beginning  to  relate  structure  and  function, 
but  it  also  emphasizes  how  little  is  known 
of  either. 

Hoagland  Compound 

During  the  past  year  a  compound  has 
been  reported  by  Dr.  Hoagland  in  which 
amino  acids  are  linked  to  nucleic  acid.  It 
is  reasonably  stable  in  acid  but  unstable 
in  basic  solution.  Such  a  compound  would 
appear  in  the  "TCA-precipitable"  fraction 
and  might  be  mistaken  for  protein.  Tests 
were  therefore  made  to  determine  how 
much  of  this  compound  is  present  in  grow- 
ing E.  coli.  A  radioactive  amino  acid  was 
added  to  a  growing  culture  of  cells,  and 
the  usual  samples  were  taken  to  measure 
the  total  and  TCA-precipitable  fractions. 
In  addition,  samples  were  injected  into 
NaOH  to  release  any  amino  acids  bound 
to  nucleic  acid.  The  samples  were  then 
neutralized  and  mixed  with  TCA  to  pre- 
cipitate protein.  In  E.  coli  this  procedure 
showed  that  only  a  minute  fraction  of  the 
amino  acids  could  be  bound  in  alkali  labile 
compounds.  With  carrier-free  amino  acids 
and  washed  cells  from  which  all  pre-exist- 
ing pools  were  removed  there  was  an  indi- 
cation that  such  compounds  were  present, 
but  only  in  quantities  of  about  1  uM/g 
cells.  The  usual  pool  would  be  about  100 
uM/g,  and  the  amino  acids  in  the  proteins, 
of  course,  would  amount  to  several  thou- 


140 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


sand  micromoles  per  gram  of  cells.  In 
yeast  (C.  utilis)  a  considerably  greater 
fraction  showed  the  characteristics  expected 
of  amino  acids  bound  to  nucleic  acid.  The 
quantity  in  this  case  was  large  enough 
(15  uM/g  dry  cells)  to  offer  an  oppor- 
tunity for  its  isolation  and  for  further 
study  of  its  kinetic  characteristics. 

Protomorphs 

For  some  time  it  has  been  apparent  that 
organization  is  important  in  the  bacterial 
cell.  The  cell  is  by  no  means  a  "bag  of 
enzymes";  disruption  of  the  cell  may  have 
little  effect  on  individual  enzymic  activi- 
ties, or  even  may  increase  them,  but  many 
of  the  more  elaborate  functions  that  re- 
quire the  co-operative  action  of  several 
enzymes  cease.  In  particular,  crushing  cells 
greatly  reduces  their  ability  to  incorporate 
amino  acids  into  protein. 

It  is  also  highly  probable  that  the  or- 
ganization of  the  cell  stems  from  a  spatial 
arrangement  of  the  constituent  molecules. 
The  localization  of  many  of  the  Krebs 
cycle  enzymes  into  the  mitochondria  of 
mammalian  cells  has  been  observed.  A 
large  part  of  the  bacterial  protein  and 
ribonucleic  acid  is  organized  into  micro- 
somal particles,  and  similar  particles  have 
been  found  to  play  a  major  role  in  protein 
synthesis  in  mammalian  cells.  In  mam- 
malian cells  the  microsomal  particles  are 
arranged  on  the  surfaces  of  membranes; 
in  the  bacterial  cell  it  is  likely  that  they 
are  also  held  in  a  definite  spatial  arrange- 
ment, perhaps  in  a  framework  of  deoxyri- 
bose  nucleic  acid. 

Since,  presumably,  the  forces  responsible 
for  these  organized  systems  are  properties 
of  the  macromolecular  constituents  of  the 
cells,  it  seems  possible  that  thoroughly  dis- 
organized cellular  material  might,  under 
the  proper  conditions,  reconstitute  some  of 
the  spatial  arrangements  of  the  cell  analo- 
gously to  the  reconstitution  of  tobacco 
mosaic  virus  from  its  protein  and  RNA 
components. 

Having  these  thoughts  in  mind,  we  were 
very  much  interested  to  observe  the  de- 


layed appearance  of  particles  in  a  clear 
preparation  of  cellular  juices.  These  parti- 
cles have  several  properties  that  distinguish 
them  from  coacervates  formed  from  the 
gelatin  and  nucleic  acid;  it  even  seems 
possible  that  they  offer  a  new  form  for 
study  which  is  intermediate  between  the 
highly  organized  cell  and  disorganized 
cell  juice.  Because  they  are  formed  from 
protoplasm  and  have  a  distinctive  shape,  it 
seems  suitable  to  refer  to  them  as  "proto- 
morphs," to  avoid  confusion  with  the 
many  other  particles  of  cellular  origin. 

Preparation.  These  particles  develop  in  a 
preparation  made  as  follows :  Wash  10  g  of 
E.  coli  growing  in  a  glucose  mineral  salts 
medium  (C)  with  a  solution  (TSS)  0.25 
M  in  sucrose  buffered  with  trishydroxy- 
methylaminomethane  (Tris)  0.01  M  and 
brought  to  pYL  8  with  succinic  acid.  Centri- 
fuge out  the  cells,  and  resuspend  them 
with  10  ml  TSS.  Break  the  cells  by  forcing 
the  suspension  through  a  small  hole  at 
10,000  psi.  Bring  the  volume  up  to  50  ml 
with  TSS,  and  centrifuge  10  minutes  at 
40,000^.  This  treatment  removes  any  un- 
broken cells  and  the  larger  fragments  of 
cell  walls.  Decant  the  supernatant  fluid, 
and  centrifuge  at  105,000^  for  15  minutes 
to  remove  the  smaller  fragments  of  cell 
walls.  Again  decant  the  supernatant  fluid, 
which  should  be  quite  clear,  and  dilute 
to  100  ml  with  TSS.  Add  MgCl2  and 
MnCl2  to  make  the  solution  0.005  M  in 
each.  Leave  overnight,  and  the  originally 
clear  solution  becomes  quite  cloudy  owing 
to  the  formation  of  protomorphs.  The 
yield  is  variable  but  may  be  as  high  as 
0.5  g.  The  pH  of  the  solution  must  be  7 
to  8;  below  pH  7  the  protomorphs  do  not 
form,  and  below  pH  6  a  precipitate  de- 
velops when  the  manganese  is  added.  All 
operations  following  the  breaking  of  the 
cells  are  performed  at  0°  to  5°  C. 

In  this  procedure  some  variation  is  prob- 
ably permissible;  only  a  few  of  the  vari- 
ables have  been  studied.  The  addition  of 
manganese  is  essential;  magnesium  is  not 
essential  but  improves  the  yield.  The  pur- 
pose of  the  low  temperature  during  the 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        141 


formation  period  is  to  reduce  bacterial  con- 
tamination and  denaturation  of  protein. 
When  the  cell  juice  is  centrifuged  for 
2l/2  hours  at  105,000^  to  remove  the  micro- 
somes (absorption  at  260  mu  reduced  by 
67  per  cent),  it  gives  a  much  lower  yield  of 
protomorphs.  The  microsome  pellet  when 
resuspended  in  TSS,  however,  gives  a 
precipitate  but  no  protomorphs  on  addition 
of  manganese.  Other  variables,  such  as  de- 
pendence on  the  presence  of  Tris,  suc- 
cinate, or  sucrose,  have  not  been  investi- 
gated. 

Appearance,  composition,  stability.  The 
protomorphs  formed  by  this  procedure  ap- 
pear as  shown  in  figure  40,  plate  5.  (Our 
thanks  go  to  Dr.  Wm.  Duryee  for  making 
this  photomicrograph.)  They  are  very 
nearly  spherical,  and  range  in  diameter 
from  about  1  to  5  microns.  Estimated  by 
the  absorption  at  260  mu  (1  mg  nucleic 
acid/ml  gives  optical  density  =  25),  the 
nucleic  acid  content  is  roughly  20  mg/g 
wet  weight.  The  Folin  reaction  indicates 
that  there  is  approximately  50  per  cent 
more  protein  per  unit  of  260-mu  absorption 
than  in  the  cell  juice  from  which  the 
protomorphs  formed;  thus,  the  protein 
content  is  roughly  120  mg/g  wet  weight. 
Paper  chromatograms  run  in  butanol/ 
formic  acid/water  show  the  presence  of 
lipid  material  in  about  the  same  proportion 
as  appears  in  preparations  of  microsomes 
from  E.  coli.  Thus,  the  protomorphs  con- 
tain several  of  the  constituents  of  bacterial 
protoplasm. 

In  contrast  to  simple  coacervate  particles, 
which  can  exist  only  in  a  narrow  range  of 
/7H,  the  protomorphs  are  quite  stable. 
They  can  be  centrifuged  down  and  resus- 
pended without  disintegrating;  they  main- 
tain their  form  in  H20,  1  M  NH4OH,  or 
5  per  cent  trichloroacetic  acid  (TCA),  or 
after  shaking  with  ether.  Sodium  phos- 
phate buffer  (0.07  M,  pH  7)  dissolves  out 
much  of  the  nucleic  acid  of  the  proto- 
morphs, leaving  a  less  optically  dense 
residue;  casein  hydrolysate  (5  per  cent) 
has  much  the  same  effect.  Ethylenedi- 
aminetetraacetic  acid  (EDT)  (0.01  M)  dis- 


solves the  protomorphs,  leaving  a  clear 
solution. 

Functions  of  the  protomorphs.  Suspen- 
sions of  the  protomorphs  in  TSS  supple- 
mented with  5  X  10~3  M  Mg  were  incu- 
bated with  P3204  (4xl0~5  M)  at  22°  C. 
Samples  were  taken  periodically  and  fil- 
tered. Other  samples  were  mixed  with 
equal  volumes  of  10  per  cent  TCA  and 
subsequently  filtered.  The  concentration 
of  P3204  in  the  protomorphs  increased 
steadily  with  time;  all  this  phosphate  was 
extracted  with  TCA,  however,  and  there 
was  no  sign  of  incorporation  of  P32  into 
nucleic  acid. 

Similar  experiments  were  carried  out  us- 
ing a  mixture  of  C14-labeled  amino  acids 
from  hydrolyzed  Chlorella  protein.  A 
steady  increase  in  the  C14  content  of  the 
protomorphs  was  observed.  In  this  case, 
however,  the  major  portion  was  not  ex- 
tracted with  TCA. 

As  this  incorporation  rate  is  very  small 
compared  with  that  of  bacteria,  it  is  neces- 
sary to  show  that  bacterial  contamination 
could  not  cause  the  incorporation.  Plate 
counts  and  microscopic  examination  of  the 
culture  indicated  that  the  bacteria  present 
could  at  most  account  for  only  1  per  cent 
of  the  observed  incorporation. 

Chemical  tests  were  made  to  determine 
whether  the  radioactivity  of  the  TCA- 
insoluble  material  was  bound  in  protein. 
The  radioactivity  was  precipitable  with 
TCA  after  the  insoluble  material  was 
dissolved  in  1  N  NaOH.  On  paper  chro- 
matograms the  radioactivity  had  the  same 
movement  as  protein;  after  hydrolysis  it 
was  found  with  the  free  amino  acids. 

Clearly,  from  this  preliminary  report, 
much  work  remains  to  be  done  to  establish 
the  nature  of  these  protomorphs.  Both  the 
yield  and  the  synthetic  ability  are  highly 
variable  from  one  experiment  to  another. 
Not  only  do  the  conditions  of  formation 
require  further  exploration,  but  also  the 
functional  properties  must  be  investigated 
in  more  detail.  It  is  not  certain  whether 
the  incorporation  of  amino  acids  represents 
net  synthesis  or  some  form  of  exchange. 


142        CARNEGIE  INSTITUTION  OF  WASHINGTON 


The  protomorphs  may  have  a  functional 
performance  inherently  different  from  the 
disorganized  cell  juices  from  which  they 
are  formed,  or  they  may  merely  represent 
the  separation  of  functional  material  from 
some  inhibitory  substance  in  that  medium. 
Studies  are  in  progress  that  should  clarify 
these  points. 

PROTEIN  SYNTHESIS  IN  MOUSE  TISSUES 

During  the  year  our  collaboration  with 
Drs.  L.  B.  Flexner  and  J.  B.  Flexner,  of  the 
University  of  Pennsylvania,  has  continued. 
Observations  on  amino  acid  and  protein 
synthesis  in  the  liver  and  cerebral  cortex 
of  the  mouse  have  been  extended  to  in- 
clude adult  as  well  as  newborn  animals. 
Kinetic  data  obtained  from  4  or  5  litter- 
mates  sacrificed  at  various  times  up  to  1 
or  2  hours  after  injection  of  glucose  or 
amino  acids  labeled  with  C14  showed  the 
concentrations  of  labeled  glucose  in  blood 
and  tissues  and  the  concentration  of  la- 
beled amino  acids  in  blood,  tissue  pool, 
and  tissue  protein. 

One  of  the  unanticipated  and  striking 
findings  is  the  high  rate  of  utilization  of 
carbon  of  glucose  for  synthesis  of  nonessen- 
tial amino  acids  in  the  cerebral  cortex.  A 
complete,  quantitative  analysis  of  the  con- 
tribution made  by  all  sources  to  any  one 
of  these  nonessential  amino  acids  is  lack- 
ing. The  importance  of  glucose,  however, 
is  made  evident  by  the  finding  that  it 
supplies  ten  times  more  carbon  to  glutamic 
acid  and  glutamine  of  cortex  than  does 
blood  glutamic  acid.  This  is  true  for  both 
the  newborn  animal  and  the  adult.  In 
contrast,  the  quantities  of  glutamic  acid 
derived  from  glucose  by  the  liver  of  new- 
born and  adult  is  about  the  same  as  that 
derived  from  blood  glutamic  acid.  In  both 
tissues,  the  rate  of  incorporation  of  glucose 
carbon  into  carbon  of  amino  acids  is  far 
higher  in  the  adult  than  in  the  newborn, 
and  correspondingly  the  rate  of  degrada- 
tion of  the  amino  acids  is  higher  in  the 
adult  than  in  the  newborn. 

At  present,  a  major  concern  of  this  work 
is  to  gain  a  measure  of  the  relative  rates 


of  protein  synthesis  and  degradation  at 
different  stages  of  growth.  The  nerve  cells 
of  the  cerebral  cortex  of  the  newborn 
mouse  must  synthesize  protein  to  provide 
both  for  the  increase  in  cell  size  and  for 
the  increase  in  number  of  nerve  processes 
that  accompanies  development.  The  nerve 
cells  of  the  adult  animal,  however,  have 
reached  their  final  size;  they  do  not  divide; 
and  consequently  they  must  synthesize 
protein  only  to  compensate  for  that  lost 
by  degradation.  Much  the  same  basic  dif- 
ference exists  between  the  liver  of  the 
newborn  and  that  of  the  adult,  although 
in  this  organ  the  situation  is  complicated 
by  the  demands  made  upon  it  for  the  syn- 
thesis of  plasma  proteins  of  the  blood. 

The  experimental  observations  made  so 
far  permit  a  first  step  in  analyzing  the 
effect  of  growth  and  degree  of  maturation 
on  rate  of  protein  synthesis.  Calculations 
have  been  made  of  the  rates  at  which  indi- 
vidual amino  acid  pools  furnish  their 
amino  acids  for  protein  synthesis.  There 
is  a  surprisingly  small  difference  between 
the  newborn  and  adult  animal.  In  the 
cerebral  cortex,  the  pools  of  the  newborn 
are  drawn  upon  at  only  twice  the  rate  of 
the  adult.  In  the  liver  even  less  difference 
between  the  two  age  groups  is  found.  Fur- 
ther analysis  of  these  findings  in  terms  of 
protein  synthesis  depends  upon  determina- 
tion of  the  concentrations  of  individual 
amino  acids  in  their  respective  pools. 

VISITORS 

During  the  year  we  benefited  by  a  num- 
ber of  visitors  who  worked  with  us  in  the 
laboratory  for  short  periods  of  time.  They 
included  Dr.  Julius  Marmur,  Harvard  Uni- 
versity; Mr.  Charles  Stroebel,  University 
of  Minnesota;  Dr.  J.  R.  Vallentyne,  Geo- 
physical Laboratory;  Mr.  Ellis  Kempner, 
Yale  University;  Mr.  S.  K.  Roberts,  Prince- 
ton University.  Co-operative  work  was 
carried  out  with  Dr.  S.  Bernhart,  Naval 
Medical  Research  Institute;  Dr.  Louis 
Flexner,  University  of  Pennsylvania;  and 
Dr.  Bill  H.  Hoyer  and  Dr.  Edgar  Ribi,  of 
Rocky  Mountain  Laboratory,  U.  S.  Public 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        143 


Health  Service.  Dr.  F.  T.  McClure,  Ap-  Program,  contributed  greatly  to  the  bio- 
plied  Physics  Laboratory,  Dr.  G.  Cohen,  physics  section.  We  also  wish  to  thank 
Pasteur  Institute,  and  Dr.  John  Leahy,  several  members  of  the  National  Institutes 
who  were  here  as  part  of  the  Fellowship  of  Health  for  the  use  of  their  equipment. 

OPERATIONS  AND  STAFF 


CO-OPERATIVE   WORK  OF  THE 
DEPARTMENT 

The  Institution's  policy  of  co-operation 
has  been  continued  with  institutions  in 
this  country  and  abroad,  including  the 
Applied  Physics  Laboratory,  Associated 
Universities,  Inc.,  Bernard  Price  Institute 
of  Geophysical  Research  (Africa),  Brook- 
haven  National  Laboratory,  Chalmers  Uni- 
versity of  Technology  (Sweden),  U.  S. 
Coast  and  Geodetic  Survey,  Department 
of  Defense,  Geological  Survey  of  Canada, 
U.  S.  Geological  Survey,  Geophysical  In- 
stitute of  Huancayo  (Peru),  Johns  Hop- 
kins University,  Lamont  Geological  Ob- 
servatory, Mount  Wilson  and  Palomar  Ob- 
servatories, National  Bureau  of  Standards, 
National  Institutes  of  Health,  National  Re- 
search Council,  National  Science  Founda- 
tion, Ontario  Department  of  Mines  (Can- 
ada), Pasteur  Institute  (France),  Rocky 
Mountain  Laboratory  of  U.  S.  Public 
Health  Service,  Universities  of  Missouri, 
Pennsylvania,  and  Virginia,  University  of 
Melbourne  (Australia),  and  Yale  Univer- 
sity. We  continued  our  collaboration  with 
the  American  Geophysical  Union,  the  In- 
ternational Union  of  Geodesy  and  Geo- 
physics, and  the  International  Scientific 
Radio  Union.  Foreign  and  domestic  vis- 
itors have  used  our  facilities,  some  on 
fellowships  of  the  Institution  from  Eng- 
land, France,  and  various  parts  of  the 
United  States. 

Research  work  concerned  with  mineral 
ages  using  isotope  measurements  was  con- 
tinued with  the  Geophysical  Laboratory. 

We  have  had  continued  assistance  in  our 
cosmic-ray  investigations  from  the  obser- 
vatories at  Cheltenham,  Maryland  (to  Sep- 
tember 30,  1956) ;  Christchurch,  New  Zea- 
land; Climax,  Colorado;  Fredericksburg, 
Virginia   (from  October   1,   1956);   God- 


havn,   Greenland;   Huancayo,   Peru;    and 
Mexico,  D.  F. 

Contracts  with  the  government  (no 
overhead  charges)  have  been  continued 
for  the  investigation  of  the  earth's  crust 
and  of  cosmic  rays.  Licenses  are  in  force 
with  the  Atomic  Energy  Commission  for 
the  procurement  of  isotopes  for  nuclear 
studies,  measurement  of  mineral  ages,  and 
biophysical  investigations. 

Three  grants  from  the  National  Science 
Foundation  for  the  activities  of  the  NSF 
Advisory  Panel  on  Radio  Astronomy  are 
being  administered,  without  charge. 

The  National  Science  Foundation  has 
also  provided  funds  for  the  partial  cost 
of  projects,  to  be  carried  out  in  South 
America  as  our  participation  in  the  Inter- 
national Geophysical  Year,  concerned  with 
seismic  crustal  investigations  and  with  the 
height  in  the  ionosphere  of  equatorial 
electrojets. 

We  have  supplied  ionium  collectors  to 
the  National  Meteorological  Service  of 
Argentina  and  to  the  Instituto  Geofisico 
de  Universidade  do  Porto  of  Portugal. 

Several  staff  members  have  continued 
their  service  on  panels  of  the  U.  S.  Na- 
tional Committee  of  the  International  Geo- 
physical Year,  and  one  is  a  member  of  the 
Executive  Committee  of  that  Committee; 
until  December  31,  1956,  one  member  con- 
tinued full  time  with  the  National  Acad- 
emy of  Sciences  on  studies  concerning  a 
world  data  center  in  connection  with  the 
International  Geophysical  Year.  One  mem- 
ber continues  as  Chairman  of  the  Advisory 
Panel  on  Radio  Astronomy  of  the  National 
Science  Foundation.  Two  members  are 
on  the  Committee  on  Growth  of  the  Na- 
tional Research  Council,  and  one  is  on  the 
Council  of  the  Biophysical  Society  and  con- 
tinues to  serve  on  the  Advisory  Committee 


144        CARNEGIE  INSTITUTION  OF  WASHINGTON 


to  the  Federal  Civil  Defense  Administra- 
tion. One  member  continues  as  Chairman 
of  the  U.  S.  A.  National  Committee,  In- 
ternational Scientific  Radio  Union.  An- 
other staff  member  (resigned  December 
31,  1956)  continued  his  full-time  research 
work  for  the  government. 

One  staff  member  visited  many  institu- 
tions abroad  on  a  world  trip  sponsored 
by  the  Carnegie  Corporation  of  New  York. 
Another  participated  in  an  electrojet  sur- 
vey in  South  America  as  a  part  of  one  of 
the  Department's  projects  for  the  Inter- 
national Geophysical  Year.  Another  mem- 
ber spent  several  months  at  the  Pasteur 
Institute  in  Paris.  One  staff  member  is 
abroad  on  a  Guggenheim  Memorial  Fel- 
lowship. 


Department  staff  members  attended  the 
Twentieth  International  Geological  Con- 
ference in  Mexico  City,  the  symposium  on 
Polar  Atmosphere  at  Oslo,  Norway,  the 
International  Conference  on  Rock  Mag- 
netism in  London,  the  Geophysics  Collo- 
quium at  Cambridge,  England,  and  the 
symposium  on  Electromagnetic  Phenom- 
ena in  Cosmical  Physics  at  Stockholm, 
Sweden. 

ADMINISTRATION  AND   OPERATION 

The  Department  continues  to  publish 
the  Journal  of  Geophysical  Research,  partly 
subsidized  by  the  Institution. 

We  have  continued  to  rent  part  of  one 
farm  for  the  activities  of  the  radio  as- 
tronomy group. 


BIBLIOGRAPHY 


Aldrich,  L.  T.  The  measurement  and  applica- 
tions of  mineral  ages.  Program  Am.  Geo- 
phys.  Union,  Washington  Meeting,  p.  12, 
1957. 

Aldrich,  L.  T.,  G.  L.  Davis,  G.  R.  Tilton,  and 
G.  W.  Wetherill.  Radioactive  ages  of  min- 
erals from  pegmatites.  (Abstract.)  XX 
Intern.  Geol.  Congr.,  Mexico  Meeting,  pp. 
207-208,  1956. 

Aldrich,  L.  T.,  G.  L.  Davis,  G.  R.  Tilton,  G.  W. 
Wetherill,  and  P.  M.  Jeffery.  Evaluation  of 
mineral  age  measurements.  I.  Natl.  Acad. 
Sci.-Natl.  Research  Council,  Nuclear  Sci. 
Series  Rept.  19,  Publ.  400,  p.  147,  1956. 

Aldrich,  L.  T.,  G.  W.  Wetherill,  and  G.  L. 
Davis.  Determinations  of  radiogenic  Sr87 
and  Rb87  of  an  interlaboratory  series  of 
lepidolites.  Geochim.  et  Cosmochim.  Acta, 
10,  238-240  (1956). 

Aldrich,  L.  T.,  G.  W.  Wetherill,  and  G.  L.  Davis. 
Occurrence  of  1350  million-year-old  granitic 
rocks  in  western  United  States.  Bull.  Geol. 
Soc.  Am.,  68,  655-656  (1957). 

Aldrich,  L.  T.,  G.  W.  Wetherill,  G.  R.  Tilton, 
and  G.  L.  Davis.  Half-life  of  Rb87.  Phys. 
Rev.,  103,  1045-1047  (1956). 

Aldrich,  L.  T.  See  also  Davis,  G.  L.;  Tilton, 
G.  R.;  Wetherill,  G.  W. 

Anderson,  C.  E.    See  Pieper,  G.  F. 

Britten,  R.  }.  Effect  of  the  osmotic  strength  of 
the  growth  medium  on  the  amino  acid  pool 
of  Escherichia  coli.  (Abstract.)  Science,  124, 
935   (1956). 

Burke,  B.  F.  Building  an  amateur's  radio  tele- 
scope. Junior  Astronomer,  6  (no.  4),  2-5 
(1956). 


Burke,  B.  F.  Systematic  distortion  of  the  outer 
regions  of  the  galaxy.  (Abstract.)  Astron. 
J.,  62,  90  (1957). 

Burke,  B.  F.,  and  M.  A.  Tuve.  Interferometers 
in  radio  astronomy.  Smithsonian  Contribs. 
to  Astrophys.,  1  (no.  1),  "New  Horizons  in 
Astronomy,"  31-36  (1956). 

Burke,  B.  F.    See  also  Forbush,  S.  E. 

Cohen,  G.  N.,  and  D.  B.  Cowie.  Remplacement 
total  de  la  methionine  par  la  selenomethio- 
nine dans  les  proteines  ^Escherichia  coli. 
Compt.  rend.  acad.  sci.,  Paris,  244,  680-683 
(1957). 

Cowie,  D.  B.,  and  B.  P.  Walton.  Kinetics  of 
formation  and  utilization  of  metabolic  pools 
in  the  biosynthesis  of  protein  and  nucleic 
acid.  Biochim.  et  Biophys.  Acta,  21,  211- 
226  (1956). 

Cowie,  D.  B.    See  also  Cohen,  G.  N. 

Davis,  G.  L.,  G.  R.  Tilton,  G.  W.  Wetherill,  and 
L.  T.  Aldrich.  Radioactive  ages  of  min- 
erals from  granites  (Abstract.)  XX  Intern. 
Geol.  Congr.,  Mexico  Meeting,  p.  212,  1956. 

Davis,  G.  L.  See  also  Aldrich,  L.  T.;  Tilton, 
G.  R.;  Wetherill,  G.  W. 

Erickson,  W.  C.  Generation  of  polarized  light 
in  the  Crab  Nebula.  Nature,  179,  773  (1957). 

Firor,  J.  W.  Inferences  from  radio  signals  from 
the  sun  and  planets.  Proc.  Natl.  Acad.  Sci. 
U.S.,  43,  2-8  (1957). 

Forbush,  S.  E.  Sobre  la  ausencia  de  efectos 
meteorologicos  en  la  variacion,  debida  a  las 
manchas  solares,  de  la  ionization  por  rayos 
cosmicos.  Rev.  mex.  fis.,  4,  125,  Mexico, 
1955. 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        145 


Forbush,  S.  E.  Solar  influences  on  cosmic  rays. 
Proc.  Natl.  Acad.  Sci.  U.S., 43,  28-41  (1957). 

Forbush,  S.  E.  The  U.  S.  program  for  cosmic 
ray  investigation  during  the  IGY.  Presented 
at  Special  Meeting  U.  S.  National  Commit- 
tee, Intern.  Geophys.  Year,  June  27-29, 
1957. 

Forbush,  S.  E.,  and  B.  F.  Burke.  Absorption  of 
cosmic  radio  noise  at  22.2  Mc/sec  following 
solar  flare  of  February  23,  1956.  (Letters  to 
Editor.)  /.  Geophys.  Research,  61,  573- 
575  (1956). 

Franklin,  K.  L.  Outer  galactic  structure  from 
O,  B,  carbon  stars,  and  neutral  hydrogen. 
Astron.  ].,  62,  15  (1957). 

Graham,  J.  W.  Paleomagnetism  and  magneto- 
striction. /.  Geophys.  Research,  61,  735- 
739  (1956). 

Hayden,  R.  J.    See  Wetherill,  G.  W. 

Heydenburg,  N.  P.,  and  G.  F.  Pieper.  Coulomb 
excitation  of  Fe57.  Bull.  Am.  Phys.  Soc, 
ser.  II,  2,  61  (1957). 

Heydenburg,  N.  P.,  and  G.  M.  Temmer.  Alpha- 
alpha  scattering  at  low  energies.  Phys.  Rev., 
104,  123-134  (1956). 

Heydenburg,  N.  P.,  and  G.  M.  Temmer.  Cou- 
lomb excitation  and  cascade  decay  of  rota- 
tional states  in  odd-mass  nuclei.  Phys.  Rev., 
104,  981-989  (1956). 

Heydenburg,  N.  P.,  and  G.  M.  Temmer.  Ex- 
citation of  nuclei  by  charged  particles.  Ann. 
Rev.  Nuclear  Sci.,  6,  77-116  (1956). 

Heydenburg,  N.  P.  See  also  Pieper,  G.  F.; 
Temmer,  G.  M. 

Jeffery,  P.  M.  The  radioactive  age  of  four 
W.  Australian  pegmatites  by  the  potassium 
and  rubidium  methods.  Geochim.  et  Cos- 
mochim.  Acta,  10,  191-195  (1956). 

Jeffery,  P.  M.     See  also  Aldrich,  L.  T. 

Nicolaysen,  L.  O.    See  Tilton,  G.  R. 

Pieper,  G.  F.,  and  N.  P.  Heydenburg.  Angular 
distributions  of  protons  in  the  F19  (a,  /?)Ne22 
reaction.  (Abstract.)  Bull.  Am.  Phys.  Soc, 
ser.  II,  2,  182  (1957). 

Pieper,  G.  F.,  N.  P.  Heydenburg,  and  C.  E. 
Anderson.  Coulomb  excitation  of  enriched 
Kr  samples.  (Abstract.)  Bull.  Am.  Phys. 
Soc,  ser.  II,  2,  69  (1957). 

Pieper,  G.  F.    See  also  Heydenburg,  N.  P. 

Scott,  W.  E.  John  Adam  Fleming,  1877-1956. 
/.  Geophys.  Research,  61,  589-592  (1956). 

Scott,  W.  E.  List  of  recent  publications.  /.  Geo- 
phys. Research,  61,  581-587,  759-767  (1956) ; 
62,  175-182,  335-342  (1957). 

Tatel,  H.  E.  Structure  of  the  earth's  crust  from 
gravity  measurements.  (Abstract.)  Science, 
124,941  (1956). 

Tatel,  H.  E.,  and  M.  A.  Tuve.  Seismic  investi- 
gation of  crustal  structure.  Rome  Meeting, 
Intern.   Union   Geod.   Geophys.,   Aug.    14- 


Sept.  25,  1954.  Compt.  rend.,  Strasbourg, 
no.  11,  p.  140  (1955). 

Temmer,  G.  M.,  and  N.  P.  Heydenburg.  Con- 
tribution of  Coulomb  excitation  to  inelastic 
scattering  between  nuclear  resonances.  Phys. 
Rev.,  104,  989-992   (1956). 

Temmer,  G.  M.,  and  N.  P.  Heydenburg.  Cou- 
lomb excitation  of  medium-weight  nuclei. 
Phys.  Rev.,  104,  967-980  (1956). 

Temmer,  G.  M.,  and  N.  P.  Heydenburg.  Ex- 
citacion  Coulombiana  Cu,  Zn,  As,  Se,  Y.  Ru. 
Rev.  mex.  fis.,  4,  133,  Mexico,  1955. 

Temmer,  G.  M.    See  also  Heydenburg,  N.  P. 

Tilton,  G.  R.  Interpretation  of  lead  ages  by  acid 
washing  experiments.  Natl.  Acad.  Sci.-Natl. 
Research  Council,  Nuclear  Sci.  Series  Rept. 
19,  Publ.  400,  p.  79,  1956. 

Tilton,  G.  R.  Uranium  and  thorium  dating. 
(Abstract.)  Program  New  Yor\  Meeting, 
A  A  AS,  Sec.  E,  Geol.  and  Geog.,  p.  21,  1956. 

Tilton,  G.  R.,  G.  L.  Davis,  G.  W.  Wetherill,  and 
L.  T.  Aldrich.  Isotopic  ages  of  zircon  from 
granites  and  pegmatites.  (Abstract.)  Pro- 
gram Am.  Geophys.  Union,  Washington 
Meeting,  p.  39,  1957. 

Tilton,  G.  R.,  G.  L.  Davis,  G.  W.  Wetherill,  and 
L.  T.  Aldrich.  Isotopic  ages  of  zircon  from 
granites  and  pegmatites  Trans.  Am.  Geo- 
phys. Union,  38,  360-371  (1957). 

Tilton,  G.  R.,  and  L.  O.  Nicolaysen.  The  use 
of  monazites  for  age  determination.  Geo- 
chim. et  Cosmochim.  Acta,  11,  28-40  (1957). 

Tilton,  G.  R.  See  also  Aldrich,  L.  T.;  Davis, 
G.  L.;  Wetherill,  G.  W. 

Tuve,  M.  A.    See  Burke,  B.  F.;  Tatel,  H.  E. 

Vestine,  E.  H.  The  Aurora  Australis  and  re- 
lated phenomena.  Antarctica  in  the  IGY. 
Geophys.  Monograph  no.  1,  pp.  91-106, 
1956. 

Vestine,  E.  H.  Exploring  the  atmosphere  with 
a  satellite-borne  magnetometer.  Scientific 
Uses  of  Earth  Satellites,  J.  A.  Van  Allen 
(Ed.).  Univ.  of  Mich.  Press,  Ann  Arbor, 
pp.  198-214,  1956. 

Vestine,  E.  H.  Introductory  remarks,  geophysics 
symposium,  Natl.  Acad.  Sci.  Proc.  Natl. 
Acad.  Sci.  U.  S.,  43,  1-2  (1957). 

Vestine,  E.  H.  John  Adam  Fleming.  Trans. 
Am.   Geophys.  Union,  37,  531-533    (1956). 

Vestine,  E.  H.  Observational  and  theoretical 
aspects  of  magnetic  and  ionospheric  storms. 
Proc.  Natl.  Acad.  Sci.  U.  S.,  43,  81-92  (1957). 

Vestine,  E.  H.  Relations  between  fluctuations  in 
the  earth's  rotation,  the  variation  of  latitude 
and  geomagnetism.  Intern.  Assoc  Geomag. 
and  Aeronomy,  Bull.  15a  (1956). 

Vestine,  E.  H.  Theoretical  geophysics.  Science, 
124,  234-236  (1956). 

Walton,  B.  P.    See  Cowie,  D.  B. 

Wasserburg,  G.  J.     See  Wetherill,  G.  W. 


146        CARNEGIE  INSTITUTION  OF  WASHINGTON 


Wells,  H.  W.  Flux  measurements  of  discrete 
radio  sources  at  frequencies  below  30  mega- 
cycles. /.  Geophys.  Research,  61,  541-545 
(1956). 

Wells,  H.  W.  Upper  atmospheric  winds,  absorp- 
tion and  other  special  projects  in  the  U.  S. 
program  in  ionospheric  physics.  Presented 
at  Special  Meeting,  U.  S.  National  Com- 
mittee, Intern.  Geophys.  Year,  June  27-29, 
1957. 

Wetherill,  G.  W.  Potassium-argon  age  determi- 
nation method.  (Abstract.)  Program  New 
Yor\  Meeting,  AAAS,  Sec.  E,  Geol.  and 
Geog.,  p.  22,  1956. 

Wetherill,  G.  W.,  G.  L.  Davis,  and  L.  T.  Aldrich. 
Age  measurements  on  rocks  north  of  Lake 
Huron.  (Abstract.)  Program  Am.  Geophys. 
Union,  Washington  Meeting,  p.  39,  1957. 

Wetherill,  G.  W.,  G.  R.  Tilton,  L.  T.  Aldrich, 
and  G.  L.  Davis.  Interpretation  of  dis- 
cordant uranium-lead  and  thorium-lead  ages. 
(Abstract.)  XX  Intern.  Geol.  Congr.,  Mexico 
Meeting,  p.  230,  1956. 

Wetherill,  G.  W.,  G.  R.  Tilton,  G.  L.  Davis,  and 
L.  T.  Aldrich.  Evaluation  of  mineral  age 
measurements.  II.  Natl.  Acad.  Sci.-Natl. 
Research  Council,  Nuclear  Sci.  Series  Rept. 
19,  Publ.  400,  p.  151,  1956. 

Wetherill,  G.  W.,  G.  J.  Wasserburg,  L.  T. 
Aldrich,  G.  R.  Tilton,  and  R.  J.  Hayden. 
Decay  constants  of  K40  as  determined  by  the 
radiogenic  argon  content  of  potassium  min- 
erals. Phys.  Rev.,  103,  987-989  (1956). 

Wetherill,  G.  W.  See  also  Aldrich,  L.  T.;  Davis, 
G.  L.;  Tilton,  G.  R. 

PERSONNEL 

Director:  M.  A.  Tuve. 

Chairmen  of  Sections:  Biophysics,  R.  B.  Rob- 
erts; Physics  of  the  Atmosphere,  H.  W. 
Wells;  Physics  of  the  Earth's  Crust,  H.  E. 
Tatel;  Laboratory  Physics,  N.  P.  Heyden- 
burg;  Analytical  Geophysics,  E.  H.  Vestine 
(on  leave  of  absence  to  December  31,  1956, 
to  engage  in  work  for  the  National  Acad- 
emy of  Sciences;  resigned  January  31, 
1957),  S.  E.  Forbush  (from  June  1,  1957). 

Staff  Members:  L.  T.  Aldrich,  E.  T.  Bolton, 
R.  J.  Britten,  D.  B.  Cowie,  S.  E.  Forbush, 
J.  W.  Graham,  N.  P.  Heydenburg,  E.  A. 
Johnson  (on  leave  of  absence  to  engage  in 
research  work  for  the  government;  resigned 
December  31,  1956),  R.  B.  Roberts,  H.  E. 
Tatel,  G.  M.  Temmer  (on  Guggenheim 
Memorial  Fellowship  abroad  from  August 
1,  1956),  E.  H.  Vestine  (on  leave  of  ab- 
sence to  December  31,  1956,  to  engage  in 


work  for  the  National  Academy  of  Sci- 
ences; resigned  January  31,  1957),  H.  W. 
Wells.  Temporary:  B.  F.  Burke,  J.  W. 
Firor,  G.  W.  Wetherill. 

Fellows  and  Visiting  Investigators:  G.  N. 
Cohen,  Institut  Pasteur,  Paris,  France  (from 
April  10,  1957);  E.  H.  Greaser,  University 
of  Cambridge,  England  (to  August  3,  1956, 
and  September  2-October  1,  1956);  W.  C. 
Erickson,  University  of  Minnesota  (entire 
report  year);  K.  L.  Franklin  (to  August 
31,  1956,  and  May  27-31,  1957);  H.  L. 
Heifer  (part  time;  full  time  from  Septem- 
ber 1,  1956);  J.  J.  Leahy,  University  of  Cali- 
fornia (entire  report  year);  F.  T.  McClure, 
Applied  Physics  Laboratory  (November  1, 
1956-May  31,  1957);  George  Pieper,  Yale 
University  (from  September  1,  1956);  Har- 
old Weaver,  University  of  California  (from 
October  1,  1956). 

Guests  and  Associates:  Carl  E.  Anderson, 
Yale  University  (October  1-5,  1956);  H. 
Faul,  U.  S.  Geological  Survey  (part  time); 
L.  B.  Flexner  and  Mrs.  J.  B.  Flexner,  Uni- 
versity of  Pennsylvania  (part  time);  W.  K. 
Ford,  Jr.,  University  of  Virginia  (part 
time);  S.  Gorodetzky,  Institute  of  Nuclear 
Research,  Strasbourg,  France  (April  10-12, 
1957);  D.  N.  Kundu,  National  Research 
Council  (October  22-November  20,  1956); 
H.  Lenhoflf,  Walter  Reed  Hospital  (part 
time,  September  17-November  8,  1956); 
J.  Marmur,  Harvard  University  (Septem- 
ber 17-October  15,  1956);  Carl  L.  McGin- 
nis,  National  Research  Council  (October 
22-November  20,  1956);  Mrs.  I.  Z.  Roberts 
(part  time);  S.  Roberts,  Princeton  Univer- 
sity (November  2,  1956);  Manik  Talwani, 
Columbia  University  (October  12-15, 
1956);  G.  J.  Wasserburg,  California  Insti- 
tute of  Technology  (June  17-21,  1957). 

Research  Assistants:  J.  B.  Doak,  E.  T.  Eck- 
lund,  C.  A.  Little,  Jr.,  W.  E.  Scott. 

Computer:  Miss  I.  Lange  (retired  March  1, 
1957). 

Laboratory  Assistants:  Miss  R.  E.  Bresnahan 
(from  April  15,  1957),  S.  J.  Buynitzky, 
Miss  E.  F.  French,  P.  A.  Johnson,  Miss 
B.  D.  North  (from  May  6,  1957),  R.  W. 
Reuschlein,  Mrs.  B.  P.  Walton  (to  June  14, 
1957). 

Chief  of  Section:  Administrative  and  Operat- 
ing, M.  B.  Smith.  Chief  of  Subsection, 
Main  Shop  and  Maintenance,  W.  F.  Steiner. 


DEPARTMENT  OF  TERRESTRIAL  MAGNETISM        147 


Librarian:    Mrs.  A.  P.  Moffett  (to  August 

31,   1956),  Mrs.  L.   J.  Prothro   (July   16- 

August  3,    1956,  and   from   September    1, 

1956). 
Accountant:   Miss  H.  E.  Russell. 
Draftsman  and  Photographer:  C.  S.  Leonard, 

Jr.  (to  December  15,  1956). 
Director's    Secretary    and    Office    Manager: 

W.  N.  Dove;  Stenographers:    Mrs.  C.  C. 

Ator,  Mrs.  C.  W.  Windmuller. 
Senior  Instrument  Makers:  B.  J.  Haase,  L.  A. 

Horton,  J.  G.  Lorz. 
Machinist:  F.  J.  Caherty. 


Foreman  of  Buildings  and  Grounds:   C.  Bal- 


sam. 


Caretaker:  E.  Quade;  Assistant  Caretakers: 
C.  R.  Domton,  C.  R.  Forshier  (from  Octo- 
ber 23,  1956),  S.  Gawrys  (from  June  17, 
1957),  P.  M.  B.  de  Macedo  (to  September 
15,  1956),  S.  Swantkowski. 

Part-Time  and  Temporary  Employees:  Mrs. 
L.  Beach,  R.  W.  Bluehdorn,  T.  J.  Delaney, 
W.  K.  Ford,  Jr.,  B.  Z.  Kile,  Jr.,  R.  C.  Kile, 
J.  E.  McLeod,  R.  L.  Peppell,  Jr.,  Mrs.  M.  T. 
Sheahan,  C.  F.  Stroebel,  W.  W.  Wyatt. 


Plate  2 


Department  of  Terrestrial  Magnetism 


Fig.  1.  A  portion  of  the  330-mc  helix  array  used  for  locating  sources  of  radio  radiation  on  the 
solar  disk.  The  two  helical  receiving  elements  are  mounted  on  a  common  ground  screen  and 
are  connected  to  an  open-wire  transmission  line.  The  present  array  contains  30  units  like  the  one 
shown  above  and  occupies  a  line  2000  feet  long  at  the  River  Road  field  station. 


Plate  3 


Department  of  Terrestrial  Magnetism 


Fig.  29.  Electron  micrograph  of  cell  walls  from  E.  coli  treated  with  lysozyme  and  osmotically 
shocked.  The  walls  appear  as  flattened  disks  which  show  a  high  incidence  of  double  structure  as 
though  the  original  condition  were  of  the  bag-within-a-bag  type.  The  dark  rods  are  unbroken  bac- 
teria about  1.5  microns  long. 


Plate  4 


Department  of  Terrestrial  Magnetism 


W 


8(DNA) 


:$.,:  ; 


Fig.  30.  Sedimentation  diagram  of  E.  coli  extract  prepared  by  lysozyme 
treatment  and  osmotic  shock.  The  picture  was  taken  about  30  minutes  after 
the  rotor  reached  a  speed  of  59,000  rpm.  The  most  obvious  components  are 
the  constituents  labeled  40  S,  26  S,  20  S,  and  8  S.  The  sharp  spike  is  due  to 
deoxynucleic  acid.  Such  a  simple  pattern  contrasts  sharply  with  the  exceed- 
ingly complex  diagrams  of  the  protein  composition  of  E.  coli  as  revealed  by 
ion  exchange  (cf.  fig.  36). 


Plate  5 


Department  of  Terrestrial  Magnetism 


Fig.  40.     Photomicrograph  of  aggregated  protomorphs    (magnification,  X  330), 


GEOPHYSICAL     LABORATORY 


Washington,  District  of  Columbia  PHILIP  H.  ABELSON,  Director 


CONTENTS 


page 

Introduction    151 

Order  and  Disorder 151 

Evidence   for    order   and   disorder   in 

minerals 151 

Short-  and  long-range  order 153 

The  linear  run  model  of  short-range 

ordering 153 

Dimensions  in  the  run  model 154 

The  numbers  and  locations  of  nearest 

neighbors     155 

Some    preliminary    experimental    re- 
sults      155 

Basalt  Magmas 156 

Stability  of  Annite 161 

The  Age  of  Roc\s  and  Minerals 164 

The  decay  constants  of  Rb87  and  K40 .  .  165 

Problems  in  the  Precambrian 165 

Study  of   a  point  in  the   fossil   time 

scale    168 

Zircon  age  work 169 

Simple  Absolute  Measurement  Technique 
for  Beta  Radioactivity;  Applica- 
tion to  Naturally  Radioactive  Ru- 
bidium    171 

The  method   172 

Results   178 

Application  to  naturally  radioactive  ru- 
bidium    178 

General  applications    178 

Paleobiochemistry    179 

Effects    of    ultraviolet    light    on    the 

"primitive  environment" 179 

Thermal  degradation  of  amino  acids.  .  185 

Ore  Minerals 186 

The  Fe-S  system 187 

Stability  relations  of  pyrite 187 

The  FeS-S  join 191 

The  Cu-S  system 195 

The  upper  stability  curve  of  covel- 

lite 195 

The  Ni-S  system 197 

The  NiS-NiS2  join 197 


page 
Phase  relations  in  the  Fe-S-O  system .      198 

The  Fe-S-Se  system 200 

The  CoAs2-NiAs2-FeAs2-As  system.  .    201 
Relations  between  composition  of  ore 

minerals  and  ore  solutions 204 

Feldspars  206 

Ternary  feldspars 206 

The  system  CaAl2Si208-Si02-H20.  .   214 
Optical    properties    of    heated    plagio- 

clases 216 

The  Crystallization  of  Roc\-Forming 
Minerals  from  Magmas  and  the 
Nature  of  the  Residual  Liquid .  .  .   217 

Granitic  Pegmatites 222 

Pyroxenes 223 

The  join  MgSi03-CaMgSi206 223 

Chloritoid   225 

Al\ali  Amphiboles   228 

Reconnaissance    in    the    System    FeO- 

Fe203-Si02-H20 230 

Isograd  Problems  in  Metamorphosed  Iron- 
Rich  Sediments 232 

Crystallography    237 

Synthetic  nephelines   237 

A  sodium  nepheline  in  nature 240 

Solid  solution  242 

Phosphates    242 

Disorder  in  crystals 243 

Polymorphism  versus  isomerism 244 

Digenite 245 

Crystallochemical  analysis 245 

Application  of  the  "Morey-Schreine- 
ma\ers'  Theorem  of  Coinci- 
dence"       246 

Miscellaneous  Administration   247 

Penologists'  Club    247 

Seminars    247 

Symposium  on  high  pressures 247 

Lectures  248 

Summary  of  Published  Wor\ 249 

Bibliography  251 

Personnel 252 


Carnegie  Institution  of  Washington  Year  Boo\  56,  1956-1957 


INTRODUCTION 

The  Geophysical  Laboratory  continues  history.  Studies  in  paleobiochemistry  po- 
as  one  of  the  active  centers  of  research  in  tentially  may  lead  to  new  and  detailed  un- 
earth science.  Through  application  of  the  derstanding  of  the  origins  and  develop- 
tools  and  viewpoints  of  physical  science  we  ment  of  life  as  well  as  to  a  better  grasp  of 
are  achieving  new  understanding  of  the  such  problems  as  the  origins  of  petroleum, 
nature  and  history  of  the  processes  by  When  equipment  currently  under  develop- 
which  the  earth  evolved  to  its  present  state,  ment  is  operable,  this  Laboratory  will  be 

The  principal  lines  of  activity   at  the  able  to  participate  very  actively  in  advanc- 

Laboratory   are   studies   of  phase-equilib-  ing  one  of  man's  great  frontiers — high- 

rium  relations  of  the  major  mineral  groups,  pressure  studies.  It  is  abundantly  clear  that 

research  on  ore  minerals,  radioactive  age  a  new  type  of  chemistry  awaits  discovery 

measurements,  paleobiochemistry,  chemical  and  exploitation. 

reactions  at  extremely  high  pressures,  crys-  Crystallography  is  becoming  one  of  the 

tallography,  and  investigations  of  order-  most  vital  fields  in  science  today.  By  means 

disorder  phenomena.  of  neutron  diffraction,  nuclear  and  para- 

Phase-equilibrium  relations  among  the  magnetic  resonance,  and  X-ray  diffraction, 

major    mineral   groups    are    providing   a  the  structural  chemist  is  learning  how  the 

whole  series  of  geological  "thermometers"  precise    determination    of    molecular    ar- 

which  may  be  applied  to  igneous  and  meta-  rangement  leads  to  real  understanding  of 

morphic   rocks,   furnishing   tools   for   ac-  chemical   reactivity.    The   nature   of   the 

quiring  a  great  deal  of  information  about  chemical  bond  as  manifested  in  covalent, 

the  conditions  under  which  such  processes  metallic,   ionic,   or   intermediate   types   is 

as  mountain  building  occurred.    Similar  closely  related  to  structure, 

types  of  thermometers  are  being  developed  During  the  past  year  Chayes  has  achieved 

for  ore  minerals.  The  ultimate  accumula-  what  may  be  a  breakthrough  in  under- 

tion  of  a  number  of  these  will  permit  cross  standing  various  types  of  order-disorder  in 

checks  and  reliable  determinations  of  the  crystals.  Using  an  optical  analogue  he  has 

temperatures  present  during  ore  formation,  produced   diffraction   patterns   similar   in 

which,  in  turn,  will  lead  to  better  under-  type  to  those  obtained  from  X-ray  studies 

standing  of  the  processes  involved  and  in-  of  crystals.   It  is  too  early  to  evaluate  the 

evitably   to   knowledge  having  economic  practical   consequences,   but  fundamental 

importance.  knowledge  in  such  an  area  as  the  physics 

The  co-operative  radioactive  dating  pro-  of  the  solid  state  will  certainly  lead  to  use- 
gram  continues  to  open  new  vistas.  Re-  ful  applications.  Detailed  description  of 
liable  dates  may  now  be  assigned  to  events  Chayes'  studies  and  of  other  work  of  the 
occurring  in  any  age  throughout  the  earth's  Laboratory  follows. 

ORDER  AND  DISORDER 

F.  Chayes 

EVIDENCE  FOR  ORDER  AND  DISORDER  nealing  temperatures,  and  it  was  largely 

the  interpretation  of  these  latter  differences 

Striking  differences  in  physical  proper-  that  led  to  the  crystallographic  superlattice 

ties  are  often  noted  in  metals  or  metallic  and  the  closely  related  notion  of  long-range 

compounds,  depending  on  whether  anneal-  ordering.   The  crystallographer's  superlat- 

ing  has  taken  place  above  or  below  some  tice  in  turn  led  directly  to  the  "interpene- 

critical  temperature.  X-ray  diffraction  pat-  trating-lattice"  models  of  ordering  used  in 

terns  may  also  differ  markedly  with  an-  statistical  thermodynamics,  in  which  long- 

151 


152        CARNEGIE  INSTITUTION  OF  WASHINGTON 


range  ordering  is  usually  treated  as  an  end 
product  of  short-range  ordering. 

Recent  progress  in  experimental  petrol- 
ogy has  focused  attention  on  solid-state 
transitions,  and  in  the  course  of  the  last 
decade  mineralogists  and  penologists  have 
gradually  adopted  much  of  the  viewpoint 
and  vocabulary  developed  in  connection 
with  order-disorder  studies  of  metallic 
compounds.  This  trend  is  perhaps  par- 
ticularly true  of  feldspar  studies.  The 
suggestion  that  the  various  known  modi- 
fications of  alkali  feldspar  are  attributable 
to  ordering  actually  dates  from  well  before 
the  war.  Immediately  after  the  war,  as 
experimental  data  became  available,  the 
notion  was  extended  to  the  plagioclase 
feldspars.  Synthetic  feldspars  are  similar 
to  those  found  frequently  in  volcanic  rocks; 
the  forms  of  alkali  feldspar  and  Ca-poor 
plagioclases  found  in  plutonic  and  meta- 
morphic  rocks  have  not  yet  been  success- 
fully synthesized.  For  a  variety  of  reasons 
it  is  now  rather  generally  supposed  that 
volcanic  rocks  form  at  temperatures  higher 
than  those  characteristic  of  plutonic  or 
metamorphic  processes.  On  the  usual  as- 
sumption that  the  mineral  associations 
found  in  common  rocks  are  equilibrium 
or  near-equilibrium  assemblages,  the  forms 
characteristic  of  volcanic  environments  are 
regarded  as  stable  at  "high  temperature," 
whereas  those  found  in  the  plutonic  and 
metamorphic  rocks  are  considered  stable  at 
"low  temperature."  1 

In  few  nonmetallic  minerals  are  the 
physical  differences  between  the  high-  and 
low-temperature  forms  pronounced,  and  in 
many  they  can  be  detected  only  with  great 

1  Although  on  the  whole  quite  reasonable  and 
conformable  with  much  experimental  evidence, 
this  position  can  sometimes  be  maintained  only 
by  rather  dexterous  argumentation;  in  some 
recent  high-pressure  base-exchange  experiments 
reported  by  Wyart,  for  instance,  what  many 
workers  now  consider  the  high-temperature 
forms  of  feldspar  are  retained  at  rather  low 
temperatures  but  the  allegedly  low-temperature 
forms  do  not  survive  except  at  rather  high 
temperatures. 


difficulty.  Frequently,  as  in  the  plagioclase 
data  described  below,  it  is  necessary  to  rely 
on  minor  differences  in  X-ray  diffraction 
patterns.  It  is  now  almost  a  convention 
to  regard  the  form  apparently  stable  at  the 
higher  temperature  as  disordered  and  to 
develop  an  ex  post  facto  argument  which 
makes  it  seem  reasonable  that  the  differ- 
ences between  the  X-ray  diffraction  pat- 
terns of  the  high-  and  low-temperature 
forms  are  such  as  might  occur  if  the  low- 
temperature  form  were  in  some  way  or- 
dered. There  is  usually  no  sound  optical 
theory  indicating  which  (if  either)  of  the 
patterns  is  actually  characteristic  of  order 
(or  disorder) .  Students  of  the  layered  min- 
erals, for  instance,  are  fairly  well  agreed 
that  the  appearance  of  streaks  or  of  weak, 
poorly  resolved  additional  reflections  is 
indicative  of  disorder;  but  in  feldspar  pat- 
terns additional  poorly  resolved  reflections 
are  called  subsidiaries,  and  some  workers 
regard  them  as  indicative  of  order. 

In  this  latter  connection  it  may  be 
pointed  out  that,  although  the  hc  subsidi- 
aries of  intermediate  plagioclase  are  now 
often  considered  evidence  of  ordering,  their 
displacement  from  the  principal  layer  lines 
can  be  predicted  quite  nicely  from  com- 
position on  the  assumption  that  the  dis- 
tribution of  Al  and  Si  among  tetrahedral 
sites  is  such  as  would  be  expected  at  com- 
plete short-range  disorder. 

If  a  is  the  proportion  of  tetrahedral  sites 
occupied  by  Al  (as  calculated  from  the 
chemical  analysis),  the  expected  number 
of  "runs"  of  Al  in  any  randomly  chosen 
consecutive  series  of  N  such  sites  is  Na 
(1  — a),  where  a  run  is  defined  as  a  se- 
quence of  i  Al  ions  bounded  at  both  ends 
by  an  Si  ion.  Since  the  entire  series  con- 
tains Na  Al's,  the  average  length,  E(Iai), 
of  runs  of  Al  ions  is  thus  Na/Na(l  —  a)  = 
1/(1  —  a) ;  similarly,  E(/si)  =  1/a.  Figure  1, 
based  entirely  on  the  data  of  P.  Gay,  shows 
the  remarkable  correlation  of  the  pseudo- 
periodicity,  indicated  by  the  displacement 
of  hc  from  the  principal  layer  line,  with 
the  average  run  length  of  Si  at  short-range 


GEOPHYSICAL  LABORATORY       153 


disorder,  calculated  from  the  composition. 
This  is  of  course  not  to  be  construed 
as  proof  that  the  plagioclases  studied  by 
Gay  are  disordered.  It  is  fair  to  point  out, 
however,  that  although  close  dependence 
of  he  spacing  on  composition  has  been 
known  for  some  time,  no  argument  based 
on  ordering  has  provided  a  reasonable  ex- 
planation of  the  spacing  actually  found. 
To  the  limits  of  error  of  the  data,  the  slope 
of  the  solid  line  shown  in  figure  1  is  unity 
and  its  intercept  is  zero;  the  average  run 
length  of  Si  at  complete  disorder  and  the 
pseudoperiodicity  indicated  by  the  hG  dis- 


Fig.  1.  Sc  separations  in  intermediate  plagio- 
clase  as  a  function  of  Si  run  length.  X=E(iSi)  — 
or1,  Y  =  36Q  S^1.    (A,  Y  =  X;  B,  line  of  best  fit 

calculated  from   data   of  P.   Gay,   Y=  1.052   X 
-0.222.) 

placement  are  evidently  estimates  of  the 
same  parent  parameter. 

SHORT-  AND  LONG-RANGE  ORDER 

According  to  now  standard  definitions, 
short-range  ordering  concerns  the  immedi- 
ate environment  of  an  atom  as  judged  by 
the  numbers  of  "right"  and  "wrong"  pairs 
it  forms  with  its  "nearest  neighbors," 
whereas  long-range  order  concerns  the 
emergence  and  strength  of  a  new  over-all 
periodicity  in  the  crystal.  In  the  ingenious 
and  often  rather  terrifying  "interpenetrat- 


ing-lattice"  models  proposed  by  statistical 
thermodynamicists,  the  elimination  of 
wrong  pairs  automatically  generates  what 
is  called  long-range  order  by  thermody- 
namicists and  a  superlattice  by  crystallog- 
raphers.  It  is  not  the  elimination  of  wrong 
pairs  as  such  that  generates  the  long-range 
order  in  these  models,  however,  but  the 
mechanism  by  which  they  are  eliminated. 
The  alleged  relation  between  long-  and 
short-range  ordering  is  not  to  be  regarded 
as  something  that  emerges  from  arguments 
based  on  interpenetrating-lattice  models; 
it  is  built  into  them.  Models  in  which 
long-  and  short-range  ordering  are  in  gen- 
eral quite  independent  can  be  constructed, 
and  in  view  of  current  interest  in  mineral- 
ogical  order-disorder  problems  considera- 
tion of  such  models  seems  eminently 
worth  while. 

THE  LINEAR  RUN  MODEL  OF  SHORT-RANGE 
ORDERING 

In  the  sequence  AABAAABBABBAB 
there  are  seven  A's  and  six  B's.  Defining  a 
"run"  as  a  sequence  of  elements  of  one 
kind  bounded  at  each  end  by  an  element 
of  the  other  kind  (or  by  the  beginning  or 
end  of  the  series),  the  sequence  above  con- 
tains eight  runs,  two  of  length  1,  one  of 
length  2,  and  one  of  length  3  in  A;  two  of 
length  1  and  two  of  length  2  in  B. 

Run  sequences  of  this  type  have  been 
studied  in  considerable  detail,  perhaps 
chiefly  in  connection  with  statistical  quality 
control,  and  several  of  their  characteristics 
useful  in  a  discussion  of  short-range  order- 
ing are  now  well  known.  Chief  among 
them  is  the  expected  number  of  runs,  from 
which  may  be  calculated  both  the  average 
length  of  run  in  either  element  and  the 
numbers  of  right  and  wrong  pairs  at  com- 
plete disorder  or  complete  short-range 
order. 

Given  a  sequence  of  sufficient  length,  in 
which  the  probability  that  any  particular 
site  will  be  occupied  by  an  A  is  simply  the 
ratio  of  the  number  of  A's  to  the  number 
of  (y4's  + J5's),  the  expected  number  of  runs 


154        CARNEGIE  INSTITUTION  OF  WASHINGTON 


is  E(d)=2Na$,  where  N  is  the  number  of 
elements  (or  sites),  a  =  T,(A)/X,(A  +  B), 
andP  =  l-a.1 

Now  the  probability  of  occupancy  speci- 
fied above  is  precisely  that  which  obtains, 
in  theory,  at  complete  disorder.  From  the 
definition  of  a  run  it  is  obvious  that  the 
last  element  in  each  run  and  the  first  ele- 
ment of  the  succeeding  run  form  a  right 
pair,  and  that  there  can  be  no  other  right 
pairs.  Since  the  last  element  of  the  last  run 
remains  unpaired,  the  expected  number  of 
right  pairs  at  complete  disorder  is  thus  1 
less  than  the  number  of  runs,  or 

E(PAB)=E(d)=2Na$-l 

Coupling  each  site  with  its  next  adjacent 
site,  it  is  evident  that  a  sequence  of  N  sites 
yields  a  total  of  (N—l)  pairs,  and  since 
(2Na$  —  1)  of  these  pairs  are  right,  the 
remaining  N(l  —  2a(3)  =Na2+Nfi2  must 
be  wrong,  i.e.  must  juxtapose  two  like  ele- 
ments as  nearest  neighbors.  It  is  easily 
shown  that  ATa2  of  these  are  in  A,  IV$2 
in  B. 

At  perfect  short-range  order  there  are  by 
definition  no  wrong  pairs  in  the  minor  ele- 
ment of  the  sequence,  which  we  shall  take 
as  A.  Since  right  pairs  must  involve  only 
the  first  or  last  element  of  a  run,  it  follows 
that  at  perfect  short-range  order  all  runs 
in  A  are  of  length  1.  This  means  that  there 
will  be  as  many  runs  in  A  as  there  are  A's. 
If  boundary  corrections  are  ignored,  there 
will  also  be  as  many  runs  in  B  as  there  are 
in  A,  and  so  the  expected  number  of  runs 
in  the  entire  sequence  will  be  IN  a.  This 
is  again  the  number  of  right  pairs,  for  each 
A  forms  a  right  pair  with  each  of  its  two 
bounding  B's.  All  the  remaining  pairs  are 
wrong  pairs  in  B,  and  their  number  is 
N(l  —  2a).  These  results  are  shown  in 
table   1.    The   frequencies   of   right   and 

1  From  the  definition  we  may  also  write 

Z(A)L(B) 
UW=L  Z(A+B) 

Although  this  and  all  succeeding  estimates  are 
large-sample  approximations,  the  approximations 
are  very  good  even  for  N  much  smaller  than  is 
likely  to  be  required  in  crystal  chemistry. 


wrong  pairs  in  the  two  limiting  cases  are 
in  agreement  with  those  calculated  from 
the  interpenetrating-lattice  models.  Noth- 
ing has  been  said,  and  except  as  the  quan- 
tity (3  —  a)— >0  nothing  is  implied,  about 
long-range  order. 

TABLE    1.    Numbers    of    Right    and    Wrong 

Pairs  at  Complete  Disorder  and  Complete 

Short-Range  Order 


Pair  Type 


Disorder 


Short-Range 
Order 


Wrong:     (A  A) Na2  0 

(BB) N(32  N(l-2o) 

Right:       (AB) 2Na(3  2Na 


DIMENSIONS  IN  THE  RUN  MODEL 

At  complete  disorder  the  run  model  is 
essentially  independent  of  direction.  It  is 
only  necessary  that  each  site  occur  once 
and  only  once,  and  that  in  some  specified 
operational  sense  the  nth.  site  always  follow 
the  (n  —  l)th  and  be  followed  by  the 
0  +  l)th. 

In  principle,  at  least,  complete  short- 
range  disorder  ought  to  be  spherically  iso- 
tropic in  a  three-dimensional  array.  As 
ordering  develops,  however,  its  level  or 
intensity  varies  vectorially,  and  the  lattice 
of  the  run  sequence  must  be  assigned  some 
direction  in  the  crystal.  We  may  then  deal 
with  sets  of  intersecting  run  sequences, 
each  site  belonging  to  a  member  of  each 
set.  The  members  of  each  set  are  parallel 
to  each  other  and  intersect  members  of 
each  other  set  at  a  common  angle.  Since 
every  site  is  included  in  one  member  of 
each  set,  and  an  element  of  either  type  may 
fall  on  any  site,  there  is  still  no  a  priori  re- 
lation between  long-  and  short-range  order. 
A  knowledge  of  the  level  of  ordering  along 
one  set  offers  no  indication  of  the  level  of 
ordering  along  other  sets;  in  particular, 
there  may  be  perfect  short-range  order 
along  one  set  and  complete  disorder  along 
all  others.  (In  the  run  model  this  could  be 
true  of  long-range  ordering  as  well.) 


GEOPHYSICAL  LABORATORY        155 


THE  NUMBERS   AND   LOCATIONS   OF 
NEAREST  NEIGHBORS 

The  interpenetrating-lattice  models  used 
in  the  standard  treatments  are  so  con- 
structed that  no  site  may  have  as  nearest 
neighbor  another  site  on  the  same  sublat- 
tice.  In  the  run  model,  on  the  contrary, 
the  nearest  neighbors  of  the  nth.  site  are 
always  the  (n  —  l)th  and  (w  +  l)th  sites 
of  the  same  run  sequence.  Thus  if  a  site 
is  a  member  of  only  one  run  sequence  it 
has  only  2  nearest  neighbors.  In  a  plane 
net  a  site  may  be  a  member  of  two  or  three 
intersecting  run  sequences  and  may  accord- 
ingly have  4  or  6  nearest  neighbors.  In 
three  dimensions  any  site  may  be  a  mem- 
ber of  three  or  four  intersecting  run  se- 
quences, and  thus  may  have  6  or  8  near- 
est neighbors.  The  interpenetrating-lattice 
models  are  not  so  limited  or  inflexible  with 
regard  to  the  number  of  nearest  neighbors, 
a  parameter  of  considerable  importance  in 
thermodynamic  calculations. 

SOME  PRELIMINARY  EXPERIMENTAL  RESULTS 

Instrumentation.  Enough  has  been  said 
to  indicate  that  knowledge  of  the  influence 
of  disorder  on  diffraction  effects  would  be 
of  considerable  value  in  studies  of  solid- 
state  transitions.  Direct  mathematical  anal- 
ysis is  rather  forbidding,  and  at  present 
there  seems  no  other  approach  to  the  prob- 
lem in  three  dimensions.  To  produce  two- 
dimensional  models  (or  masks),  however, 
is  comparatively  simple,  and  the  diffraction 
patterns  of  such  masks  are  readily  observed 
in  an  optical  diffractometer  of  the  kind 
first  described  by  Taylor,  Hughes,  and 
Lipson.  In  this  apparatus  the  optical  train 
consists  of  a  point  source,  filters,  a  collimat- 
ing  lens,  a  collecting  lens,  and  a  microscope 
or  camera.  The  mask  is  placed  in  the 
collimated  beam  (between  collimator  and 
collector),  and  its  (Fraunhofer)  diffraction 
pattern  is  observed  or  photographed  at  the 
focal  plane  of  the  collector.  During  the 
last  two  months  of  the  report  year  a  small 
instrument  of  this  type  was  constructed, 
with  a  2-watt  concentrated  arc  light  as 
point   source.    The   lenses   are   of   1-inch 


working  diameter,  and  their  focal  lengths 
are  such  that  the  image  is  brought  to  final 
focus  less  than  2  feet  from  the  point  source. 
Its  dimensions  make  the  instrument  both 
inexpensive  to  build  and  convenient  to  use. 
The  relatively  short  focal  lengths  of  the 
collimator  and  collector  generate  a  rather 
small  final  diffraction  pattern,  a  limitation 
not  critical  for  present  purposes.  The  nar- 
rowness of  the  collimated  beam  is  a  more 
serious  handicap,  for  it  requires  the  use  of 
rather  small  masks. 

For  the  production  of  suitable  masks  a 
procedure  combining  punching  and  photo- 
graphic reduction  has  been  developed.  A 
more  complete  description  of  the  instru- 
ment and  an  account  of  the  procedure  for 
making  masks  is  being  prepared  for  pub- 
lication elsewhere.  To  date  only  masks 
containing  a  single  "atom" — i.e.  in  which 
all  openings  are  of  the  same  diameter — 
have  been  prepared,  and  emphasis  has  been 
placed  on  the  effect  of  "mistakes"  in  the 
stacking  of  layered  structures.  Layering  is 
particularly  useful  as  a  starting  point,  not 
only  because  masks  portraying  varying 
levels  of  ordering  are  easily  prepared  but 
also  because  it  has  been  examined  theo- 
retically. 

Equal  numbers  of  layers  in  each  of  two 
positions.  This  is  the  case  on  which  A.  J. 
C.  Wilson  builds  his  theory  of  the  optical 
effect  of  mistakes  in  layered  structures.  The 
a  and  b  axes  lie  in  the  plane  of  layering, 
the  c  axis  normal  to  this  plane,  all  the  lay- 
ers are  supposed  identical,  and  the  mistake 
consists  of  a  shift  of  the  layer  by  half  the  b 
axis.  The  diffraction  mask  modeling  this 
situation  would  be  a  be  section,  with  lines 
containing  equal  numbers  of  equally 
spaced  holes  in  the  b  direction  and  a  ran- 
domly distributed  offset  of  b/2  from  one 
layer  to  the  next  along  c.  Figure  2a  shows 
such  a  mask,  and  figure  2b  its  diffraction 
pattern.1  The  diffuse  streaks  cutting  the 
principal  layer  lines  are  in  accord  with  the 
reciprocal  lattice  calculated  by  Wilson;  the 

1  Figures  2  and  3  are  on  plate  1.  Plates  are 
collected,  facing  page  192. 


156        CARNEGIE  INSTITUTION  OF  WASHINGTON 


weak  but  clearly  resolved  reflection  mid-  layers  in  one  position  followed  by  one  in 
way  between  layer  lines  occurs  in  a  region  the  other,  e.g.  BB  ABB  ABB  A.  .  .  .  This 
in  which  his  theory  evidently  indicates  no  arrangement  is  characterized  by  perfect 
diffraction,  either  diffuse  or  resolved.  In  short-  and  long-range  order;  e.g.,  all  As 
a  mask  in  which  short-range  ordering  was  occur  in  runs  of  length  1  along  c,  and  the 
perfect — that  is,  one  in  which  there  was  "repeat  distance"  along  c  is  3  layers.  There 
an  offset  between  each  pair  of  layers — this  are  four  principal  reflections  at  the  corners 
central  spot  would  be  of  the  same  intensity  of  a  square,  an  exceedingly  weak  one  be- 
as  the  principal  reflections  and  there  would  tween  each  pair  of  principals  on  the  layer 
be  no  diffuse  scatter  crossing  the  layer  lines,  and  two  bright  ones  symmetrically 
lines.  spaced  at  %  and  %  of  the  distance  between 

The  contrast  between  the  observed  and  layer  lines, 

expected  effect  of  disorder  on  diffraction  Figure  4# 2  is  a  2 : 1  (actually  35  per  cent) 

is  so  striking  as  to  require  further  study,  mask  in  which  there  is  perfect  short-range 

and  this  is  now  in  progress.    Since  the  but  no  long-range  order,  and  figure  Ab 

transform  of  the  perfectly  ordered  array  is  its  diffraction  pattern.    The  principals 

would  have  a   strong  central  spot,  it  is  and  weak  subsidiaries  are  as  in  figure  3a, 

tempting  to  suppose  that  the  presence  of  but  instead  of  two  bright  reflections  at  l/3 

a  weak  spot  in  this  position  in  the  trans-  and  %  of  the  layer  line  interval  there  is  a 

form  of  the  disordered  array  merely  sig-  single,  evidently  composite,  large  one  at  l/2 

nalizes  the  presence  of  an  undue  concen-  that  interval. 

tration   of   ABAB  .  .  .  sequences   in   the  Figure  5a  is  a  35  per  cent  mask  in  which 

mask.    There  is  excellent  reason  to  sup-  there  is  complete  disorder— i.e.  the  prob- 

pose,  however,  that  this  is  not  the  correct  ability  that  any  layer  is  an  A  is  simply  the 

explanation  in  this  particular  case.  proportion  of  A's  in  the  parent  population 

Preponderance  of  layers  in  one  position,  oi  layers.  Figure  5b  is  the  diffraction  pat- 
In  the  standard  derivation,  based  on  Wil-  tern  of  this  mask.  The  four  principals  are 
son's  analysis,  the  number  of  layers  in  each  as  in  figures  3  and  4,  but  there  is  much 
position  is,  at  least  by  implication,  the  diffuse  scatter,  and  there  are  also  two  well 
same.  The  remaining  work  to  be  reported  resolved  subsidiaries  at  1/6  and  5/6  the 
on  is  concerned  with  masks  in  which  there  layer  line  interval. 

is  a  preponderance  of  layers  in  one  of  the  The  patterns  yielded  by  perfect  long- 
two  positions.  Crystallographers  have  evi-  (and  snort')  ranSe  order>  Per£ect  short> 
dently  not  considered  this  possibility  in  ranSe  order>  and  complete  disorder  are 
connection  with  order-disorder  diffraction  thus  clearly  differentiable.  Investigation  of 


effects,  but  even  the  preliminary  results      the  nature  of  the  passage  from  one  pattern 

to  either  or  the  others,  as  well  ~  ■  ! 

of  similar  diffraction  effects 
A :  B  ratios,  is  now  in  process. 


ciiclls,    uul    even    liic    uiciiminai y    icbuiu>  .  ,  r    ,  *  ^  ..  .  *  , 

•i  ii  .    ,i    .    •.       •  i  .    i         to  either  or  the  others,  as  well  as  the  study 

now  available  suggest  that  it  might   be        r    .    .,       ,._-       .         *•         r       i-n- 

or  similar  difir action  effects  tor  different 


worth  close  study. 

Figure  3  is  the  diffraction  pattern  of  a 

mask  containing  a  rigid  succession  of  two  2  Figures  4  and  5  are  on  plate  2. 

BASALT  MAGMAS 

H.  S.  Yoder,  Jr.,  and  C.  E.  Tilley 

Each  of  the  two  major  basalt  magma  others  view  the  various  magmas  as  unre- 

types,  the  tholeiitic  basalt  type  and  the  lated,  each  giving  rise  to  its  own  rock  types 

alkali  basalt  type,  has  been  nominated  as  independently. 

the  parental  or  primitive  magma.    Some  New  experimental  data  bear  on  the  prob- 

believe  that  a  third  magma  as  yet  unob-  lem  of  the  alleged  primary  magma.  Speci- 

served  is  in  fact  the  primary  magma,  and  mens  of  natural  basalt  representative  of 


GEOPHYSICAL  LABORATORY        157 


three  magma  types,  (a)  tholeiite,  (b)  alkali 
basalt,  and  (c)  high-alumina  basalt,  were 
selected  for  thermal  study  at  atmospheric 
pressure.  Types  (a)  and  (£),  represented 
by  specimens  from  Hawaii,  conform  to 
the  two  chief  magma  types  recognized  by 
the  authors  of  the  Mull  Memoir,  and  (<r), 
represented  by  a  nonporphyritic  Warner 
basalt  from  California,  is  chemically  com- 
parable to  the  Porphyritic  Central  type  of 
Mull.  The  chilled  marginal  facies  of  the 
Skaergaard  layered  gabbro  of  East  Green- 
land conforms  closely  to  this  type  (Tilley, 
1950) .  Analyses  of  four  rocks  of  the  three 
types  are  given  in  table  2,  and  the  norms  in 
table  3. 

The  first  two  analyses  are  of  tholeiitic 
type:  (1)  the  1921  Kilauea  lava,  an  olivine- 
enriched  example  discussed  in  last  year's 
report;  and  (2)  a  prehistoric  lava  from 
Kilauea,  a  typical  silica-saturated  basalt 
corresponding  more  closely  to  the  primitive 
Kilauean  liquid  (Powers,  1955). 

The  pyroxenes  of  the  four  rocks  have 
been  isolated  and  analyzed;  the  results  of 
the  analyses  are  expressed  in  terms  of  the 
principal  pyroxene  components  in  figure  6. 
Three  fractions  of  pyroxene  (A,  B,  C)  ob- 
tained from  the  1921  lava  and  two  (D,  E) 
from  the  prehistoric  lava  provide  evidence 
that  some  fractionation  took  place  during 
the  crystallization. 

The  pyroxenes  have  compositions  typical 
of  those  from  the  three  magma  types.  In 
general,  the  pyroxenes  of  the  alkali  basalts 
are  along  the  Di-Hd  join,  while  the 
tholeiitic  pyroxenes  are  more  pigeonitic. 

Each  of  these  basalts,  as  well  as  others, 
was  held  at  various  temperatures  through 
the  courtesy  of  J.  F.  Schairer.  Each  basalt 
is  a  single  bulk  composition  in  a  multicom- 
ponent  system,  and  its  crystallization  his- 
tory can  be  determined  in  the  usual  way 
by  the  quenching  method.  Small  samples 
were  dried  at  110°  C,  sealed  in  platinum 
tubes,  and  held  for  1  to  24  hours  at  constant 
temperature  and  atmospheric  pressure.  Be- 
cause of  loss  of  iron  to  the  platinum  con- 
tainer and  some  oxidation  of  the  iron,  the 
temperatures  stated  should  be  considered 


approximate.    The    results    are   given   in 
figure  7. 

For  the  1921  flow  of  Kilauea,  the  liq- 
uidus  is  at  1235°  C,  and  olivine  is  the  first 
major  phase  to  appear.  At  about  1190°  C 
pyroxene  comes  in,  and  at  1170°  C  these 
are  joined  by  plagioclase.  At  1090°  C  the 
charge  is  all  crystalline.  The  temperatures 

TABLE  2. — Chemical  Analyses  of  Basalts 


1 


SiO, 49.16  51.18  48.27  49.28 

Al263   13.33  14.07  18.28  15.98 

Fe2Os   1.31  1.35  1.04  4.11 

FeO 9.71  9.78  8.31  7.94 

MnO   0.16  0.17  0.17  0.19 

MgO   10.41  7.78  8.96  4.44 

CaO 10.93  10.83  11.32  9.55 

Na,0 2.15  2.39  2.80  3.47 

K26 0.51  0.44  0.14  1.26 

H00+    0.04  0.10  0.15  0.39 

H20~    0.05  0.01  0.07  0.53 

PX>5   0.16  0.15  0.07  0.23 

TiO,   2.29  2.10  0.89  3.06 

Cr203   0.09  0.05  ....  0.02 

Total 100.30    100.40     100.47    100.45 

1.  Tholeiite  basalt:  1921  lava,  Kilauea  caldera, 
Hawaii,  No.  57364  (Cambridge  University  Col- 
lection). Analyst:   J.  H.  Scoon. 

2.  Tholeiite  basalt:  prehistoric  flow,  National 
Park  Quarry  on  highway  0.75  mile  NE  of  Vol- 
cano Observatory,  Kilauea  No.  57358  (Cambridge 
University  Collection).   Analyst:   J.  H.  Scoon. 

3.  High-alumina  basalt:  Warner  flow,  4  miles 
SE  of  East  Sand  Butte,  Medicine  Lake  High- 
lands, Calif.,  No.  127-ML-295.  Collected  by 
C.  A.  Anderson.   Analyst:    J.  H.  Scoon. 

4.  Alkali  basalt:  Papalele  Gulch,  near  highway 
NE  of  Mauna  Kea,  Hawaii,  No.  60464  (Cam- 
bridge University  Collection).  Analyst:  J.  H. 
Scoon. 

observed  by  Jagger  at  the  Halemaumau 
crater  in  1921  were  1190°  and  1200°  C. 
The  above  results  are  in  accord  with  his 
observations  and  suggest  that  the  water 
pressure  of  the  magma  was  very  low.  The 
most  significant  observation,  however,  is 
that  all  three  major  phases  appear  within 
65°  C.  Dip  samples  of  the  lava  in  1911 
showed  all  three  phases  present  even 
though  the  crystal  content  was  only  a  few 


158        CARNEGIE  INSTITUTION  OF  WASHINGTON 


per  cent.  The  index  of  refraction  of  the 
glass  so  obtained  was  given  as  1.605  by 
Merwin.  The  glass  prepared  in  the  labora- 
tory by  completely  melting  the  1921  flow 
basalt  had  an  index  of  refraction  of  1.608. 
Note  also  that  in  the  laboratory  the  basalt 
had  a  small  interval  of  crystallization  of 
about  150°  C.  A  prehistoric  lava  from 
Kilauea  (fig.  7),  which  has  less  olivine, 
shows  approximately  the  same  results  but 
has  a  liquidus  at  1195°  C.  All  three  major 
phases  appear  within  a  small  range  of  tem- 
perature, 40°  C.  The  total  range  of  crys- 
tallization is  only  130°  C.  The  liquidus 
for  the  1887  basalt  from  Mauna  Loa  is 
about  the  same  temperature  as  the  Kilau- 
ean  basalts,  each  producing  olivine  as  the 
first  major  phase.  The  alkali  basalt  from 
Mauna  Kea  has  a  liquidus  of  1185°  C, 
and  plagioclase  is  the  first  major  phase  to 


; a- 

Mouna  Kea 


oMedlcine  Lake 


Oc<bC 


Fig.  6.  Plot  of  pyroxenes  from  rocks  of  table  2 
in  the  system  diopside  (Di)-hedenbergite  (Hd)- 
enstatite  (En)-ferrosilite  (Fs).  The  fractions  A, 
B,  and  C  are  from  the  1921  flow,  and  D  and 
E  from  a  prehistoric  flow,  of  Kilauea. 


appear.  Olivine  and  pyroxene  come  in  to- 
gether at  about  1160°  C,  and  at  1040°  C 
the  charge  is  all  crystalline.  Again,  a  nar- 
row range  of  temperature  in  which  all 
three  major  phases  appear,  25°  C,  is  ob- 
served. The  total  range  of  crystallization 
is  only  150°  C.  A  representative  of  the 
third  major  basalt  type  is  the  high-alumina 
basalt  from  Medicine  Lake  Highlands, 
California.  This  basalt  yields  approxi- 
mately the  same  results. 

The  significant  conclusions  from  this 
cursory  study  of  representatives  of  the 
three  major  basalt  types  are:  (1)  all  three 
major  phases  appear  in  a  short  interval  of 
temperature  under  the  experimental  con- 
ditions; (2)  all  three  major  phases  appear 


1                 1 

1                        1 

n  of  glass 

Mauna  Kea 

XTL 

a 

PX+OL    PL 

® — A 

1.597 

Prehistoric  Kilauea 

XTL 

PL  PX         OL 

1.597 

1887  Mauna  Loa 

?<E 

OL 

o 

1.597 

Medicine  Lake 

XTL 

PX 

PL+OL 

1.592 

1921   Kilauea 

XTL 

a — 

PL      PX 

A— -X 

1 

OL 

— o 

1.608 

IIOO  1200 

TEMPERATURE    °C 


Fig.  7.  Results  of  thermal  treatment  of  se- 
lected basalts  representative  of  major  basalt 
magma  types.  The  abbreviations  are  for  olivine 
(OL),  plagioclase  (PL),  pyroxene  (PX),  and  all 
crystalline  (XTL). 


TABLE  3.    Norms  of  Basalts  Given  in  Table  2 


Tholeiite 
1921  Kilauea 


Tholeiite 

Prehistoric 

Kilauea 


High-Alumina 

Basalt 
Medicine  Lake 


Alkali  Basalt 
Mauna  Kea 


Qz 

0.30 

•  •  •  • 

Or 

..      2.781 

2.221 

0.561 

7.501 

Ab 

..     17.82  f     45.90             20.96  h      49.31             23.58  h      61.11             29.34  \-      61.16 

An 

. .     25.30J 

26.13J 

36.97J 

24.32J 

Di 

. .     22.93 

22.04 

15.23 

17.97 

Hy    

. .     15.35 

22.44 

6.43 

Ol  

9.14 

20.55 

1.83 

Mt 

. . .      2.09 

1.86 

1.39 

6.03 

11 

4.41 

3.95 

1.67 

5.78 

Ap 

. . .      0.34 

0.34 

0.17 

0.34 

H20*   

. . .      0.09 

0.11 

0.22 

0.92 

Total 

100.25 

100.35 

100.34 

100.46 

GEOPHYSICAL  LABORATORY        159 


together  at  about  the  same  temperature 
(1160°  to  1170°  C),  irrespective  of  the  bulk 
composition  of  the  basalt;  (3)  the  total 
range  of  crystallization  is  small,  of  the 
order  of  150°  C;  (4)  olivine  or  plagioclase 
appears  on  the  liquidus  to  the  exclusion  of 
pyroxene  for  the  basalts  studied.  Powers 
(1955)  records  the  fact  that  no  augite 
phenocrysts  are  found  in  most  of  the  lavas 
of  the  shield-building  stage  at  Hawaii. 

These  data  can  be  interpreted  in  terms 
of  the  synthetic  system  of  simplified  basalts 
as  determined  in  the  laboratory.  To  repre- 


Fig.  8.  The  "simplified  basalt"  system  diop- 
side  (Di)-albite  (Ab)-anorthite  (An)-forsterite 
(Fo)  based  on  the  experimental  studies  of  Os- 
born  and  Tait  (1952),  Bowen  (1915),  and 
Schairer  (unpublished  data).  Certain  liberties 
were  taken  near  the  corner  Ab,  which  are  ampli- 
fied in  part  by  figure  9. 

sent  the  compositions  of  a  simple  basalt 
(pyroxene  +  olivine  +  plagioclase),  the  tet- 
rahedron diopside  (Di)-forsterite  (Fo)- 
albite  (Ab)-anorthite  (An)  was  con- 
structed from  the  studies  of  Osborn  and 
Tait  (Di-Fo-An),  Bowen  (Di-Ab-An), 
and  Schairer  (unpublished  data:  Fo-Ab, 
Di-Ab).  The  system  given  schematically 
in  figure  8  is,  of  course,  only  pseudoqua- 
ternary,  since  the  compositions  of  all  the 
phases  cannot  be  represented  by  the  com- 
ponents chosen.  If  the  spinel  field  is  neg- 
lected, there  are  three  volumes,  each  rep- 
resenting a  major  phase — diopside,  forster- 


ite,  and  plagioclase.  Two  phases  are  in 
equilibrium  with  liquid  along  the  shared 
surfaces,  and  all  three  phases  are  in  equi- 
librium with  liquid  along  the  one  common 
curve,  the  four-phase  curve.  In  the  heating 
experiments  described,  all  three  phases  ap- 
peared over  a  small  range  of  temperature. 
For  this  reason  the  composition  of  the 
basalts  must  lie  very  close  to  a  similar  four- 
phase  curve.  Whether  olivine  or  plagio- 
clase (or  even  pyroxene)  precipitates  out 
first  is  of  small  importance.  What  is  im- 
portant is  the  temperature  at  which  all 
three  phases  begin  crystallizing  together. 
Each  composition  should  on  cooling  reach 
the  four-phase  curve  at  a  characteristic 
temperature.  Liquids  at  higher  tempera- 
tures on  the  four-phase  curve  can  give  rise, 
through  fractionation,  to  liquids  at  a  lower 
temperature  on  the  curve.  Liquids  at  the 
lower  temperatures  cannot  yield  a  magma 
having  a  higher  temperature  on  the  four- 
phase  curve.  From  the  data  on  the  natural 
rocks  given  in  figure  7,  it  is  seen  that 
neither  the  alkali  basalt  nor  the  tholeiite 
basalt  can  be  specified  as  the  parent,  since 
they  reach  the  "four-phase  curve"  at  about 
the  same  temperature.  On  the  basis  of  the 
data  presented,  it  may  be  tentatively  con- 
cluded that  all  these  basalts  are  themselves 
a  product  of  the  same  melting  process,  the 
diversity  arising  as  a  result  of  different 
initial  bulk  compositions. 

If  the  simple  basalts  represented  in  figure 
8  fractionated,  the  liquid  would  descend  to 
the  point  marked  ~1090°  C.  Certain  liber- 
ties were  taken  to  simplify  the  relations 
near  the  Ab  corner,  and  now  these  must  be 
examined  more  closely.  Schairer  has  re- 
studied  the  join  Ab-Di  in  the  larger  aspect 
of  the  nepheline-silica-diopside  join,  which 
is  not  ternary  (fig.  9).  Here  enters  an- 
other difficulty  in  choosing  the  alleged 
parental  basalt.  Consider  a  bulk  composi- 
tion in  the  diopside  field  on  the  Ab-Di 
join.  The  liquid  stays  in  the  plane  until  it 
hits  the  plagioclase  field  boundary  curve. 
Then,  if  the  liquid  were  slightly  saturated 
in  silica,  its  fractionated  liquids  would 
trend  toward  silica.    If  the  liquid   were 


160        CARNEGIE  INSTITUTION  OF  WASHINGTON 


slightly  undersaturated,  it  would  go  to  the 
nepheline  side.  In  examining  the  original 
liquid,  very  careful  analytical  work  would 
be  required  to  determine  in  advance  which 
way  it  would  go.  A  similar  situation  arises 
when  compositions  near  the  Ab-An  join 
in  the  nepheline^-silica-anorthite  system 
(Schairer,  unpublished)  are  considered.  In 
all  the  systems  involving  potash,  such  as 
An-leucite-silica   (Schairer  and  Bowen), 


of  the  two  major  magma  types,  and  its  be- 
havior bears  on  their  relationships.  The 
tholeiite  magmas  characteristically  show 
the  reaction  relation  with  olivine;  the  alkali 
basalt  magmas  do  not.  These  observations 
can  be  interpreted  in  terms  of  Bowen's 
diagram  for  Di-Fo-silica  (fig.  10).  The 
tholeiites  must  start  their  crystallization 
in  the  olivine  field  in  the  area  formed  by  a 
line  joining  Mg2Si04  to  the  point  where 


DIOPSIDE 
1391  6°    @    CoMgSigOg 


NEPHELINE 
CARNEGIEITE 
NaAlS.04 


JADEITE"  ,,,„._„ 

COMPN.  Il18-3 

WEIGHT  PERCENT 


Fig.  9.  The  system  CaMgSi206-NaAlSi04-Si02  (Schairer,  unpublished  data  given  in  Yoder,  1950, 
with  permission).  The  join  albite-diopside,  which  is  not  binary,  is  not  shown. 


Di-leucite-silica  (Schairer  and  Bowen), 
Fo-leucite-silica  (Schairer),  and  fayalite- 
leucite-silica  (Bowen  and  Schairer),  the 
liquids  trend  toward  silica  and  not  toward 
the  feldspathoid.  It  is  clear  from  these 
considerations  that  no  one  magma  can  go 
to  both  sides  if  only  the  simple  major 
phases  are  considered.  On  these  grounds 
it  must  be  concluded  that  a  single  magma 
cannot  produce  both  a  tholeiite  trend  and 
an  alkali  trend  by  fractionation.  The  dif- 
ferences between  the  magmas  capable  of 
producing  such  trends,  however,  may  be  so 
small  as  to  be  not  readily  detectable. 
Olivine  plays  an  interesting  role  in  each 


the  pyroxene  boundary  curve  crosses  the 
MgSi03-CaMgSi206  join  and  the  pyroxene 
boundary  curve.  The  alkali  basalts  appar- 
ently begin  their  crystallization  in  the  re- 
maining area  of  the  olivine  field,  or  in  the 
pyroxene  field  near  the  diopside  corner  to 
the  left  of  the  MgSi03-CaMgSi206  join. 
To  support  this  view,  Powers  notes  that  the 
lavas  showing  augite  phenocrysts  are  usu- 
ally assigned  to  the  declining  stage  of  ac- 
tivity in  the  Hawaiian  volcanoes,  the 
alkali-rich  stage. 

Water  must  be  considered  among  the 
agents  effective  in  altering  the  course  of 
crystallization,  and  the  oxidation  or  reduc- 


GEOPHYSICAL  LABORATORY       161 


tion  of  iron  may  account  for  alternative  barrier  between  the  saturated  and  unsat- 

courses.  The  problem  of  the  alleged  paren-  urated  magma  types.  The  effects  of  water 

tal  basalt  seems  to  hinge  on  finding  suit-  as  a  possible  mechanism  are  now  under 

able  mechanisms  to  bridge  the  apparent  study. 


CaMgSi206 


Mg2Si04 


MgSi03 


SiO 


Fig.  10.    The  system  CaMgSi206-Mg2Si04-Si02    (Bowen,   1914).    The  join  CaMgSi206-MgSi03, 

which  is  not  binary,  is  dashed. 

STABILITY  OF  ANNITE 
H.  P.  Eugster 


Preliminary  data  on  the  stability  of  the 
ferrous  biotite  annite  were  reported  last 
year.  Since  then  experimental  work  on  this 
mineral  has  been  completed  up  to  2000 
bars  total  pressure.  The  revised  equilib- 
rium diagrams  are  presented  in  figures  11, 
12,  13,  and  14.  Of  the  three  independent 
variables,  temperature  T,  total  pressure 
Ptot  (  =  Ph2o),  and  partial  pressure  of 
oxygen  Po2,  only  two,  namely  T  and  Ptot, 
can  be  varied  continuously.  Po2  is  defined 


by  the  five  buffers  that  surround  the  semi- 
permeable sealed  platinum  tube.  The 
buffers  are  mixtures  of  iron  oxides,  fayal- 
ite,  and  quartz.  Hydrogen  formed  by  the 
dissociation  of  water  and  passing  through 
the  platinum  tube  acts  as  a  transfer  agent 
in  equalizing  Po2  between  buffer  and  sam- 
ple. Ph2  and  Po2  are  not  independent 
variables,  since  the  dissociation  of  water  is 
constant  for  a  given  T  and  Ptot.  The  five 
buffers  used  are  (a)  fayalite  + iron  +  quartz, 


162        CARNEGIE  INSTITUTION  OF  WASHINGTON 


(b)  iron  +  wiistite,  (c)  wiistite  +  magnetite,  presented  in  figures  11  and  12.   In  terms 

(d)  magnetite  +  quartz  +  fayalite,  and  (e)  of  the   three  variables    T,  Ptot,   and  Po2, 

hematite  +  magnetite.  annite  occupies  a  volume  within  which  it 

The  Po2-T  curves  for   these  pairs  are  represents  the  stable  phase.   This  volume 


500  600  700 

TEMPERATURE.  °C 


800 


900 


Fig.   11.    Isobar ic  section  of  the  stability  field  of  annite  for  Ptot  =  Ph2o  =  2000  bars.    The  curves 

are  Po2-T  curves  for  the  following  buffers:    (a)  iron  +  fayalite  +  silica,  (b)  iron  +  wiistite,  (c)  wiist- 

ite  + magnetite,    (d)    fayalite  +  magnetite-}- silica,  and  (e)  magnetite  +  hematite.   For  further  expla- 
nation see  text. 


600 
TEMPERATURE, 


800 


Fig.  12.  Isobaric  section  of  the  stability  field 
of  annite  +  quartz  for  Ptot=PH2o  =  2000  bars. 
For  the  significance  of  curves  {a),  (b),  (c),  (d), 
and  (e)  see  legend  to  figure  11  and  text. 


is  separated  by  curved  surfaces  from  four 
other  volumes  representing  the  phase 
assemblages  hematite  +  sanidine + vapor, 
magnetite  +  sanidine  +  vapor,  fayalite  +  leu- 
cite  +  kalsilite  +  vapor,  and  iron  +  sanidine 
+  vapor.  Figure  11  shows  a  section 
through  these  volumes  at  Ptot =Ph2o  =  2000 
bars.  The  effect  of  Po2  and  T  on  the  loca- 
tion of  the  reversible  equilibria  is  clearly 
discernible.  For  points  A,  B,  C,  D,  and  E, 
reversibility  of  the  reactions  has  been 
demonstrated  and  the  temperatures  are 
known  within  ±5°  C.  Figure  12  shows  a 
section  also  at  Ptot =Ph2o  =  2000  bars,  but 
for  the  bulk  composition  of  annite  + 
quartz.  Fayalite  +  sanidine  +  quartz  can  co- 
exist over  a  rather  wide  Po-T  field,  thereby 
restricting  the  stability  of  annite  in  the 
presence  of  quartz  considerably. 

Figure  13  shows  Ptot-T  curves  for  the 
reactions  studied  to  demonstrate  the  influ- 


GEOPHYSICAL  LABORATORY       163 


ence  of  total  pressure.  Along  the  univari- 
ant  curves,  Po2  is  not  constant  but  changes 
according  to  the  Po-T  curves  of  the  buffer 
assemblages  used  for  a  specific  reaction. 
The  Ptotr-T  curves  show  slopes  common  to 
curves  of  most  hydration-dehydration  reac- 
tions. 

Figure  14  is  a  three-dimensional  drawing 
showing  the  stability  volumes  of  the  five 
phase    assemblages    for    the    annite    bulk 


which  annite  represents  the  stable  phase. 
It  is  convenient  to  present  the  stability  re- 
lations of  hydrous  iron  silicates  in  terms 
of  total  pressure,  partial  pressure  of  oxy- 
gen, and  temperature  as  independent  vari- 
ables. But  it  should  be  remembered  that  a 
representation  in  terms  of  Ptot,  Pn2,  and  T 
is  equally  justified.  This  is  particularly 
significant,  since  hydrogen  and  not  oxygen 
equalizes   gradients    between   buffer    and 


or 

=> 
o-> 
oo 

LU 

<r 
a. 


2500 


2000  - 


1500  - 


1000  - 


500  - 


400 


500                             600                             700 
TEMPERATURE.  °C  


800 


900 


Fig.  13.  Temperature-total  pressure  (^>tot  =  jf>H20)  diagram  for  systems  annite  and  annite  +  quartz. 
For  each  of  the  selected  univariant  curves  the  partial  pressure  of  oxygen  is  equal  to  that  of  the  buffer 
used  (brackets)  and  changes  with  temperature  accordingly. 


composition.  Two  additional  volumes  are 
not  represented,  because  their  existence 
could  not  be  verified  experimentally.  From 
phase-rule  considerations  we  know  that  the 
magnetite  +  sanidine  +  vapor  volume  must 
be  separated  from  the  f ayalite  +  leucite  -h 
kalsilite  +  vapor  volume  by  a  narrow  vol- 
ume for  magnetite  +  f  ayalite  +  leucite  + 
vapor,  whose  width  is  narrower  than  the 
experimental  error  (±5°  C).  A  second 
narrow  volume  for  iron  +  f ayalite  +  leucite 
+  vapor  must  separate  the  volumes  for 
fayalite  + leucite +  kalsilite  + vapor  and  for 
iron  +  sanidine  +  vapor.  These  modifica- 
tions  do   not   affect   the   volume   within 


sample.  In  the  geologically  important  re- 
gion the  partial  pressures  of  hydrogen 
range  from  tenths  to  several  hundred  bars. 
Annite  is  the  first  hydrous  phase  for 
which  the  relationships  in  a  portion  of  the 
Ptot-Po2-T  space  have  been  worked  out. 
The  reactions  involved  are  hydration-de- 
hydrations  combined  with  reduction-oxi- 
dations. The  two  main  conclusions  de- 
rived from  the  work  on  annite  can  be 
stated  as  follows:  Iron  silicates  possess  a 
definite  range  of  partial  pressures  of  oxy- 
gen over  which  they  are  stable.  This  range 
changes  with  change  in  temperature.  In 
the  case  of  annite  the  upper  limit  for  Po2 


164        CARNEGIE  INSTITUTION  OF  WASHINGTON 


is  that  of  the  magnetite-hematite  boundary,  oxygen  between  some  of  the  participating 
The  equilibrium  temperatures  of  all  reac-  phases  will  depend  on  the  magnitude  of 
tions  that  show  a  transfer  of  hydrogen  or      the  partial  pressure  of  oxygen. 


o 


Q- 


Q-     2000 


CO 

< 

CD 


IjJ 

DC 
3 
CO 
CO 
UJ 
CC 
Q_ 


o 


1000 


500 


600        700        800 
->   TEMPERATURE 


Fig.  14.  Ptot-Po2-T  model  of  the  stability  volume  of  annite,  presented  in  isobaric  sections.  The 
curved  surfaces  separating  the  five  individual  volumes  are  defined  in  this  drawing  by  Po2-T  and 
Ptot-T  curves. 

THE  AGE  OF  ROCKS  AND  MINERALS 

(A  co-operative  program  of  the  Geophysical  Laboratory  and  the  Department 
of  Terrestrial  Magnetism  of  the  Carnegie  Institution  of  Washington) 

G.  L.  Davis,  G.  R.  Tilton,  L.  T.  Aldrich}  G.  W.  Wetherdl,1  and  H.  Paul 2 


We  have  to  remember  that  while  nature  is 
complex  with  time-less  subtlety,  human 
thought  issues  from  the  simple-mindedness 
of  beings  whose  active  life  is  less  than  half 
a  century. — A.  N.  Whitehead,  1919 

Now  that  reliable  methods  of  age  de- 
termination have  been  developed  a  num- 
ber of  additional  problems  have  become 
accessible  to  study.  Fossils  have  been  used 
to  establish  relative  ages  in  post-Precam- 
brian  times,  but  they  can  give  only  a  rough 
indication  of  the  actual  periods  of  time 

1  Department  of  Terrestrial  Magnetism. 

2  Visiting  Investigator,  U.  S.  Geological  Survey. 


involved.  The  fossil  time  scale  currently 
employed  is  based  on  only  four  points,  all 
of  questionable  value,  either  because  of 
lack  of  concordancy  in  the  isotopic  ages 
used  in  calibration  or  because  the  strati- 
graphic  position  of  the  samples  cannot  be 
accurately  established.  The  recently  de- 
veloped ability  to  measure  ages  on  granite 
greatly  increases  the  number  of  samples 
suitable  for  gaining  information  for  this 
time  scale. 

In  Precambrian  rocks,  fossils  are  absent, 
and  relative  ages  are  difficult  to  establish 
over    any    great    distances    in    the    field. 


GEOPHYSICAL  LABORATORY        165 


Younger  orogenic  belts,  such  as  the  Appa- 
lachian Province,  contain  considerable 
bodies  of  igneous  and  metamorphic  rocks 
that  were  formed  at  about  the  same  time. 
Perhaps,  when  a  sufficient  number  of  age 
measurements  are  completed  in  the  Pre- 
cambrian,  vestiges  of  a  number  of  older 
orogenic  belts  will  be  found.  For  example, 
the  wide  prevalence  of  1000-million-year- 
old  igneous  rocks  in  the  Grenville  is  gen- 
erally believed  to  indicate  such  a  belt.  A 
major  long-range  goal  of  work  on  age 
determination  is  to  establish  the  space-time 
relationship  of  orogenic  chains  of  the  past 
as  a  prelude  to  understanding  the  role 
played  by  such  belts  in  the  development  of 
the  continents. 

Reliable  age  determinations  depend  on 
finding  concordant  ages — that  is,  agree- 
ment between  two  uranium-lead  ages  and 
between  uranium-lead,  rubidium-stron- 
tium, and  potassium-argon  ages.  Such 
agreement  is  not  always  found.  Often  the 
rubidium-strontium  and  potassium-argon 
ages  agree  with  each  other  but  the  two 
uranium-lead  ages  are  discordant.  Some- 
times even  the  rubidium-strontium  and 
potassium-argon  ages  are  discordant.  Po- 
tentially, useful  information  is  buried  in 
these  results.  It  may  be  possible  in  the 
future  to  specify  within  reasonably  narrow 
limits  the  conditions  that  brought  about 
the  discordancies  and  thereby  gain  infor- 
mation on  the  post-crystallization  history 
of  these  rocks.  Workers  in  the  field  of  age 
determination  have  not  yet  begun  a  serious 
attack  on  this  problem. 

In  the  past  year  some  progress  has  been 
made  in  all  the  phases  of  activity  men- 
tioned. Precambrian  problems  have  been 
studied  in  the  Rocky  Mountains  of  western 
United  States  and  at  Sudbury,  Ontario. 
Information  of  potential  use  to  the  fossil 
time  scale  has  been  obtained  from  the 
Hercynian  Chain  in  western  Europe  and 
from  the  Wichita  Mountains  in  Oklahoma. 
A  study  was  begun  to  test  the  influence,  if 
any,  of  orogenies  in  producing  discordant 
ages  in  the  mineral  zircon.  These  results 
will  be  discussed  in  more  detail  below. 


THE  DECAY   CONSTANTS  OF  Rb87  AND  K40 

A  year  ago  the  report  of  this  group 
stated  that  the  uncertainties  in  the  decay 
constants  of  Rb87  and  K40  appeared  to  be 
resolved  by  comparing  K40-A40  and  Rb87- 
Sr87  ratios  in  micas  with  the  concordant 

TJ238_pb206     an(J     U235„pb207  giyen     by 

uraninites  from  the  same  mineral  assem- 
blages. Since  the  decay  constants  of  U238 
and  U235  are  known  to  within  2  to  3  per 
cent,  it  was  possible  to  calculate  the  decay 
constants  for  Rb87  and  K40  from  the 
uranium-lead  age.  The  calculated  con- 
stants were  in  agreement  for  six  mica- 
uraninite  assemblages  ranging  in  age  from 
370  to  2700  million  years.  This  agreement 
led  to  the  belief  that  alteration  of  the  Rb-Sr 
and  K-A  ratios  in  the  micas  by  processes 
other  than  radioactive  decay  was  not  a 
serious  problem.  Crystal  counting  experi- 
ments on  K40  by  Wetherill  (see  Report  of 
the  Director  of  the  Department  of  Ter- 
restrial Magnetism)  during  the  past  year 
have  confirmed  the  geologic  value  of  Xe  for 
the  decay  of  K40  to  A40  within  5  per  cent, 
assuming  that  none  of  the  K40  decays  di- 
rectly to  the  ground  state  of  A40.  Wether- 
ill's  value  for  Xe  is  enough  higher  than  the 
geologic  value  to  indicate  that  even  the 
best  micas  may  have  lost  on  the  average 
4  or  5  per  cent  of  the  A40.  The  geologically 
determined  constants  are  used  for  pur- 
poses of  age  determination,  but  these  con- 
stants must  agree  closely  with  the  labora- 
tory values  if  any  great  confidence  is  to  be 
placed  in  age  measurements  using  them. 
The  agreement  now  appears  to  be  close 
for  most  micas. 

PROBLEMS  IN  THE  PRECAMBRIAN 

The  occurrence  of  1300-  to  1400 -million- 
year-old  granitic  roc\s  in  western  United 
States.  Rubidium-strontium  and  potas- 
sium-argon ages  have  been  measured  on 
eleven  micas,  including  biotite,  muscovite, 
and  lepidolite,  from  Precambrian  granites 
and  pegmatites  occurring  in  the  Cordil- 
leran  System  in  Arizona,  New  Mexico, 
Colorado,  and  Wyoming.  The  ages  are 
given  in  table  4.  All  these  micas  have  ages 


166        CARNEGIE  INSTITUTION  OF  WASHINGTON 


between  1300  and  1400  million  years,  indi- 
cating that  there  was  a  widespread  crystal- 
lization of  granitic  rocks  at  this  time  and 
that  the  micas  have  preserved  their  ages  in 
spite  of  more  recent  events,  including  the 
Laramide  orogeny.  These  mica  ages  are 
believed  to  date  a  period  of  regional  rock 
formation  of  a  type  comparable  to  the 
later   periods    of   igneous    intrusion    and 

TABLE  4.     Age  Determinations  on  Micas  from 
Western  United  States 

K-A  ages  are  calculated  from  decay  constants 
of  K40  of  Xe  =  0557x  lO"10  yr-1,  X/5  =  4.72  X  10"10 
yr-1,  or  a  total  half-life  for  K40  of  1.31  X  109  yr. 
Rb-Sr  ages  are  calculated  using  a  half-life  for 
Rb87  of  50X109  yr. 


Location 


Age, 
million  years 

K-A   Rb-Sr 


1.   Gneiss,  Zoroaster  Creek, 

Grand  Canyon,  Ariz 1380  1350 

2a.  Lawler  Peak  granite,  Bagdad, 

Ariz 1410  1390 

2b.  Pegmatite  in  Lawler  Peak 

granite 1420  1500 

3.  Pegmatite,  Wickenberg,  Ariz. . .  1160  1300 

4.  Pidlite  Mine,  Mora  Co.,  N.M..  1330  1490 

5.  Granite,  Sandia  Mts.,  Albuquer- 

que, N.  M 1350  1340 

6.  Harding  Mine,  Dixon,  N.M...  1300  1300 

7.  Uncompahgre  granite,  Mesa 

Co.,  Colo 1320  1320 

8.  Granite,  Doyleville,  Colo 1320  1310 

9.  Brown  Derby  pegmatite,  Ohio 

City,  Colo 1330  1420 

10.  Granite,  Sherman,  Wyo 1420  1410 

11.  Silver  Plume  granite,  Colo 1280 

metamorphism  in  the  Appalachian  and 
Grenville  Provinces. 

Zircon  ages,  reported  previously  from 
the  Lawler  Peak  and  Quartz  Creek  gran- 
ites, have  been  found  to  be  discordant  in 
such  a  way  that  the  Laramide  orogeny 
could  have  been  partly  responsible. 

Precambrian  ages  in  Ontario.  The  Lau- 
rentian  Shield  in  central  and  eastern 
Canada  and  northern  Michigan,  Wiscon- 
sin, and  Minnesota  has  long  been  recog- 
nized as  a  favorable  area  for  the  study  of 
problems  in  Precambrian  geochronology. 


Approximately  2  million  square  miles  of 
glaciated  volcanic,  plutonic,  and  sedimen- 
tary rocks  are  exposed.  To  the  northwest, 
rocks  of  the  Timiskiming-Keewatin  Prov- 
ince are  cut  by  pegmatites  having  ages  of 
about  2600  million  years.  To  the  southeast 
in  the  Grenville  Province,  numerous  in- 
trusive igneous  rocks  have  ages  of  about 
1000  million  years.  Between  these  two 
provinces  is  another,  narrower  belt,  the 
Huronian  series,  which  is  known  to  be 
younger  than  the  Timiskiming-Keewatin 
rocks,  but  is  of  unknown  relation  to  the 
Grenville  rocks  since  the  Huronian  and 
Grenville  are  bounded  by  a  fault  zone. 

There  are,  then,  several  reasons  for  mak- 
ing detailed  age  studies  on  rocks  in  the 
Laurentian  Shield.  Precambrian  rocks  are 
exposed  over  a  great  area,  and  they  repre- 
sent a  long  span  of  time,  at  least  1000 
million  to  2500  million  years  ago.  There 
is  a  need  to  determine  the  relations  of  the 
Huronian  to  the  Timiskiming-Keewatin 
series  on  an  absolute  time  scale  and,  if 
possible,  to  fit  the  Grenville  series  into  this 
sequence.  Studies  were  commenced  on 
these  problems  in  the  past  year,  with  par- 
ticular reference  to  the  Huronian  series. 
Valuable  information  has  been  obtained, 
although  no  conclusive  solutions  have  re- 
sulted as  yet. 

Mica  ages  have  been  determined  for  a 
number  of  igneous  and  metamorphic  rocks 
of  known  stratigraphic  relation  to  the  sedi- 
mentary rocks  around  Sudbury:  the 
Huronian,  Sudbury,  and  Keewatin  series. 
Their  absolute  time  sequence  and  their 
geographic  extent  have  been  among  the 
major  unsolved  problems  in  Precambrian 
geology.  The  present  studies  have  at- 
tempted to  place  limiting  values  on  the 
ages  of  the  various  series  by  studying  the 
ages  of  micas  from  rocks  known  to  be 
older  or  younger  than  a  particular  series. 
This  approach  is  necessary  since  there  is  no 
proven  way  at  present  to  date  the  sedi- 
ments directly. 

The  results  obtained  so  far  appear  in 
tables  5,  6,  and  7.  Immediately  evident  are 
the  numerous  discordances  between  the 


GEOPHYSICAL  LABORATORY        167 


rubidium-strontium  and  potassium-argon 
ages  for  many  of  the  micas,  in  sharp  con- 
trast to  our  past  experience.  Moreover,  the 
few  discordances  found  previously  were  of 
the  type  for  which  the  potassium-argon 
age  was  less  than  the  rubidium-strontium 
age;  they  were  considered  an  indication  of 
argon  leakage.  Several  of  the  Sudbury 
micas  give  potassium-argon  ages  that  are 
much  greater  than  the  rubidium-strontium 


ages.   As  yet  there  is  no  explanation  for 
these  rather  surprising  inconsistencies. 

Although  the  data  contain  a  large  num- 
ber of  discordant  ages,  some  conclusions 
may  be  drawn.  The  Wavy  Lake  granite 
represents  an  outlier  of  igneous  rock  of 
the  same  age  as  the  igneous  rocks  that  in- 
trude the  Grenville  sediments  in  the  Gren- 
ville  subprovince.  The  sediments  called 
Huronian  in  this  area  appear  to  be  more 


TABLE  5.    Age  Determinations  on  Micas  from  the  Sudbury  District 


Location  and  Sample 


Stratigraphic  Position 


.   Age> 
million  years 

Rb-Sr   K-A 


Wavy  Lake  granite Intrudes  Huronian   1075  1025 

Sudbury  gabbro  Intrudes  lower  Huronian 1325  1830 

Sudbury  breccia  (matrix) Younger  than  Sudbury  series  and  Copper  Cliff 

rhyolite 1440  1870 

Levack  norite  1830 

Haleyburian  lamprophyre  Pre-Cobalt  (middle  Huronian) 2050  2160 

Hearst  pegmatite  Intrudes  Keewatin 2595  2605 

Round  Lake  lamprophyre Pre-Huronian,  Post-Keewatin  2600  2450 

Round  Lake  batholith,  granite Pre-Huronian,  Post-Keewatin 2640  2530 

Timmins,  granite Pre-Huronian,  Post-Keewatin   2470  2520 


TABLE  6.    Age  Determinations  on  the  Cutler 
Batholith 

(Intrudes  the  Sudbury  series) 


Sample 


Age, 
million  years 

Rb-Sr   K-A 


Pegmatite  1     Muscovite 1750  1440 

Feldspar  1760  1165 

Pegmatite  2    Muscovite 1700  1420 

Granite  Biotite  1325  1380 


TABLE  7.    Age  Determinations  on  the  Copper 
Cliff  Rhyolite 

(Stratigraphic  position  uncertain) 


Sample 


Age, 
million  years 

Rb-Sr   K-A 


Muscovite 1730     1390 

Biotite 1220    2130 

Feldspar  2360     1400 


than  1300  million  and  less  than  2600  mil- 
lion years  old.  They  are  actually  less  than 
2150  million  years  old  if  the  nearly  con- 
cordant age  obtained  for  the  Haleyburian 
lamprophyre  is  significant  and  if  the  age 
of  the  mica  from  the  lamprophyre  does  not 
represent  a  period  of  metamorphism  subse- 
quent to  its  formation.  Since  so  many  dis- 
cordant ages  have  been  found  in  this  area, 
the  2150-million-year  limit  must  be  viewed 
with  caution  until  further  samples  of  the 
same  age  are  found.  The  Sudbury  series 
is  older  than  1400  million  years  because  it 
is  intruded  by  the  Cutler  batholith.  It  is 
possibly  older  than  1750  million  years  since 
most  of  the  rubidium-strontium  ages  ob- 
tained from  the  Cutler  give  this  value. 
The  Keewatin  series  is  older  than  2600 
million  years.  It  should  be  emphasized 
that  these  conclusions  apply  only  to  these 
series  as  they  are  identified  around  Sud- 
bury. The  results  cannot  be  extrapolated 
with  certainty  to  form  conclusions  regard- 


168        CARNEGIE  INSTITUTION  OF  WASHINGTON 


ing  rocks  called  "Huronian"  or  "Keewa-  The  large  (30-lb  or  more)  rock  samples 

tin"  elsewhere.  were  crushed,  ground,  and  separated  into 

The  close  proximity  of  the  2600-million-  their  principal  mineral  constituents  with 

year-old  rocks  at  Timmins  and  the  Round  particular  attention  to   zircon  and  mica. 

Lake  batholith  at  Kirkland  Lake  to  the  The  separations  were  made  at  the  institutes 

lOOO-million-y ear-old  rocks  at  Wavy  Lake  of   mineralogy   and   physics   at   the  Uni- 

is  interesting.    Between  these  areas,  only  versity  of  Strasbourg. 

150  miles  apart,  rocks  of  intermediate  age  Analyses  of  selected  zircon  samples  for 

occur,   so   that   repeated   igneous   activity  uranium,  thorium,  and  lead  and  of  some 

must  have  occurred  in  this  rather  restricted  of  the  mica  samples  for  potassium,  rubid- 

area.  The  large  number  of  discordant  ages  ium,  strontium,  and  argon  have  been  made 

found  in  the  micas  may  bear  some  relation  by  the  isotope  dilution  methods  described 

to  this  fact.  in  previous  reports,  as  part  of  the  co-opera- 

The  2600-million-year-old  rocks  listed  in  tive    program   with   the    Department   of 

table  5  have  about  the  same  age  as  a  num-  Terrestrial  Magnetism, 

ber  of  intrusions  found  elsewhere.  Rocks  The  zircon  data  obtained  thus  far  are 

of  this  age  have  now  been  found  in  north-  summarized  in  table  8.   They  show  that 

ern  Wyoming,  southern  Montana,  north-  all  the  zircons  contain  original  lead,  with 

ern  Minnesota,  and  southeastern  Manitoba,  the  possible  exception  of  the  Oslo  sample 

as  well  as  at  Hearst  and  north  of  Sudbury  (which  contains  too  little  lead  to  determine 

in  Ontario.  Rocks  with  ages  of  2600  mil-  whether  or  not  original  lead  is  present  in 

lion  to  2700  million  years  on  the  continents  significant  proportion) .  In  agreement  with 

of  North  America,  Africa,  and  Australia  our  previous  experience,  reliable  age  in- 

are  still  the  oldest  reliably  dated  rocks.  It  formation  cannot  be  obtained  from  zircons 

seems  probable  that  reliable  dates  for  older  with   appreciable   common   lead   content, 

rocks  will  be  determined  in  the  future,  and  these  rocks  cannot  be  dated  by  analyz- 

because  these  old  rocks  are  intruded  into  ing  zircon  alone. 

sediments  that  must  have  been  derived  in  As  part  of  the  zircon  program,  a  suite  of 

turn    from    substantially    older    igneous  galenas  from  the  Vosges  Mountains  was 

rocks.  analyzed  for  lead  isotopes  (see  table  9). 

As  expected,  the  composition  of  these  leads 

STUDY  OF  A  POINT ^N  THE  FOSSIL  TIME  is  very  similar  t0  that  Q£  the  common  leads 

from  Germany,  analyzed  by  Geiss,  so  that 
While  serving  as  Fulbright  lecturer  to  we  cannot  justifiably  calculate  the  zircon 
the  University  of  Strasbourg  during  the  jata  into  concordance  by  accepting  some 
academic  year  1954-1955,  Faul  collected  a  unusUal  isotopic  composition  for  the  origi- 
suite  of  granitic  rocks  from  the  general  nai  ieacj  tney  contain, 
area  of  the  Hercynian  Chain  and  some  of  Rubidium-strontium  and  potassium- 
its  suspected  outliers.  Samples  were  taken  argon  analySes  of  micas  from  some  of  these 
in  the  Oslo  area,  the  Harz  Mountains,  the  same  rocks  show  a  much  more  consistent 
Schwarzwald  Mountains,  the  Vosges  picture  (see  table  10) .  Within  the  limits  of 
Mountains,  the  Alpine  complex,  and  the  error  tne  age  is  the  same  for  all  the  rocks, 
Massif  Central.  Field  work  in  each  area  about  345  million  years, 
was  carried  out  in  close  co-operation  with,  The  stratigraphic  age  of  these  rocks  is 
and  where  possible  in  the  company  of,  a  known  to  be  pre-Westphalian  (pre-middle 
local  geologist  who  was  particularly  inter-  Carboniferous),  and  they  are  usually  as- 
ested  in  the  igneous  petrology  of  the  area,  signed  to  the  Dinantian  (lower  Carbon- 
The  field  assistance  of  Drs.  Barth,  Denkel,  iferous).  According  to  the  U.  S.  Geologi- 
Gjelsvik,  Hiigi,  Roques,  Siat,  Wedepohl,  cal  Survey  version  of  the  Holmes  time 
Weil,  Wenk,  and  Wimmenauer  is  grate-  scale,  the  Carboniferous  began  265  million 
fully  acknowledged.  years  ago.   By  this  time  scale  the  present 


GEOPHYSICAL  LABORATORY       169 


measurements  would  place  the  Hercynian 
rocks  in  the  middle  Silurian.  It  follows 
that  either  the  time  scale  is  not  correct 
here  or  the  accepted  stratigraphic  assign- 
ment must  be  in  error. 


ured  as  well.  In  general,  the  new  deter- 
minations have  not  altered  the  conclusions 
stated  a  year  ago — that  discordant  isotopic 
ages  are  accompanied  by  the  presence  of 
common  lead  in  the  samples,  and  zircons 


TABLE  8.     Age  Determinations  on  Zircons  from  the  Hercynian  Chain 


Location 


Pb 

(total), 

ppm 


Pb 
(origi-         U,  Th, 

nal),        ppm         ppm 
per  cent 


Age,  million  years 


TJ238/     JJ235/    Th232/  Pb207/ 

pi^OG       p[}207       Pb208  Pb206 


Natzwiller,  Vosges 73  32 

Col  de  la  Grosse  Pierre,  Vosges.  .166  20 

Wembach,  Schwarzwald   46  11 

Martinskapelle,  Schwarzwald   . .    163  59 

Martinskapelle,  Schwarzwald, 

leached  with  hot  HC1 86  34 

Halbmeil,   Schwarzwald    78  40 

f  18 
Oslo  nordmarkite  S  .  7 


T989 
1991 
2850 
740 
1730 

1251 

784 
J363 
\365 


534 

865 
382 
343 

345 

177 

J388 

\396 


292 

293  312 
337  326 
247 

292 

374 

267       282 


263        

291  440  ±60 

283  260  ±60 

272        

285  ....... 

225  395  ±60 


Braces  show  duplicate  determinations. 

Errors  (standard  deviations)  are  less  than  2  per  cent  except  where  shown  otherwise. 
When  ages  involving  Pb207  are  not  given,  too  much  primary  Pb207  was  present  to  permit  accu- 
rate determination  of  radiogenic  Pb207. 

TABLE  9.    Isotopic  Composition  of  Galenas  from  the  Vosges  Area 


Location  

206/204 

Ste.  Marie 18.80 

±0.14 
Musloch,  Ste.  Croix 18.37 

±0.16 
La    Croix    18.88 

±0.27 
"Donner"  mine 18.37 

±0.05 
"Aurora"  mine    18.65 

±0.08 
Steinbach   18.74 

±0.065 
Wegscheid  18.24 

±0.23 
Auxelles-Haut  18.72 

±0.05 


Isotopic  Ratios 


206/207 


206/208 


207/204    208/204 


1.206 

0.485 

15.58 

38.73 

±0.005 

±0.008 

1.186 

0.482 

15.49 

38.08 

±0.002 

±0.004 

1.211 

0.481 

15.60 

38.90 

±0.007 

±0.001 

1.184 

0.483 

15.52 

38.03 

±0.007 

±0.003 

1.189 

0.481 

15.68 

38.73 

±0.004 

±0.0015 

1.200 

0.487 

15.62 

38.45 

±0.0015 

±0.0015 

1.157 

0.467 

15.76 

39.00 

±0.009 

±0.005 

1.190 

0.483 

15.72 

38.77 

±0.003 

±0.007 

The  errors  indicated  are  the  observed  mean  deviations  of  usually  about  ten  sets  of  ratios. 

ZIRCON  AGE  WORK  with  no  detectable  common  lead  give  con- 

Isotopic  age  determinations  have  been  cordant,    or    nearly    concordant,    isotopic 

completed  for  six  zircons,  excluding  those  ages.  Among  the  zircons  reported  in  table 

from  the  Hercynian  Chain.  In  three,  the  11,  those  from  Conway,  Canada  Hill,  and 

ages  of  associated  micas  have  been  meas-  Finland  contained  no  detectable  common 


170        CARNEGIE  INSTITUTION  OF  WASHINGTON 


TABLE  10.    Mica  Age  Results 


Location 


Age, 
million  years 

Rb-Sr   K-A 


336 


344 


Vosges 

Lac  Blanc   *  i|40 

\346 

Natzwiller  350 

Col  de  la  Grosse  Pierre 333 

Schwarzwald 

Wembach 345 

Martinskapelle    341 

Halbmeil    334 

Sasbach-Walden   331 

Massif  Central 

Royat    351 


328 


at  present  for  the  cause  of  the  relation  be- 
tween the  common  lead  content  of  a  zircon 
sample  and  the  age  results. 

Our  previous  work  showed  that  three 
zircons  from  the  Grenville  subprovince  in 
Ontario  gave  concordant  isotopic  ages  in 
spite  of  the  fact  that  the  samples  varied 
greatly  in  crystal  size  and  amount  of  radia- 
tion damage.  The  two  zircons  from  the 
Fenno-Scandian  Shield  have  likewise  given 
quite  satisfactory  age  results.  The  result 
for  the  Rapakivi  granite  is  somewhat  dis- 
cordant, but  not  so  discordant  as  the  re- 
sults found  for  zircons  containing  common 
lead,  in  which  the  U238-Pb206  and  Pb207- 

"DU206      „^.^n     U/-.-.r^      A1CC*.~£±A      U»,      C^~*-^~r.      ^C 


*  Duplicate  determination. 

neat 

ly 

2. 

TABLE  11.    New 

Age  Results  for  Zircon 

i  and  Associated  Biotite 

Mineral 

Age,  millior 

t  years 

Location 

u238/ 

U235/ 

Pb207/ 

Th232/ 

Rb87/ 

K40/ 

p^206 

Pb207 

p^206 

p^208 

Sr87 

A40 

Conway,  N.  H., 

Zircon 

187 

184 

140  ±60 

190 

granite 

Biotite 

185 

182 

Wichita  Mts.,  Okla., 

Zircon  A 

520 

527 

550 

506 

pegmatite  (zircon)* 

Zircon  B 

514 

522 

550 

493 

granite  (biotite) 

Biotite 

500 

480 

Bodom  granite, 

Zircon 

1590 

1625 

1675 

1540 

Finland  f 

Rapakivi  granite, 

Zircon 

1165 

1350 

1650 

1050 

Finland  f 

Canada  Hill  gneiss, 

Zircon 

1020 

1060 

1150 

Bear  Mt.,  N.  Y. 

Biotite 

1030 

930 

Hybla,  Ontario, 

Cyrtolite 

1350 

1190 

900 

435 

McDonald  Mine 

*  Zircons  A  and  B  are  separate  zones  separated  from  a  single  large  crystal.    A  has  uranium  and 
thorium  contents  about  six  times  those  of  B  and  correspondingly  more  radiation  damage, 
t  The  Bodom  and  Rapakivi  determinations  were  made  by  O.  Kouvo  at  these  laboratories. 


lead  and  all  give  reasonably  concordant 
ages.  The  Wichita  Mountains  samples  are 
a  notable  exception  to  the  generalization, 
for  while  they  give  nearly  concordant  ages 
the  lead  in  sample  A  contains  10  per  cent 
common  lead  and  that  in  sample  B  con- 
tains 5  per  cent  common  lead.  These  are 
the  exceptions  that  have  been  found  in  the 
16  zircons  analyzed  to  date.  The  Hercyn- 
ian  zircons  must  be  left  out  of  the  present 
discussions  until  studies  can  be  completed 
in  that  area.  No  explanation  can  be  given 


The  report  of  a  year  ago  mentioned  the 
observation  that  discordant  isotopic  ages 
were  found  for  zircons  from  Precambrian 
granites  from  the  Cordilleran  System  in 
western  United  States,  where  orogenies 
have  occurred  in  more  recent  (Mesozoic) 
times.  In  contrast  to  the  zircons,  micas 
separated  from  the  same  granites  appear  to 
have  preserved  their  ages  through  whatever 
events  were  responsible  for  the  discordant 
zircon  ages.  One  observation  was  made  in 
the  Appalachian  Province  to  test  further 


GEOPHYSICAL  LABORATORY        171 


the  possible  influence  of  orogenies  on  zir- 
con age  results.  The  Canada  Hill  gneiss 
from  the  Hudson  highlands  has  been  stud- 
ied. The  rock  is  of  Precambrian  age  and 
has  been  folded  during  the  Taconic  orog- 
eny. From  past  experience  it  was  ex- 
pected that  the  mica  might  preserve  the 
original  age  of  the  rock  but  the  zircon 
might  give  discordant  age  results  which 
would  have  some  connection  with  the 
orogeny.  Actually,  the  biotite  and  zircon 
ages  appear  to  have  been  relatively  un- 
affected by  the  orogeny,  although  the 
potassium-argon  age  of  the  biotite  is  prob- 
ably somewhat  low. 

Geologic  implications  of  the  ages.  The 
Wichita  Mountains  biotite  was  separated 
from  the  Lugert  granite,  and  the  zircon 
came  from  a  pegmatite  in  the  same  granite. 
The  results  from  table  11  give  an  age  of 
about  500  million  years  for  the  granite. 
This  granite  has  been  called  "Precambrian" 
in  published  works  by  geologists.  Recent 
discussions  with  Professor  Clifford  Merritt, 
of  the  University  of  Oklahoma,  and  Dr. 
William  Ham,  of  the  Oklahoma  Geolog- 
ical Survey,  indicate  that  some  uncertainty 
attaches  to  this  stratigraphic  assignment. 
If  the  granite  is  in  fact  Precambrian,  it 
would  be  the  youngest  Precambrian  rock 
known  and  would  thus  be  of  considerable 
importance  to  the  fossil  time  scale. 

The  northern  and  central  Appalachian 
Mountains  have  provided  many  mica  age 
measurements  grouping  at  300  to  350  mil- 
lion years,  but  the  zircon  and  mica  from 


the  Canada  Hill  gneiss  in  the  heart  of  the 
chain  are  1000  million  years  old,  the  same 
age  found  for  a  zircon  in  the  Adirondack 
Mountains  just  to  the  west  and  for  the 
igneous  rocks  that  intrude  the  Grenville 
sediments  in  Ontario.  It  would  appear  that 
some  parts  of  the  Appalachian  Mountain 
rock  were  not  affected  by  the  Taconic 
orogeny  about  350  million  years  ago. 

The  Bodom  and  Rapakivi  granites  ap- 
pear to  be  1600  million  to  1650  million 
years  old.  They  are  considered  to  be  of 
post-Karelidic  age. 

ACKNOWLEDGMENTS 

J.  E.  Thomson,  of  the  Ontario  Depart- 
ment of  Mines,  and  T.  C.  Phemister,  of 
Aberdeen  University,  Scotland,  provided 
intimate  knowledge  of  field  relations  in 
the  Sudbury  District  and  supervised  the 
collection  of  samples  there.  P.  W.  Gast,  of 
the  Lamont  Geological  Observatory,  as- 
sisted us  in  the  collection  of  the  Canada 
Hill  gneiss  and  the  Storm  King  granite. 
The  Lugert  granite  from  the  Wichita 
Mountains  was  obtained  through  the  ad- 
vice and  assistance  of  W.  B.  Hamilton  and 
E.  E.  Glick,  of  the  U.  S.  Geological  Survey. 

Several  of  the  general  statements  in  this 
report  are  based  on  the  data  of  our  col- 
leagues at  the  University  of  Minnesota,  the 
Lamont  Geological  Observatory,  the  Mas- 
sachusetts Institute  of  Technology,  the 
University  of  Toronto,  and  the  California 
Institute  of  Technology,  as  well  as  on  our 
own  data. 


SIMPLE  ABSOLUTE  MEASUREMENT  TECHNIQUE  FOR 

BETA  RADIOACTIVITY;  APPLICATION  TO 

NATURALLY  RADIOACTIVE  RUBIDIUM 

W.  F.  Libby 


The  earlier  method  of  Suttle  and  Libby 
for  routine  simple  absolute  assay  of  solids 
did  not  specifically  take  account  of  the  fact 
that  the  back-scattered  radiation  is  some- 
what softer  than  the  original  3  radiation 
and  depends  in  both  intensity  and  softness 
on  the  atomic  number  of  the  back  scatterer. 
This  effect  has  been  recognized  during  the 
course  of  the  present  research,  and  agree- 


ment with  the  known  standard  3  samples 
as  furnished  by  the  National  Bureau  of 
Standards  and  the  Oak  Ridge  National 
Laboratory  has  been  improved. 

An  important  new  finding  is  that  the 
rough  surface  of  a  crystalline  powder  re- 
quires a  larger  correction  for  geometry 
than  a  smooth  surface.  This  fact  has  been 
shown  by  direct  calculation  and  proved 


172        CARNEGIE  INSTITUTION  OF  WASHINGTON 


experimentally.  The  geometrical  effect  of 
the  surface  roughness  of  a  powdered  solid 
is  most  marked  for  soft  (3  rays,  for  which 
the  surface  looks  much  rougher  than  for 
hard  (3  rays.  Empirically,  for  powders  as 
ordinarily  prepared,  a  half-thickness  of 
about  7  mg/cm2  seems  to  be  a  good  divid- 
ing line;  (3  radiations  of  smaller  half-thick- 
ness require  a  geometry  factor  some  40 
per  cent  larger  than  those  of  larger  half- 
thickness.  The  geometry  factor  for  hard 
(3's  is  the  same  one  calculated  for  a  smooth 
surface. 

With  these  changes,  the  technique  of 
measuring  the  absolute  radioactivity  of 
solids  and  liquids  by  placing  them  in  a 
cylindrical  position  around  an  ordinary 
Geiger  counter  gives  results  agreeing  with 
the  true  absolute  assays  within  5  per  cent. 

The  technique  was  applied  to  the  meas- 
urement of  the  half-life  of  naturally  radio- 
active rubidium.  The  value  found  was 
50.7  ±2  billion  years,  in  good  agreement 
both  with  that  determined  by  Aldrich, 
Wetherill,  Tilton,  and  Davis  on  old  rocks 
by  the  uranium-lead  method  and  with  the 
latest  value  determined  by  Huster,  Rausch, 
and  Geese-Bahnisch  by  4tt  counting  of 
very  thin  deposits  of  rubidium  salts. 

This  technique  should  have  wide  appli- 
cation in  the  development  of  new  uses  of 
isotopes,  particularly  in  introducing  iso- 
topes into  the  ordinary  chemistry  class- 
room. 

THE  METHOD 

Suttle  and  Libby  showed  that,  under 
conditions  of  cylindrical  geometry  in 
which  the  sample  lies  on  the  surface  of  a 
cylinder  whose  axis  is  identical  with  that 
of  the  Geiger  counter  used  to  measure  the 
radiation,  (3  radiations  resulting  from  a 
single  transition  between  two  nuclear  en- 
ergy states  are  absorbed  exponentially,  even 
though  the  transition  may  be  highly  for- 
bidden as  in  K40.  The  cylindrical  position 
of  the  sample  is  essential  for  the  control  of 
the  very  large  effects  of  (B-ray  scattering; 
it  is  for  this  reason  that  the  popular  end- 
window  type  of  counter  with  its  flat  sample 


does  not  give  exponential  absorption  with- 
out special  orifice  windows  to  control  the 
scattering.  These  ordinary  counters  can  be 
used  for  absolute  counting  only  with  rigor- 
ous controls  and  exacting  disposition  of 
sample  which  present  considerable  diffi- 
culty in  the  usual  laboratory;  as  a  result, 
applications  of  isotopes  that  involve  the  use 
of  absolute  counting  have  not  been  gener- 
ally made. 

The  fact  that  nearly  exponential  absorp- 
tion curves  can  be  obtained  under  certain 
conditions  has  long  been  known.  As  has 
been  shown  earlier,  if  the  absorption  of 
the  radiation  is  exponential,  the  total  self- 
absorption  in  an  ordinary  solid  or  liquid 
sample,  which  has  finite  thickness  and 
therefore  can  be  readily  made  and  handled, 
can  be  easily  calculated  and  the  relation 
between  the  absolute  disintegration  rate 
and  the  observed  count  rate  obtained.  It 
was  assumed  that  the  effects  of  the  self- 
scattered  radiation  would  be  encompassed 
in  the  geometrical  constant  G  used  in  the 
formula.  This  point  is  examined  in  the 
present  research. 

Let  o  =  absolute  specific  radioactivity, 
disintegrations  /  min  /  mg  of 
sample. 
1/Xs  —  absorption  coefficient  of  the 
radiation  in  the  material  of 
the  sample,  cm2/mg. 
l/Xw  —  absorption  coefficient  in  coun- 
ter-wall material,  cm2/mg. 

/=wall  thickness  of  counter,  in- 
cluding the  air  between  the 
surface  of  the  sample  and  the 
counter  wall,  mg/cm2. 

G  =  geometry  factor,  the  ratio  of 
4tt  to  the  average  solid  angle 
subtended  by  the  inner  sur- 
face of  the  cylindrical  counter 
wall  at  the  sample  surface. 

x  =  sample   thickness    (less   than 

__     saturation),  mg/cm2. 

Z  =  atomic  number  of  the  sample 
on  a  weight  average  basis. 

v\  =  back-scattering  coefficient  for 
close  geometry. 

A  —  area  of  sample,  cm2. 


GEOPHYSICAL  LABORATORY        173 


Then,  for  a  layer  of  sample  at  depth 
y  (mg/cm2)  below  the  top,  and  of  thick- 
ness dy,  the  count  rate  will  be: 

dR=(Aa/G)(l  +  Y])e^/x»-l/x^  dy  (1) 

or,  integrating  over  the  sample  thickness, 

R=(Ao/G)\s(l  +  v\)(l-e-x/K)e-l/K  (1)' 

Seliger  has  shown  that  the  back-scattered 
radiation  is  of  lower  energy  and  softer  in 
penetrating  power  than  the  original  radia- 
tion, the  softening  depending  on  the  angle 
of  scattering  as  well  as  on  the  atomic  num- 
ber of  the  back-scattering  material.  Muller 
has  very  carefully  studied  the  variation  of 
back  scattering  with  the  atomic  number 
of  the  material  causing  the  back  scattering 
under  a  particular  set  of  geometrical  condi- 
tions, with  applications  to  analytical  chem- 
istry in  mind.  It  is  generally  agreed  that 
the  back-scattered  radiation  is  softer  than 
the  original,  that  for  materials  of  Z  below 
15  the  factor  by  which  the  absorption  coeffi- 
cient of  the  back-scattered  radiation  meas- 
ured under  2n  conditions  is  increased  is 
about  2,  and  that  for  larger  values  of  Z 
the  factor  decreases  essentially  linearly  to 
about  1.2  at  atomic  number  90.  Therefore, 

for  ordinary  materials  in  which  Z  is  less 
than  15  we  can  write  a  new  equation  for 
the  relation  between  the  count  rate  and 
the  absolute  specific  activity: 

R  (cPm)  =  ^  (1  +  \  e-l/x*>)e-VK  • 

(l-e-*/K)     (1)" 

On  the  right-hand  side  of  this  equation  the 
first  term  in  parentheses  takes  account  of 
the  fact  that  the  counter  wall  and  the  air 
between  the  sample  and  the  counter  wall 
will  absorb  the  back-scattered  radiation 
more  than  they  do  the  original.  It  also  of 
course  takes  account  of  the  magnitude  of 
the  back-scattered  radiation. 

The  corresponding  formula  for  larger 
values  of  Z  is  easily  obtained  by  replacing 
the  coefficient  2  in  this  term  by  the  appro- 
priately smaller  softening  factor  of  the 
back-scattered  radiation  and  including  in 
the  exponential  term  in  the  parentheses 


the  value  of  this  new  coefficient  less  1. 
For  samples  that  are  thick  with  respect  to 
Xs,  the  last  parenthetical  factor  (the  satura- 
tion term)  disappears,  and  for  material  of 
Z  less  than  15,  the  softening  of  back  scat- 
tering can  be  combined  with  the  geometry 
factor  into  a  new  factor,  G\  to  obtain  the 
formula  of  Suttle  and  Libby: 

R=(Ao\/G')e~l/K  (2) 

Bothe  and  Danziger  in  theoretical  stud- 
ies of  3  absorption  deduced  the  main  fea- 
tures of  the  whole  phenomenology,  and 

their  curve  for  y\  versus  Z  agrees  well  with 
the  experimental  data  of  others.  Since  it 
is  clear  from  the  theory  that  the  scattering 

effect  for  materials  of  low  Z  should  be 
particularly  simple,  it  is  not  surprising 
that  for  these  materials  the  very  simple 
equation  2  is  nearly  as  accurate  as  the  more 
detailed  equations  1'  and  1". 

An  empirical  equation  for  v\  which  has 
been  used  in  this  research  and  which  fits 
quite  well  both  the  experimental  and  the 
theoretical  relations  between  y\  and  Z  for 
close  geometry  conditions  approaching  2n 
in  the  solid  angle  subtended  by  the  counter 


is 


y]=0.65(l-^/35)  (3) 

The  absorption  coefficient,  1/X,  has  been 
found  to  depend  on  the  maximum  energy 
of  the  (3  spectrum,  E,  in  the  following  way : 

X  (mg/cm2)  =55E%  (4) 

or 

/i/2  (mg/cm2)  =38E%  (4)' 

where  h/2  is  the  half-thickness  in  alumi- 
num, and  X  similarly  refers  to  the  recipro- 
cal of  the  absorption  coefficient  in  alumi- 
num. 

Lerch  has  shown  that  X,  the  reciprocal 
of  the  absorption  coefficient,  depends  on 
the  average  atomic  weight,  M,  of  the  ab- 
sorbing medium.  The  relation  is: 

Am  =  Ao/[1  +  (M/100)]  (5) 

Equation  5  has  been  used  in  this  research, 
and  figure  15  shows  the  adequate  degree  to 
which  it  fits  the  experimental  data  for  X 
given  in  table  12. 


174        CARNEGIE  INSTITUTION  OF  WASHINGTON 


2.00 


1.00 


tr 


50 


•  CI14      155  kev 

hS35      167  kev 

oCI36     716  kev 

®TI204770kev 

xP32     1708  mev 

Solid  curve: 

*l/2 

(/l/2)Al 

1 

® 

.^c> 

/       At^wtA 

V         ioo  J 

1 

(-if) 

O 

100 

Atomic  weight  of  absorber 


150 


Fig.  15.     Half-thickness  versus  atomic  weight  of  absorber. 


200 


TABLE 

12.    Absorption 

Data 

Isotope 

Maximum 

Energy 

of  (3 

Spectrum, 

Mev 

Absorbing 
Material 

Half-Thickness, 

mg/cm2 

Reciprocal  of 

Absorption 

Coefficient, 

mg/cm2 

T 

Zr93     

0.0189 

0.060 

He 
Al 
Al 
Al 
Mylar  plastic* 
Al* 
Mylar* 
Al 
Al* 
Al 
Al 
Al* 
Cu* 
Sn* 
Pb* 
Al 
Al 
Cu* 
Sn* 
Al* 

0.050 
0.35 
0.63 
1.9 

2.2* 
2.3* 
2.7* 
4.85 
4.9* 
6.09 

22 

32* 

26* 

21* 

18* 

67 

84 

60* 

50* 
130* 

0.0720 
0.506 

Sm151 

C14   

0.0755 

0.155 

0.91 
2.74 

g35# 

0.167 

3.16* 
3.3* 

Rb87   

0.270 

3.9* 
7.0 

Ca45*   

0.255 

7.1* 

Tc"   

0.296 

8.8 

^204 
Q]36* 

0.762 

0.716 

32 
46* 

K40 

p32 

1.36 

1.708 

37* 
30* 
26* 
96 
122 

y90# 

2.275 

86* 

72* 

189* 

*  New  data. 


GEOPHYSICAL  LABORATORY        175 


Of  course,  the  fact  that  the  back-scattered 
radiation  is  softened  relative  to  the  original 
radiation  means  strictly  that  the  absorption 
curve  cannot  be  entirely  exponential  for 
the  thinnest  layers  of  absorber,  since  the 
absorption  relation  must  be  as  given  in 
equation  1".  The  verification  of  this  state- 
ment is  to  be  seen  in  figure  16,  which 
shows  actual  absorption  curves  of  various 
soft  (3  emitters  taken  in  the  screen  wall 
counter,  which  allows  the  very  softest  ra- 
diation to  be  measured.  Here  we  see  that 


*f.U 

> 

2.0 

»    \ 

•      \ 

1.0 
0.8 

©          ^ 

0.6 

-\ 

\         \Co45  (CoS04) 
o\            ^v. 

0.4 

- 

\                 \c14  (C0CO3) 

0.2 

- 

\S35  (No2S04) 

01 

1 

0  5 

Mylar  absorber  thickness,  mg/cm2 


10 


Fig.  16.    Absorption  curves  for  bare  soft  (3's. 
Sources  in  screen-wall  counter. 

there  is  a  soft  component  that  is  quickly 
absorbed  out,  and  then  the  long  normal 
exponential  absorption  curve  is  left,  which 
is  the  only  curve  observed  with  Geiger 
counters  of  usual  wall  thickness.  There- 
fore, the  absorption  is  not  strictly  exponen- 
tial for  soft  |3  emitters.  Exponential  curves 
will  be  found  for  hard  (3  emitters,  for  in 
this  case  the  back-scattered  radiation  is  lost 
in  the  large  percentage  of  hard  radiation 
that  is  present  from  thick  solids.  Clearly, 
however,  for  hard  radiations  and  thin 
sources  the  absorption  term  should  not  be 
strictly  exponential. 
The  absorption  curves  for  the  naturally 


radioactive  element  rubidium  observed  in 
the  earlier  work  of  Suttle  and  Libby 
showed  a  nonexponential  character  in  a 
way  that  was  difficult  to  understand  at  that 
time.  This,  we  now  see,  is  the  result  of 
the  large  Z  for  rubidium  compounds  in 
increasing  the  back-scattering  coefficient  /), 
and  of  the  fact  that  the  radiation  from  ru- 
bidium is  soft  (cf .  table  12) .  For  counters 
with  walls  as  thin  as  2  mg/cm2,  the  absorp- 
tion curves   normally   are  exponential   as 


Emax  =  255  kev 
Substrate    Al  half- thickness 
/cm2 
9 


n  on  thick  Pb 


ly  thin  on  thick  Cu 


thin   on    thick   Al 


0  10  20 

Thickness  of  absorber,  mg/cm2 

Fig.  17.     Ca45  absorption  curves  in  aluminum. 

shown  in  figure  17,  in  agreement  with  fig- 
ure 18  for  the  corresponding  values  of 
absorber  plus  counter  wall  thickness. 

The  value  of  G,  the  geometry  factor  in 
the  full  equation  1",  is  precisely  the  ratio 
of  4n  to  the  average  solid  angle  subtended 
at  the  sample  surface  by  the  inner  wall  of 
the  counter.  If  the  counter  is  long  relative 
to  the  sample,  and  if  the  radius  of  the  inner 
wall  is  p  and  the  radius  of  the  sample  sur- 
face relative  to  the  counter  wire  is  r,  then 
it  can  be  shown  that 

G^n/tn/2-cos-1  (p/r)]  (6) 

is  the  equation  for  the  geometrical  value 
of  G. 


176        CARNEGIE  INSTITUTION  OF  WASHINGTON 


A  very  important  question  had  to  be  kindness   of   Mr.   S.   A.   Reynolds).    By 

answered  in  the  course  of  the  attempt  to  means  of  equations  1',  1",  and  2,  G  was 

apply  this  simple  absolute  assay  technique  calculated  from  the  observed  count  rate  R 

to  soft  (3  emitters.   It  was  found  that  the  and   the  known   specific  radioactivity   o. 

results  obtained  for  the  specific  radioac-  The  results  are  given  in  table  13. 

tivity  were  normally  and  uniformly  about  The  counter  used  consisted  of  a  thin 

30  per  cent  low  for  all  isotopes  with  X  metallized  plastic  cylindrical  wall  inflated 

values  below  about  10.  The  effect  was  the  by  the  counting  gas  gently  flowing  through 

purely  geometrical  one  of  the  roughness  at   pressure   slightly   in   excess  of  atmos- 

of  the  surface  of  a  crystalline  powder.  For  pheric.  The  counter  had  a  wall  thickness 

soft  (3  rays  for  which  the  range  in  the  solid  of  1.82  mg/cm2,  and  the  sample  was  placed 

was  less  than  the  thickness  of  the  crystals,  around  the  counter  on  the  inner  surface  of 

the  only  radiation  escaping  was  from  the  a  plastic  cylinder  on  which  was  placed  a 

surfaces  of  the  crystals.   With  harder  (3's,  sheet  of  rubber  1.5  mm  thick  with  a  square 

however,  the  entire  crystal  emitted  and  the  or  circular  hole  of  accurately  known  area 

surface-effect  roughness  disappeared.  punched  in  it.   The  distance  between  the 

The  effect  of  roughness  of  the  sample  is  counter  wall  and  the  surface  of  the  sample 

important.  The  expression  (6)  is  applica-  was  0.27  mg/cm2  of  air.  By  the  use  of  the 

ble  only  to  a  smooth  sample  constituting  rubber  sheet,  the  sample  area  was  accu- 

the  wall  of  a  cylinder  of  inner  radius  r,  rately  known.    The  sample  powder  was 

or  a  portion  of  the  wall  of  such  a  cylinder,  placed  in  the  recess  of  the  rubber  sheet 

Consider  a  normal  crystalline  powder  con-  and  smoothed  with  a  spatula.  Under  these 

sisting  of  cubes  50  \x  on  edge.  If  the  density  conditions  the  counter  wall  radius,  p,  was 

were  2  gm/cm3,  then  the  cube  edge  would  1.5  cm  and  the  inner  sample  surface  radius 

correspond  to  an  x  value  in  equations  1'  was  1.8  cm. 

and  1"  of  10  mg/cm2.  Therefore,  we  see  The  larger  G  factor  for  soft  radiation  as 
immediately  that,  for  hard  3  emitters  with  shown  in  table  13  was  further  established 
X  values  larger  than  10  mg/cm2,  the  sur-  experimentally  by  making  a  finely  divided 
face  of  the  solid  powder  of  randomly  ori-  Na2COs  which  had  C14  in  it.  This  was 
ented  cubes  would  appear  to  be  smooth  and  done  by  powdering  Na2C#03*H20  and 
the  powder  would  have  a  G  value  close  to  then  dehydrating  it  at  low  oven  tempera- 
that  for  a  smooth  surface  as  given  by  tures  so  that  sintering  did  not  occur.  Under 
equation  6.  For  soft  3  emitters,  on  the  these  conditions  the  value  of  G  was  the 
other  hand,  only  the  surfaces  of  the  crystals  smaller  one  for  hard  3's  rather  than  the 
can  emit,  and  the  surface  therefore  must  larger  one  found  for  the  same  salt  before 
appear  rough.  The  fact  that  roughness  dehydration,  as  shown  in  table  13.  In  all 
causes  a  reduction  in  the  total  outward  other  cases  for  soft  3  radiations  the  G  was 
flux  of  radiation  relative  to  that  from  a  true  higher,  and  the  average  for  all  soft  3's 
smooth  cylindrical  surface  of  the  same  ma-  with  X  values  less  than  10  was  3.9  versus 
terial  at  the  same  specific  radioactivity  may  2.72  for  the  hard  3's.  Table  13  gives  the 
not  be  obvious,  but  detailed  calculation  for  final  G  values  as  determined  according  to 
various  likely  powders,  such  as  randomly  the  three  equations  1',  1",  or  2. 
oriented  cubes  or  hexagonally  packed  It  is  clear,  of  course,  that  the  necessity 
spheres,  shows  that  this  is  a  general  result  for  deciding  which  value  of  G  applies  to 
and  that  the  magnitude  of  the  effect  agrees  a  particular  solid  sample  (and  3  radio- 
with  the  results  on  the  various  3-radiation  activity)  being  measured  is  a  point  of  con- 
standards  obtained  from  the  National  cern.  How  can  one  tell?  For  3's  with  X 
Bureau  of  Standards  (through  the  kind-  values  well  above  10  mg/cm2,  the  rough- 
ness of  Dr.  W.  B.  Mann)  and  the  Oak  ness  necessary  for  the  larger  value  of  G  will 
Ridge  National  Laboratory  (through  the  be  easily  visible  and  easily  destroyed  by 


GEOPHYSICAL  LABORATORY        177 


grinding  with  a  mortar  and  pestle.  There- 
fore, for  this  class  of  radioactivity  suc- 
cessive measurements  after  grinding  will 
bring  the  count  rate  to  a  constant  high 
value  independent  of  the  degree  of  fine- 
ness of  the  solid  which  is  characteristic  of 
the  smooth  surface  and  the  lower  G  value. 
For  the  softer  (3's,  however,  it  is  neces- 
sary to  do  the  opposite — to  grow  the  crys- 


The  procedure  for  converting  the  (3 
standards,  which  were  solutions  of  very 
high  specific  activity,  to  solid  form  for 
measurement  was  to  add  a  solution  of  an 
appropriate  salt  to  a  known  volume  of  the 
standard,  mix,  evaporate  or  precipitate 
chemically,  and  grind  the  resultant  solid. 
Sometimes  it  was  difficult  to  obtain  solids 
that   were   chemically   identical   with   the 


TABLE  13.     Experimental  Geometry  Factors,  G 


Isotope 


Substrate 


mg/cm2 


Fully  Corrected 

for  Back 

Scattering  and 

Softening, 

equation  1" 


Partly 
Corrected, 
equation  V 


No  Back- 
Scattering 
Correction, 
equation  2 


P32  Na2S04  129  2.65±0.02 

(NH4)H2P04  141  2.87  ±0.03 

K40    K2S04  98  2.73±0.06 

CI36   NaCl  45  2.85±0.03 

AgCl  34  2.74  ±0.03 

BaCl2  34.4  2.61  ±0.03 

Tl204   T1C02H  27.1  3.09  ±0.04 

Average 
for  A>10 2.72 

Ca45 CaC03  7.5  4.12  ±  0.04 

CaS04-2H20  7.9  4.18  ±0.04 

CaO  7.0  4.28  ±0.04 

CaS04  7.4  3.73  ±0.03 

S35   Na,S04  3.5  3.46±0.3 

BaS04  3.0  4.4  ±0.2 

C14 CaC03  2.9  3.4  ±0.1 

Na2C03-H20  3.1  4.15  ±0.16 
Very  fine 

Na2C03  3.0  2.55  ±0.08 

Average 
for  X<10 
(omitting  fine  Na2COs)   3.9 


2.73  ±0.02 

2.85  ±0.03 
2.83  ±0.06 
2.97  ±0.03 

2.86  ±0.03 
2.71  ±0.03 
3.11  ±0.05 

2.82 

4.41  ±0.05 
4.47  ±0.04 
4.60  ±0.04 
4.01  ±0.03 
3.78  ±0.3 
5.0  ±0.3 
3.76  ±0.1 
4.56  +  0.18 

2.78  ±0.09 


4.2 


2.33  ±0.02 
2.02  ±0.03 
2.28  ±0.05 

2.43  ±0.03 
1.99  ±0.03 
1.87  ±0.03 
2.01  ±0.05 

2.20 

3.72  ±0.04 
3.76  ±0.04 
3.71  ±0.04 
3.28  ±0.03 
3.16  ±0.3 
3.5  ±0.3 
3.16±0.1 
3.95  ±0.1 

2.44  ±0.09 


3.5 


tals  larger  and  larger  by  sintering  or  other 
device,  and  thus  to  reach  a  constant  count 
rate  independent  of  crystalline  size.  Any 
doubt  can  be  settled  by  a  cursory  examina- 
tion with  a  microscope,  the  relative  mag- 
nitude of  the  crystal  size  and  X  being 
borne  in  mind.  It  appears  that  the  soft  3 
geometry  factors  for  various  powders  are 
essentially  the  same,  as  can  be  seen  in  table 
13,  though  there  is  some  evidence  of  scat- 
ter, which  could  be  due  to  the  size  or 
shape  of  the  particular  crystals. 


radioactive  molecules,  and  attempts  were 
made  to  use  substitutes  with  which  the 
radioactive  species  was  likely  to  form 
mixed  crystals.  For  the  harder  (3  radia- 
tions, the  requirement  that  mixed  crystals 
be  formed  seemed  to  be  less  necessary.  For 
example,  radioactive  phosphate  containing 
P32  (Aai=  122  mg/cm2)  was  measured  on 
Na2S04  powder.  It  seems  unlikely  that 
any  substrate  not  chemically  identical  can 
be  used  in  the  case  of  soft  3's. 


178        CARNEGIE  INSTITUTION  OF  WASHINGTON 


RESULTS 

In  table  14  are  shown  the  results  of  the 
application  of  the  method  to  a  series  of 
(3-radiation  standards  furnished  by  the  Na- 
tional Bureau  of  Standards  and  the  Oak 
Ridge  National  Laboratory.  From  these 
data  it  appears  that  the  method  is  good  to 
about  5  per  cent.  Equation  2,  which  is  the 
simplest,  does  nearly  as  well,  except  for 
the  large  atomic  numbers,  as  the  more 
complete  equations  1'  and  1" '. 


was  applied.  The  results  are  given  in  table 
15. 

In  calculating  the  final  error  for  the 
half-life  as  determined  on  the  three  rubid- 
ium samples,  the  average  deviation  of 
3.3  per  cent  for  equation  1"  as  applied  to 
soft  (3's  with  a  G  value  of  3.9  was  used. 
The  average  deviation  of  9.5  per  cent  for 
a  single  determination  as  given  in  table 
14  was  divided  by  the  square  root  of  the 
number   of   determinations   to   determine 


TABLE  14.     Results  for  Standard  Sources 
(Per  cent  deviation)  calculation 


Isotope  and 
Substrate 


Fully  Corrected, 
equation  1" 


Partially 
Corrected, 
equation  V 


Uncorrected  for 

Back  Scattering, 

equation  2 


P32        Na2S04 +1.1  +0.7 

(NH4)H2P04 +  5.6  +1.2 

(NBS) 

CI36      NaCl  +4.7  +5.4 

AgCl  +0.7    ave.3.9  +1.5    ave.4.4 

BaCl2    -4.0  -3.9 

(ORNL) 

T1204     T1C02H + 13.6  + 10.4 

(NBS) 

Ca45      CaC03    +5.6  +5.1 

CaS04-2H20    +7.1  +6.5 

CaO +9.6  +9.5 

CaS04 -4.4  -4.5 

(ORNL) 

S35        Na2S04 -11       ave.9.5  -10       ave.9.8 

BaS04  +13  +20 

(NBS) 

C14       CaC03 -13  -10 

Na2C03-H20 +6.4  +7.4 

(NBS) 


+  5.5 
-8.0 

+  10.5 

-9.4    ave.8.3 
-15 

-8.7 


+  6.5 
+  7.6 
-6.1 
-6.3 

-8.6    ave.7.8 
+  0.3 

-9.7 
+  13 


APPLICATION  TO  NATURALLY  RADIOACTIVE 
RUBIDIUM 

Aldrich,  Wetherill,  Tilton,  and  Davis 
compared  the  ratio  of  radiogenic  Sr87  to 
Rb87  found  in  several  minerals  differing 
in  rubidium  content  in  rocks  of  known 
age  as  determined  by  the  uranium-lead 
method.  They  calculated  the  half-life  of 
natural  radioactive  Rb87  to  be  50  ±2  billion 
years.  Strassman  and  Walling  found  63 
billion  by  a  similar  method.  Because  of  the 
importance  of  this  determination  to  geo- 
chronology,  the  technique  described  above 


the  average  deviation  of  the  mean  from 
the  true  value.  The  agreement  among  the 
three  different  rubidium  samples  in  table 
15  indicates  that  the  error  of  the  deter- 
mination is  the  error  in  the  determination 
of  G,  which  as  explained  should  be  3.3 
per  cent. 

GENERAL  APPLICATIONS 

Equation  2  certainly  is  simple  enough 
for  use  in  high-school  laboratory  experi- 
ments. In  this  way  isotopes  of  real  chemi- 
cal interest,  convenient  lifetime,  and  low 


GEOPHYSICAL  LABORATORY       179 


enough  specific  activity  to  be  completely 
safe  can  be  introduced  into  the  ordinary 
high-school  chemistry  course.  Among  these 
isotopes  are  C14,  CI36,  S35,  and  Ca45.  Thus 
the  radioactive  forms  of  acetic  acid,  hydro- 
chloric acid,  sulfuric  acid,  and  the  calcium 
salts  can  be  placed  on  the  reagent  shelves 
and  the  label  can  carry  the  specific  activity, 
so  that  the  students  by  using  a  known 
volume  can  introduce  a  known  amount  of 
radioactivity,  and  by  subsequent  absolute 
counting  of  the  various  solids  produced  in 
the  experiment  can  calculate  an  isotopic 
balance  to  compare  with  the  ordinary  ma- 
terial balance.  This  technique  makes  pos- 
sible the  ready  application  of  isotopic  dilu- 
tion techniques. 


In  industrial  applications  the  possibility 
of  keeping  an  analytical  check  on  a  known 
amount  of  C14  added  in  appropriate  chemi- 
cal form  at  the  beginning  of,  or  during,  an 
industrial  organic  chemical  process  cer- 
tainly affords  many  opportunities  for  con- 
trolling the  process.  The  labeling  of  a 
particular  constituent  of  the  crude  feed 
for  an  oil  refinery  for  a  fixed  period  would 
make  possible  a  detailed  examination  of 
the  flow  rates  and  patterns  throughout  the 
plant,  e.g.  the  contribution  of  this  constit- 
uent to  coke  in  the  catalytic  crackers,  the 
completeness  of  the  burn-off  of  the  coke 
from  this  constituent  in  the  burn-off  cycle, 
or  the  general  holdup  in  various  stages  in 
the  plant. 


TABLE  15.     Determination  of  the  Half-Life  of  Rb87 


Sample                                    K  n               Specific  Activity,  Half-Life, 

mg/cm2  dpm/mg  billion  years 

RbCl   3.85  0.384                  53.1  ±1  49.6  ±1 

Purified  by  Dr.  Suttle 

RbCl  3.85  0.384                  51.7±0.8  51.0±0.8 

Johnson,  Mattie  &  Co.,  London; 

spectrographically  pure 

Rb2COs    3.83  0.361                  54.0±0.5  51.1  ±0.5 

Average 50.7±2 


PALEOBIOCHEMISTRY 


EFFECTS   OF   ULTRAVIOLET   LIGHT   ON  THE 
"PRIMITIVE  ENVIRONMENT" 

P.  H.  Abelson 

The  origin  of  life  is  a  topic  of  tran- 
scending interest  which  has  drawn  the  at- 
tention of  many  investigators.  Many  of 
them  have  sought  to  isolate  a  part  of  the 
problem  both  crucial  and  capable  of  solu- 
tion— the  synthesis  of  biological  building 
blocks,  especially  amino  acids,  from  simple 
chemicals  of  the  environment.  To  accom- 
plish these  reactions  a  number  of  energy 
sources  have  been  employed,  including  a, 
3,  and  y  radiation  and  electrical  discharges. 
A  variety  of  test  chemicals  has  been  em- 
ployed, many  of  which  make  convenient 
experimental  objects  but  could  hardly  have 
existed  in  substantial  quantities  on  the 
primitive  earth. 


It  is  difficult  to  be  certain  concerning 
processes  that  might  have  occurred  three 
billion  years  ago.  It  is  feasible,  however, 
to  set  some  limits  on  the  areas  of  permis- 
sible speculations.  An  analysis  of  the  na- 
ture of  the  primitive  environment  could 
be  expected  to  point  up  the  importance  of 
a  few  key  compounds  and  reactions.  Study 
of  the  effects  of  energy  on  these  substances 
might  then  disclose  reactions  of  major  im- 
portance on  the  primitive  earth. 

The  relative  scarcity  of  the  gases  neon, 
argon,  krypton,  and  xenon  in  our  present 
atmosphere  is  a  most  significant  phenom- 
enon. The  abundance  curves  of  isotopes 
of  the  various  elements  are  fairly  well 
known,  and  neon  has  been  observed  as 
an  important  constituent  of  stellar  atmos- 
pheres while  being  scarce  on  earth.  Brown 


180 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


and  Suess  have  estimated  that  neon  is 
present  on  our  planet  to  an  extent  only 
10~10  of  probable  cosmic  abundance,  and 
that  similarly  argon,  krypton,  and  xenon 
are  relatively  absent.  We  do  not  know  the 
nature  of  the  processes  by  which  the  earth 
was  formed,  whether  these  inert  gases 
were  lost  during  the  accumulation  period 
or  subsequently;  but  at  any  rate  they  were 
lost,  and  it  seems  reasonable  that  such 
other  volatile  constituents  as  hydrogen,  ni- 
trogen, methane,  and  carbon  monoxide 
would  also  have  been  lost  at  the  same  time. 
Rubey  has  calculated  the  amounts  of 
volatiles  that  have  appeared  in  the  atmos- 
phere, hydrosphere,  or  biosphere  since 
weathering  first  began.  He  advances  many 

TABLE  16.    Inventory  of  Organic  Matter 


oxygen  or  oxidation  to  match  the  reduced 
substances  in  the  sediments.  It  is  possible 
that  this  unaccounted-for  oxygen  was  con- 
sumed in  the  oxidation  of  carbon  monox- 
ide and  hydrogen  issuing  from  volcanoes. 
The  reducing  nature  of  these  gases  is  a 
consequence  of  the  physical-chemical  equi- 
libria of  water  and  carbon  dioxide  with 
the  reduced  iron  compounds  and  possibly 
other  substances. 

A  calculation  shows  that  3  atm  of  hydro- 
gen would  be  in  equilibrium  with  1000  atm 
of  water  at  1200°  K,  and  that  at  the  same 
temperature  1  atm  of  hydrogen  would  be 
in   equilibrium   with    100   atm   of   water 

TABLE  17.    Inventory  of  Oxygen 


O, 


Grams 


Element 


Grams 


Carbon  68xl02° 

Oxygen  25  X  102° 

Hydrogen  9.6  X  1020 
Oxygen  needed  to 

burn  to  C02  +  H20  235  X  1020 


powerful  arguments  that  these  volatiles 
were  not  originally  present  on  the  surface 
of  the  earth  but  came  from  the  interior  of 
the  earth  through  a  gradual  degassing 
process.  Of  interest  to  the  present  argu- 
ment are  data  that  he  has  provided  on 
the  inventory  of  organic  matter  in  sedi- 
ments, shown  in  table  16.  These  permit 
construction  of  an  oxidation-reduction  bal- 
ance. To  measure  the  reducing  side  of  the 
ledger,  the  amount  of  oxygen  required  to 
burn  this  organic  matter  to  water  and 
carbon  dioxide  can  be  calculated.  The 
amount  of  oxygen  in  the  atmosphere  at 
present  and  that  consumed  in  the  oxida- 
tions of  ferrous  to  ferric  iron  and  sulfur 
to  oxidized  sulfur  may  be  noted  in  table  17. 
Considerable  uncertainty  attaches  to  the 
amount  of  oxygen  consumed  in  oxidation 
of  sulfur,  since  the  relative  proportions  of 
the  original  forms  of  this  substance  are 
not  known;  the  value  quoted  represents 
an  upper  limit.    There   is   not   sufficient 


In  atmosphere 
Consumed  in  oxidation 

FeO-^Fe2Os 
Consumed  in  oxidation 

S->SOs 

Total  accounted  for 
Unaccounted  for 

Total 


12X1020 

14X1020 

41X1020 

67  X1020 
168  X1020 

235  XIO20 


along  the  wiistite,  fayalite,  and  magnet- 
ite join.  The  equations  governing  equi- 
libria involving  carbon  dioxide,  carbon 
monoxide,  water,  and  hydrogen  in  the 
presence  of  fayalite,  wiistite,  and  magnet- 
ite may  be  combined  to  eliminate  the 
common  oxygen  component.  As  a  result 
there  can  be  obtained  an  equation  involv- 
ing the  equilibrium  of  water,  carbon  di- 
oxide, hydrogen,  and  carbon  monoxide. 
If  the  volatile  constituents  that  have  ap- 
peared at  the  surface  were  in  equilibrium 
with  one  another,  and  with  a  basaltic 
crust,  the  original  chemical  form  of  some 
of  the  constituents  can  be  estimated,  tak- 
ing into  account  the  oxidation-reduction 
balance.  Results  can  be  noted  in  table  18, 
where  it  is  apparent  that,  since  water  is 
the  major  volatile  that  has  been  released, 
hydrogen  was  the  major  reduced  substance 
accompanying  such  a  mixture.  Later  it  will 


GEOPHYSICAL  LABORATORY       181 


be  seen  that  a  highly  important  feature  of 
the  composition  of  these  volatiles  is  the 
comparative  amounts  of  carbon  dioxide 
and  hydrogen. 

Relatively  soon  after  the  earth  was 
formed  it  cooled  to  about  its  present  tem- 
perature. Hence,  only  a  very  small  pro- 
portion of  water  remained  in  the  atmos- 
phere. The  oldest  rocks  that  have  been 
dated  contain  the  same  minerals  as  those 
found  today.  Weathering  of  these  rocks 
led  to  sediments  similar  in  composition 
to  those  formed  recently.  There  are  argu- 
ments and  evidence  making  it  reasonable 
to  assume  that  the  pH  of  the  primitive 
oceans  was  not  much  different  from  that 
today.  As  carbon  dioxide  was  liberated 
most  of  it  dissolved  in  those  waters,  leav- 

TABLE    18.    Composition   of  Volatiles   on   the 
Basis  of  Equilibrium  Conditions 


H20.    A    wide    variety    of   compositions 
yielded  mixtures  of  amino  acids. 

Analysis,  however,  shows  that  corpuscu- 
lar radiation  and  electrical  discharge  are 
relatively  limited  as  sources  in  comparison 
with  the  energy  coming  in  sunlight.  In 
table  19  is  shown  the  relative  energy  avail- 
able per  year.  It  can  be  noted  that  energy 
from  sunlight  far  exceeds  that  from  other 
kinds  of  sources,  lightning  is  relatively  in- 
significant, and  cosmic  rays  are  of  very 
little  consequence  in  terms  of  their  energy 
content.  Levels  of  radiation  due  to  natural 

TABLE   19.    Energy  Input  to  Earth 


Source  of  Energy 


cal/cm2/yr 


Sunlight 
Lightning 
Cosmic  rays 


260,000 

0.9 

1.5  XlO"3 


Gas 


Moles 


H20 
H2 

co2 

CO 

N„ 


920  XlO20 
10.3  XlO20 

21  XlO20 
0.24  XlO20 

1.5  XlO20 


TABLE  20.    Rocket  Measurements  by  the  Naval 

Research  Laboratory  of  Energy  Incident 

on  Earth 


A 


Energy, 
watts/cm2/u 


ing  hydrogen,  nitrogen,  and  carbon  mon- 
oxide as  the  principal  constituents  of  the 
atmosphere.  This  mixture  was  altered  fur- 
ther through  the  action  of  various  forms  of 
energy. 

In  attempts  to  set  up  models  for  produc- 
tion of  compounds  in  the  primitive  en- 
vironment, several  different  kinds  of  en- 
ergy sources  have  been  tried.  Earlier  at 
the  University  of  California  the  cyclotron 
a-particle  beam  was  employed.  Recently,  |3 
and  y  radiation  have  been  used  as  sources. 
The  experiments  of  Stanley  Miller  have 
demonstrated  the  production  of  amino 
acids  in  an  environment  of  methane,  am- 
monia, and  water  as  a  result  of  the  action 
of  an  electric  discharge.  Abelson  has  con- 
firmed these  findings  and  extended  them 
by  testing  the  effects  of  electrical  discharges 
on  twenty  other  mixtures  of  gases,  includ- 
ing CO,  N2,  H2,  H2O;  C02,  NH3,  H2, 


4500 
3000 
2800 
2600 
2400 
2200 


0.22 

0.061 

0.024 

0.013 

0.0058 

0.003 


radioactivity  are  variable,  but  in  many 
areas  are  about  equivalent  to  those  due  to 
cosmic  rays. 

Only  part  of  the  sun's  energy  is  in 
the  ultraviolet  region,  but  this  portion  is 
particularly  effective  in  causing  chemical 
transformations.  Rocket  experiments  car- 
ried on  by  the  Naval  Research  Laboratory 
have  measured  the  energy  incident  upon 
the  top  of  the  atmosphere  with  results 
shown  in  table  20.  From  these  data  it  can 
be  estimated  that  468  cal/cm2  of  wave- 
lengths shorter  than  2540  A  fall  on  the 
top  of  the  atmosphere  annually.  Such 
radiation  is  absorbed  by  carbon  dioxide. 
Simultaneously  19  cal/cm2  of  wavelengths 


182        CARNEGIE  INSTITUTION  OF  WASHINGTON 


shorter  than  1800  A  strike  the  atmosphere. 
This  radiation  can  be  absorbed  by  water. 
Carbon  monoxide  exhibits  some  slight 
band  absorption  at  2056  A,  but  major  in- 
teraction begins  at  1546  A.  Only  5.5  cal/ 
cm2/yr  are  found  in  shorter  radiation. 

Another  way  of  assessing  the  possible 
role  of  ultraviolet  radiation  is  to  match  an- 
nual production  of  chemicals  and  radia- 
tion. Such  a  comparison  may  be  noted  in 
table  21,  where  it  is  evident  that  the  energy 
available  far  exceeds  the  annual  produc- 
tion of  chemicals. 

Ultraviolet  light  decomposes  carbon  di- 
oxide to  carbon  monoxide  plus  atomic 
oxygen.  In  the  presence  of  hydrogen, 
atomic  oxygen  reacts  to  form  OH  +  H. 
OH  in  turn  reacts  with  hydrogen  to  form 

TABLE  21.    Annual   Production   of  Chemicals 
and  Energy  per  Square  Centimeter 


Quanta 


Moles 


X<2900 

1.4  X1022 

co2 

8  XlO16 

A  <  2540 

2.3  xlO21 

CO 

9  XlO14 

X=  1100-1345 

3X1018 

N2 

6  XlO15 

H2 

4  XlO16 

water  plus  more  atomic  hydrogen.  One 
may  speculate  that,  as  carbon  dioxide  of 
the  primitive  atmosphere  was  used  up, 
being  split  into  carbon  monoxide  plus 
oxygen,  the  partial  pressure  of  carbon  di- 
oxide was  maintained  by  the  carbonate 
buffering  system  of  the  oceans.  As  long 
as  there  were  large  amounts  of  molecular 
hydrogen  in  the  atmosphere,  the  oxygen 
liberated  by  the  breakup  of  carbon  dioxide 
would  be  converted  into  water.  However, 
after  most  of  the  hydrogen  had  been  used 
up,  small  amounts  of  free  oxygen  would 
appear,  and  they  would  recombine  with 
carbon  monoxide  or  any  other  reducing 
substance.  Carbon  dioxide  must  have  acted 
as  a  sort  of  buffer  in  the  oxidation-reduc- 
tion system,  guaranteeing  that  the  atmos- 
phere could  never  have  been  very  reducing. 
It  seems  impossible  to  visualize  any  great 
concentration  of  substances  such  as  meth- 
ane present  together  with  carbon  dioxide. 


The  values  given  by  Rubey  indicate  that 
in  the  last  3  billion  years  considerably  more 
carbon  dioxide  has  been  liberated  than  is 
needed  to  supply  oxygen  to  react  with  all 
the  hydrogen  or  other  reducing  substances. 

In  an  atmosphere  consisting  predomi- 
nantly of  carbon  monoxide,  nitrogen,  and 
hydrogen,  the  action  of  short  ultraviolet 
light  could  lead  to  a  number  of  additional 
substances,  including  ammonia  and  hydro- 
gen cyanide.  Under  any  reasonable  as- 
sumptions of  the  nature  of  the  primitive 
oceans,  all  ammonia  and  hydrogen  cyanide 
would  be  found  in  the  aqueous  phase  with 
almost  none  remaining  in  the  atmosphere. 
Carbon  monoxide  is  slightly  soluble  in 
water,  being  slowly  converted  into  for- 
mate. The  interactions  of  ultraviolet  light 
with  the  atmosphere  and  subsequent  ab- 
sorption of  products  in  the  oceans  thus 
would  modify  the  composition  of  both 
atmosphere  and  oceans.  Later  in  this  re- 
port some  effects  of  ultraviolet  light  on  the 
substances  dissolved  in  the  oceans  will  be 
considered. 

In  enumerating  the  kinds  of  organic 
compounds,  formation  of  which  would  be 
crucial  to  the  creation  of  building  blocks 
essential  for  life,  one  is  impressed  by  the 
possible  important  role  of  the  aldehydes. 
This  class  of  compounds  could  serve  as 
important  materials  in  the  building-up  of 
long  carbon  chains  through  reactions  that 
can  occur  in  the  aqueous  phase.  No  other 
set  of  organic  substances  can  perform  in 
quite  such  a  manner.  Strecker  in  1850 
found  that,  if  formaldehyde,  hydrogen 
cyanide,  and  ammonia  are  all  simulta- 
neously present  in  solution,  glycinonitrile 
is  formed.  This  substance  subsequently  is 
hydrolyzed  by  water  to  form  the  amino 
acid  glycine.  The  Strecker  synthesis  is  not 
limited  to  formaldehyde  but  may  be  car- 
ried out  with  other  aldehydes.  It  is  inter- 
esting that  this  type  of  synthesis  gives  rise 
to  a-amino  acids,  which  are  the  principal 
type  of  amino  acids  used  in  biological 
processes. 

It  seemed  important  to  determine 
whether    ultravolet   light   acting   on   for- 


GEOPHYSICAL  LABORATORY       183 


mate  could  lead  to  the  extremely  impor- 
tant substance  formaldehyde.  In  alkaline 
solutions  formate  has  little  absorption  at 
wavelengths  longer  than  2540  A;  above 
2700  A  it  is  virtually  transparent.  It  was 
recalled  that  iron  is  a  ubiquitous  constitu- 
ent of  the  crust,  and  that,  if  there  was 
little  or  no  oxygen  in  the  atmosphere, 
appreciable  concentrations  of  ferrous  iron 
might  be  present  in  solution.  AIM  solu- 
tion of  formate  containing  0.004  M  ferrous 
iron  at  a  pH  of  8.3  was  irradiated,  in  an 
evacuated  vessel,  by  ultraviolet  light  of 
wavelength  2536  A.  After  1  hour,  a  non- 
condensable  gas  was  noted,  and  formalde- 
hyde could  be  detected  in  the  solution.  At 
the  end  of  3  hours,  approximately  three 
times  as  much  noncondensable  gas  was 
present  but  the  same  amount  of  formalde- 
hyde was  determined.  In  order  to  obtain 
a  better  measure  of  the  rate  of  formation 
of  formaldehyde,  experiments  were  per- 
formed using  a  trapping  mechanism  de- 
signed to  take  formaldehyde  out  of  the 
scene  of  destruction.  For  this  purpose  the 
Strecker  synthesis  was  employed.  Solu- 
tions 0.4  M  in  formate,  0.4  M  in  ammo- 
nium hydroxide,  0.2  M  in  sodium  cyanide, 
and  0.0016  M  in  ferrous  sulfate  were  ir- 
radiated for  periods  of  an  hour  to  several 
days,  and  the  resulting  glycinonitrile  was 
hydrolyzed  and  determined  as  glycine. 
Relatively  large  quantities  of  this  amino 
acid  were  found. 

In  another  series  of  experiments  the 
hydantoin  reaction  was  employed  as  the 
trapping  mechanism.  For  this  purpose  a 
solution  0.1  M  in  ammonium  carbonate, 
0.1  M  in  formate,  0.1  M  in  sodium  cyanide, 
and  0.001  M  in  ferrous  sulfate  was  irradi- 
ated for  2  days  with  2536  A  radiation.  The 
resulting  hydantoin  was  hydrolyzed  with 
NaOH,  and  glycine  was  isolated.  A  10 
per  cent  yield  based  on  formate  was  ob- 
tained. 

An  important  series  of  reactions  is  the 
condensation  of  aldehyde  and  cyanide  fol- 
lowed by  hydrolysis.  The  kinetics  of  the 
first  of  these  two  reactions  has  been  studied 
using  initial  concentrations  of  10~3  M  cya- 


nide and  10~4  M  formaldehyde.  Some 
results  are  shown  in  table  22.  The  reaction 
proceeds  rapidly  until  the  concentration  of 
formaldehyde  drops  to  10~7  M  or  3  parts 
in  109.  The  effect  of  pH  on  the  reaction 
was  also  investigated.  The  optimum  pW 
for  the  reaction  was  found  to  lie  in  the 
range  8  to  9.5.  The  reaction  thus  proceeds 
best  at  a  pYL  near  that  of  sea  water.  Hy- 
drolysis of  glycolonitrile  to  glycolic  acid 
is  an  irreversible  reaction  which  progresses 
at  a  moderate  rate  at  20°  C.  With  the 
appearance  of  glycolic  acid  the  stage  is  set 
for  further  synthesis.  Irradiation  by  ultra- 
violet light  again  could  yield  an  aldehyde; 

TABLE  22.    Reaction  Kinetics  at  20°  C 

H2 
HCN + CH20<=±HOC  -  C  =  N 

10~3  M  NaCN,  1.05  X  10-4  M  CH20,  pH  8.1 


Time, 

CH20, 

Time, 

CH20, 

min 

10-4mole 

min 

10~4  mole 

0 

1.05 

6.0 

0.100 

1.1 

0.64 

7.0 

0.078 

2.1 

0.433 

9.0 

0.035 

3.1 

0.320 

10.0 

0.025 

4.0 

0.207 

12.0 

0.010 

5.0 

0.147 

20.0 

0.001 

evidence  for  this  step  is  discussed  later. 
Condensation  with  cyanide  would  result  in 
a  dihydroxynitrile,  glyceronitrile.  A  series 
of  condensations  followed  by  hydrolysis 
could  lead  to  6-carbon  compounds  very 
similar  to  carbohydrates. 

Several  experiments  have  tested  the  ef- 
fect of  ultraviolet  light  on  glycolic  acid. 
The  irradiation  was  carried  out  in  a  so- 
lution containing  hydrogen  cyanide,  am- 
monia, and  a  small  amount  of  ferrous  iron 
in  addition  to  the  glycolic  acid.  No  at- 
tempt was  made  to  attain  a  maximum 
yield  of  amino  acids.  Nevertheless  hydrol- 
ysis of  the  nitriles  formed  revealed  a  yield 
of  amino  acids  of  15  per  cent,  based  on 
the  original  amount  of  glycolic  acid.  Ex- 
amination of  the  products  by  paper  chro- 
matography produced  a  rather  interesting 
result.   Serine,  the  expected  product,  was 


184        CARNEGIE  INSTITUTION  OF  WASHINGTON 


present,  but  alanine  and  glycine  were  also  ing  which  creatures  were  forced  to  develop 
identified,  as  well  as  other  substances.  Fur-  photosynthesis  suddenly  to  survive.  Rather 
thermore,  substantial  quantities  of  more  a  sharp  competition  for  a  limited  food  sup- 
complex  colored  substances  were  formed,  ply  favored  those  creatures  that  could  de- 
These  were  opaque  to  ultraviolet  light  and  velop  alternative  energy  sources  such  as 
relatively  easily  adsorbed  on  talc.    In  na-  photosynthesis. 

ture,  complex  organic  substances  would  be         One  of  the  products  of  this  research  was 
adsorbed  and  ultimately  buried  in  sedi-  an  observation  of  the  effect  of  ultraviolet 
ments.   Here  is  a  possible  mechanism  for  light  on  ferrous  iron.    Many   who  have 
production  of  carbonaceous,  organic  sedi-  considered  Precambrian  geology  have  cited 
ments  that  does  not  invoke  the  action  of  the  widespread  occurrence  of  ferric  iron 
living  creatures.  as  evidence  that  in  those  times  an  oxygen 
Others  who  have  speculated  on  the  ori-  atmosphere  was  present.    Recent  experi- 
gin  of  life  have  postulated  that  a  thick  ments  have  brought  this  assumption  into 
organic  soup  was  formed  and  that  when  question.  Dilute  ferrous  iron  at  about  pH 
living  creatures  were  available  they  quickly  8  was  placed  in  a  silica  flask,  which  was 
depleted  this  broth.    Once  the  broth  was  subsequently  evacuated  and  subjected  to 
gone  the  creatures  had  no  alternative  but  ultraviolet   light  of  wavelength  2536  A. 
to  develop  photosynthesis  in  order  to  sur-  Hydrogen  was  formed,  and  a  precipitate 
vive.  Consideration  of  the  model  that  has  of  ferric  iron  noted.   Search  of  the  litera- 
been  presented  here  does  not  lead  to  quite  ture  then  revealed  that  similar  effects  of 
these  same  conclusions.  If  all  the  available  ultraviolet  light  on  ferrous  iron  had  been 
hydrogen  were  used  up  in  processes  lead-  demonstrated  by  Chastaing  in  1877  and 
ing  to  formate,  the  maximum  concentra-  that  a  threshold  of  2900  A  had  been  estab- 
tion  of  this  substance  would  be  0.6  M;  lished  for  the  reaction, 
even  allowing  for  the  reducing  capacity  of         Others    have   pointed    out   that   ozone 
sulfur  and  ferrous  iron,  the  figure  would  which  today  absorbs  ultraviolet  light  of 
rise  to  no  more  than  0.8  M  as  a  maximum,  wavelengths   shorter   than  3000  A  prob- 
The  concentration  of  organic  substances  ably  did  not  appear  in  quantity  until  living 
in  the  aqueous  phase  after  a  time  would  creatures  invented  photosynthesis.    Com- 
actually  be  considerably  less  as  the  longer,  paratively  large  amounts  of  energy  in  the 
more  complicated  organic  compounds  were  band  2540  to  2900  A  were  hence  available 
precipitated  or  adsorbed  out  of  the  system  at  the  surface  to  act  on  the  new  ferrous 
while  relatively  little  of  the  diluting  water  iron  released  by  weathering  each  year.  No 
was  lost.   It  can  be  conceived  that  in  the  claim  is  made  that  these  experiments  prove 
early  stages  of  the  earth  as  the  oceans  that  ferric  iron  in  the  Precambrian  was 
gradually  grew  in  magnitude  there  was  a  due  to  the  action  of  ultraviolet.   On  the 
relatively  constant  production  of  various  other  hand,  it  seems  clear  that  the  presence 
kinds  of  organic  molecules,  some  of  which  of  ferric  iron  is  not  necessarily  proof  that 
were  lost  by  precipitation.   Owing  to  this  either  oxygen  or  photosynthesizing  organ- 
loss   and   to   the   continuing   addition   of  isms  were  present  at  the  time  the  ferric 
water  to  the  system,  the  concentration  of  iron  was  laid  down, 
organic  molecules  would  actually  diminish         The  result  of  this  experiment  with  iron 
somewhat  in  spite  of  the  constant  rate  of  suggested  still  another,  employing  a  solu- 
production.    Under  this  picture  the  first  tion  of  sodium  sulfite  at  pH  8  together 
living  creatures  which  could  extract  or-  with  a  small  amount  of  ferrous  iron.  Again 
ganic  compounds  from  the  medium  had  the  solution  was  placed  in  a  silica  vessel, 
available    an    annual    supply    of    organic  which  was  evacuated  and  irradiated  with 
molecules,  and  hence  there  was  not  neces-  2536  A  ultraviolet  light.  Sulfate  appeared 
sarily  a  catastrophic  starvation  period  dur-  in  the  solution.    It  would  seem  that  the 


GEOPHYSICAL  LABORATORY       185 


occurrence  of  sulfate  in  the  Precambrian  is 
not  necessarily  diagnostic  of  oxygen  in  the 
atmosphere. 

THERMAL   DEGRADATION   OF   AMINO   ACIDS 
/.  R.  Vallentyne 

Approximately  1017  g  of  organic  matter 
is  synthesized  annually  on  the  earth's  sur- 
face by  plants.  Although  most  of  this  is 
recycled  in  the  biosphere,  a  small  fraction 
becomes  buried  in  sediments  and  soils, 
thus  leaving  the  biochemically  active  part 
of  the  biosphere.  Once  sedimented,  this 
organic  matter  is  subjected  to  further  de- 
composition, dependent  on  subsequent  bio- 
logical and  chemical  attack.  If  the  fossil 
compounds  occur  in  materials  that  are 
protected  from  biological  attack  (such  as 
a  calcite  shell),  then  to  a  first  approxima- 
tion the  system  could  be  treated  in  terms 
of  chemical  kinetics.  It  is  now  well  known 
(Year  Book  53,  p.  99)  that  amino  acids 
occur  in  fossils  as  old  as  the  Devonian. 
It  is  also  known  that  certain  amino  acids 
are  geologically  less  stable  than  others,  for 
example  serine,  threonine,  and  phenyl- 
alanine as  compared  with  the  more  stable 
glutamic  acid,  glycine,  and  alanine. 

From  a  knowledge  of  the  relative  de- 
composition rates  of  amino  acids  under  de- 
fined conditions  in  the  laboratory,  coupled 
with  analyses  of  fossil  materials,  geological 
temperatures  of  preservation  might  be  in- 
ferred if  age  is  known.  Two  difficulties 
of  interpretation  should  be  clearly  stated, 
however.  In  the  first  place,  the  medium 
of  preservation  (for  example,  calcite,  bone, 
or  shale)  must  be  expected  to  influence 
the  decomposition  rates  of  amino  acids. 
For  the  exact  interpretation  of  data  from 
fossil  materials  kinetic  experiments  must 
be  conducted  in  media  that  simulate  their 
geological  counterparts.  For  example,  the 
decomposition  rates  of  amino  acids  in 
modern  shells  could  be  determined  by  an- 
alyzing for  amino  acids  before  and  after 
a  given  treatment.  Second,  since  kinetic 
experiments  are  limited  in  duration  to  a 
few  years  at  the  most,  a  high  degree  of 


extrapolation  is  required  to  obtain  esti- 
mates of  decomposition  rates  at  low  tem- 
peratures. Extrapolation  is  always  danger- 
ous. Extremely  sensitive  methods  for  the 
analysis  of  decomposition  products  aid  in 
extending  experimental  values  to  low  tem- 
peratures, but  do  not  overcome  the  diffi- 
culty completely.  We  will  probably  have 
to  rely  on  the  type  of  argument  used  by 
geochronologists  in  measuring  age :  if  two 
independent  measurements  lead  to  a  pre- 
diction of  a  single  age,  that  value  is  more 
reliable  than  the  same  value  determined  by 
either  method  alone.  Thus,  if  a  tempera- 
ture determination  based  on  amino  acids 
agrees  with  another  based  on  a  different 
set  of  compounds,  a  qualitative  feeling  of 
confidence  results. 

A  preliminary  attack  on  some  of  these 
problems  has  been  made  by  studying  the 
decomposition  rates  of  amino  acids  in  di- 
lute aqueous  solution.  These  data  will 
serve  as  a  base  line  with  which  future  data 
(with  the  medium  as  the  variable)  can  be 
compared.  Decomposition  rates  for  a  va- 
riety of  reactions  can  be  expressed  in  terms 
of  the  Arrhenius  equation: 

h  =  se-AHa/RT 

The  specific  reaction  rate  constant,  \,  is  the 
reciprocal  of  t±/e,  where  ti/e  is  the  time 
(in  seconds)  required  to  decompose  63 
per  cent  of  the  initial  amount  of  the  com- 
pound, at  a  given  temperature.  The  fre- 
quency factor,  s,  depends  on  the  type  of 
reaction.  It  has  a  value  of  1013  sec-1  for 
unimolecular  reactions  and  much  lower 
values  for  bimolecular  reactions.  In  log- 
arithmic form  the  Arrhenius  equation  is: 

log  h/e  =  AHa/2303RT-\og  s 

An  increase  in  AHa,  the  activation  en- 
ergy, will  thus  markedly  increase  ti/e,  but 
an  increase  in  s  leads  to  a  decrease  in  ti/e. 
For   a-alanine    (Year   Book   53,    p.    101), 

^  =  3X1013  e-^000/RT 

The  comparable  equation  for  phenyl- 
alanine (0.002  M  solution)  is: 

^  =  1.7xl08^-3O'8OoABr 


186        CARNEGIE  INSTITUTION  OF  WASHINGTON 


with  both  sets  of  data  shown  graphically 
in  figure  18.  At  temperatures  below  280° 
C,  phenylalanine  decomposes  more  quickly 
than  alanine  under  the  same  conditions. 
It  can  be  predicted  that  after  5  to  10  mil- 
lion years'  storage  at  30°  C  most  of  the 
phenylalanine  will  have   been   degraded. 


portance   of   extending   the    approach   to 
other  amino  acids. 

That  water  is  involved  in  the  decomposi- 
tion of  phenylalanine  under  the  conditions 
employed  is  evidenced  by  the  fact  that  the 
decomposition  follows  first-order  kinetics 
over  the  concentration  range  2  X  10~4  M  to 


(lO,0yr)- 


10' 


(I08   yrh 


J4 
(lO%r) 
o 

I       !0'2 
I"  (lO4  yr)" 


10" 


•5  x  IOy  yr 


O o       a  "  Alanine 

• •       Phenylalanine 


I  x  10°  yr 


1      io» 

fe  (lO2  yr)- 

"-        I08 
"tf      0  yO-l 


10* 


10' 


10 : 


30 


50 


75  100 

Temperature,  °C 


150 


200 


250 


300 


Fig.  18.  Time  required  for  63  per  cent  decomposition  of  a -alanine  and  phenylalanine  (in  dilute 
aqueous  solution)  at  various  temperatures.  The  scale  of  the  horizontal  axis  is  in  units  of  the  recip- 
rocal of  the  absolute  temperature. 


Abelson  (Year  Book  53,  p.  101)  has  noted 
that  recent  shells  of  the  clam  Mercenaria 
mercenaries  contain  both  alanine  and  phen- 
ylanine,  whereas  in  Miocene  shells  of  the 
same  species  alanine  is  present  but  phen- 
ylalanine is  lacking.  This  qualitative  agree- 
ment between  analytical  and  (extrapo- 
lated) experimental  data  suggests  the  im- 


4xl0-3  M,  with  the  value  of  the  specific 
reaction  rate  constant,  \,  independent  of 
concentration.  Only  the  Arrhenius  equa- 
tion reveals  that  the  reaction  is  bimolecu- 
lar.  Since  water  is  involved  in  the  decom- 
position of  phenylalanine,  it  may  be  im- 
portant to  record  the  water  contents  of 
fossil  materials  before  analysis. 


ORE  MINERALS 

Results  important  to  our  understanding  from  systematic  laboratory  studies  of  the 
of  mineral  associations  found  in  nature  subsolidus  relations  among  some  of  the 
have  been  obtained  during  this  past  year      more  common  ore  minerals.   The  investi- 


GEOPHYSICAL  LABORATORY        187 


gations  of  the  stability  relations  of  the  most 
common  sulfide,  pyrite,  and  of  the  impor- 
tant ore  mineral  covellite  have  been  com- 
pleted. Studies  of  the  composition  of  pyr- 
rhotites  formed  in  equilibrium  with  pyrite 
at  various  temperatures  and  pressures  are 
near  completion.  In  addition,  the  phases 
and  solid  solutions  occurring  in  the  CoAs2- 
NiAs2-FeAs2-As  system,  as  well  as  those 
in  the  Fe-S-O  system,  are  nearly  finished. 
Studies  are  also  progressing  on  the  Cu- 
Fe-S,  Fe-Ni-S,  Fe-Zn-S,  and  Fe-S-Se 
systems. 

Some  of  the  geological  thermometers 
based  on  sulfide  assemblages  appear  to  be 
well  established  as  useful  tools.  The  FeS- 
ZnS  system  has  been  employed  in  measure- 
ments on  more  than  a  hundred  ore  de- 
posits. As  studies  of  more  systems  are 
completed  in  the  laboratory,  it  should  be 
possible  to  obtain  cross  checks  between 
temperatures  determined  by  observations 
of  different  assemblages  occurring  in  the 
same  deposit. 

Detailed  studies  of  ore  deposits,  aided 
by  such  laboratory  tools,  may  in  the  future 
materially  assist  the  field  investigator  in 
his  interpretation  of  mineral  associations 
and  textures  and  will  enable  him  to  deter- 
mine temperature,  and  possibly  pressure, 
of  formation  of  a  host  of  mineral  assem- 
blages. These  data  are  essential  if  attempts 
are  to  be  made  to  estimate  the  composi- 
tion of  the  solutions  that  transported  the 
ore  minerals  to  their  site  of  deposition  and 
to  determine  the  direction  of  movement 
of  these  solutions. 

THE  Fe-S  SYSTEM 

Stability  relations  of  pyrite  (Kullerud, 
Yoder) .  The  upper  stability  limits  of  py- 
rite, FeS2,  have  been  carefully  determined, 
and  the  role  of  this  binary  compound  in 
the  Fe-S  system  can  now  be  specified. 
Interpretation  of  the  significance  of  the 
existence  of  an  invariant  point  in  which 
the  phases  pyrrhotite,  pyrite,  liquid,  and 
vapor  are  stable  unites  many  seemingly 
unrelated  experiments.  For  example,  pre- 
vious work  at  pressures  less  than  1  atm 
has  been  related  to  new  studies  at  high 


pressures.  A  critical  theoretical  evaluation 
of  the  P-T-X  diagram  of  the  system  Fe-S 
has  brought  forth  the  advantages  and  limi- 
tations of  the  various  types  of  experimental 
techniques  employed.  These  theoretical 
deductions  and  experimental  techniques, 
some  applied  for  the  first  time  to  sulfides, 
permit  a  new  understanding  of  many  of 
the  ore-forming  mineral  assemblages. 

The  revised  upper  stability  curve  of  py- 
rite, FeS2<^Fei-;rS  +  L,  is  given  in  figure 


75.000  - 


_  30,000  - 


15.000  - 


5,000  - 


400 


500        600        700        800        900 
Temperature    °C 


1000 


1100 


Fig.  19.    Revised  upper  stability  curve  of  py- 
rite, FeSo^Fe^S  +  L. 

19.  It  is  to  be  noted  that  the  reaction  does 
not  involve  a  gas  phase.  The  experimen- 
tally determined  points  are  815°  C,  75,000 
psi;  770°  C,  30,000  psi;  755°  C,  15,000  psi; 
748°  C,  5000  psi.  The  curve  terminates 
at  the  invariant  point  c,  which  lies  at  743° 
±  3°  C  and  about  180  psi.  All  these  points, 
with  the  exception  of  c,  were  determined 
using  collapsible  gold  tubes  (see  Year 
Book  55,  p.  181).  Point  c,  where  the  four 
phases  pyrrhotite,  pyrite,  liquid,  and  vapor 


188 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


coexist,  was  determined  in  evacuated,  rigid, 
silica-glass  tubes.  Since  some  of  the  experi- 
mental methods  restrict  the  possible  prod- 
ucts, it  was  necessary  to  consider  the  rela- 
tion of  these  products  to  the  Fe-S  system. 
In  figure  20  is  given  the  schematic 
pressure-temperature  diagram  for  the  Fe-S 
system  as  deduced  from  published  and 
new  data  using  principles  based  on  Gibbs' 
phase  rule.  Because  of  the  large  pressure 
range,  only  a  schematic  diagram  is  pos- 
sible, although  an  attempt  was  made  to 
maintain  the  temperature  scale  where  pos- 


"the  minimum  temperature  of  liquefac- 
tion," of  the  primitive  system  Fe-S.  The 
four  univariant  curves  originating  from  a 
can  be  deduced  by  means  of  the  principles 
outlined  by  Morey  and  Williamson  (1918). 
One  of  these,  the  curve  labeled  L+V  +  S, 
terminates  at  the  invariant  point  b,  which 
has  been  found  by  experiment  to  lie  at 
115°  C  and  0.018  mm  Hg  (Tuller,  1954). 
Point  b  is  the  triple  point  of  monoclinic 
sulfur.  Portions  of  the  curves  L+S  and 
V+S  have  been  investigated  previously, 
and  the  curve  L+V,  which  terminates  at 


800  1000 

Temperature,  °C 


1800 


Fig.  20.    Schematic  pressure-temperature  diagram  for  the  Fe-S  system.   The  pressure  Px  is  ap- 
proximately 1  atm;  P2,  several  thousand  atmospheres. 


sible.  The  pressure  Pi  is  approximately  1 
atm,  and  P2  may  be  considered  equal  to 
several  thousand  atmospheres.  Tempera- 
ture-composition sections  at  these  two  pres- 
sures are  given  below.  The  details  of 
construction  of  the  P-T  diagram  are  pre- 
sented in  order  of  increasing  temperature. 
For  clarity  of  presentation  the  polymorphic 
phase  changes  have  been  neglected.  The 
phases  Fe2S3  and  Fe3S4  (smythite)  have 
also  been  neglected  because  their  stability 
fields,  if  any,  are  not  known  with  certainty. 
The  invariant  point  a  is  the  temperature 
and  pressure  at  which  the  four  phases 1 
FcSo  +  L+V  +  S  coexist;  it  is  the  eutectic, 

1  The  phases  are  arranged  in  the  order  of  their 
composition,  from  the  most  iron-rich  first  to  the 
most  sulfur-rich  last. 


a  critical  point,  has  been  estimated.  The 
critical  point  of  sulfur  is  believed  to  be 
about  1040°  C  and  approximately  116  atm, 
and  the  boiling  point  (1  atm)  is  444.6°  C, 
according  to  West  (1950).  The  curve  FeS2 
+L+V,  for  which  few  experimental  data 
are  known  to  the  writers,  terminates  at  the 
point  c,  743°  C  and  about  180  psi.  The 
pressure  of  point  c  was  ascertained  by  ex- 
trapolating the  data  on  the  curve  Fei-^S  + 
FeS2  +  F  given  by  Allen  and  Lombard 
(1917)  to  743°  C,  the  temperature  deter- 
mined by  the  present  writers  for  the  break- 
down of  pyrite  in  the  presence  of  vapor. 
Some  data  for  the  remaining  three  curves 
originating  at  c  have  been  obtained.  The 
curve  Fei-tfS  +  FeS2+L  is  that  given  in 
figure  19.   Allen  and  Lombard  (1917)  as 


GEOPHYSICAL  LABORATORY       189 


well  as  others  give  data  on  the  curve  Fei-#S 
+  FeS2  +  F  in  the  region  of  about  1  to  680 
mm  Hg.  They  indicate  that  this  curve 
probably  reaches  1  atm  at  about  689°  C. 
No  data  are  available  for  the  solubility 
curve  Fei-tfS+L+1/  except  in  the  vicinity 
of  e.  The  continuation  of  this  curve,  L+ 
Fei^S  +  F,  now  a  decomposition  curve, 
terminates  at  d.  The  phases  remain  the 
same;  the  liquid  becomes  more  iron  rich 
than  the  crystalline  phase,  however. 

The  point  e  was  carefully  investigated 
by  Jensen  (1942) ;  it  marks  the  congruent 
melting  of  the  binary  compound  Fei-^S. 
The  temperature  is  given  as  1190°  C; 
moreover,  the  pressure,  which  was  not 
determined,  is  that  of  the  vapor  of  the 
system.  Jensen  also  determined  the  curve 
L  +  Fei-arS  +  F  and  the  invariant  point  d 
where  Fe,  L,  Fei-*S,  and  V  are  in  equi- 
librium. Point  d  is  given  as  988°  C,  and 
the  pressure,  not  determined,  is  that  of  the 
system.  No  data  are  known  for  the  curves 
Fei-tfS  +  L,  Fe  +  Fei-*S+L,  or  Fe  +  Fei^S 
+  V.  The  curve  Fe  +  L+F  has  been 
studied  by  Friedrich  (1908,  1910)  and 
others.  The  point  /  is  the  triple  point  of 
iron.  The  melting  point  of  iron  under  1 
atm  of  helium  is  1539°  C,  according  to 
Roeser  and  Wensel  (1942).  The  vapor- 
pressure  curve  of  pure  iron,  Fe+F,  has 
been  calculated  by  Jones,  Langmuir,  and 
MacKay  (1927),  and  the  vapor  pressure 
at  the  melting  temperature  is  estimated  to 
be  about  0.03  mm  Hg.  On  the  basis  of 
these  data  the  point  /  lies  near  1539°  C 
and  0.03  mm  Hg.  The  same  authors  give 
the  boiling  point  of  iron  as  about  3202°  C, 
and  the  critical  point,  therefore,  must  lie 
at  a  temperature  greater  than  3202°  C  and 
at  a  pressure  in  excess  of  1  atm.  The  criti- 
cal point  of  iron,  not  indicated  in  figure 
20,  is  joined  by  the  critical  curve  (dashed) 
to  the  critical  point  of  sulfur. 

Two  isobaric  sections  through  the  P-T 
diagram  are  presented  in  figures  21  and 
22  for  pressures  Pi  and  P2,  respectively. 
The  T-X  diagram  of  figure  21  is  believed 
to  represent  the  equilibrium  relations  that 
would  be  observed  at  a  pressure  of  about 


1  atm.  The  numbered  points  on  the  P-T 
diagram  (fig.  20)  along  the  line  Pi  may 
be  located  on  the  T-X  diagram  (fig.  21). 
Similarly  the  schematic  T-X  diagram  for 
Pi  is  believed  to  represent  the  relations  at 
a  pressure  of  several  thousand  atmospheres. 
These  sections  differ  from  the  customary 
projection    of    the    so-called    "condensed" 


i  l  r 


L  +    V 


Fe  *  FeS 


Fe,.vS«  V 


Fe,_xS< 

FeS2 


Fe  S2  ♦  V 


FeS2  «  L 


FeS2 


0 

Fe 


30/     40/     \50     \60  70 

FeS      Fe3S4      Fe2S3^FeS2 
Weight  per  cent 


Fig.  21.  The  T-X  diagram  for  the  Fe-S  sys- 
tem at  the  pressure  P13  approximately  1  atm  (see 
fig.  20). 

diagram  (see,  for  example,  Ricci,  1951, 
p.  63)  given  in  figure  23,  wherein  the  sys- 
tem is  under  its  own  pressure  and  gives 
those  phases  in  equilibrium  with  vapor. 
The  term  "condensed"  is,  therefore,  a  mis- 
nomer, especially  in  systems  containing 
volatile  components,  since  vapor  is  present 
even  though  it  is  neglected.  A  truly  con- 
densed diagram  would  be  one  from  which 
vapor  (or  gas)  is  absent  for  all  assem- 
blages. Such  a  T-X  diagram  at  constant 
P  is  not  possible  for  the  Fe-S  system.  The 
diagram  of  figure  23  is  produced  by  pro- 


190        CARNEGIE  INSTITUTION  OF  WASHINGTON 


jecting  onto  the  T-X  plane  those  curves 
in  figure  20  that  contain  a  vapor  phase. 
The  pressure  is  not  constant,  and  is  fixed 
only  when  two  phases  in  addition  to  vapor 
are  present  as  given  by  the  three-phase 
curves.  When  only  one  or  two  phases  are 
present  the  pressure  is  indeterminate  un- 
less the  volume  of  the  system  is  specified. 
With  the  aid  of  these  diagrams  the  na- 


is  limited  by  the  strength  of  the  heated 
silica-glass  tube.  The  tube  may  be  sup- 
ported by  an  external  pressure  in  some 
applications  in  order  to  increase  its  usable 
pressure  range.  It  should  be  emphasized 
that  the  rigid  silica-glass-tube  experiments, 
regardless  of  an  external  supporting  pres- 
sure, cannot  yield  data  for  those  reactions 
in  which  vapor  is  absent,  as  the  curve  in 


Fe  +  FeS 


0  o- 

o 

Fe 


FeS,+  S 


-L-o-o— L-6 


1600 


1400 


1200 


1000 


400 


200 


Fe-FeS'V 


Fe,xS. 

FeS2« 

V 


30    /    40/     \50    V  60 

FeS     Fe^    Fe2S3    FeS2 
WEIGHT   PER   CENT 


100 

S 


10        20        30  /  40/ 


FeS 


FeSo'L'V 


i-v-s^ 


Fe,S 


FeS  ^V'S 


60       70        80        90 


100 
S 


Fe,S, 


FeS, 


Fig.  22.  The  T-X  diagram  for  the  Fe-S  sys- 
tem at  the  pressure  P2,  several  thousand  atmos- 
pheres (see  fig.  20). 

ture  of  the  various  types  of  experiment 
employed  can  now  be  elucidated.  The 
evacuated  rigid  silica-glass  tube  is  the  con- 
tainer most  commonly  used  for  systems 
involving  sulfur.  Since  the  tube  is  rigid 
(^constant  volume),  and  free  space  is 
available,  a  vapor  phase  is  always  present. 
For  this  reason  the  silica-glass  tube  can 
yield  only  data  which  pertain,  for  example, 
to  a  diagram  of  the  type  given  in  figure 
23,  the  so-called  condensed  diagram.  The 
pressure  is  usually  unknown  and,  of  course, 


3^4  " "  "2 

Weight  per  cent 


Fig.  23.  The  so-called  "condensed"  diagram 
of  the  system  Fe-S.  Vapor  is  present  in  all 
assemblages,  and  the  pressure  of  the  system  is 
not  constant. 

figure  19  and  the  other  essentially  vertical 
curves  in  figure  20. 

A  second  type  of  experiment  employs 
collapsible  gold  tubes.  Here  the  walls  of 
the  container  are  deformed  by  application 
of  an  external  pressure:  the  internal  pres- 
sure is  taken  to  equal  the  external  pres- 
sure. If  the  applied  pressure  is  greater 
than  the  vapor  pressure  of  the  chemical 
system,  then  the  vapor  is  condensed  and 
no  vapor  is  permissible.  On  the  other  hand, 


GEOPHYSICAL  LABORATORY        191 


if  the  applied  pressure  is  less  than  the  composition  of  pyrrhotite  when  coexisting 
vapor  pressure  of  the  chemical  system,  then  in  equilibrium  with  pyrite  is  a  function 
a  vapor  may  exist.  By  this  technique  the  of  temperature  and  pressure.  Two  experi- 
entire  P-T-X  space  may  be  investigated,  mental  methods  are  used  for  studying  the 
yielding  data  both  on  the  regions  in  which  equilibrium  relations  between  the  coexist- 
vapor  is  permitted  and  on  those  in  which  ing  phases.  The  first  employs  silica-glass 
it  is  prohibited.  tubes  as  sample  containers;  as  a  result,  a 
A  third  type  of  experiment  employs  two  vapor  exists  at  each  temperature  above  the 
silica-glass  bulbs  connected  by  a  tube.  Sul-  solid  and/or  liquid  phases  by  virtue  of  the 
fur  is  maintained  at  a  given  temperature  presence  of  a  vapor  space  in  each  tube, 
in  one  bulb,  and  its  vapor  pressure  is  The  second  method  involves  the  use  of 
thereby  fixed.  In  the  other  bulb  the  sulfur-  collapsible  gold  tubes  as  sample  containers, 
containing  system  to  be  investigated  is  These  two  methods  and  the  results  ob- 
maintained  at  a  series  of  temperatures.  In  tained  are  discussed  separately, 
this  way  the  system  in  the  latter  bulb  is  The  equilibrium  relations  between  pyr- 
held  at  a  constant  vapor  pressure.  Such  rhotite  and  pyrite  were  studied  by  the 
experiments  would  yield  data  for  those  silica-tube  method  from  325°  to  743°  C 
regions  in  figure  21,  for  example,  where  at  vapor  pressures  from  a  few  millimeters 
vapor  is  permitted.  The  regions  in  which  of  mercury  to  about  10  bars,  respectively; 
vapor  is  prohibited  (namely,  Fe  +  FeS,  Fe  pyrite  and  liquid  were  studied  up  to  743° 
+L,  Fei-#S,  Fei-tfS4-FeS2)  could  not  be  C,  where  the  vapor  pressure  was  about  10 
studied  by  this  technique.  bars;  and  pyrrhotite  and  liquid  were  stud- 
In  a  fourth  technique  the  pressure  of  the  ied  from  743°  to  785°  C  at  vapor  pres- 
system  is  measured  by  the  deflection  of  the  sures  from  10  to  25  bars,  respectively.  The 
spiral  of  a  spiral  silica-glass-tube  pressure  magnitude  of  the  vapor  pressure  above 
gauge.  Here  again  free  space  exists,  and  pyrrhotite  and  pyrite  at  a  specific  tempera- 
only  those  regions  in  which  vapor  is  per-  ture  is  estimated  from  the  data  of  Allen 
mitted  can  be  studied.  and  Lombard,  De  Rudder,  D'Or,  Roedder, 

Since  the  compositions  of  the  coexisting  Juza  and  Biltz,  and  Rosenqvist. 
sulfides  in  nature  indicate  that  ore  deposits  Equilibrium  at  each  temperature  was 
may  form  in  either  the  absence  or  the  approached  from  two  directions.  All  runs 
presence  of  a  sulfur  vapor  (or  gas),  it  is  withdrawn  from  a  furnace  were  immedi- 
of  paramount  importance  that  the  complete  ately  quenched  in  cold  water.  Tempera- 
P-T-X  space  be  investigated  for  the  sulfide  ture  measurements  were  within  4°  C  un- 
sy stems.  These  results  in  conjunction  with  less  otherwise  indicated.  Pyrrhotite  corn- 
hydrous  systems  will  have  important  bear-  positions  were  determined  to  a  precision 
ing  on  the  problem  of  how  metals  are  of  ±0.08  atomic  per  cent  iron  by  the 
transported  to  the  site  of  accumulation.  lattice-spacing  technique  described  in  last 
The  FeS-S  join  (Arnold).  The  phase  year's  report.  Pyrite,  as  pointed  out  in  that 
relations  involving  pyrrhotite,  pyrite,  liq-  publication,  shows  no  measurable  variation 
uid,  and  vapor  are  being  studied  between  in  its  cell  dimensions  at  a  considerable 
the  compositions  stoichiometric  FeS  and  range  of  temperatures,  indicating  little  or 
pure  sulfur  from  325°  to  785°  C.  The  no  variation  in  its  metal-to-sulfur  ratio, 
relationship  between  pyrrhotite  and  pyrite,  Figure  24  is  a  diagram  for  a  condensed 
which  is  a  portion  of  this  system,  promises  system  at  30  bars  pressure  (refer  to  the 
to  provide  a  method  for  estimating  the  discussion  by  Greig,  Year  Book  54,  p.  131), 
temperature  of  formation  of  naturally  oc-  which  summarizes  the  equilibrium  rela- 
curring  pyrrhotites  and  pyrite  assemblages,  tions  between  pyrrhotite,  pyrite,  and  liquid 
a  pressure  of  formation  being  assumed,  as  calculated  on  the  basis  of  this  study  and 
The  method  is  based  on  the  fact  that  the  by  the  work  of  Jensen.  Although  the  ex- 


192        CARNEGIE  INSTITUTION  OF  WASHINGTON 


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Plate  1  Geophysical  Laboratory 


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(a) 

Fig.  2.  "Layers"  of  equal  scattering  power  with  displacement  of  b/2  ran- 
domly distributed;  equal  numbers  of  "layers"  in  each  of  the  two  positions. 
a,  the  mask;  b,  diffraction  pattern  of  2a. 


*  ♦ 

•       •      • 

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Fig.  3.     Diffraction  pattern  of  a  perfectly  ordered  sequence  of  two  lines  in 
one  position  followed  by  one  line  in  the  other  (BB ABB ABB A  .  .  .). 


Plate  2  Geophysical  Laboratory 


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t  *  *  w  - 


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5  (*)  5  (a) 

Fig.  4.  Short-range  ordering  in  a  "2:1"  mask:  «,  a  mask  in  which  NB  = 
2NA,  each  A  is  neighbored  by  Fs  but  the  run  lengths  of  B's  are  random; 
b,  diffraction  pattern  of  4a. 

Fig.  5.  Disordered  "2:1"  mask:  a,  a  mask  in  which  NB  =  2NA,  but  run 
lengths  and  sequences  of  both  A  and  B  are  random;  b,  diffraction  pattern 
of  5a. 


Plate  3 


Geophysical  Laboratory 


Fig.  25.  Photograph  showing  exsolution  lamellae  in  pure  pyrrhotite. 
Slight  granularity  due  to  the  second  dark  phase  may  be  seen  in  the  host. 
The  veinlet  in  the  center  of  the  photograph  is  pyrite.    X  1200. 


GEOPHYSICAL  LABORATORY       193 


periments  were  made  at  various  pressures 
lower  than  30  bars,  it  is  practicable  to  con- 
struct a  section  at  this  pressure,  because 
the  effect  of  pressure  on  the  melting  points, 
field  boundaries,  and  inversion  tempera- 
tures is  comparatively  small.  For  instance, 
a  calculation  based  on  the  data  presented 
by  Kullerud  and  Yoder  in  last  year's  re- 
port shows  that  the  melting  point  of  py- 
rite  at  30  bars  is  only  about  l/2°  C  higher 
than  at  about  10  bars.  Also  by  calculation 
based  on  the  data  presented  in  figure  27 
the  position  of  the  field  boundary  aPo(Py) 
at  30  bars  is  shifted  only  0.006  atomic  per 
cent  iron  towards  the  iron  side  of  the 
diagram. 

The  supercell  and  monoclinic  forms  of 
pyrrhotite  stable  below  138°  C  discussed 
by  Haraldsen  have  been  omitted  from  the 
diagram  because  the  relationships  in  this 
area  are  not  understood.  Also  marcasite 
(FeS2)  and  smythite  (FesS^  have  not 
been  included,  as  their  fields  of  stability 
are  not  known.  The  melting  relations  of 
pyrrhotite  were  determined  by  Jensen.  The 
datum  points  plotted  on  the  diagram  rep- 
resent compositions  determined  from  the 
silica-tube  runs  projected  on  this  isobaric 
section. 

The  notation  suggested  by  Greig  for  des- 
ignating the  fields,  field  boundaries,  and 
isothermal  lines  representing  the  condi- 
tions under  which  one  or  more  phases 
exist  in  equilibrium  has  been  found  to  be 
very  useful,  as  the  relations  between  the 
various  phases  become  immediately  ob- 
vious. For  example,  aPo(Py)  designates 
the  line  indicating  the  conditions  under 
which  a-pyrrhotite  may  coexist  in  equilib- 
rium with  pyrite;  Py(aPo)  designates 
the  conjugate  line  indicating  the  condi- 
tions under  which  pyrite  can  coexist  in 
equilibrium  with  a-pyrrhotite. 

As  is  indicated  in  figure  24,  pyrite  melts 
incongruently  at  743°  C  to  pyrrhotite  hav- 
ing a  composition  of  45.95  atomic  per  cent 
iron  and  a  liquid  close  to  pure  sulfur  in 
composition.  The  compositions  of  the 
liquid  that  can  coexist  with  pyrrhotite  and 
of  the  liquids  that  can  coexist  with  pyrite 


have  not  been  determined.  The  arrange- 
ment for  the  liquidus  curves  shown  dia- 
grammatically,  however,  is  correct  for  the 
case  that  pyrite  melts  incongruently. 

An  inversion  in  the  most  sulfur-rich 
pyrrhotites  was  observed  between  666°  and 
675°  C  in  four  runs;  it  is  tentatively  placed 
at  670°  ±  5°  C.  The  inversion  tempera- 
ture is  believed  to  decrease  with  increasing 
iron  content  in  pyrrhotite.  The  low-tem- 
perature form  designated  a-pyrrhotite  is 
quenchable  and  has  the  normal  NiAs-type 
structure  at  room  temperature.  The  high- 
temperature  form  designated  y-pyrrhotite 
is  apparently  nonquenchable,  and  inverts 
to  the  a  form  on  quenching. 

Preparations  of  pyrrhotite  coexisting 
with  pyrite,  quenched  from  above  the 
inversion  temperature,  frequently  showed 
exsolution  lamellae  when  examined  under 
the  microscope  (fig.  25)  .*  The  lamellae 
have  the  following  general  characteristics: 
they  generally  possess  straight  parallel 
sides,  but  occasionally  occur  in  irregular 
blebs,  both  up  to  several  microns  in  width; 
in  some  grains  they  are  arranged  in  three 
or  four  intersecting  sets;  they  have  a  re- 
flectivity higher  than  the  host,  but  much 
lower  than  pyrite;  they  are  softer  than  the 
host,  and  are  anisotropic.  Both  the  pyr- 
rhotite host  and  the  lamellae  may  contain 
a  second  separate  phase  having  a  lower 
reflectivity  and  a  greater  hardness  than 
either  the  host  or  the  lamellae.  This  phase 
appeared  as  dispersed  black  dots  in  both 
the  lamellae  and  the  host,  being  preferen- 
tially concentrated  in  the  host  and  impart- 
ing a  granular  texture  to  it.  Occasionally 
this  phase  in  the  host  also  appeared  as  very 
fine  subparallel  lines  producing  a  crepe- 
paper-like  textural  effect.  Pyrrhotite  struc- 
tures with  similar  physical  characteristics 
have  been  described  from  natural  occur- 
rences by  Ramdohr,  by  Schneiderhohm 
and  Van  Der  Veen,  and  by  Scholtz. 

Powder  camera  photographs  of  these 
exsolved  pyrrhotites  at  room  temperature 
show  no  additional  reflections  that  can  be 

1  Figure  25  is  on  plate  3. 


194        CARNEGIE  INSTITUTION  OF  WASHINGTON 


attributed  to  a  second  phase  with  a  differ- 
ent symmetry  or  composition.  Insufficient 
data  are  available  to  explain  the  presence 
of  the  various  phases  or  to  decide  whether 
the  lamellae  were  exsolved  as  the  a  or  the 
Y  form.  Very  likely  this  pyrrhotite  ex- 
solution  is  related  to  the  inversion  that 
takes  place  at  670°  ±  5°  C. 

The  presence  of  the  inversion  and  re- 
lated exsolution  raises  the  question  of  the 
applicability  of  the  lattice-spacing-compo- 
sition curve  for  evaluating  pyrrhotite  com- 
positions. Because  the  pyrrhotites  on  which 
the  spacing  curve  was  based  were  homo- 
geneous, this  curve  is  pertinent  only  to 
homogeneous  pyrrhotite.  Only  composi- 
tions of  homogeneous  pyrrhotites  were 
used  as  a  basis  for  constructing  the  equi- 
librium diagram. 

The  pyrrhotite-pyrite  equilibrium  was 
also  studied  between  325°  and  600°  C  at 
1000  and  2000  bars  pressure.  The  appara- 
tus was  the  standard  cold-seal  bomb  fed 
by  flexible  capillary  tubing.  Quenching 
was  effected  by  plunging  the  hot  bomb 
directly  from  the  furnace  into  water  while 
simultaneously  releasing  the  pressure.  All 
runs  were  made  in  collapsible  gold  tubes, 
which  transmitted  the  water  pressure,  es- 
sentially hydrostatically,  to  the  contained 
sulfides.  Equilibrium  was  approached  from 
two  directions  at  each  pressure  and  tem- 
perature. The  results  are  shown  in  figure 
26,  together  with  the  equilibrium  results 
determined  at  <1  atm  included  for  com- 
parison. The  results  show  that  pressures 
up  to  2000  bars  do  not  measurably  alter 
the  equilibrium  relations  between  pyrrho- 
tite and  pyrite  as  determined  under  their 
own  vapor  pressure  at  325°  C  and  lower. 
However,  at  600°  C  and  1000  and  2000 
bars  the  equilibrium  composition  of  pyr- 
rhotite coexisting  with  pyrite  was  46.18  and 
46.46  atomic  per  cent  iron,  respectively, 
while  at  <1  atm  pressure  at  600°  C  the 
pyrrhotite  composition  was  46.03  atomic 
per  cent  iron. 

The  fact  that  the  composition  of  pyr- 
rhotite when  coexisting  in  equilibrium 
with  pyrite  is  a  function  of  temperature 


and  pressure  raises  the  possibility  of  the 
application  of  these  relations  to  problems 
of  geological  thermometry.  In  applying 
this  "thermometer"  in  its  present  state  of 
development,  however,  at  least  one  diffi- 
culty should  be  kept  in  mind. 

Because  the  experimental  system  con- 
tained only  iron  and  sulfur,  the  effect  of 
impurities  on  the  equilibrium  value  of  the 
metal-to-sulfur  ratio  of  pyrrhotite  should 


650  — 


600 


500 


400 


300 


Limit  of  pyrrhotite  solid  solution 
at  2000  bars,  1000  bars.  <  I  bar. 


1000  bars-, 
2000  bars 


<l  bar 


49.00     48.50 


47.50  4700        46.50 

—  Atomic   percent    Fe 


46.00 


Fig.  26.  Curves  showing  the  effect  of  pres- 
sure of  <  1,  1000,  and  2000  bars  on  the  com- 
position of  pyrrhotite  that  can  coexist  in  equi- 
librium with  pyrite. 

be  investigated.  Quantitative  analyses  of 
natural  pyrrhotites  indicate  that  cobalt  and 
nickel  are  the  most  significant  impurities, 
although  rarely  occurring  in  combined 
concentrations  greater  than  2  weight  per 
cent. 

An  attempt  was  made  to  study  the  effect 
of  0.65  to  6.50  per  cent  cobalt  on  the 
equilibrium  between  pyrrhotite  and  pyrite 
at  600°  C.  It  was  hoped  that  the  compo- 
sition of  the  resulting  cobalt-rich  pyrrho- 
tite coexisting  in  equilibrium  with  cobalt- 
rich  pyrite  could  be  determined  by  means 


GEOPHYSICAL  LABORATORY       195 


of  an  X-ray  spacing  technique.  The  curve 
determined  at  730°  C  and  intended  for 
this  purpose  is  given  in  figure  27.  It  shows 
the  change  of  the  pyrrhotite  ^(102)  as 
various  amounts  of  cobalt  are  substituted 
for  iron  in  the  stoichiometric  pyrrhotite 
structure.  In  nonstoichiometric  pyrrhotite, 
measurements  indicated  that  a  phenom- 
enon additional  to  the  replacement  of  iron 
by  cobalt  had  taken  place.  Apparently  a 
specific  amount  of  cobalt  as  a  function  of 
pressure  and  temperature  filled  vacant  iron 
positions  in  the  nonstoichiometric  pyrrho- 
tite structure,  producing  a  large  increase 
in  the  d(\02);  additional  cobalt  replaced 
iron  and  caused  a  decrease  in  d(l02)  pro- 
portional to  the  amount  available. 


2  0920  t- 


g    2.0900  - 


2.0880 


Wt.  percent   Co  in  (Fe,Co)S  » 

Fig.  27.  Curve  showing  the  effect  of  substi- 
tuting cobalt  for  iron  on  the  ^(102)  of  stoichio- 
metric FeS.  Amounts  of  cobalt  in  excess  of  1.95 
weight  per  cent  cause  a  decrease  in  the  d(\02). 

Because  of  this  additional  replacement 
effect,  the  proposed  X-ray  spacing  tech- 
nique could  not  be  employed  and  the 
influence  of  cobalt  on  the  equilibrium  be- 
tween pyrrhotite  and  pyrite  could  not  be 
evaluated.  Because  nickel  will  no  doubt 
produce  similar  problems,  at  this  stage  this 
thermometer  should  be  applied  only  to 
deposits  containing  no  more  than  small 
amounts  of  cobalt  and  nickel. 

THE  Cu-S  SYSTEM 

The  upper  stability  curve  of  covellite 
(Kullerud) .  Covellite  is  one  of  the  most 
important  sulfides  of  copper.  It  occurs  in 
association  with  other  copper  minerals  such 
as  chalcopyrite,  chalcocite,  or  digenite.  It 
is  found  in  zones  of  secondary  alteration, 
or  as  a  primary  mineral  associated  with 
chalcocite  or  digenite  (Butte),  and  has 
even  been  reported  as  a  sublimation  prod- 
uct  (Vesuvius).    Knowledge   of  the  sta- 


bility field  of  covellite,  therefore,  would 
contribute  to  an  understanding  of  the  con- 
ditions existing  during  the  formation  of 
many  copper-bearing  sulfide  ore  deposits. 

Covellite  may  be  readily  synthesized  in 
the  dry  way  in  silica  tubes  by  mixing 
copper  with  appropriate  amounts  of  sul- 
fur. Copper  and  sulfur  in  the  atomic 
ratio  of  1 : 1  will,  in  evacuated,  sealed  silica 
tubes,  react  even  at  20°  C  to  form  some 
covellite  in  a  few  hours.  Even  after  5 
months  at  this  temperature,  however,  the 
tubes  still  contained  small  amounts  of 
unreacted  copper  and  sulfur.  At  100°  C 
all  copper  had  reacted  to  form  covellite 
in  about  5  weeks,  and  at  200°  C  in  about 
2  weeks. 

The  lengths  of  the  silica  tubes  were 
adjusted  so  that  the  copper-sulfur  mixtures 
occupied  a  third  to  a  half  of  the  tube 
volume.  It  was  noticed  that  at  235°  C 
some  digenite  (CuoS5)  was  already  formed 
with  the  covellite  in  the  tubes.  Thus  covel- 
lite under  such  conditions  starts  to  break 
down  to  digenite  and  sulfur  vapor  below 
235°  C.  Sulfur  vapor  produced  by  this 
process  builds  up  pressure  to  stabilize  the 
remaining  covellite.  The  dissociation  pres- 
sures of  covellite  at  temperatures  ranging 
from  400°  to  490°  C  were  determined  by 
Wasjuchnowa,  by  Preunner  and  Brock- 
moller,  and  by  Allen  and  Lombard. 

By  adding  sulfur  beyond  the  1 : 1  copper- 
to-sulfur  ratio  in  the  silica  tubes  so  that 
liquid  as  well  as  vapor  is  always  present, 
covellite  was  found  to  be  stable  up  to  507° 
±3°  C.  Above  this  temperature  digenite 
+  liquid  +  vapor  are  stable.  The  pressure 
at  the  invariant  point  of  507°  ±3°  C  where 
CuS  +  CuoSs  +  L+I7  coexist  may  be  deter- 
mined by  extrapolation  of  the  P-T  curve 
given  for  dissociation  of  covellite  by  the 
above-mentioned  workers.  Such  extrapo- 
lation gives  a  pressure  of  880  mm  Hg  for 
the  invariant  point.  At  this  point  the  fol- 
lowing four  curves  intersect:  (1)  CuoS5  + 
CuS  +  F;  (2)  CuS  +  L+F;  (3)  Cu9S54- 
CuS  +  L;  and  (4)  Cu9S5  +  L4-F.  The 
situation  at  the  invariant  point  is  shown 
schematically  in  figure  28.  Curve  3,  C119S5 


196        CARNEGIE  INSTITUTION  OF  WASHINGTON 


+  CuS  +  L,  is  the  upper  stability  curve  of 
covellite.  It  was  determined  by  using  sealed 
collapsible  gold  tubes  as  described  in  last 
year's  report  for  the  determination  of  the 
upper  stability  curve  of  pyrite. 

The  upper  stability  curve  of  covellite  is 
shown  in  figure  29.  Points  on  the  curve 
are:  507°  C  at  about  880  mm  Hg  (invari- 
ant point  c),  510°  C  at  7500  psi,  515°  C 
at  15,000  psi,  and  525°  C  at  30,000  psi. 

Covellite  below  the  invariant  point  c 
breaks  down  to  digenite  +  vapor,  not  to 
chalcocite  +  vapor  as  reported  by  earlier 
workers.    Above    the    invariant   point   c, 


urable  variations  in  the  cell  dimensions. 
Digenite  formed  in  these  experiments  by 
breakdown  of  covellite  commonly  grows 
as  well  developed  crystals.  They  always 
occur  as  octahedra,  which  occasionally  are 
extremely  malformed  and  frequently  mod- 
ified by  cube  faces.  Sometimes  two  oppo- 
site octahedral  faces  predominate  over  all 


400 


500 
Temperature   °C 


600 


Fig.  28.  Curves  showing  schematically  in- 
variant point  c  where  the  four  phases  Cu9S5  + 
CuS  +  L+V  are  stable. 

covellite,  in  collapsible  tubes,  breaks  down 
to  digenite  +  liquid.  In  the  diagram  the 
stability  field  of  covellite  is  on  the  left  of 
the  curve  and  the  field  of  digenite  +  liquid 
is  on  the  right. 

Covellite  grown  in  silica  tubes  is  dark 
blue,  is  commonly  massive,  and  rarely 
shows  crystal  faces.  Single  crystals  were 
in  a  number  of  experiments  grown  at  high 
pressure  in  collapsible  gold  tubes.  These 
crystals,  less  than  0.1  mm  long,  appear  to 
be  hexagonal  plates.  Powder  X-ray  dif- 
fraction studies  of  covellite  crystals  grown 
under  varied  pressure  and  temperature 
conditions  (from  100°  C  at  less  than  1  mm 
Hg  to  520°  C  at  2000  bars)  show  no  meas- 


30,000 

- 

1                  1                  1 

1                1 
■  00 

- 

- 

Covellite  (CuS) 

4- 

Digenite  +■  liquid 

- 

- 

3 
0 

■1- 
m 

in 
0 

- 

15.000 

0 

; 

7.500 

« 

- 

1                1                l.< 

1         1 

200 


300 


400  500  600 

Temperature  °C 


700 


800 


Fig.  29.    The  upper  stability  curve  of  covel- 
lite CuS<r±Cu9S5+L. 

other  faces  to  such  an  extent  that  the 
crystal  looks  like  a  flat  hexagonal  plate. 
Other  times,  observed  at  15,000  and  30,000 
psi,  cube  faces  dominate.  The  digenite 
crystals  vary  in  size  from  about  0.1  to  4 
mm,  depending  on  time,  temperature,  and 
pressure.  The  larger  crystals  were  grown 
in  silica  tubes,  and  the  smaller  in  collapsed 
gold  tubes.  The  cell  dimensions  of  dige- 
nite formed  at  various  temperatures  and 
pressures  were  determined  by  X-ray  dif- 
fraction methods.  The  cell  size,  however, 
remained  constant  within  the  limits  of  the 


GEOPHYSICAL  LABORATORY       197 


experimental  accuracy,  an  indication  that 
digenite  is  essentially  a  stoichiometric  com- 
pound. 

The  liquid  formed  by  decomposition  o£ 
covellite  when  quenched  appears  white  to 
yellow  and  consists  of  almost  pure  sul- 
fur. X  rays  at  room  temperature  of  such 
quenched  liquids,  produced  at  various 
pressures  and  temperatures,  always  gave 
the  pattern  of  orthorhombic  sulfur. 


crystals  and  NiS2  were  described.  A  dia- 
gram was  also  presented  showing  variation 
in  d  spacings  for  the  (102)  X-ray  reflec- 
tions as  a  function  of  mix-crystal  (Nii-^S) 
composition.  This  curve  was  used  to  de- 
termine the  composition  of  the  Nii-^S 
when  formed  in  equilibrium  with  NiS2. 
Experiments  with  mixtures  of  Ni  and  S 
in  the  atomic  ratio  of  3:4  have  established 
the  subsolidus  relations  between  the  two 


34   NlS2     32 


At.   per  cent    Ni 


Fig.  30.     Subsolidus  phase  relationships  in  the  NiS-NiS2  binary  join. 


THE  Ni-S  SYSTEM 

The  NiS-NiS2  join  {Arnold,  Kulle- 
rud).  This  study  of  the  subsolidus  rela- 
tions in  the  millerite  (NiS)-vaesite  (NiS2) 
binary  join  is  part  of  an  investigation  of 
the  entire  Ni-S  system.  A  systematic  in- 
vestigation of  this  system  is  necessary  be- 
fore a  detailed  exploration  of  the  extremely 
important  Fe-Ni-S  system  can  be  under- 
taken. 

In  last  year's  report  methods  of  prepara- 
tion of  NiS  as  well  as  of  Nii-^S   mix- 


phases  in  the  300°  to  700°  C  temperature 
range.  When  stoichiometric  NiS  is  heated 
a  rapid  inversion  from  the  millerite  to  the 
hexagonal  Ni-As  structure  occurs  at  374° 
C.  This  inversion  temperature  is  lowered 
markedly  by  omission  of  Ni  from  the  NiS 
lattice.  Thus  when  Nii-^S  is  formed  in 
equilibrium  with  NiS2  the  inversion  takes 
place  at  about  325°  C. 

The  Ni3S4  phase,  reported  in  the  litera- 
ture to  be  stable  up  to  325°  C,  did  not 
appear  at  300°  C  even  after  6  months. 


198        CARNEGIE  INSTITUTION  OF  WASHINGTON 


No  sign  of  melting  was  detectable  in 
Nii-a>S  and  NiS2  mixtures  at  temperatures 
as  high  as  790°  C,  in  spite  of  the  fact  that 
stoichiometric  NiS  melts  at  800.5  ±1°  C. 

Figure  30  shows  the  phase  relations  in 
the  NiS-NiS2  join.  The  amount  of  nickel 
omission  solid  solution  in  Nii-^S  when 
this  phase  forms  in  equilibrium  with  NiS2 
is  seen  to  vary  from  1.7  atomic  per  cent 


V  in  silica  tubes,  as  well  as  with  NiS  +  S 
and  NiS2  in  collapsible  gold  tubes  at  2000 
bars,  have  shown  that  NiS2  under  such 
conditions  is  stable  beyond  the  melting 
point  of  NiS  (800.5° ±1°  C).  The  con- 
clusion is  that  the  four  phases  Nii-a?S  + 
NiS2  +  L+F  cannot  coexist  at  any  pres- 
sure or  temperature. 
Powder  X-ray  diffraction  studies  of  NiS2 


2(gas) 


Fig.  31.   Phase  relations  in  the  Fe-S-O  system:  (a)  below  about  675°  C. 


Ni  at  325°  C  to  about  2.4  atomic  per  cent 
Ni  at  700°  C,  giving  rise  to  a  very  steep 
solvus  curve. 

Biltz  (1936)  determined  the  curve  for 
dissociation  of  NiS2:  at  650°  C,  42.5  mm 
Hg;  at  700°  C,  154  mm  Hg;  at  720°  C, 
260  mm  Hg;  at  730°  C,  324  mm  Hg;  and 
at  760°  C,  649  mm  Hg.  NiS2  in  this  range 
breaks  down  to  Nii-«?S  +  V.  Extrapolation 
of  these  data  gives  breakdown  of  NiS2 
under  1  atm  sulfur  pressure  at  765°  C. 
Preliminary  experiments  at  850°  C  with 
NiS2  with  excess  sulfur  to  give  NiS2  +  L+ 


grown  at  temperatures  from  350°  to  854° 
C  and  at  pressures  ranging  from  a  few 
millimeters  of  mercury  to  2000  bars  show 
an  apparent  variation  in  the  cell  lengths 
of  the  NiS2  crystals  from  a  =  5.685  ±0.002 
A  at  350°  C  and  pressure  of  less  than  1 
mm  Hg  to  *= 5.690 ±0.002  A  at  854°  C 
and  2000  bars. 

PHASE  RELATIONS  IN  THE  Fe-S-O  SYSTEM 
G.  Kullerud 

The    Fe-S-O    system    includes    pyrite 
(FeS2),  the  most  common  sulfide  mineral, 


GEOPHYSICAL  LABORATORY       199 


and  pyrrhotite  (Fei-^S),  as  well  as  the 
very  important  oxides  hematite  (Fe2Os) 
and  magnetite  (Fe304).  A  series  of  pre- 
liminary experiments  with  mixtures  of 
iron  oxides  and  sulfur  in  evacuated,  sealed 
silica  tubes  have  reproduced  some  of  the 
interesting  mineral  assemblages  common 


hematite,  and  pyrite  form  a  stable  assem- 
blage, and  hematite  may  be  transformed 
into  pyrite  and  S02  gas  by  introduction 
of  sulfur.  Further,  hematite  and  S02  may 
be  produced  from  pyrite  by  introduction 
of  oxygen,  as  perhaps  takes  place  on  the 
Isle  of  Elba.  It  is  seen  that  hematite  below 


T=  675°-  -700  °C 


2  (gas) 


Fig.  31.  Phase  relations  in  the  Fe-S-O  system: 
(b)  between  about  675°  and  700°  C,  (c)  be- 
tween 700°  and  743°  C,  (d)  above  743°  C. 

in  nature.  In  the  following  discussion  of 
the  phase  relationships  shown  in  figure  31, 
solid  solutions  in  FeS,  Fe203,  and  FesCX 
have  been  neglected. 

Figure  3la  shows  that  at  temperatures 
below  about  675°  C  pyrite  and  pyrrhotite 
can  coexist  with  magnetite.  This  relation- 
ship has  been  observed  in  localities  such  as 
the    Coeur    d'Alene    district.     Magnetite, 


T  =  —  700-743  °C 


S°2  (gas) 


this  temperature  is  not  stable  in  the  pres- 
ence of  pyrrhotite.  The  above-mentioned 
phase  relations  are  expected  to  remain  un- 
changed at  the  lower  temperatures  at 
which  many  ore  deposits  are  believed  to 
have  formed. 

At  about  675°  C  the  following  reaction 
takes  place :  pyrite  +  magnetite^pyrrho- 
tite  + hematite.  Figure  31£  shows  that  py- 
rite, pyrrhotite,  and  hematite  now  are 
stable  together,  and  that  hematite,  mag- 
netite, and  pyrrhotite  may  coexist,  but  mag- 
netite and  pyrite  do  not  form  a  stable 
mineral  assemblage  above  this  temperature. 

Further  changes  in  the  phase  relations 
occur  at  about  700°  C  with  the  reaction: 
pyrite  +  hematite^pyrrhotite  +  S02.  Fig- 
ure 3\c  shows  that  neither  hematite  nor 
magnetite  now  is  stable  with  the  pyrite  + 
pyrrhotite  assemblage,  whereas  pyrrhotite, 
hematite,  and  magnetite  still  can  coexist. 

At  743°  C  pyrite  is  no  longer  stable  in 
a  rigid  silica  tube  regardless  of  the  amount 
of  sulfur  present.  (See  discussion  of  the 
stability  limits  of  pyrite  elsewhere  in  this 
report.)  Figure  3ld  shows  the  phase  rela- 


200        CARNEGIE  INSTITUTION  OF  WASHINGTON 


tions  above  743°  C,  where  pyrite  no  longer 
exists.  Hematite,  magnetite,  and  pyrrho- 
tite  remain  a  stable  mineral  assemblage. 
The  geological  significance  of  these  phase 
relations  is  far-reaching,  since  these  min- 
erals are  of  almost  ubiquitous  occurrence. 

THE  Fe-S-Se  SYSTEM 
G.  Kullerud  and  H.  L.  Barnes 

Until  recently  the  selenide  minerals  had 
received  relatively  little  attention  from 
geologists  and  laboratory  workers,  but  the 
rapidly  developing  industrial  and  elec- 
tronic applications  of  selenium  have  fo- 
cused increasing  attention  on  the  modes 
of  occurrence  of  this  element.  Thus,  fer- 
roselite  (FeSe2),  which  was  first  recog- 
nized as  a  mineral  about  2  years  ago,  has 
already  been  reported  from  15  to  20  lo- 
calities on  the  Colorado  Plateau  alone. 
By  chemical  analyses  of  natural  minerals, 
FeSe2  and  FeS2  (pyrite)  have  been  found 
to  enter  into  solid  solution  with  each  other. 
These  Fe(S,Se)2  mix-crystals,  which  often 
occur  with  uranium  minerals,  may  ulti- 
mately serve  as  geological  temperature  in- 
dicators when  the  FeS2-FeSe2  system  has 
been  studied  in  the  laboratory.  The  present 
investigation  is  also  designed  to  explore 
the  distribution  of  selenium  at  various 
temperatures  and  pressures  between  pyr- 
rhotite  and  pyrite. 

Stoichiometric  FeSe  was  synthesized  at 
various  temperatures  from  325°  to  925°  C. 
X-ray  diffraction  patterns  made  at  room 
temperature  showed  that  eskebornite  in 
this  temperature  range  is  of  the  NiAs 
structure  type  (provided  that  nonquench- 
able  polymorphs  do  not  exist).  FeSe  and 
FeS,  therefore,  are  isostructural.  FeSe,  like 
FeS,  can  omit  iron  from  its  structure,  and 
the  chemical  formula  of  natural  eskeborn- 
ite, therefore,  should  be  written  Fei-^Se. 
Although  FeS,  according  to  the  literature, 
cannot  take  excess  iron  in  solid  solution, 
eskebornite  was  found  to  take  about  2 
weight  per  cent  iron  in  solid  solution  at 
800°  C.   Mixtures  of  FeS  and  FeSe  were 


made  up  at  10  weight  per  cent  intervals 
and  heated  at  800°  C  for  60  days.  X-ray 
diffraction  and  polished-section  studies 
showed  that  the  solubility  of  FeSe  in  FeS 
at  this  temperature  is  between  30  and  40 
weight  per  cent.  The  solubility  of  FeS  in 
FeSe  is  between  40  and  50  weight  per  cent. 
X-ray  diffraction  studies  of  Fe(S,Se) 
mix-crystals  of  varying  composition  show 
appreciable  variation  in  the  (102)  d  spac- 


40          50          60 

70 

80 

90 

100 
FeSe 

Mol  per  cent    Fe  Se ► 

Fig.  32.  The  curve  showing  variation  in  d 
spacings  for  the  (102)  X-ray  reflections  as  func- 
tion of  mix-crystal  Fe(S,Se)  composition. 

ings.  The  (102)  d  spacings  versus  com- 
position have  been  plotted  in  figure  32. 
Sodium  chloride  (#=5.62869  kX)  was  used 
as  internal  standard  for  all  measurements. 
The  dotted  part  of  the  spacing  curve  shows 
where  the  immiscibility  gap  occurs  at 
800°  C. 

Experiments  with  FeS  and  FeSe  mix- 
tures at  temperatures  between  850°  and 
400°  C  established  the  limits  of  the  binary 
solid  solution  within  a  few  per  cent.  The 
top  of  the  solvus  curve  is  situated  at  about 
850°  C  and  at  a  composition  of  approxi- 
mately 55  weight  per  cent  FeS  and  45 


GEOPHYSICAL  LABORATORY        201 


weight  per  cent  FeSe.  The  solubility  of 
FeSe  in  FeS  decreases  rapidly  with  de- 
creasing temperature,  and  at  600°  C  is 
about  10  weight  per  cent.  The  solubility 
of  FeS  in  FeSe  at  600°  C  is  about  30 
weight  per  cent.  The  two-phase  field  in 
this  system  is  not  binary.  Beyond  the  limit 
of  FeS  solubility  in  FeSe  and  of  FeSe  sol- 
ubility in  FeS  the  two  phases  Fei-a;(S,Se) 
and  Fei+#(S,Se)  coexist.  The  amount  of 
iron  deficiency  in  the  first  and  excess  of 


The  crystal  chemistry  of  these  arsenides 
is  of  particular  interest,  as  most  chemical 
analyses  have  suggested  that  compositions 
with  marked  departures  from  stoichio- 
metric proportions  might  be  common.  The 
different  arsenides  are  commonly  zoned 
or  intergrown  with  one  another,  however, 
and  can  be  distinguished  only  by  means 
of  the  polarizing  reflecting  microscope  or 
X-ray  techniques.  The  few  analyses  that 
have  been  made  on  material  checked  for 


o<8  26  — 


Composition,   mole  percent 

Fig.  33.  Curves  showing  unit  cell  dimensions  of  synthetic  skutterudites  as  a  function  of  cobalt- 
to-nickel  ratio,  cobalt-to-iron  ratio,  and  cobalt-to-nickel-and-iron  ratio  (where  the  nickel-to-iron  ratio 
is   1:1). 


iron  in  the  second  of  these  compounds 
at  various  S :  Se  ratios  must  be  carefully 
studied  before  the  tie  lines  can  be  deter- 
mined in  the  ternary  system. 

THE  CoAs2-NiAs2-FeAs^As  SYSTEM 
E.  H.  Roseboom,  Jr. 

Ore  deposits  mined  for  arsenic,  cobalt, 
nickel,  and  silver,  although  not  abundant, 
are  of  world-wide  distribution  and  consti- 
tute a  distinctive  type.  They  are  remark- 
ably low  in  sulfur,  with  cobalt,  nickel,  and 
iron  present  as  arsenides  or  sulfarsenides 
and  with  silver  and  bismuth  present  in 
the  native  state. 


homogeneity  have  indicated  nearly  stoi- 
chiometric compositions  for  diarsenides, 
but  metal-to-arsenic  ratios  as  low  as  1 : 2.65 
for  skutterudites,  (Co,Ni,Fe)As3-*.  Such 
ratios  might  vary  sufficiently  with  tem- 
perature to  provide  a  means  of  determin- 
ing the  temperature  of  formation  of  ore 
deposits. 

Very  little  was  known  about  the  system 
Co-Ni-Fe-As,  which  contains  eight  natu- 
rally occurring  minerals.  The  present  study 
was  undertaken  to  explore  the  portion  of 
the  system  pertaining  to  natural  deposits. 
It  was  hoped  that  phase  changes  suitable 
for  establishing  limits  of  temperature  and 


202        CARNEGIE  INSTITUTION  OF  WASHINGTON 


pressure  during  formation  might  be  dis- 
covered for  this  group  of  minerals.  As 
most  natural  skutterudites  contain  cobalt, 
iron,  and  nickel,  and  as  so  little  was  known 
of  the  phase  relations,  it  was  thought  that 
a  reconnaissance  of  the  arsenic-rich  por- 
tion of  the  quaternary  system  would  be  of 
more  value  than  a  detailed  study  of  a 
binary  or  ternary  system  in  the  quaternary. 
In  preliminary  attempts  to  make  skutter- 
udites of  mixed  cobalt,  iron,  and  nickel 


amount  of  arsenic  that  combined  with  the 
metal  was  determined  by  weighing  the 
inner  tube  after  the  run.  The  contents  of 
the  tube  were  reground  and  reheated  in 
the  same  way  until  there  was  no  further 
increase  in  weight.  The  maximum  arsenic 
contents  given  below  for  cobalt  skutterud- 
ite  (CoAs3-a?),  loellingite  (FeAs2),  and 
rammelsbergite  (NiAs2)  are  each  the  av- 
erage and  standard  deviation  of  three 
samples.   The  minimum  arsenic  contents 


Phases   stable  with  excess  arsenic  at  800  C 
(opprox.  23atm    of  vapor  pressure). 

Light  lines  and  numbers  in  the  friarsenide  field 
indicate  lines  of  equal  cell  dimension  in  angstroms 

Dashed  lines  indicate  field  boundaries 

Heavy  lines  connect  compositions  of  coexisting 
diarsenides  and  triarsenides 


CoAs2 


True  shape  of  projected  surface 

is  shown  by  cross  halching 


Rammelsbe 


Fig.  34.    The  cobalt-nickel-iron  content  of  solid  phases  in  the  system  Co-Ni-Fe-As  which  are 
stable  with  excess  arsenic  and  a  vapor  phase  at  800°  C. 


composition,  it  was  decided  to  work  at 
800°  C  after  runs  of  several  days'  duration 
at  600°,  700°,  and  750°  C  failed  to  ap- 
proach equilibrium. 

The  present  work  is  an  isothermal  pro- 
jection of  the  solid  phases  stable  with  a 
vapor  at  800°  C  and  with  total  pressure 
equal  to  the  equilibrium  vapor  pressure 
of  the  solid  phases  present.  The  runs  were 
made  in  evacuated  sealed  silica-glass  tubes. 

The  maximum  arsenic  content  was  de- 
termined for  the  phases  stable  with  arsenic 
by  heating  at  800°  C  a  known  amount 
of  metal  in  an  open  tube  inside  a  larger 
closed  tube  containing  excess  arsenic.  The 


were  determined  by  making  runs  of  suc- 
cessively lower  arsenic  content  until  the 
presence  of  another  phase  was  detected  by 
microscopic  examination  of  polished  sec- 
tions of  the  samples.  The  arsenic  contents 
determined  in  this  manner  may  be  too 
large  by  as  much  as  0.01,  as  a  much  larger 
proportion  of  arsenic  than  cobalt  is  in- 
volved in  the  vapor  phase. 

At  800°  C  cobalt  skutterudite  has  a  min- 
imum arsenic  content  between  CoAs2.94 
and  CoAs2.95  and  a  maximum  of 
CoAs2. 960  ±o,ooi.  Loellingite  has  a  lower 
limit  between  FeAsi.97  and  FeAsi.os  and 
an  upper  limit  of  FeAsi.998  ±0.002.  Rammels- 


GEOPHYSICAL  LABORATORY        203 


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204        CARNEGIE  INSTITUTION  OF  WASHINGTON 


bergite  has  a  lower  limit  above  NLA.S1.99  FeAs2  80  per  cent  CoAs2,  and  reaches  a 

and  an  upper  limit  of  NiAs1.999iO.001.   In  maximum  at  CoAs2.    NiAs2  and  CoAs2, 

no  case  was  there  a  measurable  difference  and  FeAs2  and  CoAs2,  apparently  form  a 

in  X-ray  d  spacings  between  the  phases  complete  solid  solution  series.   The  series 

made  with  excess  arsenic  and  the  same  NiAs2-FeAs2  is  discontinuous  at  800°  C 

phases  made  with  deficient  arsenic.  because  of  an   asymmetrical  solvus  with 

The  name  skutterudite  is  used  for  all  a  crest  estimated  at  about  900°  C  and  about 

cubic   "triarsenides"  of  cobalt,  iron,  and  15  per  cent  FeAs2  85  per  cent  NiAs2. 

nickel.    Thus    the   formula   may   be    ex-  The  condensed  diagram  of  the  systems 

pressed  approximately  as  (Co,Fe,Ni)As3-;r.  CoAs2-NiAs2-As,    NiAs2-FeAs2-As,    and 

Skutterudites  of  varied  cobalt,  iron,  and  FeAs2-CoAs2-As  at  800°   C  is  shown  in 

nickel  content  were  made  in  the  presence  figure  35  as  the  unfolded  sides  of  a  tetrahe- 

of  excess   arsenic.    Figure  33   shows   the  dron  with  arsenic  at  the  apex.   The  dia- 

effect  of  composition  on  cell  size  for  vari-  gram  is  based  on  relatively  few  runs.  After 

ous  series  of  skutterudites.  Figure  34  shows  the  diarsenide  and  skutterudite  solid  solu- 

the   cobalt-iron-nickel   content   of   phases  tion  series  were  established,  it  was  possible 

stable  with  excess  arsenic  at  800°  C.  The  to  locate  the  corners  of  the  three-phase 

lines  of  equal  cell  dimension  for  the  skut-  fields  from  the  d  spacings  of  the  phases, 

terudites  are  also  shown.  In  the  iron  and  As  arsenic  melts  at  about  818°   C  under 

nickel  corners  of  the  triangle  there  are  its  own  vapor  pressure,  a  eutectic  between 

fields  in  which  loellingites  and  rammels-  arsenic  and  the  arsenides  of  highest  arsenic 

bergites  of  varied  compositions  are  stable  content  might  extend  below  800°  C.  Hence 

with  excess  arsenic.   Between  these  fields  [t  [s  possible  that  at  800°  C  there  are  some 

and  the  skutterudite  field,  a  skutterudite  \[qu[^  fields  in  the  arsenic-rich  portion  of 

is    stable   with   either   a   loellingite   or   a  the  diagram,  although  no  evidence  of  them 

rammelsbergite,  plus  arsenic.  was  0bservecL 

Runs  made  at  800°  C  in  the  diarsenide 

+  skutterudite  +  arsenic  fields  and  annealed  relations  BETWEEN  COMPOSITION  OF  ORE 

at  600°  and  700°  C  for  3  months  indicated  MINERALS  AND  ORE  SOLUTIONS 

that  the  limits  of  the  binary  series  of  skut-  h.  L.  Barnes  and  G.  Kullerud 

terudites  decrease  by  1  to  3  per  cent  except  „            .            ,     .              111 

£        i_.         •  1         1     c  ft        •  1    1  •  Economic     geologists     and     laboratory 

for  the  iron-rich  end  or  the  nickel-iron  .                          11            •     •        c  .i_ 

,             ,.            1  •  1     •                      ee  scientists  agree  that  the  majority  or  the 

skutterudites,   which  increases  to  55  per  ,,,       .5,           ...          '     1         u 

„-.                    •  t    1       rAAo  ^r  worlds  sulfide  ore  bodies  must  have  been 

cent  iron  45  per  cent  nickel  at  6UU    C  .        .     ,  ,                           ,   ..            a   •  1 

^,      ,.     .   r   £  .              11           1      .11  deposited  from  aqueous  solutions  or  fluids. 

The  limits  or  iron,  cobalt,  and  nickel  _,r                     fl  .1             L                       1 

c  1           t-r  •  1   1    J      a-^  These  aqueous  rluids  must  have  contained 

content  of  these  artificial  skutterudites  con-  1         1      1  r             1  •      1  •      1      r 

.     on                    r   1              •   •             1  metals  and  sulrur  combined  in  the  rorm 

tain  87  per  cent  or  the  remaining  analyses  ,             .                ., 

for  natural  skutterudites  compiled  from  °£  «>mPlex  ^ns  Such  complexes  could 
the  literature  by  Holmes  (1947)  after  he  b[eak  ^  a;>  the  1'esultJof  changej.  m 
had  eliminated  analyses  made  on  material  Physical  and  chemical  conditions,  leading 
that  was  probably  not  skutterudite.  Only  t0  sulfide  deposition. 
6  per  cent  of  these  analyses  were  more  than  In  some  ore  bodies  limits  can  be  placed 
5  per  cent  beyond  the  limits.  on  tne  conditions  existing  at  the  time  of 
Although  both  loellingite  and  rammels-  °^  formation  on  the  basis  of  subsolidus 
bergite  are  orthorhombic,  cobalt  diarsenide  relations  and  mineral  solubilities,  but  even 
appears  to  be  monoclinic.  The  evidence  where  the  phase  relations  give  relatively 
for  this  was  the  splitting  of  the  110  and  accurate  physical  data,  the  chemistry  in- 
Ill  d  spacings  into  two  spacings.  The  volved  during  transport  and  precipitation 
split  begins  at  about  25  per  cent  NiAs2  is  not  well  understood.  A  complete  under- 
75  per  cent  CoAs2  and  at  about  20  per  cent  standing  of  the  chemistry  of  such  trans- 


GEOPHYSICAL  LABORATORY        205 


porting  agents  could  undoubtedly  be  de- 
veloped into  a  powerful  tool  for  prediction 
of  ore  occurrence. 

Although  the  considerable  economic  and 
theoretical  importance  of  an  understand- 
ing of  the  chemistry  of  ore  solutions  has 
been  clear  to  numerous  workers  in  the 
field  of  geology,  the  ore  solutions  involve 
extremely  complicated  chemistry  which  of 
necessity  has  been  commonly  oversimpli- 
fied in  its  treatment. 

Thus,  many  recent  papers  using  mineral 
compositions  for  data  on  the  composition 
of  hydrothermal  ore  solutions  have  been 
based  on  simple  ionic  chemistry  without 
a  clear  statement  of  the  implicit  assump- 
tions involved.  By  summarizing  the  physi- 
cal and  chemical  conditions  which  must 
necessarily  be  evaluated,  these  assumptions 
become  self-evident: 

1.  Equilibrium  conditions  must  occur 
during  deposition  of  the  minerals.  In  other 
words,  metastable  phenomena  such  as  su- 
persaturation  or  coprecipitation  must  not 
modify  conditions  of  precipitation,  or  cal- 
culations of  equilibria  would  be  mean- 
ingless. 

2.  If  the  ratio  of  concentrations  of  any 
given  element  in  two  minerals  is  to  be 
used  for  defining  the  ore  solution,  the  two 
minerals  must  have  been  precipitated  un- 
der physically  and  chemically  identical  con- 
ditions. Practically,  this  limitation  requires 
either  that  the  two  minerals  were  precipi- 
tated simultaneously  or  that  there  has  been 
no  change  in  the  composition,  pressure,  or 
temperature  of  the  ore  solution  between 
the  time  of  precipitation  of  the  first  and 
second  mineral. 

3.  There  must  be  no  post-depositional 
changes  in  the  composition  of  mix-crystals 
used  for  data  on  depositional  environment, 
though  these  mineral  compositions  may  be 
far  out  of  equilibrium  with  subsequent 
environments.  Neither  exsolution  nor  so- 
lution is  permissible,  although  both  proc- 
esses are  favored  by  recrystallization  or 
changes  in  chemical  environment,  pressure, 
or    temperature,    especially    during    slow 


cooling  of  deep-seated  deposits  or  heating 
in  later  metamorphism. 

4.  The  relative  distribution  and  types 
of  ions  present  in  the  ore  solution  must  be 
known.  Specifically,  information  on  the 
extent  to  which  dissociation,  hydrolysis, 
and  complexing  take  place  is  important  in 
order  to  estimate  the  total  ionic  strength 
and  to  ascertain  the  metal  transporting 
ions. 

5.  Activity  coefficients  of  both  the  aque- 
ous ions  and  the  mix-crystals  need  to  be 
evaluated  as  functions  of  the  four  inde- 
pendent variables  temperature,  pressure, 
ionic  species,  and  ionic  strength. 

Lack  of  information  necessitated  the  as- 
sumption of  specific  conditions  for  theo- 
retical treatment  even  without  direct  evi- 
dence. Geologic  data  on  the  history  of  a 
particular  mineral  sample  are  very  difficult 
to  collect,  and,  at  present,  there  exist  vir- 
tually no  chemical  data  obtained  under  the 
difficult  experimental  conditions  approxi- 
mating those  at  which  ore  deposits  were 
formed. 

Knox  (1908)  and  Dickson  and  Tunell 
(1955)  have  studied  the  chemical  behavior 
of  HgS  under  varied  chemical  conditions 
simulating  ore  transport.  Experimental 
work  on  the  solubility  of  ZnS  in  H20  un- 
der elevated  pressures  and  temperatures 
in  a  H2S  atmosphere  is  now  in  progress  in 
this  Laboratory. 

If  sufficient  data  were  available,  four 
simultaneous  equations  could  be  derived 
to  relate  these  four  independent  variables 
to  mix-crystal  concentration  ratios.  For  a 
unique  solution  at  least  four  accurate  con- 
centration ratios  are  necessary.  These  ra- 
tios may  be  of  two  types :  (a)  the  fractional 
content  of  one  trace  element  in  one  min- 
eral may  be  expressed  and  used  as  a  ratio 
provided  that  there  is  an  excess  of  the  trace 
element  present  at  the  time  of  deposition 
to  assure  that  the  mineral  is  saturated  with 
the  trace  element  at  that  temperature  and 
pressure;  and  (b)  the  distribution  ratio 
of  one  trace  element  between  two  min- 
erals may  be  used  where  neither  is  satu- 
rated with  the  trace  element.    The  four 


206 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


ratios  required  could  be  measured  theoreti- 
cally for  any  combination  of  the  two  types 
where  the  distribution  ratio  could  be  meas- 
ured for  one  trace  element  in  several  min- 
erals, several  trace  elements  in  the  same 
two  minerals,  or  any  intermediate  com- 
bination. 

From  a  practical  point  of  view,  the  trace- 
element  concentration  in  a  mineral  can  be 
used  only  if  it  is  sufficiently  high  for  ac- 
curate analysis  and  if  the  mineral  can  be 


effectively  separated  from  potentially  con- 
taminating foreign  minerals.  In  order  to 
use  these  ratios,  the  minerals  involved 
must  have  been  deposited  contemporane- 
ously. It  is  doubtful  whether  minerals 
fulfilling  these  conditions  and  providing 
a  sufficient  number  of  ratios  for  the  solu- 
tion of  the  simultaneous  equations  can  be 
found  in  actual  ore  deposits;  it  remains  a 
crucial  question,  however,  and  must  be 
investigated. 


FELDSPARS 


TERNARY  FELDSPARS 


H.  S.  Yoder,  D.  B.  Stewart,  and  J.  R.  Smith 

The  ternary  feldspar  study  briefly  out- 
lined last  year  has  advanced  to  a  very 
fruitful  stage.  The  relations  of  the  various 
feldspars,  of  greatest  import  to  the  petrolo- 
gist,  may  now  be  defined  more  closely 
and  the  results  applied  to  natural  rocks. 
The  principal  feldspars  lie  in  the  system 
NaAlSi308  (Ab)  -KAlSi308  (Or)  -CaAL- 
Si2Og  (An) ;  this  system  has  been  investi- 
gated with  water  under  a  pressure  of  5000 
bars,  mainly  using  glasses  prepared  by 
Franco,  Schairer,  and  Bowen. 

Projections  of  the  bounding  ternary  sys- 
tems Ab-An-H20,  Or-An-H20,  and  Ab- 
Or-H20  are  given  in  figures  36,  37,  and 
38,  respectively.  The  uncertainty  of  the 
nature  of  the  melting  of  compositions  near 
anorthite  mentioned  last  year  has  been 
resolved.  The  "3-alumina"  of  unknown 
composition  that  appeared  in  some  runs 
has  dissolved  with  longer  runs,  and  it  may 
be  stated  with  confidence  that  anorthite 
melts  congruently  at  5000  bars  water  pres- 
sure. Much  effort  was  put  into  fixing  the 
limits  of  the  solvus  in  the  Or-Ab-H20 
system  (fig.  38).  The  solvus  as  pictured 
is  based  on  1-month  runs  using  only  the 
results  from  glass  starting  materials.  The 
number  of  phases  was  identified  by  means 
of  powder  X-ray  diffraction  patterns,  since 
optical  recognition  was  not  always  possible. 
Equilibrium  was  demonstrated  by  holding 
previously  crystallized  glasses  known  to 
consist  of  a  single  phase  at  the  same  tem- 


peratures and  pressure.  In  the  unmixing 
region  as  outlined  by  runs  using  glass  as 
a  starting  material  most  of  the  composi- 
tions began  to  unmix.  Unfortunately,  sin- 
gle feldspars  formed  previously  from  a 
glass  did  not  unmix  to  the  same  composi- 
tions of  feldspars  as  those  obtained  from 
glass  crystallized  in  the  unmixing  region 
even  in  a  month's  time  on  the  basis  of  the 

201  spacings  of  the  X-ray  diffraction  pat- 
tern. The  201  spacings  do  not  give  a  suit- 
able measure  of  the  composition  in  un- 
mixed feldspars,  according  to  Coombs  and 

others,  and  so  the  201  spacing  could  be 
used  as  only  an  approximate  measure  of 
the  attainment  of  equilibrium.  However, 
the  incompleteness  of  unmixing  of  those 
single  feldspars  previously  formed  from 
glass  was  well  outside  the  errors  of  esti- 
mating the  composition  by  the  201  spacing. 
From  runs  made  to  test  the  possibility  of  a 
solvus  in  the  Ab-An-H20  system,  only 
single-phase  crystalline  products  were  ob- 
tained. The  peristerites  may  be  the  result 
of  complex  phase  relationships  arising  in 
the  Ab-Or-An  system. 

Because  the  lines  in  the  diagrams  in 
figures  36,  37,  and  38  are  projections  of 
boundary  surfaces  between  assemblages  in 
equilibrium  with  gas,  they  cannot  be  read 
in  the  same  manner  as  anhydrous  dia- 
grams of  similar  appearance.  In  order  to 
illustrate  this  fact,  two  sections  determined 
experimentally  at  constant  temperature  and 
pressure  are  given  for  Ab-Or-H20,  one 
of  the  bounding  systems.   In  figure  39  is 


GEOPHYSICAL  LABORATORY        207 


1300 


Pu  o  =  5000  bars 


700  — 


600 


J I 


NaAISUO 


3W8 


20 


40  60 

WEIGHT  PER    CENT 


80 


CaAI2Si20g 

Fig.  36.    Projection  of  the  ternary  system  NaAlSi308-CaAl2Si208-H20  at  5000  bars  H20  pressure. 


i r 


1300 


1200 


N00 


o5  1000 
W 

h-900A-     O        O 
0_ 


Ph20  "  5000  bars 


o      o      o      o 


LU 


500 


700 


600 


+ 


KAISi308 


bO 


CaAI2Si208 


40  60 

WEIGHT    PER    CENT 
Fig.  37.    Projection  of  the  ternary  system  KAlSi308-CaAl2Si208-H20  at  5000  bars  H20  pressure. 


208 


CARNEGIE  INSTITUTION  OF  WASHINGTON 


the  720°  C,  5000  bar  section,  and  all  these 
data  project  onto  the  720°  C  line  in  figure 
38.  Attention  is  called  to  the  large  amount 
of  H20  in  the  liquids  (~11  per  cent)  and 
the  resulting  large  area  in  which  a  gas 
phase  is  prohibited.  The  second  section,  fig- 
ure 40,  at  710°  C,  5000  bars,  shows  some- 
what the  same  relations,  and  in  addition  in- 
dicates that  the  solvus  has  been  transected 
in  the  region  where  a  gas  phase  is  prohib- 
ited. The  maximum  on  the  solvus  does  not 
appear  on  the  projection   (fig.  38),  since 


that  they  contain  about  1  to  2  per  cent  of 
the  feldspar  components  (see  figs.  39  and 
40). 

With  the  knowledge  gained  from  the 
three  bounding  ternary  systems,  it  was  then 
possible  to  study  the  quaternary  Ab-Or- 
An-H20  at  5000  bars.  If  the  problem  is 
described  loosely  in  terms  of  the  anhydrous 
systems,  the  study  consisted  of  tracing 
the  way  in  which  the  three  fundamental 
bounding  systems,  one  of  the  continuous- 
series  type  (fig.  36),  another  of  the  eutec- 


1000 


900 


PH  0=5000  bars 


Liquid  +  gas 
__    Feldspar  +  liquid  +  gas 


500 


400 


0 

Ab 


10 


20 


70 


80 


90 


100 
Or 


30  40  50  60 

WEIGHT   PER    CENT 
Fig.  38.    Projection  of  the  ternary  system  NaAlSi308-KAlSi308-H20  at  5000  bars  H20  pressure. 


only  those  assemblages  in  equilibrium  with 
gas  are  indicated.  On  the  basis  of  the  data 
in  these  two  sections,  the  maximum  on  the 
solvus  at  5000  bars  total  pressure  is  placed 
at  715°  ±5°  C  and  Ab55Or45±3  weight 
per  cent.  Bowen  and  Tuttle  determined 
the  maximum  of  the  solvus  at  1000  kg/cm2 

to  be  660°  C  and  Ab550r45,  using  the  201 
method  for  two  points  and  determining 
the  number  of  phases  for  a  third  point  at 
the  maximum.  With  the  latter  datum,  the 
pressure  raises  the  maximum  on  the  solvus 
about  14°/1000  bars.  Although  the  compo- 
sition of  the  gases  has  not  been  studied  in 
great   detail,   preliminary   results   suggest 


tic  type  (fig.  37),  and  the  third  of  the 
minimum  type  (fig.  38),  merge  in  T-X 
space.  The  projection  of  the  determined 
liquidus  diagram  when  gas  is  present  is 
given  in  figure  41.  One  of  the  most  sig- 
nificant features  is  the  generally  low  tem- 
peratures, temperatures  readily  available 
in  the  crust,  as  compared  with  the  an- 
hydrous system  determined  by  Franco  and 
Schairer.  Also  of  importance  is  the  OrAb- 
rich  nature  of  the  liquids  along  the  four- 
phase  boundary  curve.  This  observation 
has  bearing  on  many  geological  problems, 
particularly  those  involving  partial  melting 
or  metasomatism.  The  four-phase  bound- 


GEOPHYSICAL  LABORATORY        209 


H,0 


PT  ,   ,     =    5000  bars 
Total 


Or 


Weight  per  cent 

Fig.  39.   The  720°  C  section  at  5000  bars  of  the  system  NaAlSi308  (Ab) 
KAlSi308  (Or)  -  H20. 


PTotal  =  500°  bQrs 
T  =      710  °C 


Weight    per  cent 


Fig.  40.   The  710°  C  section  at  5000  bars  of  the  system  NaAlSi3Os  (Ab) 
KAlSi308  (Or)  -  H20. 


210        CARNEGIE  INSTITUTION  OF  WASHINGTON 


ary  curve  becomes  a  three-phase  trough  (in-  join.    With    fractionation,    the    range    of 

cheated  by  short  dash)  at  a  fixed  tempera-  simultaneous  crystallization  would  be  ex- 

ture  between  695°  and  698°  C.  The  change  tended. 

takes  place  at  the  temperature  at  which  Some  notion  as  to  the  way  in  which 
two  feldspars  react  with  liquid  and  gas  to  the  tie  lines  connecting  coexisting  feld- 
produce  one  feldspar,  liquid,  and  gas.  The  spars  in  equilibrium  with  liquid  and  gas 
one  feldspar  produced  has  the  composition  sweep  across  the  5000-bar  projection  may 
of  the  point  of  contact  of  the  solidus  and  be  gained  from  figure  44.  The  family  of 
the  solvus.  such  tie  lines,  which  include  the  four  deter- 
In  order  to  understand  more  fully  the  mined  experimentally,  generates  a  surface, 
relations  in  the  complex  quaternary  sys-  the  boundary  curves  (dashed)  marking 
tern,  three  isothermal,  isobaric  projections  the  maximum  solid  solution  of  coexisting 
have  been  studied.  The  770°  C,  5000  bar  feldspars  in  equilibrium  with  liquid  and 
projection,  given  in  figure  42,  presents  only  gas.  A  third  isothermal,  isobaric  projec- 
those  assemblages  that  are  in  equilibrium  tion  is  now  being  investigated  at  660°  C, 
with  gas.  The  chief  observations  are  the  5000  bars,  to  determine  the  relations  when 
composition  of  feldspars  in  equilibrium  only  crystals  and  gas  are  present.  It  is 
with  liquid  and  gas  and  the  orientation  realized  that  many  of  the  phases  obtained 
of  the  tie  line  (light  line)  which  separates  in  these  studies  undergo  transitions  of  the 
the  two  feldspars  +  gas  field  from  the  first  order  and  of  higher  orders.  Although 
two  feldspars  +  liquid  +  gas  field.  The  powder  X-ray  diffraction  patterns  have 
tie  lines  that  connect  coexisting  feldspars  been  taken  of  many  of  the  synthetic  crys- 
or  coexisting  feldspar  and  liquid  in  the  tals,  none  of  the  crystals  was  suitable  for 
three-phase  regions  do  not  appear  on  the  single-crystal  X-ray  study.  Minor  changes 
diagram,  since  no  data  are  known  for  fix-  may,  therefore,  be  required  in  the  equi- 
ing  the  composition  of  ternary  feldspars  librium  diagrams  when  sufficient  knowl- 
except  along  univariant  curves  or  at  in-  edge  of  the  exact  structural  form  of  each 
variant  points.  At  invariant  points  or  along  phase  is  obtained.  In  addition,  hydrous 
univariant^  curves  the  points  were  fixed  phases  will  appear  at  temperatures  lower 
by  observing  the  number  and  kind  of  than  those  investigated, 
phases  about  the  point.  In  advance  of  these  data  the  subsolidus 
In  figure  43  the  relations  of  the  720°  C,  regions  of  one  and  two  feldspars,  those  re- 
5000  bar  projection  are  given  for  only  those  gions  of  most  importance  to  the  geologist, 
phases  in  equilibrium  with  gas.  The  ori-  may  be  illustrated  schematically.  Figure 
entation  of  the  tie  line  fixing  the  composi-  45  outlines  the  field  boundary  surfaces  at 
tion  of  the  two  feldspars  in  equilibrium  5000  bars  which  separate  the  two-feldspar 
with  liquid  and  gas  should  be  noted  and  region  (inside  the  truncated  "dome")  from 
compared  with  the  similar  tie  line  in  fig-  the  one-feldspar  regions.  The  top  surface 
ure  42.  In  general,  the  change  of  composi-  Gf  the  "dome,"  the  intersection  of  the  sol- 
tion  of  the  AbAn-rich  feldspar  with  tern-  vus  ancl  the  solidus,  represents  the  ex- 
perature  is  greater  than  that  change  for  perimentally  determined  relations  already 
the  OrAb-rich  feldspar.  The  small  tri-  given  in  figure  44.  For  comparison,  a 
angular  area  of  the  projected  four-phase  similar  picture  (fig.  46)  is  presented  for  a 
region  in  both  isothermal,  isobaric  projec-  water  pressure  of  about  2000  bars.  This 
tions  (figs.  42  and  43)  indicates  the  limited  schematic  figure  was  deduced  mainly  from 
range  of  temperature  through  which  two  the  work  of  Bowen  and  Tuttle  on  the 
feldspars  may  crystallize  simultaneously  Ab-Or-H20  system  at  2000  bars.  In  fig- 
from  a  given  magma  under  equilibrium  ure  46  it  is  seen  that  the  surface  mark- 
conditions.  The  range  is  zero  at  the  Or-  ing  the  solvus-solidus  intersection  does  not 
An-H20  join  and  near  the  Or-Ab-H20  meet  the  Ab-Or  join.   The  resulting  ori- 


PH   0=5000  bars 


876° 


695-  Qr 

Weight  per  cent 

Fig.  41.  Projection  of  the  quaternary  system  NaAlSi308  (Ab)  -  KAlSi3Os 
(Or)  -  CaAl2Si208  (An)  -  H20  at  5000  bars  H20  pressure.  The  circles  indicate 
compositions  for  which  a  bracket  was  obtained.  The  dots  indicate  composi- 
tions for  which  a  bracket  was  not  obtained;  significant  temperatures  were 
investigated,  however. 


5000  bars 


Weight  per  cent 


Fig.  42.  Projection  of  the  NaAlSi308  (Ab)-KAlSi308  (Or)  -CaAl2Si208 
(An)-H20  system  at  770°  C  and  5000  bars  H20  pressure.  Only  those  assem- 
blages in  equilibrium  with  gas  are  given. 

211 


=    5000  bors 


Liquid  +  Gas 


Or 


Weight   per  cent 

Fig.  43.  Projection  of  the  NaAlSi308  (Ab)-KAlSi308  (Or)-CaAl2Si208 
(An)-H20  system  at  720°  C  and  5000  bars  H20  pressure.  Only  those  assem- 
blages in  equilibrium  with  gas  are  given. 


5000  bars 


Weight  per  cent 


Fig.  44.  Plot  of  experimentally  determined  tie  lines  connecting  coexisting 
feldspars  in  equilibrium  with  liquid  and  gas.  These  appear  from  the  highest 
to  the  lowest  temperature  in  figures  37,  42,  43,  38,  respectively. 

212 


GEOPHYSICAL  LABORATORY        213 


entation  of  the  tie  lines  connecting  coexist- 
ing feldspars  is  therefore  different  from 
those  at  5000  bars  water  pressure.  Further- 
more, the  extent  of  solid  solution  increases 
on  this  surface  with  lower  pressure  for  a 
given  bulk  composition.  In  general,  the 
tie  lines  make  a  smaller  angle  to  the  Or- 
An  side  at  high  temperatures  and  low 
pressures  than  at  low  temperatures  and 
high  pressures.  If  the  pressure  or  tem- 
perature were  known,  then  the  tempera- 
ture or  pressure  of  formation,  respectively, 


In  figure  47  are  assembled  some  of  the 
analyzed  pairs  of  coexisting  feldspars  re- 
corded in  the  literature.  Most  of  the  sam- 


Fig.  45.  Schematic  presentation  of  the  field 
boundary  surfaces  separating  the  two-feldspar 
region  (inside  the  truncated  "dome")  from  the 
one-feldspar  and  the  two-feldspar  +  liquid  +  gas 
regions  of  the  Ab-Or-An-H20  system  at  5000 
bars  H20  pressure. 

could  be  estimated  from  knowledge  of  the 
compositions  of  the  coexisting  feldspars. 
Since  the  field  geologist  can  often  make 
an  estimate  of  the  depth  at  which  a  rock 
may  have  formed,  assuming  that  Ph2o  = 
Ptotai,  the  compositions  of  the  coexisting 
feldspars  can  yield  a  measure  of  the  tem- 
perature of  formation,  provided  that  equi- 
librium was  attained.  If  the  pressure  of 
formation  cannot  be  specified,  but  is  be- 
lieved to  be  constant,  the  relative  change 
of  the  compositions  of  coexisting  feldspars 
in  a  series  of  rocks  indicates  the  relative 
temperatures  of  formation. 


Fig.  46.  Schematic  presentation  of  the  field 
boundary  surfaces  separating  the  two-feldspar 
region  (inside  the  "dome")  from  the  one-feld- 
spar and  the  two-feldspar  +  liquid  +  gas  regions 
of  the  Ab-Or-An-H20  system  at  2000  bars  H20 
pressure.  Based  on  the  work  of  Bowen  and 
Tuttle  (1950)  on  the  Or-Ab-H20  system. 


WEIGHT    PER   CENT 


Fig.  47.  Plot  of  chemically  analyzed  pairs  of 
coexisting  feldspars  recorded  in  the  literature. 
Homogeneity  of  phase  has  not  been  tested  by 
X  rays  in  most  cases. 

pies  were  not  available  to  test  for  homo- 
geneity by  X  rays.  The  orientations  of 
the  tie  lines,  with  the  exception  of  two 
having  the  most  An-rich  plagioclases,  are 


214        CARNEGIE  INSTITUTION  OF  WASHINGTON 


in  accord  with  those  obtained  experimen- 
tally. The  two  exceptions  are  indicative 
of  a  lower  pressure  and  a  higher  tempera- 
ture; in  fact,  the  feldspars  from  these  speci- 
mens are  phenocrysts  from  surface  flows. 
However,  another  specimen  from  a  surface 
flow,  having  a  plagioclase  of  Ann,  cannot 
be  readily  identified  as  having  formed  at 
low  pressure,  and  it  is  likely  that  the 
properties  of  these  feldspars  are  inherited 
from  an  environment  at  depth. 

The  present  study,  giving  quantitative 
information  on  the  number  of  feldspars, 
their  relative  proportions,  and  the  extent 
of  their  solid  solutions,  emphasizes  the 
need  for  determining  the  composition  of 
each  feldspar  phase  in  a  rock.  The  com- 
positions of  the  feldspars,  or  any  pair  of 
minerals  sharing  components,  may  yield 
specific  clues  to  the  temperature  and  pres- 
sure of  formation.  Inasmuch  as  more  than 
half  of  the  earth's  crust  is  composed  of 
feldspar,  the  feldspars  are  potentially  most 
valuable  geothermometers  and  geopiezom- 
eters. 

THE  SYSTEM  CaAl2Si208-Si02-H20 
D.  B.  Stewart 

Despite  the  dominance  of  the  feldspars 
as  constituents  of  the  earth's  crust,  rocks 
composed  entirely  of  feldspar  are  not  com- 
mon. In  addition  to  femic  minerals,  most 
feldspar-bearing  rocks  contain  significant 
amounts  of  either  free  silica  or  more  rarely 
a  feldspathoid.  The  phase  relations  of  feld- 
spars and  silica  have  been  studied  inten- 
sively at  this  Laboratory  by  Schairer  and 
Bowen,  and  Tuttle  and  Bowen  have  inves- 
tigated the  systems  NaAlSi308-Si02-H20, 
KAlSi308-Si02-H20,  and  NaAlSi308- 
KAlSisOs-SiOs-HsO  ("synthetic  granite") 
to  pressures  of  4000  bars. 

The  present  study  complements  these 
investigations,  as  the  great  bulk  of  all 
granitic  rocks  contain  the  CaAl2Si20s  com- 
ponent, and  the  work  on  ternary  feldspars 
reported  in  this  Year  Book  indicates  the 
profound  effect  of  small  amounts  of  this 
component  on  the  phase  relations  of  the 
feldspars.    A   feldspar,   silica   polymorph, 


gas,  and  liquid  saturated  with  H20  coexist 
at  a  given  pressure  at  only  one  tempera- 
ture. One  of  the  purposes  of  this  investi- 
gation of  the  system  CaAl2Si208-Si02- 
H20  is  to  determine  the  locus  of  four- 
phase  points  as  the  pressure  is  changed. 
The  system  CaAl2Si208-Si02-H20,  to- 
gether with  the  results  of  Tuttle  and 
Bowen  for  the  same  pressure,  fixes  the 
end  points  of  the  H20-saturated  liquidus 
where  feldspar  and  silica  coexist.  At  this 
fixed  pressure  the  assemblage  including 
anorthite  as  one  of  the  four  phases  coexists 
at  a  higher  temperature  than  any  similar 
assemblage  of  feldspar,  silica,  saturated 
liquid,  and  gas.  To  the  extent  that  the 
three  limiting  ternary  systems  are  known 
at  various  pressures,  the  direction  and  mag- 
nitude of  the  changes  of  the  liquidus 
caused  by  variations  of  H2O  pressure  dur- 
ing crystallization  can  be  described. 

All  the  present  results  were  obtained 
with  Yoder's  apparatus,  and  his  unpub- 
lished results  for  the  system  CaAl2Si208- 
H2O  have  been  utilized  and  confirmed. 
The  Si02-H20  liquidus  passes  through 
the  points  1130° ±5°  C  at  2000  bars  H20 
pressure  and  1065°  ±5°  C  at  5000  bars. 
These  data  modify  and  extend  the  diagram 
given  by  Tuttle  and  England  (1955),  and 
such  high  temperatures  and  pressures  in- 
dicate that  quartz  veins  or  the  quartz  cores 
of  pegmatites  could  not  have  crystallized 
in  situ  from  a  hydrous  Si02  melt.  The  rate 
of  lowering  of  the  saturated  liquidus  in 
the  interval  2000  to  5000  bars  is  about  22° 
C  per  1000  bars  H2O  pressure,  a  rate  two- 
thirds  of  the  rate  of  lowering  of  the  satu- 
rated liquidus  of  any  feldspar  in  the  same 
interval. 

A  projection  of  the  results  at  2000  bars 
H20  pressure  is  given  in  figure  48.  The 
only  silica  polymorph  found  was  high 
quartz;  the  saturated  liquids  contained 
approximately  6  per  cent  H20  by  weight. 
The  four-phase  point  is  at  922°  ±3°  C,  and 
the  ratio  of  the  solid  phases  at  this  point 
is  CaAl2Si208  37  :  Si02  63. 

Schairer  and  Bowen  (1947)   found  the 


GEOPHYSICAL  LABORATORY        215 


eutectic  of  the  anhydrous  system  to  be  at 
1368°  ±2°  C  and  CaAl2Si208  50.5  :  Si02 
49.5  weight  per  cent.  The  shift  of  this 
point  toward  increasing  Si02  at  low  H20 
pressures  is  a  consequence  of  the  greater 
lowering  of  the  saturated  liquidus  of  the 
silica  polymorphs  cristobalite  and  tridymite 
relative  to  that  of  CaAl2Si208.  A  trend 
toward  a  lower  Si02  content  at  the  four- 
phase  point  was  anticipated  at  pressures 
higher  than  2000  bars  because  at  such  pres- 
sures the  rate  of  lowering  of  the  saturated 


conditions  the  proportion  of  quartz  crys- 
tallizing from  the  liquid  relative  to  feld- 
spar crystals  will  decrease  on  that  large 
portion  of  the  liquidus  where  CaAl2Si2Os- 
rich  plagioclase  is  the  first  feldspar  phase 
to  appear  with  quartz. 

When  a  silica  mineral  and  feldspar  are 
crystallizing  simultaneously,  the  ratio  of 
silica  mineral  to  feldspar  crystallizing  will 
also  vary  with  the  H20  pressure,  increas- 
ing as  the  H20  pressure  increases  to  about 
500   bars   and   decreasing   as   it   increases 


1500 


1400 


1000 


Liquid  +  gas 


PH2Ol2000barS 


1500 


1400 


Anorthite  +  liquid  +  gas 


Anorthite  +   /3quartz    +    gas 


j 1 L 


CoAI2Si202 


20  30  40  50  60 

Weight   per  cent 


70 


80 


90 


-  800 
Si02 


Fig.  48.    Projection  of  the  ternary  system  CaAl2Si208-Si02-H20  at  2000  bars  H20  pressure. 


liquidus  of  anorthite  with  increasing  H20 
pressure  is  greater  than  the  rate  of  lower- 
ing of  the  saturated  liquidus  of  quartz. 
Preliminary  results  on  the  four-phase  point 
at  5000  bars  indicate  a  shift  toward  a  lower 
ratio  of  Si02  and  suggest  that  the  ratio 
is  close  to  An  42  :  Si02  58.  A  similar  shift 
of  the  four-phase  point  toward  Si02  at  low 
H20  pressures  and  reversal  at  higher  pres- 
sures was  shown  by  Tuttle  and  Bowen  in 
the  systems  NaAlSi308-Si02-H20  and 
KAlSi308-Si02-H20.  The  ratio  of  Si02 
to  CaAl2Si208  is  greater  than  that  for 
either  NaAlSisOs  or  KAlSi308  at  corre- 
sponding pressures.  Accordingly,  during 
isobaric  crystallization  under  equilibrium 


above  this  pressure.  These  relations  sug- 
gest a  possible  geological  barometer  for 
H20  pressure.  The  difference  between  the 
Si02  content  at  the  field  boundary  in  the 
anhydrous  system  and  the  maximum  ratio 
of  Si02  in  the  corresponding  hydrous  sys- 
tems is  of  the  order  of  10  per  cent,  and 
should  be  easily  detectable  from  the  rela- 
tive abundances  of  silica  mineral  and  feld- 
spar phenocrysts  in  lavas.  In  a  sequence 
of  flows  of  the  same  composition  it  may 
prove  possible  to  use  the  variation  of  the 
ratio  of  these  phenocrysts  to  each  other  as 
a  measure  of  the  H20  pressure  on  the 
magma  chamber  where  the  phenocrysts 
formed,  and  to  demonstrate  a  relation  be- 


216        CARNEGIE  INSTITUTION  OF  WASHINGTON 


tween  the  intensity  of  volcanic  activity  and  clases.    In  view  of  the  occurrence  of  dif- 

H20  pressure.  ferent  structural  modifications  of  plagio- 

Another  application  is  indicated  by  J.  }.  clases  in  rocks,  it  is  important  to  know 
Norton,  of  the  U.  S.  Geological  Survey,  what  differences,  if  any,  exist  between  the 
through  his  detailed  mineralogical  studies  optical  properties  of  the  different  modifi- 
of  the  Hugo  pegmatite.  This  pegmatite  cations.  In  last  year's  report  (Year  Book 
contains  quartz  and  feldspar  in  all  its  55),  it  was  shown  that  the  optic  axial 
zones,  and  Norton's  data  indicate  that  angle  (217)  of  natural  plagioclases  through- 
starting  from  the  wall  zone  the  composi-  out  most  of  the  composition  range  is 
tions  of  successive  zones  of  the  pegmatite,  changed  significantly  by  heat  treatment, 
neglecting  mica,  first  increase  in  Si02  and  2V  is  therefore  a  convenient  measure  of 
then  decrease.  As  the  CaAl2Si208  content  the  structural  state  of  a  plagioclase.  Meas- 
is  low,  these  observations  suggest  that  the  urements  of  the  changes  produced  by  heat 
H2O  pressure  was  changing,  presumably  treatment  in  refractive  indices  and  in  total 
increasing,  during  crystallization  of  the  birefringence  have  now  been  made.  The 
successive  pegmatite  zones.  methods  of  measurement,  described  in  de- 

If   the   effect    of  other    components   is  tail  elsewhere   (in  press),  are  such  as  to 

neglected,  the  fact  that  granitic  rocks  in  give  an  estimated  accuracy  of  ±0.0004  for 

general  plot  near  the  silica-feldspar  field  refractive  indices  and    ±0.0002  for  total 

boundary    of    the    anhydrous    "synthetic  birefringence. 

granite"  system  could  be  taken  to  mean  Ten  samples  of  chemically  analyzed  nat- 
that  the  liquids  from  which  these  granitic  Ural  plagioclases  whose  optical  properties 
rocks  crystallized  formed  at  low  H2O  are  accurately  known  were  heated  either 
pressures.  This  need  not  be  so,  however,  in  tne  dry  way  or  hydrothermally  until 
as  a  similar  position  for  this  boundary  also  X-ray  powder  diffraction  patterns  showed 
occurs  at  H2O  pressures  between  2000  and  them  to  be  inverted  to  the  "maximum" 
5000  bars,  a  value  well  within  geologically  high-temperature  forms.  The  optical  prop- 
probable  limits.  The  Si02  ratio  apparently  erties  were  then  measured  again  by  the 
continues  to  decrease  at  higher  pressures,  same  methods.  The  data  are  shown  in 
so  that  crystallization  of  granitic  rocks  at  fi         49?  wMch  is  j        1    self-explanatory; 

JeT      grlbdedPreSSUreS  the  m°St  imPortant  Point  t0  note  is  that 
TTTf.      1      *             ^aio-^o-^  the  difference  in  Nx  between  the  high- 
Work  in  the  system  CaAl2Si208-Si02-  11                              r           •               r  u*. 
TT^-ii-ii              ••       1              1  and  low-temperature  rorms  is  very  slight 
H20  will  include  quantitative  data  on  the  11          1          •             J     .? 
TT  r\                   £  Jl     v     »j    £         j       j  or  zero  throughout  the  entire  composition 
H2U  content  or  the  liquids  formed  and  .   °                              r  tTt        mi 
mi  •   j-         1         ,1  .          •           ^1  range,  so  that  measurements  or  Nx  will 
will  indicate  how  this  varies  as  the  tern-  ,  "'     ..  . .        .            r   . 

1                    1              n-i      1.      •  give  a  reliable  estimate  or  the  composition 

perature  and  pressure  change.    Ihe  liqui-  r        1     •    1                 n         r  •                    1 

dus  will  be  determined  at  5000  and  10,000  o£  a  P^gioclase  regardless  of  its  structural 

bars.   These  data  will  be  useful  for  quan-  sAtate'    For  plagioclases  more  calcic  than 

titative  aspects  of  the  theory  of  the  effects  An20'  ^  o£  ^  three  refractive  indices 

of  H20  in  silicate  systems.  maY    be    usecL     The  composition    being 

known,  the  structural  state  can  be  deter- 
OPTICAL  PROPERTIES  OF  HEATED  mined  by  the  optical  or  X-ray  methods 
plagioclases  described  in  previous  Year  Books  (54,  55) . 
/.  R.  Smith  Studies   of  natural   plagioclases  by   these 
Optical  measurements  continue  to  be  the  methods  will  undoubtedly  aid  in  the  in- 
most widely  used  method  of  determining  terpretation  of  the  crystallization  and  cool- 
compositions    of    the    ubiquitous    plagio-  ing  history  of  many  rocks. 


GEOPHYSICAL  LABORATORY        217 


0.0140 
0.0130 
0  0120 
0  0110 
0.0100 
0.0090 
0.0080 
0.0070 


1.560 


i  i  i  i  i  I  1 1 1  1 1 1  1 1 1 1 1  1 1  i  i  1 1  1 1  i  i  i  i  1 1 1 1  1 1  I  1 1 1 1  1 1 1 1  i  |  i  1 1 1 1  i  i  1 1  1 1  1 1 1 1 


I  580 


.550 


1.540 


1.530 


Refractive     indices 


I  320   '  '  '  ]  '  '  '  '  '  '  '  '  '  '  ' 


I  '  I  i  i  i  i  :  i  I  i  i  I  i  i  I  i  i  i  I  I  i  I I  i  I  I  i  I  i  i  I  i  I  I  I  I  I  i  I  I  I  I  I  i  I  I  i  i  I  I  I  I  I  I  I  I  I  I  I 


I  560 


0 


10 


30 


40 


50 


60 


70 


80 


90 


100 


Mole  per  cent  anorthite 


Fig.  49.  Light  lines  are  total  birefringence  and  refractive  indices  of  natural  plagioclases  from 
large  plutonic  intrusions.  The  circles  and  the  heavy  lines  represent  total  birefringence  and  refrac- 
tive indices  of  some  of  the  same  plagioclases  after  they  had  been  inverted  to  the  "maximum"  high- 
temperature  modifications  by  heating. 

THE  CRYSTALLIZATION  OF  ROCK-FORMING  MINERALS  FROM 
MAGMAS  AND  THE  NATURE  OF  THE  RESIDUAL  LIQUID 

/.  F.  Schairer 


All  the  important  rock-forming  minerals 
of  the  igneous  rocks,  with  the  exception  of 
quartz,  have  a  variable  composition.  They 
are  solid  solutions  which  undergo  progres- 
sive changes  in  chemical  composition  dur- 
ing progressive  cooling  and  crystallization 
of  the  magma.  Even  when  there  are  no 
interruptions  in  the  cooling  cycle,  there 
are  continuous  or  discontinuous  changes 
in  the  compositions  of  individual  minerals 
and  in  the  kinds  of  minerals  crystallizing 
from  the  liquid  phase.  A  mineral  or  as- 
semblage of  minerals  stable  at  an  early 
stage  in  the  crystallization  process  may 
become  unstable  at  a  later  stage  and  un- 
dergo transformation  to  new  mineral  as- 
semblages with  changes  in  both  chemical 
composition  and  crystal  system.  Because 
of  the  very  complexity  of  the  mutual  melt- 
ing and  stability  relations,  much  informa- 


tion can  be  gleaned  from  the  nature  of  the 
minerals  and  mineral  assemblages. 

Two  years  ago  (Year  Book  54,  pp.  141- 
142)  we  discussed  the  relations  between 
early-  and  late-crystallizing  minerals  from 
melts  and  the  nature  of  residual  liquids 
from  crystallization.  During  the  past  year 
we  have  acquired  specific  information  on 
mineral  assemblages,  the  direction  of 
change  of  composition  of  the  liquid  phase 
during  crystallization,  and  the  nature  of 
the  residual  liquid  in  a  large  part  of  the 
quaternary  system  Na20-MgO-Al203- 
Si02. 

The  three  volumes  albite-corundum- 
spinel-silica,  albite-forsterite-cordierite-spi- 
nel,  and  albite-cordierite-spinel-silica  con- 
stitute a  large  portion  of  the  regular  (equi- 
lateral) tetrahedron  employed  to  describe 
the    phase-equilibrium    relations    in    the 


218        CARNEGIE  INSTITUTION  OF  WASHINGTON 


quaternary     system     Na20-MgO-Al203-  piercing  points  of  curved  lines  within  the 

Si02.  These  volumes  include  that  portion  tetrahedron  in  the  plane  (join)  which  the 

of  the  quaternary  system  of  most  interest  particular  diagram  represents.  Along  these 

to  the  geologist  or  petrologist  who  is  con-  curved  lines,  three  curved  surfaces  (faces 

cerned  with  the  origin  of  igneous  rocks  or  of  adjacent  primary  phase  volumes)  inter- 

with   the   mineral   assemblages   of   meta-  sect.  Such  a  curved  line  is  called  a  quater- 

morphic  rocks.   All  the  crystalline  phases  nary    univariant   line   or    quintuple    line, 

found  in  these  volumes  are  common  rock-  Along  such   univariant  lines  three  solid 

forming  minerals  or  accessory  minerals  of  phases  are  in  equilibrium  with  the  liquids 

either  igneous  or  metamorphic  rocks.  whose  compositions  lie  on  such  lines.   In 

That  portion  of  the  quaternary  system  figures  50,  51,  and  52,  light  lines  show 
lying  between  albite,  corundum,  forsterite,  contours  of  temperature  (isotherms) . 
spinel,  and  silica  is  being  studied  by  a  series  Figure  50  shows  the  phase-equilibrium 
of  triangular  joins.  Some  years  ago  at  this  relations  in  the  join  albite-cordierite-silica. 
Laboratory  Greig  made  a  reconnaissance  This  join  cuts  the  phase  volumes  of  mul- 
of  the  system  albite-forsterite-silica,  a  lite,  cordierite,  spinel,  albite,  tridymite,  and 
ternary  system  within  this  quaternary  sys-  cristobalite.  Three  univariant  lines  pierce 
tern  (unpublished  data  of  J.  W.  Greig).  this  join  at  the  points  C,  G,  and  I,  re- 
He  located  two  ternary  invariant  points,  spectively.  The  point  /  is  a  ternary  eutectic, 
albite  +  forsterite  +  magnesium  metasilicate  and  is,  therefore,  a  temperature  maximum 
+  liquid  and  albite  +  tridymite  +  magne-  on  the  univariant  line  albite  +  cordierite  + 
sium  metasilicate  +  liquid,  which  lie  quite  tridymite + liquid.  The  point  F  is  the 
close  in  composition  to  the  binary  side  line  binary  eutectic  albite  +  cordierite  +  liquid, 
albite-silica.  During  the  past  year  we  pre-  Mixtures  whose  compositions  lie  near  the 
pared  an  extensive  series  of  melts  in  three  ternary  eutectic  are  viscous  and  quite  diffi- 
triangular  joins;  we  present  the  data  on  cult  to  crystallize  completely.  They  require 
them  now.  runs  of  several  weeks'  duration  to  attain 

In   figures  50,  51,   and  52,  the  phase-  equilibrium  between  crystals  and  liquid, 

equilibrium  data  obtained  by  the  method  Experiments  are  still  in  progress  to  locate 

of  quenching  are  presented  graphically,  the  position  and  temperature  of  point  / 

In  these  figures,  open  double  circles  repre-  more  accurately. 

sent  the  compositions  of  chemical  com-         Figure  51  shows  the  phase-equilibrium 

pounds,  and  black  dots  represent  the  com-  relations  in  the  join  albite-forsterite-cordi- 

positions  of  mixtures  studied.    The  dia-  erite.  This  join  cuts  the  phase  volumes  of 

grams   are   divided  into   areas  by   heavy  forsterite,  albite,  spinel,  mullite,  and  cordi- 

curves.   The  areas  labeled  mullite,  cordi-  erite.  This  last  phase  volume  is  cut  twice 

erite,  spinel,  albite,  etc.,  are  plane  sections  by  this  join.  Three  univariant  lines  pierce 

of   phase   volumes    (with    curved   faces)  this  join  at  the  points  N,  0,  and  P,  re- 

within  the  tetrahedron  in  the  join  which  spectively.  The  point  P  is  a  ternary  eutectic 

the  particular  diagram  represents.    Each  and  is,  therefore,  a  temperature  maximum 

phase  volume  within  the  tetrahedron  gives  on  the  univariant  line  albite  +  forsterite + 

the  compositions  of  all  quaternary  liquids  cordierite  +  liquid.    The  point   Q   is   the 

(one  liquid  phase)  in  equilibrium  with  a  binary  eutectic  albite  +  forsterite + liquid, 
single  crystalline  phase.  The  heavy  curves         Figure  52  shows  the  phase-equilibrium 

on  the  joins  are  traces  of  the  curved  bound-  relations    in    the    join    albite-magnesium 

ary  surfaces  between  two  adjacent  primary  metasilicate-cordierite.   This  join  cuts  the 

phase  volumes  within  the  tetrahedron  in  phase    volume    forsterite,    protoenstatite, 

the  plane  (join)  which  the  particular  dia-  albite,  cordierite,  spinel,  and  mullite.  Three 

gram  represents.  Where  three  heavy  curves  univariant   lines   pierce   this   join  at  the 

meet  at  a  point  in  the  join,  these  points  are  points  U,  V ,  and  W,  respectively. 


GEOPHYSICAL  LABORATORY        219 


H  /062*3" 
3° 


CORDIERITE 

2Mg0.2AI?03.5SiO; 


40  SO  60D  70 

/374*3° 
WE/  GHT     PERCEN  T 


80  E  90  F     ALBITE 

tests'    ,098+3°  Na20  AI203.6SiO2 


Fig.  50.    Equilibrium  diagram  of  the  join  albite-cordierite-silica,  showing  compositions  studied, 
primary  phase  volumes  cut  by  this  join,  piercing  points  of  quaternary  univariant  lines,  and  isotherms. 


CORDIERITE 
.   @2Mg0.2AI203.5Si02 

/468t?jt\m  \ 

/O, 
/44S*2J\ 

20k 

I    \V 

\  °  \  A 

WW 

I890±20\ 
FORSTERITE 
2MgO.Si02 


40  SO 

WE/GHT     PERCENT 


1098*3"'  ALB  IT E 

Na20.AI20,.6Si0, 


Fig.  51.    Equilibrium  diagram  of  the  join  albite-forsterite-cordierite. 


220        CARNEGIE  INSTITUTION  OF  WASHINGTON 


The  data  just  presented  on  three  triangu- 
lar joins  indicate  within  approximate  limits 
the  temperatures  and  compositions  of  seven 
quaternary  invariant  points  and  describe 
the  crystallization  behavior  of  compositions 
in  the  volumes  albite-corundum-spinel- 
silica,  albite-forsterite-cordierite-spinel,  and 
albite-cordierite-spinel-silica.  The  relations 
between  univariant  lines  and  ternary  and 
quaternary  invariant  points  are  shown 
diagrammatically  in  figure  53.    All  uni- 


A,  B,  C,  and  D  from  the  other  quater- 
nary invariant  points  and  that  D  is  the  crys- 
tallization goal  of  the  liquid  in  the  vol- 
ume albite-corundum-spinel-silica;  simi- 
larly, that  the  temperature  maxima  in  CE 
and  EF  separate  the  quaternary  invariant 
point  E  from  the  other  quaternary  invari- 
ant points  and  that  E  is  the  crystallization 
goal  of  the  liquid  in  the  volume  albite- 
forsterite-cordierite-spinel;  and,  similarly, 
that  the  temperature  maxima  in  EF  and 


CORDIERITE 

^2Mg0.2Ai203.5Si02 


Mg  METASILICATE  /a 

MgO.Si02 


WEIGHT     PERCENT 


-1097 ±3°      ALBITE 

Na20.AI203.6Si02 


Fig.  52.    Equilibrium  diagram  of  the  join  albite-magnesium  metasilicate-cordierite. 


variant  lines  within  the  tetrahedron  are 
curved  lines.  For  simplicity,  they  are 
shown  as  straight  lines  in  the  figure,  which 
is  not  spatial  but  merely  depicts  the  rela- 
tions of  quaternary  invariant  points  to 
one  another  and  to  certain  ternary  invari- 
ant points  lying  in  a  face  of  the  tetra- 
hedron. The  lengths  of  the  univariant  lines 
in  figure  53  are  arbitrary  and  without  sig- 
nificance. Arrows  on  the  univariant  lines 
indicate  the  direction  of  falling  tempera- 
ture. 

An  examination  of  figure  53  shows  that 
the  temperature  maxima  in  CE  and  DG 
separate  the  quaternary  invariant  points 


DG  separate  the  quaternary  invariant 
points  F  and  G  from  the  other  quaternary 
invariant  points  and  that  G  is  the  crystal- 
lization goal  of  the  liquid  in  the  volume 
albite-cordierite-spinel-silica. 

An  examination  of  figure  50  shows  that 
the  ternary  eutectic  albite  +  cordierite  + 
tridymite  +  liquid  (/  of  fig.  50)  lies  very 
close  in  temperature  and  composition  to  the 
binary  eutectic  albite  +  tridymite  +  liquid 
(H  of  fig.  50).  An  examination  of  figure 
53  and  a  study  of  the  tetrahedral  model  of 
the  quaternary  system  shows  that  both  D 
and  G  (fig.  53)  must  also  lie  close  in  tem- 
perature and  composition  to  each  other 


GEOPHYSICAL  LABORATORY        221 


(MgO-AI203-3i02) 

146015° 


(MgO-AI203-Si02) 

i -^ 


SAP 
CORD 


(Na20-Al203-Si02) 


(AB-COR-SP) 


AB 
COR 


145315° 


1104+3° 


AB 

COR 

MU 


/ 


AB 
COR 
MU 
SP 


AB 

MU 


(MgO-AI203-Si02)  )4I575±5 


COR 

MU 
SP 


(AB-FO-SP) 


FO 
SP 


1360  +  5° 


FO 
PR 


(MgO-AI203-Si02) 


MU 

CORO 

SAP 


MU 

CORO 

SP 


MU 

CORO 

SAP 

MU  (Mg°-Al203-Si02) 

<SAP £ 

148213° 

(No20-AI203-Si02) 
►  1050110° 


AB 
MU 
TR 


kSP 


/ 


MU 
CORO 
SP 
AB 


MU 
CORO 


AB 

MU 
TR 
CORO 

MU 
..  TR 


(MgO-AI203-S'02) 
_f  144315° 


AB 

CORO 
*SP 


/ 


AB 

CORO 
SP 
FO 


FO 
CORD 


137015° 


(MgO-Ai203-Si02) 


AB 
■  CORO 
,  FO 

AB 

CORO 
^/FO 
p     PR 


AB 
CORO 


A8 

TR 
CORD 


AB 
TR 

CORD 

PR       AB 
PR 


TR 


(A6-F0-SiG2) 


CORD 

PR 

TR 


g©  134515° 
(MgO-Al203-Si02) 


(AB-FO-Si02) 


Fig.  53.  Diagram  showing  univariant  lines  and  their  relation  to  ternary  invariant  points  (small 
black  dots  and  letters  a  through  /')  in  the  limiting  systems  to  quaternary  invariant  points  (large  black 
dots  and  capital  letters).  These  lines  and  points  do  not  lie  in  a  plane.  Only  their  relations  to  one 
another  are  shown  in  this  diagram,  which  is  not  intended  to  depict  their  angular  spatial  relations. 
The  length  of  the  lines  and  the  position  of  a  temperature  maximum  on  a  line  are  arbitrary  and 
without  significance.  Arrows  indicate  the  direction  of  falling  temperature.  Abbreviations  for  crys- 
talline solid  phases  along  the  lines  and  at  the  points:  AB,  albite;  COR,  corundum;  MU,  mullite; 
SP,  spinel;   CORD,  cordierite;  SAP,  sapphirine;   TR,  tridymite;  FO,  forsterite;  PR,  protoenstatite. 


222        CARNEGIE  INSTITUTION  OF  WASHINGTON 


and  to  the  ternary  eutectic  albite  +  cordier- 
ite  + liquid.  Thus  we  see  that  during 
crystallization  all  compositions  in  two  large 
volumes  albite-corundum-spinel-silica  and 
albite-cordierite-spinel-silica  proceed  to- 
ward a  similar  goal  for  the  composition  of 
the  residual  liquid.  This  goal  is  a  soda 
granite  in  composition  in  these  potash- 
and  lime-free  mixtures. 

Some  of  the  liquids  in  the  two  volumes 
just  discussed  are  not  too  far  removed  from 
possible  magmas.  The  "simplified  mag- 
mas" in  Na20-MgO-Al203-Si02  are,  o£ 
course,  anhydrous  instead  of  having  at 
least  a  small  water  content.  There  is  only 
soda  present  with  potash  lacking,  only 
magnesia  present  with  ferrous  oxide  lack- 
ing, and  only  alumina  present  with  ferric 
oxide  lacking;  there  is  no  lime.   In  spite 


of  these  deficiencies,  it  can  be  seen  that  a 
large  range  of  rock-forming  compositions 
would  give  a  common  end  product  of 
crystallization,  particularly  if  differentia- 
tion proceeded  by  fractional  crystallization. 
Note  the  significant  fact  that  this  same  end 
product,  a  soda  granite,  would  be  reached 
even  if  these  simplified  magmas  were  con- 
taminated with  numerous  small  fragmen- 
tal  xenoliths  of  basic  rocks  such  as  peri- 
dotites  or  dunites,  or  if  they  were  con- 
taminated by  assimilation,  in  whole  or  in 
part,  with  xenoliths  of  highly  aluminous 
sediments. 

Thus  these  studies  of  soda-bearing  melts 
add  further  quantitative  evidence  to  sup- 
port Bowen's  arguments  for  the  impor- 
tance in  petrogenesis  of  KAlSiCX-NaAl- 
Si04-Si02  as  "petrogeny's  residua  system." 


GRANITIC  PEGMATITES 


P.  M.  Orville 


The  origin  of  granitic  pegmatites  and 
the  unusual  textures  and  structures  within 
them  have  been  the  subject  of  geological 
investigation  and  speculation  for  many 
years.  Recent  laboratory  investigations  in 
the  Ab-Or-Si02-H20  ("synthetic  gran- 
ite") system  enable  the  course  of  crystal- 
lization in  melts  which  closely  approxi- 
mate the  granitic  pegmatites  in  composi- 
tion to  be  considered  on  a  quantitative 
basis. 

Pegmatites  enriched  in  potassic  feldspar 
in  their  upper  portions  are  common  in  the 
Black  Hills,  South  Dakota;  Pala,  Cali- 
fornia; Colorado;  New  England;  and  the 
southern  Appalachian  states.  In  1954  at 
Yale  University  a  study  of  a  complex  of 
layered  pegmatites  in  the  southern  Black 
Hills,  South  Dakota,  showing  such  a  dis- 
tribution of  potassic  feldspar,  was  begun 
in  the  hope  that  the  field  and  laboratory 
data  together  might  lead  to  an  under- 
standing of  the  process  by  which  this 
segregation  took  place. 

The  pegmatites  studied  are  thin,  steeply 
tabular  bodies  separated  parallel  to  their 
median  plane  into  an  upper  unit  contain- 


ing large  perthitic  microcline  crystals  set 
in  a  fine-grained  plagioclase-quartz  matrix 
and  a  lower  unit  consisting  of  plagioclase- 
quartz-muscovite  aplite.  Such  sharply  lay- 
ered pegmatite  dikes  are  gradational  into 
dikes  having  a  uniform  composition  and 
aplitic  texture  from  wall  to  wall  and  a 
mineralogic  and  bulk  chemical  composi- 
tion identical  with  that  of  the  layered 
pegmatites. 

The  bulk  compositions  of  the  pegmatites 
(neglecting  muscovite)  fall  on,  or  very 
near,  the  field  boundary  between  the 
quartz  and  alkali  feldspar  fields  approxi- 
mately halfway  between  the  "granitic  mini- 
mum" composition  and  the  Ab-Si02  side 
line  of  the  liquidus  in  the  system  Ab-Or- 
Si02-H20  at  2000  bars.  The  composition 
of  the  upper  unit  corresponds  closely  to 
the  composition  of  the  minimum  in  the 
synthetic  granite  system  at  this  pressure, 
and  the  composition  of  the  lower  unit 
falls  near  the  Ab-Si02  side  line  on  the 
quartz-alkali  feldspar  field  boundary. 

The  presence  of  a  few  per  cent  An  in  the 
melt  raises  the  crest  of  the  ternary  feldspar 
solvus  by  a  large  amount,  and  the  solvus 


GEOPHYSICAL  LABORATORY        223 


intersects  the  liquidus  within  a  short  dis- 
tance of  the  Or-Ab  side  line  (Yoder,  Stew- 
art, and  Smith,  this  report).  The  plagio- 
clase  from  these  pegmatites  is  a  calcic 
albite  (Ab93An7),  and  this  amount  of  An 
may  be  sufficient  so  that  crystallization 
of  two  feldspars  takes  place  from  the 
magma. 

It  is  possible  that  the  separation  of  these 
pegmatites  into  two  compositional  units 


is  the  result  of  fractional  crystallization  of 
a  hydrous  silicate  melt.  The  aplitic  unit 
might  represent  the  first  stage  of  crystal- 
lization as  quartz  and  albite  crystallize  to- 
gether along  the  quartz-plagioclase  field 
boundary.  The  coarse-grained  unit  con- 
taining potassic  feldspar  might  represent 
the  crystallization  of  the  rest  liquid  that 
approaches  the  composition  of  the  synthetic 
granite  minimum. 


PYROXENES 


For  a  petrologist  concerned  with  the 
genesis  of  igneous  and  high-grade  meta- 
morphic  rocks  there  is  no  more  important 
system  than  the  pyroxene  quadrilateral 
MgSiOs-CaMgSisOe-CaFeSisOe-FeSiOs. 
Pyroxenes  whose  compositions  (neglecting 
minor  components)  lie  in  this  quadri- 
lateral are  major  constituents  of  basalts, 
gabbros,  andesites,  and  important  groups 
of  metamorphic  rocks  such  as  the  iron 
formations.  Rhyolites  often  contain  iron- 
rich  pyroxenes  in  minor,  though  geneti- 
cally significant,  amounts.  The  pyroxenes 
also  form  monomineralic  and  bimineralic 
aggregates  in  the  pyroxenites  and  perido- 
tites.  Laboratory  study  of  the  pyroxenes 
will  not  only  provide  quantitative  data 
about  the  physical  conditions  under  which 
these  rocks  have  formed  but  will  also  give 
us  a  better  understanding  of  the  courses 
of  chemical  fractionation  in  magmas. 

The  importance  of  pyroxenes  has  long 
been  recognized  by  experimental  penolo- 
gists. The  melting  relations  along  the  join 
MgSi03-CaMgSi206  were  first  studied  at 
this  Laboratory  in  1914.  The  joins 
CaFeSisOe-FeSiOs  and  MgSi03-FeSi03 
have  been  studied  more  recently.  Investi- 
gations along  the  side  lines  of  the  quadri- 
lateral MgSi03-CaMgSi206-CaFeSi206- 
FeSiOs  have  yielded  data  of  vital  interest, 
but  inasmuch  as  most  natural  pyroxene 
compositions  fall  well  within  the  quadri- 
lateral the  major  gains  have  yet  to  be  made. 

It  is  our  intention  to  carry  through  a 
study  of  both  the  melting  and  subsolidus 
equilibria  in  the  entire  quadrilateral.  The 


/.  F.  Schairer  and  F.  R.  Boyd,  Jr. 

data  discussed  below,  on  the  join  MgSiOs- 
CaMgSi206,  represent  our  initial  effort  in 
what  will  be  a  continuing  program  in  com- 
ing years. 


THE  JOIN  MgSiO;r-CaMgSi206 
F.  R.  Boyd,  Jr.,  and  J.  F.  Schairer 

The  crystal-liquid  equilibria  along  the 
join  MgSi03-CaMgSi206  were  determined 
many  years  ago  by  Bowen  (1914)  in  his 
study  of  the  system  forsterite-diopside- 
silica.  Bowen's  work  has  been  checked  in 
detail  and  found  to  be  substantially  ac- 
curate. We  have  determined  liquidus  tem- 
peratures on  compositions  between  MgSi03 
and  CaMgSi2Oe  prepared  at  5  weight  per 
cent  intervals.  All  our  data  lie  precisely 
on  the  curves  of  Bowen.  For  those  com- 
positions with  a  forsterite  liquidus  we  have 
determined  the  temperature  of  appearance 
of  pyroxene.  These  data  are  in  agreement 
with  those  interpolated  from  Bowen's  data. 
The  beginning  of  melting  was  determined 
for  all  these  compositions,  and  the  results 
check  those  of  Bowen  closely. 

Atlas  (1952)  has  investigated  the  sub- 
solidus region  in  the  system  MgSiOs- 
CaMgSi2Oe  using  a  lithium  fluoride  flux. 
Our  work  confirms  that  of  Atlas  on  the 
existence  and  approximate  position  of  the 
solvus.  Our  locations  of  the  solvus  curves 
differ  from  those  in  the  Atlas  diagram 
largely  in  that  we  have  found  that  the 
solvus  intersects  the  solidus;  i.e.,  there  is 
not  a  complete  solid  solution  between 
MgSiOs  and  CaMgSi2Oe. 


224        CARNEGIE  INSTITUTION  OF  WASHINGTON 


Our  work  on  the  join  MgSiOs- 
CaMgSi206  is  not  yet  finished.  We  have 
presented  in  figure  54  only  those  portions 
of  the  subsolidus  diagram  that  we  think 
are  unlikely  to  undergo  any  further  modi- 
fication. Our  principal  uncertainty  re- 
mains the  relations  involving  the  various 
polymorphs  of  MgSiOs. 

We  have  used  a  variety  of  techniques 
in  determining  the  subsolidus  phase  rela- 


liquid   or  crystals  +  liquid 


orfhoenstatite  ♦  diopside 


Q  Point  on  so'vus  boundary  I 

Q  Point  on  solvus 
^     ot  500  bars    n 
Q*  Solvus  boundory  li 

a  Single-phase  njn    .  dry 

0  Single -phase  njn  ,  500  bars   H-0 


to  about  1200°  C  on  the  diopside  side  of  the 
solvus  and  down  to  about  1100°  C  on  the 
enstatite  side. 

The  determinations  of  compositions  of 
phases  along  the  solvus  curves  have  been 
made  by  X-ray  methods.  We  have  devel- 
oped four  curves  relating  X-ray  spacing  to 
composition  in  this  system.  Two  of  these, 
which  have  proved  to  be  superior  in  prac- 
tice and  have  been  used  almost  exclusively, 
are  presented  in  figures  55  and  56. 

Figure  55  shows  the  variation  in  spacing 

of  the  311  peak  in  diopside  as  a  function 
of  composition.    This  curve  is  linear  be- 


MgSiOj       K>  20  30  40  50  60 

Weight  per  cent 


70 


90       CoMqSi206 


Fig.  54.  Subsolidus  diagram  of  the  system 
MgSi03-CaMgSi206. 

tions  along  this  join.  Runs  on  the  solvus 
curves  (A,  B,  C,  and  D  in  fig.  54)  have 
been  made  dry  in  the  temperature  range 
between  1100°  and  1400°  C.  Runs  have 
been  made  in  hydrothermal  quenching 
apparatus  from  a  temperature  of  1150°  C 
down  to  about  850°  C.  We  have  also  used 
a  heating  stage  on  an  X-ray  diffractometer 
up  to  a  temperature  of  about  1350°  C. 

Our  starting  material  for  both  dry  and 
hydrothermal  runs  has  generally  been 
glass.  We  have,  however,  been  able  to 
unmix  homogeneous,  crystalline  phases 
(prepared  at  temperatures  just  below  the 
solidus  temperature)  at  temperatures  down 


Fig.  55.  Variation  of  the  311  spacing  of  di- 
opside with  composition  in  the  system  MgSiOs- 
CaMgSi2Oe. 

tween  Dig5En5  and  DieoEn4o.  Between 
DigsEns  and  pure  diopside  there  is  an 
abrupt  change  in  slope,  which  does  not  ap- 
pear to  be  an  inversion  since  the  X-ray 
parameters  of  both  pure  diopside  and 
DigsEn5  prepared  hydrothermally  at  about 
900°  C  show  no  significant  differences 
from  the  parameters  of  samples  prepared 
dry  above  1300°  C.  The  solvus  curve 
ceases  to  be  of  interest  in  the  composition 
region  between  DigsEns  and  pure  diopside; 
accordingly,  we  have  not  further  pursued 
the  matter  of  this  break  in  slope. 

Figure  56  shows  the  variation  in  spacing 
with  composition  of  a  clinoenstatite  peak 
at  about  57°  20  CuKa.  This  spacing  has 
been  used  to  determine  the  position  of  the 
solvus  curve  C. 

Points  on  the  solvus  boundaries  deter- 


GEOPHYSICAL  LABORATORY        225 


mined  with  the  aid  o£  these  X-ray  curves 
are  plotted  as  circles  in  figure  54:  open 
circles  represent  data  from  dry  runs;  circles 
with  a  horizontal  bar,  data  from  hydro- 
thermal  runs  at  500  bars  (H20).  Hydro- 
thermal  data  and  dry  data  overlap  at  1150° 
C  on  curve  A.  The  agreement  is  within 
experimental  error.  Along  curves  A  and  B 
each  point  represents  an  average  of  up  to 
five  runs  using,  generally,  two  or  more 


Weight  per  cent  CoMgSi0206 


Fig.  56.  Variation  of  a  clinoenstatite  spacing 
with  composition  in  the  system  MgSi03- 
CaMgSi2Os. 

bulk  compositions.  The  spread  of  data  at 
a  given  temperature  is  seldom  more  than 
2  per  cent  in  composition.  Along  curve  C 
we  have  had  trouble  with  X-ray  interfer- 
ence from  the  coexisting  diopside  phase, 
and  only  bulk  compositions  in  the  two- 
phase  region  closest  to  the  solvus  curve 
were  used  to  fix  its  composition. 

We  have  checked  our  locations  of  the 
solvus  curves  by  making  runs  in  the  single- 
phase  regions  close  to  the  curves  over  a 
wide  range  in  temperature.  These  runs 
are  indicated  in  figure  54  by  squares  or 
rectangles.  The  agreement  in  X-ray  spac- 


ing of  these  runs  with  those  made  at 
1365°  C,  just  below  the  solidus,  has  been 
within  X-ray  error  (about  ±0.02°  20). 

There  is  a  pronounced  change  in  slope 
of  the  solvus  boundary  on  the  diopside  side 
at  about  1075°  C.  It  is  probably  produced 
by  the  inversion  of  orthoenstatite  to  a 
higher-temperature  form. 

We  have  not  yet  established  a  determina- 
tive curve  for  orthoenstatite  solid  solutions. 
In  the  temperature  range  below  1050°  C, 
however,  diopside  appears  in  our  hydro- 
thermal  runs  whose  composition  is  richer 
in  CaMgSi2Oe  than  EngoDiio.  Curve  D 
must,  therefore,  lie  approximately  as 
shown. 

We  are  not  yet  sure  of  the  stable  crystal- 
line form  of  the  pyroxene  in  the  single- 
phase  region  bordering  curve  C.  In  dry 
runs  bordering  curve  C  we  have  generally 
obtained  clinoenstatite;  in  hydrothermal 
runs  (all  below  1100°  C)  we  obtain  proto- 
enstatite.  We  have  located  curve  C  by 
means  of  the  clinoenstatite  spacing  in  fig- 
ure 56.  Whatever  form  of  enstatite  turns 
out  to  be  stable  along  curve  C,  it  is  improb- 
able that  the  position  of  the  solvus  curve 
itself  will  have  to  be  modified.  The  inver- 
sions involving  clino-  and  protoenstatite  are 
very  rapid,  whereas  the  unmixing  reaction 
is  relatively  sluggish.  Hence,  it  is  most  un- 
likely that  any  unmixing  takes  place  dur- 
ing inversion  in  the  quench. 

In  our  hydrothermal  studies  on  pure 
MgSi03  we  have  prepared  well  crystallized 
orthoenstatite  and  protoenstatite.  Unlike 
protoenstatite  prepared  dry,  the  hydro- 
thermal  material  shows  little  tendency  to 
invert  to  clinoenstatite.  We  shall  withhold 
our  detailed  results  on  this  aspect  of  the 
problem,  however,  until  we  are  sure  of  the 
stable  fields  of  these  various  polymorphs. 


CHLORITOID 

L.  B.  Halferdahl 

Chloritoid  is  a  geologically  significant  mineralogists.  Many  petrologists  believe 
mineral  which  has  been  described  from  that  it  can  form  only  under  restricted  con- 
many  occurrences,  and  yet  its  properties  ditions,  notably  those  in  which  stress  plays 
and  composition  are  still  disputed  among  a  part,  despite  the  fact  that  its  growth  has 


226        CARNEGIE  INSTITUTION  OF  WASHINGTON 


been  recorded  in  other  geological  environ- 
ments. Some  preliminary  results  of  an  in- 
vestigation of  the  chemical  composition, 
the  optical  and  X-ray  properties,  the  sta- 
bility, and  the  nature  of  the  occurrences  of 
chloritoid  were  reported  last  year.  Addi- 
tional results  are  given  here. 

Five  new  chemical  analyses  of  chloritoid, 
including  one  so-called  "ottrelite"  from 
Salm  Chateau,  Belgium,  and  all  the  other 
available  analyses  that  are  considered  re- 
liable indicate  that  the  composition  of 
chloritoid  can  be  represented  by  the  gen- 
eral formula  FeO  •  Al2Os  •  SiOa  •  HaO  with 
the  following  ranges  in  the  amounts  of 
substitutions  now  on  record : 


Substitution 

Atomic  Per  Cent 

Mg    ->Fe" 

0to40 

Mn    ->Fe" 

0tol7 

Fe'"  -»A1 

OtolO 

F       ->OH 

Less  than  0.25 

Fe'"  -»Fe"H 

Small 

2Fe'"-»3Fe" 

Very  small 

orientation  of  the  optical  indicatrix,  how- 
ever, one  or  even  two  principal  optic  direc- 
tions may  chance  to  lie  in  (001)  with 
neither  coinciding  with  the  b  axis.  There- 
fore, an  observation  that  one  principal 
optic  direction  lies  in  (001)  may  not  be 
sufficient  to  establish  monoclinic  symmetry 
for  the  chloritoid  grain  in  question,  par- 
ticularly if  no  principal  optic  direction  lies 
in  (001)  in  other  grains. 

Optical  measurements  made  on  samples 
of  chloritoid  from  11  localities  including 
both  triclinic  and  monoclinic  polymorphs 
show  that  Z  makes  angles  varying  from 
2°  to  30°  with  the  normal  to  (001).   In 

TABLE  23.  Unit  Cell  Parameters  of 
Chloritoid  Polymorphs 


Locality 


Cstiiaciksaring, 
Turkey 


Chibougamau, 
Quebec 


Polymorph  Monoclinic 


Triclinic 


It  is  important  to  realize  that  these  may 
not  represent  the  maximum  possible 
amounts  of  substitutions.  Nevertheless,  the 
purity  of  the  chloritoid  used  in  all  previ- 
ously published  analyses  showing  more 
than  this  amount  of  manganese  is  subject 
to  question. 

X-ray  investigations  have  revealed  two 
chloritoid  polymorphs  with  the  unit  cell 
parameters  given  in  table  23.  On  a  geo- 
metrical basis  it  is  possible  to  consider  the 
unit  cell  of  the  structure  of  monoclinic 
chloritoid  determined  by  Harrison  and 
Brindley  (1957)  as  consisting  of  two  tri- 
clinic unit  cells  in  a  zigzag  arrangement. 
Such  cells  have  parameters  very  similar  to 
those  of  the  triclinic  chloritoid  from  Chi- 
bougamau, Quebec.  This  structural  rela- 
tionship is  similar  to  that  of  the  clino-  and 
orthopyroxenes. 

Measurements  made  on  the  universal 
stage  show  that  the  orientation  of  the  op- 
tical indicatrix  varies  considerably  in  differ- 
ent grains  of  the  same  chloritoid  sample. 
In  triclinic  chloritoid  no  principal  optic 
direction  is  required  by  symmetry  to  lie 
in  (001).  Because  of  the  variations  in  the 


a    9.48 

b   5.48 

c    18.19 

a   90°  0' 

0   101°  46' 

Y  90°  0' 

G(meas.)    ..  3.79 

G(calc)    ...  3.80 


9.50 
5.48 
9.16 

96°  53' 
101°  49' 

90°  2' 
3.79 
3.79 


the  monoclinic  polymorphs  measured, 
X=b.  In  the  triclinic  polymorphs,  X  and 
Y  make  angles  from  0°  to  30°  with  (001), 
but  in  many  Y  is  closer  to  (001)  than  X. 
The  orientation  of  X  and  Y  with  respect 
to  the  a  and  b  axes  in  triclinic  chloritoids 
was  not  determined,  because  no  crystallo- 
graphic  directions  other  than  the  (001) 
cleavage  were  identified  with  certainty  in 
the  thin  section  and  grain  mounts  of  the 
specimens  studied.  In  chloritoids  from  11 
localities  the  optic  angle  about  Z  ranges 
from  36°  to  125°.  Most,  however,  are 
optically  positive  with  2Vz  in  the  range 
45°  to  60°.  The  refractive  indices  of  chlori- 
toid measured  in  this  study  and  those 
previously  published  show  that  a  varies 
from  1.713  to  1.730,  (3  from  1.719  to  1.734, 
and  y  from  1.723  to  1.740.  All  indices  de- 


GEOPHYSICAL  LABORATORY        227 


crease  with  increasing  magnesium  content 
of  the  chloritoids. 

The  results  of  hydrothermal  experiments 
on  natural  chloritoid  and  on  some  oxide 
mixtures  of  the  chloritoid  composition  are 
presented  in  figure  57.  Because  of  the  slug- 


1        1 

1 

A  L 

1        1 

a  a     a 

1               1 

- 

- 

A  C 

a  a     b 

Chloritoid 

Staurolite    + 

+  Fluid 

Almandine 
+    Hercynite 

+  Fluid 

- 

A 

A  A 

• 

i  a  a      ■ 
/ 
/ 
S 
/ 
/ 

\ 

0 

/         Iron  Cordierite 

\  Hercynite  + 

0 

/           +  Hercynite 
/               +  Fluid 

\    Mullite  + 
\  Liquid  + 
\   Fluid 

-     O                    O    0 

XX                              X 

\ 

-     O                 0            , 

1        1  y 

1 

I        1        1        1 

i     V  i 

Temperature   in  °C 

Fig.  57.  Preliminary  univariant  curves  for  the 
reactions  chloritoid^±iron  cordierite  +  hercynite 
+  fluid  (solid  lines),  chloritoid^±almandine + 
staurolite  +  hercynite  +  fluid  (solid  lines),  iron 
cordierite  +  hercynite  +  fluid^±staurolite  +  alman- 
dine  (long  dashes),  and  iron  cordierite -r-fluid^=± 
mullite  +  liquid  +  fluid  (short  dashes). 

Explanation  of  Symbols 

Runs  made  in  sealed  platinum  tubes  and  one 
in  an  evacuated  glass  tube:  Solid  circle,  chlori- 
toid synthesized  from  mixes  of  oxides.  Open 
circle,  natural  chloritoid  did  not  change.  Cross, 
natural  chloritoid  broke  down  to  iron  cordierite, 
hercynite,  and  fluid;  iron  cordierite  +  hercynite 
synthesized  from  oxide  mixes.  Solid  square, 
natural  chloritoid  broke  down  to  almandine, 
staurolite,  hercynite,  and  fluid;  almandine -f- 
staurolite  +  hercynite  synthesized  from  oxide 
mixes. 

Runs  made  in  co-operation  with  Boyd  and 
England  in  squeezer  apparatus  built  by  them: 
Open  triangle,  natural  chloritoid  persisted.  Open 
square,  natural  chloritoid  broke  down  to  alman- 
dine, staurolite,  hercynite,  and  fluid. 

Solid  rectangle,  point  determined  by  quench- 
ing (Schairer  and  Yagi,  1952). 


gishness  of  the  reactions  at  pressures  below 
10,000  bars  and  the  difficulty  of  controlling 
the  state  of  oxidation,  these  results  must  be 
regarded  as  preliminary.  Nevertheless, 
they  do  provide  an  acceptable  alternative 
to  the  widely  held  belief  that  the  action  of 
stress  at  any  particular  temperature  and 
composition  determines  the  mineral  asso- 
ciations in  regional  metamorphism.  This 
alternative  is  that  the  differences  in  min- 
eralogy between  regionally  metamorphosed 
rocks  and  those  formed  in  contact  aureoles 
may  be  the  result  of  different  pressures 
prevailing  in  the  two  environments.  Thus, 
in  quartz-bearing  rocks  containing  chlori- 
toid, the  reaction  chloritoid  +  quartzrfron 
cordierite  +  fluid  might  be  expected  in  con- 
tact metamorphism,  and  the  reaction 
chloritoid  +  quartz  ^  almandine  +  stauro- 
lite +  fluid  in  regional  metamorphism. 
Chloritoid-cordierite  associations  are  known 
in  the  Vredefort  Dome  area  of  South 
Africa  and  the  Santa  Monica  Mountains  of 
California.  Chloritoid-almandine-staurolite 
associations  are  known  from  many  places 
in  the  Alps  and  from  Unst  in  the  Shetland 
Islands.  At  intermediate  pressures  the 
association  staurolite-cordierite  might  be 
expected.  Such  associations  are  known 
from  the  Lizard  area  of  Cornwall  and 
from  the  contact  aureole  of  the  Bushveld 
complex  in  South  Africa. 

The  conditions  under  which  one  of  the 
chloritoid  polymorphs  will  form  in  prefer- 
ence to  the  other  are  still  unknown.  The 
differences  in  energy  required  to  produce 
one  in  place  of  the  other  are  probably  very 
small,  and,  hence,  could  be  detected  only 
with  very  great  difficulty  by  the  methods 
at  present  available.  Natural  occurrences, 
however,  do  provide  some  clues.  Chlori- 
toids obtained  from  hydrothermal  veins 
and  from  hydrothermally  altered  rocks 
have  been  found  to  be  triclinic.  Chloritoids 
from  regionally  metamorphosed  rocks  have 
been  found  to  be  monoclinic  or  triclinic  or 
both.  Chloritoids  associated  with  alman- 
dine, kyanite,  or  staurolite  are  monoclinic. 
This   information   may   suggest  that  the 


228        CARNEGIE  INSTITUTION  OF  WASHINGTON 


monoclinic  polymorph  forms  more  readily 
than  the  triclinic  under  severe  conditions 
of  pressure  and  temperature,  or  under 
more  moderate  conditions  prevailing  for 
a  long  time. 

Studies  of  chloritoid-bearing  rocks,  pub- 
lished reports  of  chloritoid  occurrences, 
and  phase-rule  considerations  indicate  that 
chloritoid  can  exist  under  certain  conditions 
in  equilibrium  with  one  or  more  of  the 
following  minerals:  quartz,  chlorite,  mus- 
covite,  magnetite,  hematite,  ilmenite,  rutile, 
paragonite,  almandine,  staurolite,  cordi- 
erite,  biotite,  pyrophyllite,  kaolinite,  kya- 
nite,  andalusite,  and  possibly  sillimanite, 
corundum,  diaspore,  glaucophane,  albite, 


anorthite,  epidote,  zoisite,  margarite,  cal- 
cite,  and  siderite.  The  most  common  min- 
eral assemblage  in  chloritoid-bearing  rocks 
is  chloritoid-quartz-chlorite-muscovite-ru- 
tile-iron  oxide,  the  iron  oxide  being  one  or 
more  of  magnetite,  hematite,  ilmenite. 
These  mineral  associations  and  the  en- 
vironment in  which  they  occur — regional 
rnetamorphism,  contact  metamorphism, 
hydrothermal  veins  and  hydrothermally 
altered  rocks,  emery  deposits — give  further 
support  to  the  suggestion  that  stress  plays 
no  greater  part  in  the  formation  of  chlori- 
toid than  in  the  formation  of  such  minerals 
as  muscovite,  andalusite,  pyroxene,  or 
feldspar. 


ALKALI  AMPHIBOLES 

W.  G.  Ernst 


Alkali  amphiboles,  one  of  the  three 
principal  groups  of  amphiboles,  occur  in 
a  wide  variety  of  rock  types.  Riebeckite  is 
an  important  constituent  of  alkalic,  silicic 
igneous  rocks;  it  has  also  been  described 
as  a  low-temperature  authigenic  mineral. 
Glaucophane  and  crossite  (an  intermediate 
member  of  the  riebeckite-glaucophane  se- 
ries) are  abundant  in  certain  metamorphic 
rocks. 

Hydrothermal  study  of  the  riebeckite- 
glaucophane  series  was  initiated  in  1956; 
preliminary  data  are  now  available.  Mag- 
nesian  riebeckite,  Na2Mg3Fe2+3Si8022- 
(OH)2,  and  ferrous  riebeckite,  Na2Fe3+2- 
Fe2+3Si8022(OH)2,  have  been  synthesized, 
and  work  on  these  minerals  as  well  as  on 
magnesian  glaucophane,  Na2Mg3Al2Si8- 
022(OH)2,  is  in  progress. 

With  the  exception  of  magnesian  glauco- 
phane, all  compositions  investigated  con- 
tain iron  capable  of  existing  in  two  oxida- 
tion states;  therefore  the  physical  param- 
eters governing  stability  include  the  partial 
pressure  of  oxygen  as  well  as  the  tempera- 
ture and  total  (H20)  pressure.  Accord- 
ingly, in  experiments  employing  iron- 
bearing  minerals  the  Po2  was  fixed  using 
buffers  as  described  by  Eugster. 

Magnesian       riebeckite.        Preliminary 


Ph2o-T  stability  diagrams  for  Na2Mg3- 
Fe2+3Sis022(OH)2  using  several  Po2  buff- 
ers are  presented  in  figures  58,  59,  and  60. 
Each  diagram  represents  the  intersections 
of  boundary  surfaces  occurring  within  the 
Ph2o-T-Po2  volume  with  the  surface  de- 
fined by  a  specific  buffer,  and  projected 
along  the  Po2  axis  (compare  fig.  13  with 
%•  H). 

All  three  riebeckite  diagrams  exhibit  the 
same  general  sequence  of  phases.  The 
form  of  the  riebeckite  stability  field  is 
similar  to  that  of  other  hydrous  minerals. 
At  low  T  and  at  a  Ph2o  too  low  to  form 
riebeckite,  the  stable  assemblage  consists 
of  one  or  two  iron  oxides,  an  olivine, 
Na20  •  2MgO  •  6Si02,  Na20  ■  5MgO  •  12Si02 
(compounds  previously  reported  in  the 
system  Na20-MgO-Si02  by  Schairer, 
Yoder,  and  Keene),  and  vapor,  except  for 
the  magnetite-hematite  diagram,  where 
acmite  takes  the  place  of  Na20'2MgO' 
6Si02.  At  slightly  higher  temperatures,  the 
assemblage  consists  of  one  or  two  iron  ox- 
ides, Na20  •  5MgO  •  12Si02,  an  olivine,  liq- 
uid, and  vapor.  In  a  still  higher  tempera- 
ture range  the  Na20-5MgO'12Si02  melts 
incongruently  to  orthopyroxene  and  liquid, 
and  the  assemblage  then  becomes  one  or 
two  iron  oxides,  an  olivine,  an  orthopy- 
roxene, liquid,  and  vapor. 


1000 


950 


900 


850 


800 


Hematite  ♦  magnetite  +  forsterite  (?) 
+  Na20-  5MgO-  l2Si02+ 
-liquid  +  vapor 


Hemotite  +  magnetite  +  forsterite  (?) 
+  enstotite  +    liquid  +    vapor 


Riebeckite  +  vapor 


^Hematite  +  mognetite  +  forsterite  D(?) 
+   Na20     5MgO     l2Si02 
+  acmite  +  vapor 


500  1000 

Pressure    H20,  bars 


1500 


2000 


Fig.  58.    Pn2o-T  diagram  for  magnesian  riebeckite  using  the  hematite-magnetite  buffer. 


Magnetite  +  olivine 
+  N020  5MgO-l23i02v 
.+  liquid  +  vapor 


Magnetite  +  olivine  +  hypersthene 
+  liquid  +  vapor 


a     Riebeckite  +  vapor 

a 
a 


Magnetite  +  olivine 
+  Na20-  5MgO-  l2Si02  + 
No20  ■  2MgO  ■  6S1O2  +  vapor 


Pressure  (H20),  bars 
Fig.  59.    Ph2o-T  diagram  for  magnesian  riebeckite  using  the  magnetite-fayalite-quartz  buffer. 


O  850 


1000 

Pressure  (H20).  bars 


2000 


Fig.  60.    Ph2o-T  diagram  for  magnesian  riebeckite  using  the  magnetite-wiistite  buffer. 

229 


230        CARNEGIE  INSTITUTION  OF  WASHINGTON 


The  upper  stability  limit  of  riebeckite  at 
a  given  Ptot  is  elevated  by  increasing  the 
partial  pressure  of  oxygen.  The  iron  in 
the  amphibole  is  predominantly  ferric,  and 
much  of  the  iron  is  bivalent  in  the  high- 
temperature  phases.  During  decomposi- 
tion there  is  an  evolution  of  free  oxygen. 
The  evolution  of  oxygen  results  in  a  vol- 
ume increase,  so  increased  oxygen  partial 
pressure  tends  to  drive  the  reaction  to- 
ward the  assemblage  of  smaller  volume 
(riebeckite) . 

All  phases  containing  MgO  also  contain 
some  FeO,  the  amount  depending  on  the 
bulk  composition  and  Po2  as  well  as  on 
the  temperature  and  total  pressure.  Rie- 
beckite contains  some  ferrous  iron,  too,  and 
breaks  down  over  a  small  temperature 
interval  (approximately  20°).  For  this 
reason,  curves  bounding  the  riebeckite 
fields  in  figures  58,  59,  and  60  define  the 
highest  temperature  at  which  amphibole 
is  stable. 

Na20  •  5MgO  •  12Si02  and  Na20  •  2MgO  • 
6Si02  apparently  increase  their  upper  sta- 
bility limits  as  the  partial  pressure  of  oxy- 
gen declines.  Some  ferrous  iron  is  probably 
incorporated  in  these  minerals.  Oxygen  in 
equilibrium  with  these  compounds  is  used 
up  during  breakdown  (an  oxidation  proc- 
ess   in    regard    to    the    liquid    and    solid 


phases).  Hence  a  diminished  Po2  tends 
to  increase  the  stability  field  of  the  large- 
volume  assemblage  (sodic  silicate  plus 
oxygen) . 

The  experimental  formation  of  riebeck- 
ite in  equilibrium  with  a  melt  rich  in 
Na20  and  Si02  agrees  with  natural  oc- 
currences where  riebeckite  appears  as  a 
magmatic  mineral  in  certain  alkalic,  silicic 
intrusives. 

Ferrous  riebeckite.  Exploratory  runs  on 
the  composition  Na2Fe3+2Fe2+3Si8022- 
(OH)2  using  a  fayalite-magnetite-quartz 
buffer  indicate  that  ferrous  riebeckite 
breaks  down  at  a  temperature  approxi- 
mately 150°  lower  than  the  breakdown 
temperature  of  its  magnesian  analogue. 
Decomposition  products  below  about  1500 
bars  Ph2o  are  fayalite,  acmite,  magnetite, 
quartz,  and  vapor;  above  this  pressure 
riebeckite  melts  incongruently  to  fayalite, 
magnetite,  quartz,  liquid,  and  vapor. 

Magnesian  glaucophane.  Reconnaissance 
runs  on  the  composition  Na2Mg3Al2Si8- 
022(OH)2  have  yielded  an  amphibole 
whose  upper  stability  limit  is  20°  to  80° 
lower  than  that  of  magnesian  riebeckite. 
The  high-temperature  assemblages  include 
forsterite,  albite,  enstatite  (?),  liquid,  and 
vapor. 


RECONNAISSANCE  IN  THE  SYSTEM  FeO-Fe203-Si02-H20 

/.  R.  Smith 


The  problem  of  the  origin  and  subse- 
quent enrichment  and  metamorphism  of 
iron  ores  of  the  Lake  Superior  type  con- 
tinues to  be  of  great  importance  to  eco- 
nomic geologists  and  petrologists.  The 
bulk  compositions  of  many  of  the  ores 
and  related  rocks  lie  close  to  the  quater- 
nary system  FeO-Fe203-Si02-H20.  Ex- 
perimental studies  in  the  FeO-Fe203  bi- 
nary system  have  already  contributed  to 
our  understanding  of  the  conditions  under 
which  the  iron  oxides  might  have  formed, 
but  little  is  known  of  the  stability  relations 
of  ternary  and  quaternary  compounds  in 
the  quaternary  system,  largely  because  of 
the  experimental  difficulties  involved  in 


controlling  the  partial  pressures  of  oxygen 
in  the  presence  of  water  under  pressure. 
The  technique  developed  by  Eugster  of 
using  as  buffers  polyphase  assemblages  for 
which  the  temperature  versus  partial  pres- 
sure of  oxygen  equilibrium  relations  are 
known  offered  a  means  of  investigating 
portions  of  the  system.  It  was  planned  to 
investigate  first  the  stability  fields  of  min- 
nesotaite  (3FeO'4Si02*H20)  and  green- 
alite  (3FeO-2Si02-2H20),  both  of  which 
occur  with  the  iron  ores  of  the  Lake  Su- 
perior region.  Knowledge  of  the  stability 
fields  of  these  minerals  in  terms  of  partial 
pressure  of  oxygen  as  well  as  of  tempera- 
ture  and  water  pressure  would  provide 


GEOPHYSICAL  LABORATORY        231 


further  evidence  of  the  conditions  existing 
during  the  formation  and  later  history  of 
the  ores. 

In  attempts  to  synthesize  minnesotaite 
and  greenalite,  over  100  experiments  have 
been  made  at  temperatures  from  250°  to 
600°  C,  at  total  water  pressures  from  500 
to  30,000  psi,  and  at  various  partial  pres- 
sures of  oxygen.  In  the  experiments  it  was 
found  that,  at  temperatures  above  400°  C 
and  at  a  partial  pressure  of  oxygen  in 
equilibrium  with  iron  and  magnetite, 
fayalite  forms  readily  from  finely  ground 
mixtures  of  silica  glass  and  any  of  the  fol- 
lowing: ferrous  oxalate,  hematite,  magnet- 
ite, wiistite,  or  native  iron.  Silica  in  ex- 
cess of  that  required  by  the  fayalite  formula 
crystallizes  as  quartz.  Small  amounts  of 
phases  other  than  fayalite  and  quartz  ap- 
peared in  the  products  of  these  experi- 
ments: In  charges  which  were  initially 
ferrous  oxalate  and  silica  glass  in  minne- 
sotaite proportions,  a  phase  with  an  atomic 
spacing  of  10.2  A  was  formed  at  tempera- 
tures between  450°  and  600°  C;  when  the 
charge  was  held  for  longer  periods  under 
the  same  conditions,  this  phase  was  re- 
placed by  another  with  an  atomic  spacing 
of  7.2  A,  which  is  similar  to  the  basal  spac- 
ing of  greenalite.  Still  longer  treatment  of 
the  same  material  failed  to  increase  the 
amount  of  the  phase  with  the  7.2-A  spac- 
ing relative  to  the  amount  of  fayalite  and 
quartz,  which  made  up  the  bulk  of  the 
products  of  the  experiment.  Similarly,  in 
experiments  starting  with  native  iron  and 
silica  glass  in  either  minnesotaite  or  greena- 
lite proportions,  at  temperatures  above 
400°  C,  a  total  water  pressure  of  30,000  psi, 
and  a  partial  pressure  of  oxygen  in  equi- 
librium with  iron  and  magnetite,  small 
amounts  of  a  phase  with  an  atomic  spac- 
ing of  13.1  A  form  with  predominant 
fayalite  and  quartz;  these  small  amounts 
persist  after  further  treatment  under  the 


same  conditions,  but  do  not  grow  at  the 
expense  of  fayalite  and  quartz. 

In  experiments  of  long  duration  at  tem- 
peratures between  300°  C  and  400°  C, 
mixtures  of  wiistite  and  silica  glass  with 
an  Fe :  Si  ratio  of  3 : 4  react  to  give  a  green 
isotropic  material  which  has  a  refractive 
index  near  that  of  minnesotaite,  but  which 
gives  no  X-ray  diffraction  pattern,  even 
with  long  exposures  on  the  powder  camera. 
When  this  material  was  held  for  6  weeks 
at  350°  C,  30,000  psi  water  pressure,  and 
a  partial  pressure  of  oxygen  in  equilibrium 
with  iron  and  magnetite,  fayalite  and  silica 
glass  were  obtained.  Fayalite  forms  from 
wiistite  and  silica  glass  mixed  in  greenalite 
proportions  (Fe:Si  =  3:2)  at  temperatures 
as  low  as  315°  C,  in  spite  of  the  high  water 
pressures.  In  experiments  with  other  start- 
ing materials,  such  as  ferrosilicon  alloys, 
ethyl  orthosilicate,  and  colloidal  silica, 
fayalite  was  the  only  identifiable  iron  sili- 
cate formed.  Natural  fayalite  held  for  46 
days  at  250°  C,  30,000  psi  water  pressure, 
and  a  partial  pressure  of  oxygen  in  equi- 
librium with  iron  and  magnetite  showed 
no  sign  of  decomposition. 

Under  the  conditions  of  these  experi- 
ments, it  therefore  appears  either  that 
hydrous  silicates  of  iron  are  unstable  or 
that  fayalite  forms  metastably  and  there- 
after fails  to  react  with  silica  and/or  water. 
In  nature,  fayalite  is  absent  from  rocks 
whose  bulk  compositions  fall  in  or  near 
the  system  FeO-Fe203-Si02-H20,  except 
in  the  highest  grades  of  metamorphism. 
This  makes  it  highly  probable  that  in  the 
experiments  described  above,  especially  in 
those  below  about  500°  C,  fayalite  formed 
metastably,  and  that  equilibrium  was  not 
attained.  Investigation  of  this  geologically 
important  system  under  controlled  pres- 
sures of  oxygen  therefore  remains  a  chal- 
lenging problem. 


232        CARNEGIE  INSTITUTION  OF  WASHINGTON 


ISOGRAD  PROBLEMS  IN  METAMORPHOSED 
IRON-RICH  SEDIMENTS 

H.  S.  Yoder,  Jr. 


The  iron-rich  sediments  are  sensitive  to 
changes  in  pressure  and  temperature;  their 
mineral  assemblages  are,  therefore,  very 
useful  as  indicators  of  metamorphic  grade. 
Ferruginous  sediments,  however,  are  not 
common  rocks,  and  their  metamorphosed 
equivalents  are  even  less  common  on  a 
world-wide  basis.  For  this  reason  the  fer- 
ruginous metamorphic  rocks  have  not  been 
studied  in  the  field  as  intensively  as  those 
derived  from  the  dominantly  magnesian 
and  aluminous  sediments.  The  principles 
obtained  from  field  investigations  of  the 
magnesium-  and  aluminum-rich  rocks, 
however,  and  the  physicochemical  princi- 
ples derived  from  laboratory  studies  of 
analogous  systems,  are  directly  applicable 
to  the  problems  in  the  iron-rich  meta- 
morphic rocks. 

The  metamorphism  of  two  critical  types 
of  iron-rich  sediments,  those  containing 
principally  greenalite  and  those  consisting 
dominantly  of  the  chamosites,  will  be  ex- 
amined in  the  light  of  the  established 
principles.  For  the  most  part  the  rocks 
containing  greenalite  can  be  represented  in 
the  system  FeO-Si02-H20,  and  those  con- 
taining chamosite,  in  FeO-Al203-Si02- 
H20.  The  members  of  the  two  principal 
mineral  groups  have  a  kaolinite-like  struc- 
ture, and  it  is  probable  that  a  complete 
series  of  solid  solutions  exists  between  the 
end  members  greenalite,  Feti+2Si4Oio- 
(OH)8,  and  Fe4+2Ai4Si2Oio(OH)8,  as  yet 
not  named.  Substitutions  of  the  type  Mg— > 
Fe+2,  Fe+3->Al+3,  and  Fe+3-+Fe+2H+1  are 
known,  but  their  extent  has  not  been  de- 
lineated. In  addition,  more  complex  sub- 
stitutions trending  from  trioctahedral  to- 
ward dioctahedral  character  are  possible. 

The  minerals  in  the  FeO-Si02-H20  sys- 
tem are  plotted  in  figure  61,  and  the  tie 
lines  are  those  believed  to  exist  at  room 
temperature,  for  example.  Two  important 
concepts  may  be  obtained  from  a  study  of 
this  diagram.   All  the  possible  phases  are 


present  at  the  lowest  temperatures,  yet  only 
those  assemblages  greenalite  +  quartz  + 
water  (analogous  to  a  sediment)  or  green- 
alite +  fayalite  +  water  (analogous  to  a 
partly  serpentinized  dunite)  are  commonly 
observed.  In  the  sediments,  for  example, 
the  phases  are  in  equilibrium  with  water, 
and,  therefore,  only  those  assemblages  in 
which  water  can  occur  as  a  phase  are  per- 
missible. The  remaining  assemblages  may 
occur  in  environments  where  water  does 
not  exist  as  a  phase. 

The  second  concept  arises  from  a  con- 
sideration of  the  corner  (FeO) .  The  com- 
pound wiistite,  FeO,  which  has  not  been 
found  occurring  naturally,  is  not  stable  be- 
low approximately  570°  C,  and  its  bulk 
composition  is  represented  by  magnetite + 
iron.  In  nature  most  rocks  contain  magnet- 
ite; on  the  other  hand,  native  iron  is  ex- 
ceedingly rare.  For  the  present  purposes, 
therefore,  only  those  assemblages  in  equi- 
librium with  magnetite  will  be  considered. 
Oxygen,  an  important  component  in  the 
iron-bearing  rocks,  is  itself  worthy  of  a 
detailed  discussion.  For  the  present  prob- 
lems, however,  only  a  few  brief  remarks 
are  necessary. 

In  the  tetrahedron  in  the  upper  left  cor- 
ner of  figure  61  are  plotted  the  possible 
phases  in  the  system  Fe-Si-02-H2.  The 
evolution  of  the  Fe-Si-O  face  of  the  tetra- 
hedron may  be  followed  from  the  sche- 
matic diagrams  in  figure  62,  which  is  based 
on  the  work  of  Darken  and  Gurry  (1946). 
The  total  pressures  in  nature  far  exceed 
those  represented  by  the  top  curve  in  fig- 
ure 62,  which  is  less  than  approximately 
10~5  atm.  It  is  seen  in  figure  61  (inset) 
that  the  bulk  compositions  of  rocks  con- 
taining the  silicates  and  magnetite  must 
lie  in  the  tetrahedron  magnetite-fayalite- 
quartz-water.  Here  "water"  represents  the 
homogeneous  gas  phase,  the  composition 
of  which,  although  close  to  H2O,  may  be 
enriched  in  the  component  oxygen  or  the 


GEOPHYSICAL  LABORATORY        233 


component  hydrogen  as  well  as  iron  and 
silica.  If  the  component  oxygen  is  in  ex- 
cess of  that  of  the  saturated  gas  in  equi- 
librium with  magnetite  and  silicates,  all 
the  silicates  and  some  or  all  of  the  magnet- 
ite would  be  oxidized  to  an  assemblage 
of  magnetite  +  hematite  +  quartz  +  gas  or 
hematite  +  quartz  +  gas. 

Consider  a  finely  banded  rock  of  alter- 
nating layers  of  magnetite,  hematite,  and 


it  is  concluded  that  in  these  cases  oxygen 
does  not  diffuse  freely  from  one  layer  to 
another.  In  addition,  James  (1955)  finds 
as  a  result  of  his  field  studies  in  Michigan 
that  the  oxygen  content  of  a  given  layer 
does  not  appear  to  change  with  meta- 
morphism.  A  hematite  +  quartz  layer  per- 
sists through  all  grades  of  metamorphism. 
Since  none  of  the  silicates  with  the  excep- 
tion of  quartz  can  coexist  with  hematite 


H90 


lFeO)/ v 


Quartz 


Fayalite 


FerrosiliteC?) 

MOL   PER   CENT 


SiO, 


Fig.  61.  Projection  of  the  system  fayalite-quartz-water-magnetite  onto  the  FeO-Si02-H20  plane 
at  approximately  room  temperature.  The  composition  FeO  is  represented  by  iron  +  magnetite  at 
this  temperature.   The  inset  shows  the  location  of  the  system  in  the  tetrahedron  Fe-Si-02-H2. 


a  mineral  such  as  greenalite  or  stilpnome- 
lane  which  may  possess  FeO/Fe203  in 
various  ratios.  Only  the  hematite  layer 
could  be  in  equilibrium  with  a  gas  phase 
containing  oxygen  in  excess  of  the  gases 
in  equilibrium  with  magnetite  and  the 
silicates;  the  others  are  prohibited  from 
occurring  with  such  a  gas.  It  is  believed, 
therefore,  that  each  layer  is  in  itself  essen- 
tially a  closed  system  with  regard  to  oxy- 
gen. Under  equilibrium  conditions  all  the 
minerals  may  exist  at  the  same  total  pres- 
sure but  with  varying  oxygen  contents  of 
the  layers.  Since  such  layering  is  common, 


and  a  gas  containing  oxygen  in  excess  of 
that  in  equilibrium  with  magnetite  or 
the  silicates,  no  iron-bearing  silicates  are 
formed  during  metamorphism.  In  beds 
initially  consisting  of  magnetite  +  quartz, 
the  various  iron  silicates  form.  The  gas 
plays  an  important  role  because  it  acts  as 
a  stabilizer  even  though  the  amount  of 
solids  far  outweighs  the  amount  of  gas 
present. 

Considering  only  those  assemblages  in 
equilibrium  with  magnetite,  the  sequence 
of  metamorphic  changes  in  beds  consist- 
ing dominantly  of  greenalite  can  be  de- 


234        CARNEGIE  INSTITUTION  OF  WASHINGTON 


duced.  The  basis  for  the  deductions  is  the  highest  temperature  is  fayalite  +  quartz  + 

general  principle  that  the  thermal  stability  vapor.  At  all  temperatures,  all  assemblages 

of  the  hydrous  minerals  increases  with  de-  are  in  equilibrium  with  magnetite.   Each 

creasing  water  content.   The  first  triangle  of  these  reactions  will  be  marked  by  an 

in  figure  63  is  the  same  as  that  given  in  isograd.  If  the  initial  bulk  composition  of 


3 
UJ 

<r 


TEMPERATURE 


Fig.  62.  Schematic  representation  of  the  assemblages  in  the  Fe-Si-O  system  stable  at  various  tem- 
peratures and  pressures.  The  curves  are  based  on  the  work  of  Darken  and  Gurry  (1946).  The 
stippled  areas  indicate  those  bulk  compositions  for  which  oxygen  exists  as  a  phase. 


figure  61.  With  increasing  temperature 
greenalite  reacts  with  quartz  to  yield  min- 
nesotaite  +  vapor.  Next  greenalite  decom- 
poses. Minnesotaite  reacts  with  fayalite, 
and  grunerite  now  appears  in  the  presence 
of  vapor.  Minnesotaite  breaks  down  at 
higher  temperatures,  and  finally  grunerite 
decomposes.  The  assemblage  stable  at  the 


the  sediment  were  in  the  field  greenalite 
+  quartz  +  water  +  magnetite,  then  the  in- 
dex minerals  to  appear  with  progressive 
metamorphism  would  be  minnesotaite, 
grunerite,  and  fayalite  (or  hypersthene) . 
This  sequence  has  been  observed  in  north- 
ern Michigan  and  elsewhere. 
The  minerals  in  the  FeO-Al203-Si02- 


GEOPHYSICAL  LABORATORY        235 


H2O  system  are  projected  onto  the  FeO-  quartz    is    probably    detrital.     Magnetite 

Al203-Si02  plane  from  H2O  in  figure  64.  may  be  detrital  or  may  be  diagenic  in  ori- 

All  the  phases  that  appeared  in  figure  61  gin,  through  the  reduction  of  hematite  by 

are  projected  onto  the  side  line  FeO-Si02.  organic  means,  for  example.  The  2M  mica 

The  chamosites,  which  are  critical  to  the  arises  from  the  IMd  mica  (illite  or  glau- 


H?0 


(FeO) 


Fayalite 


Grunerite 


Quartz 


(FeO) 


(FeO) 


(FeO) 


(FeO) 


(FeO) 


Fig.  63.  Assemblages  stable  at  successive  elevated  temperatures  in  the  system  (FeO)-Fe304- 
Si02-H20  projected  onto  the  (FeO)-Si02-H20  plane.  The  phase  "H20"  or  "V"  represents  the 
homogeneous  gas  phase. 


formation  of  many  of  these  minerals,  are 
the  low-temperature  polymorphs  of  the 
chlorites  that  lie  along  part  of  the  join 
extending  from  greenalite  to  pseudothu- 
ringite.  At  the  lowest  grade  of  metamor- 
phism,  a  schist  containing  chlorite +  2M- 
muscovite  +  quartz  +  magnetite  is  usually 
recognized  first.  It  is  of  interest  to  examine 
the  source  of  even  these  minerals.    The 


conite)  laid  down  in  the  sediment,  prob- 
ably passing  through  the  stages  IMd— »1M 
-*2M.  It  is  likely  that  when  the  poly- 
morphs of  the  micas  are  examined  more 
closely  an  isograd  may  be  established  to 
mark  the  1M— »2M  transition.  The  iron 
chlorite,  which  has  a  14-A  structure,  arises 
from  the  polymorphic  transition  of  the 
7-A  chamosites,  marking  the  chlorite  iso- 


236        CARNEGIE  INSTITUTION  OF  WASHINGTON 


grad.  It  is  believed  that  the  initial  schist 
is  produced  in  these  ways.  With  increasing 
temperatures,  the  minerals  in  the  schist 
react  and  form  new  minerals. 

Most  field  workers  agree  that  the  first 
new  mineral  to  appear  in  the  chamosite- 
rich  sediments  is  stilpnomelane.  Although 
the  composition  of  this  interesting  mineral 
is  not  known  with  certainty,  its  ferrous  end 
member,  ferrostilpnomelane,  probably  lies 
close  to  5FeO-Al203-7Si02-2H20.  Stilp- 


progressive  metamorphism  of  a  ferrugi- 
nous sediment.  It  may  appear  with  a  pure 
muscovite  as  the  result  of  the  reaction  of 
glauconite  with  a  chlorite  as  given  in  figure 
65,  or  it  may  simply  form  as  the  result  of 
the  reaction  of  a  high-silica  sericite  with  a 
chlorite,  as  suggested  by  Lambert  for  the 
magnesian  biotites. 

The  iron-rich  garnet  almandite  usually 
appears  at  higher  grades  than  biotite.  Al- 
though garnet  is  one  of  the  most  easily 


S1O2  Quartz 
Tridymite 
Cristobalite 


Pyrophyllife 
Montmorillonite 


Minnesotaite 
Ferroonthophyllite 
Grunerite, 
Ferrosilite 


Greenahte 
Ferroantigonte/^' 

Fayalite 


FeO 


Hercynite 
Mole  per  cent 


Fig.  64.    Minerals  in  the  FeO-Al203-Si02-H20  system  projected  onto  the  FeO-Al203-Si02  plane. 


nomelane  presumably  arises  from  the  re- 
action of  an  iron  chlorite  solid  solution 
(along  the  join  greenalite-daphnite)  with 
quartz. 

Chloritoid  is  next  to  appear,  but  it  cannot 
form  in  rocks  containing  stilpnomelane. 
The  join  chlorite-quartz,  which  appears  to 
persist  to  higher  grades  of  metamorphism, 
prohibits  their  association.  For  chloritoid 
to  appear  there  must  be  a  source  of  AI2O3, 
and  diaspore,  boehmite,  and  gibbsite  are 
the  only  possible  sources.  Sediments  con- 
taining large  amounts  of  these  minerals 
are  known.  The  reaction  for  the  formation 
of  chloritoid  might  be,  for  example,  chlo- 
rite +  diaspore  +  quartz. 

A  biotite   usually   appears  next  in  the 


recognized  minerals,  the  precise  nature  of 
the  reaction  leading  to  its  formation  is  not 
readily  observed.  It  is  believed  by  most 
field  investigators  to  form  as  a  result  of 
the  reaction  chlorite  (on  the  join  daphnite- 
pseudothuringite)  +  quartz.  In  the  event 
that  the  chlorite  has  been  consumed  in 
previous  reactions,  the  garnet  may  arise 
with  orthoclase  from  the  reaction  of  musco- 
vite +  biotite  +  quartz.  Orthoclase  normally 
appears  at  higher  grades  of  metamorphism. 
Another  possibility  is  the  reaction  of  biotite 
+  plagioclase,  yielding  garnet  and  musco- 
vite. Some  observers  have  noted  an  in- 
crease in  the  muscovite  content  with  the 
formation  of  garnet. 
Staurolite   (fig.  64)   is  next  to  appear, 


GEOPHYSICAL  LABORATORY        237 


and,  like  chloritoid,  its  presence  depends  on 
a  high  alumina  content.  There  is  some 
doubt  as  to  the  exact  composition  of  stauro- 
lite.  Juurinen's  recent  formula  for  stauro- 
lite, H4Fe4Ali8Si8048,  does  not  balance  in 
charge.  Many  analyses  closely  approach 
FeO-2Al203-2Si02-H20,  but  the  water 
content  is  usually  low  and  the  alumina 


AI203>Fe20j-  (K20«Na20) 


Koolinite 
Pytophyllite 


K20«  No20 


^>Greenah1e 
Celoilomte  Anmie         Fe0-Mg0-Ti02 


MOL    PER    CENT 


Fig.  65.  Projection  of  the  reacting  pairs  glau- 
conite  and  daphnite  which  produce  biotite  and 
muscovite.  The  same  products  may  result  from 
the  reaction  of  a  high-silica  sericite  with  daphnite. 

content  appears  to  be  too  high.  Possibly 
(Fe,Al)+3  is  replacing  Fe+2H+1,  as  in  the 
chamosites.  Staurolite  may  arise  with  gar- 
net as  the  result  of  the  reaction  of  chlori- 
toid +  quartz.    Some   workers   have   sug- 


gested that,  in  those  rocks  in  which  chlori- 
toid is  absent,  staurolite  forms  with  quartz 
at  the  expense  of  garnet  +  kyanite  (the 
reacting  pairs  may  be  visualized  in  fig.  64) . 
The  appearance  of  kyanite  at  the  next 
higher  grade  is  in  some  cases  dependent 
on  the  reverse  of  this  reaction. 

Cordierite  appears  at  the  highest  tem- 
peratures in  the  hornfels  of  the  contact 
aureoles  and  is  absent  or  rare  in  progressive 
regional  metamorphism.  It  is  a  breakdown 
product  of  many  of  the  hydrous  iron  sili- 
cates. 

The  first  appearance  of  an  index  mineral 
as  the  result  of  a  reaction  has  been  taken 
as  the  marker  of  an  isograd.  The  examples 
given  above,  unfortunately,  are  probably 
not  the  only  possible  ways  in  which  an 
index  mineral  may  arise.  It  is  clear  that  the 
specific  reaction  marking  an  isograd  must 
be  stated.  There  is  a  great  need,  therefore, 
for  accurately  identifying  minerals  on  each 
side  of  an  isograd.  It  may  be  more  im- 
portant to  establish  the  disappearance  of 
a  mineral  than  its  appearance,  as  was  em- 
phasized by  Bowen  (1940)  in  his  discus- 
sion of  the  progressive  metamorphism  of 
a  siliceous  dolomite.  Since  most  of  the 
iron  minerals  have  now  been  synthesized 
in  the  laboratory,  quantitative  data  on 
the  principal  reactions  will  doubtless  be 
forthcoming. 


CRYSTALLOGRAPHY 


G.  Donnay 


SYNTHETIC  NEPHELINES 


The  substitution  solid  solution  Nas-^Kar 
AlsSisC^  is  of  particular  interest  because 
of  the  two  transitions  that  occur  at  two 
definite  compositions,  namely  at  x=^Y^ 
and  #  =  2.00,  first  found  by  }.  V.  Smith 
(Year  Book  52,  pp.  53-56).  They  were 
characterized  as  high-order  transitions  in 
a  report  to  the  Third  International  Meeting 
on  Reactivity  of  Solids  (Geophysical  Lab- 
oratory Paper  1264),  which  is  summarized 
in  the  present  Year  Book.  Such  transitions 
differ  from  the  familiar  high-order  transi- 
tions found  in  metallurgical  systems  in 
that  they  are  not  associated  with  changes 


in  temperature  but  accompany  composi- 
tional changes.  Only  preliminary  data  had 
been  obtained  to  locate  the  transition  com- 
position in  the  neighborhood  of  x=l/4.  In 
view  of  the  interest  of  such  high-order 
transitions  in  mineralogical  systems,  addi- 
tional work  was  undertaken  (jointly  with 
J.  F.  Schairer  and  J.  D.  H.  Donnay)  in  an 
effort  to  check  and  refine  previous  results. 
Pure  sodium  nepheline  glass  was  synthe- 
sized and  crystallized  by  being  held,  for 
various  lengths  of  time,  at  different  tem- 
peratures (table  24) .  Cell  dimensions  were 
determined  by  the  method  of  least  squares 
from  X-ray  diffraction  patterns,  obtained 


238        CARNEGIE  INSTITUTION  OF  WASHINGTON 


TABLE  24.    X-Ray  Data  for  Pure  Sodium  Nepheline 

(Synthetic  samples  with  different  thermal  histories) 

NaAlSKL 


Thermal  History,  °  C 


a,  A 


c,  A 


V,A} 


c/a 


1100° 

900° 

900° 

1000° 

1000° 

1050° 

1050° 

1200° 

1200° 

540° 


6  hr 
20  days 
34  days 

6  days 
34  days 

6  days 
34  days 

2  days 
10  days 


(sy 
(s) 
(s) 
(s) 
(s) 
(s) 
(s) 

(S) 

(s) 


2000  bars,  hydrothermal,  1  week  (B) 


9.971f 

8.362f 

720.0f 

0.8386 

9.984 

8.333 

719.3 

0.8346 

9.988 

8.333 

719.9 

0.8343 

9.986 

8.331 

719.5 

0.8343 

9.986 

8.328 

719.2 

0.8340 

9.984 

8.333 

719.3 

0.8346 

9.991 

8.331 

720.2 

0.8339 

9.984 

8.328 

719.1 

0.8341 

9.984 

8.328 

719.1 

0.8341 

9.989 

8.328 

719.6 

0.8337 

#  (B)  Boyd,  (S)  Schairer. 

t  Quenched  high-temperature  form. 


Weight  per  cent  Kp 


Fig.  66.  Change  of  cell  dimensions  (c,  a  in  A;  V  in  A3)  in  solid  solution  Nag^K^AlgSigOga- 
The  lower  abscissa  scale  gives  the  number  x  of  potassium  atoms  per  cell.  The  upper  scale  gives 
the  weight  percentage  of  Kp  in  the  system  Ne-Kp,  where  Ne  stands  for  NaAlSi04  and  Kp  for 
KAlSi04.  Black  circlets,  quenched  high-temperature  form;  white  circlets,  low-temperature  form. 
For  comparison  previous  data   (Geophysical  Laboratory  Paper  1267)   are  shown  by  double  rings. 


GEOPHYSICAL  LABORATORY 


239 


with  the  Norelco  instrument,  usually  for 
two  samples  crystallized  at  the  same  tem- 
perature but  for  different  lengths  of  time. 
The  patterns  yielded  by  the  samples  that 
were  held  at  800°  C  for  at  least  27  days 
show  one  faint  nepheline  line;  they  were 
identified  as  low-carnegieite  patterns.  The 
samples  held  at  900°  C  for  20  days  did  not 
contain  detectable  carnegieite;  those  pre- 


cause  in  one  sample  a  high-temperature 
form  was  obtained  by  quenching;  its  cell 
dimensions  are  #  =  9.971,  c  —  8.362  A,  V  = 
720.0  A3.  Within  the  limits  of  accuracy 
claimed  here  for  the  method  of  cell-dimen- 
sion determination,  we  therefore  have  evi- 
dence for  the  existence  of  two  nepheline 
forms  in  the  temperature  range  considered. 
In  contradistinction  to  albite,  which 


ex- 


TABLE  25.    X-Ray  Data  for  Low-Potassium  Nephelines 
(Synthetic  samples  with  different  thermal  histories) 
Nafi  JCAloSLO 


l8-X1^'X 


8W32 


Wt.% 

KAlSiQ4 


Thermal  History,  °  C 


a,  A 


c,  A 


V,A3 


2.00 0.144 

2.50 0.180 

3.00 0.2165 

3.75 0.270 

4.00 0.289 

5.00 0.361 

6.00 0.434 


1200° 

8  days  ( 

1200°: 

5  days  ( 

1200° 

8  days  ( 

1060°. 

29  days  ( 

1200°. 

6  days  ( 

1200° 

,  72  hr   ( 

1200° 

7  days  ( 

1050° 

12  days  ( 

1100° 

10  days  ( 

1200° 

12  days  ( 

1100° 

10  days  ( 

1200° 

5  days  ( 

1200° 

8  days  ( 

1100° 

7  days  ( 

1200° 

5  days  ( 

1200° 

8  days  ( 

s) 
s) 
s) 

S) 

s) 

s) 
s) 

S) 
S) 
S) 

s) 

S) 
S) 
B) 

s) 
s) 


9.971f 

8.356 

719.4 

9.989 

8.333 

719.7  (a)t 

9.980 

8.333 

719.2  (b) 

9.973t 

8.358 

719.9 

9.977 

8.341 

719.1 

9.970 

8.332 

719.2 

9.977 

8.337 

718.6 

9.985 

8.335 

719.7 

9.966 

8.356 

718.7 

9.971f 

8.358 

719.6 

9.975f 

8.360 

720.4 

9.975f 

8.358 

720.2 

9.969 

8.354 

719.0 

9.963 

8.354 

718.3 

9.971 

8.355 

719.4 

9.968 

8.353 

718.8 

'9.963 

8.347 

717.2  (a) 

9.971 

8.354 

718.8  (b) 

9.976 

8.361 

720.6 

*  (B)  Bowen,  (S)  Schairer. 

t  Quenched  high-temperature  form. 

t(a)1/47minute,  (b)    ^/minute. 

pared  at  1000°  and  1050°  C  for  5  days  or  at 
1200°  C  for  2  days  showed  only  nepheline. 
On  all  the  runs  but  one  the  cell  dimen- 
sions (fig.  66)  were  found  to  be:  a— 9.986 
±0.005,  <r= 8.331  ±0.004  A,  V= 719.5  A3. 
The  numerical  value  of  a  ranges  from 
9.984  to  9.991;  that  of  c,  from  8.328  to  8.333. 
A  sample  of  pure  sodium  nepheline  crystal- 
lized (by  F.  R.  Boyd)  hydrothermally  at 
540°  C  and  2000  bars  for  1  week  gave  cell 
dimensions  in  good  agreement  with  the 
above  values.  The  above  samples  prepared 
at  high  temperature  must  have  inverted  to 
a  low-temperature  form  on  cooling,  be- 


hibits  a  unique  stable  crystalline  form  for 
each  temperature  (MacKenzie,  Year  Book 
55,  1955-1956,  p.  188),  nepheline  shows 
only  two  forms. 

New  samples  were  also  prepared  by 
Schairer  with  compositions  in  the  low- 
potassium  region  of  the  NaAlSiOi-KAl- 
Si04  solid  solution  (table  25).  Most  of 
the  samples  transformed  to  the  low-tem- 
perature form,  for  which  the  following 
data  were  obtained  by  X  rays.  For  2.50 
weight  per  cent  KAlSiO^,  that  is  #  =  0.180, 
a  decreases  slightly  whereas  c  remains  con- 
stant.   For  3.00  weight  per  cent,  or  x  — 


240        CARNEGIE  INSTITUTION  OF  WASHINGTON 


0.2165,  large  changes  are  suddenly  observed 
in  the  samples  studied.  From  this  point 
on,  to  27.07  weight  per  cent,  that  is  x  = 
2.00,  the  cell  dimensions  are  found  to  in- 
crease linearly,  in  agreement  with  previous 
results  of  Smith  and  Tuttle  (Geophysical 
Laboratory  Paper  1267).  The  composi- 
tional transition  that  takes  place  near  x  = 
0.20  is  thus  marked  by  discontinuities  in 
the  curves  of  a  and  c;  the  curve  of  cell 
volume  V ,  on  the  other  hand,  shows  small 
variation;  it  consists  of  two  straight-line 
portions,  one  with  nearly  zero  slope,  the 
other  with  positive  slope.  The  compen- 
sating effect  of  the  opposite  variations  in 
a  and  c  accounts  for  the  smallness  of  the 
offset  between  the  two  line  segments  of 
the  V  curve  in  the  region  in  which  the 
transition  composition  must  lie.  It  is  im- 
possible to  decide  whether  the  V  curve 
shows  a  discontinuity,  which  would  indi- 
cate a  first-order  transition,  or  a  singular- 
ity, which  would  be  the  sign  of  a  second- 
order  transition.  Since  we  have  no  evidence 
in  favor  of  the  two-phase  region,  near  x= 
0.20,  that  would  be  required  by  a  first-order 
transition,  the  hypothesis  of  a  second-order 
transition  appears  to  be  the  more  reason- 
able one. 

The  problem  of  determining  the  order 
of  a  transition  on  the  basis  of  cell  volume 
is  likely  to  lead  to  the  kind  of  difficulty 
encountered  here,  as  it  did  in  the  study 
of  high-temperature  alkali  feldspars  (Geo- 
physical Laboratory  Paper  1179),  in  view 
of  the  uncertainty  of  the  composition  and 
the  limited  accuracy  (0.05  per  cent)  with 
which  cell  dimensions  can  be  determined 
by  the  usual  X-ray  method. 

Some  of  the  synthetic  samples  of  low- 
potassium  nephelines  (table  25)  gave  the 
high-temperature  form  on  quenching, 
namely:  two  samples  out  of  three  at  i= 
0.144  (2.00  weight  per  cent  KAlSi04)  and 
all  three  samples  at  #  =  0.289  (4.00  weight 
per  cent  KAlSi04) .  Their  cell  dimensions 
are  shown  in  figure  66y  where  it  may  also 
be  noted  that  the  upper  limit  of  potassium 
content  of  the  high-temperature  form  is 
probably  x  =  03  or  0.4,  where  the  cell  di- 


mensions of  the  high-temperature  form 
merge  into  those  of  low-temperature  neph- 
eline  (beyond  the  discontinuity  of  x= 
-0.20). 

In  view  of  the  above  results,  it  was  de- 
cided to  take  powder  patterns  at  varying 
temperature.  The  Gordon  Davis  heating 
sample-holder,  recently  rebuilt  by  F.  R. 
Boyd,  was  used.  A  sufficiently  large 
amount  of  synthetic  pure  sodium  nepheline 
could  be  gathered  from  the  samples  avail- 
able. The  chief  difficulty  came  from  the 
lack  of  standard  material  with  interplanar 
spacings  calibrated  at  different  tempera- 
tures. Inasmuch  as  the  purpose  of  the 
experiment  was  to  ascertain  the  existence 
of  a  transition,  already  suggested  by  pre- 
vious results,  rather  than  to  make  absolute 
measurements  of  spacings  or  to  determine 
the  transition  point  with  accuracy,  un- 
corrected 20  readings  would  be  satisfactory. 

The  range  of  20  extending  from  26°  to 
30°  C  was  covered  twice,  that  is,  with 
increasing  and  decreasing  20,  for  each  of 
the  following  temperatures:  240°,  410°, 
610°,  810°,  1050°,  and  1150°  C.  The  av- 
erage value  of  20_was  plotted  (fig.  67)  for 

two  spacings:  2022  and  2130.  The  curve 
of  20  (2022)  shows  a  break  in  the  neighbor- 
hood of  810°  C;  it  is  difficult  to  confirm 
the  break  by  means  of  the  curve  of  20 
(2130),  which  by  itself  can  be  regarded  as 
a  straight  line  within  the  limits  of  error. 
We  note  that  the  temperature  scale  is 
only  roughly  calibrated,  so  that  the  values 
given  here  may  be  in  error  by  about  ±50° 
C,  but  this  fact  does  not  invalidate  the 
conclusion  that  a  transition  exists.  Smith 
and  Tuttle  (Geophysical  Laboratory  Paper 
1267)  place  the  transition  in  the  neighbor- 
hood of  900°  C. 

A  SODIUM  NEPHELINE  IN  NATURE 

In  the  course  of  a  study  of  nepheline 
solid  solutions  (jointly  with  }.  F.  Schairer 
and  J.  D.  H.  Donnay),  we  had  the  oppor- 
tunity to  gather  from  the  literature  a  large 
number  of  chemical  analyses  of  nephelines, 
together  with  corresponding  cell  dimen- 


GEOPHYSICAL  LABORATORY        241 


sions  determined  by  X  rays.  Among 
them  one  sample  stands  out  as  abnormal, 
in  that  its  cell  dimensions  are  quite  dif- 
ferent from  those  of  all  the  others.  It  is 
a  sample  of  nepheline  from  Monte  Somma 
(British  Museum  No.  51495),  described 
by  Bannister  (1931).  The  chemical  anal- 
ysis can  be  recast  in  the  following  formula 

Kl.l8Na4.46Cao.9l[Zll.45Al7.780l8.3o032 

on  the  basis  of  the  32  oxygen  atoms  con- 
tained in  the  cell.    The  cell  dimensions, 


-30  00c 


-29.50c 


...20(2022) 

uncorrected 


CD 

(\J 
o 


-  27.50° 


-  2700 


20(2130) 
*'cx-.       uncorrected 


"XX. 


J 1__L 


500 

Temperature  °C 


1000 


Fig.  67.  Uncorrected  28  angles  obtained  with 
CuKcc  radiation  for  spacings  2022  and  2130  of 
synthetic  pure  sodium  nepheline  at  varying  tem- 
peratures (°  C,  ±50°).  The  transition  between 
low-temperature  and  high-temperature  forms  is 

marked  by  a  break  in  the  curve  of  20(2022). 

determined  by  Bannister  by  the  oscillating 
crystal  method,  are:  a  =  9.96,  c  =  8.33  (A 
from  kX),  which  lead  to  a  calculated  den- 
sity of  2.645  g/cm3.  The  reported  observed 
density,  2.576  g/cm3,  is  unusually  low.  No 
other  natural  nepheline  has  so  low  a  value 
for  c. 

Dr.  M.  Hey  (Mineral  Department  of 
the  British  Museum)  kindly  sent  us  part 
of  the  original  sample,  consisting  of  frag- 
ments, among  which  could  be  found  a 


small  euhedral  crystal  suitable  for  X-ray 
work.  Its  cell  dimensions  were  determined 
on  the  precession  camera:  a—  9.988,  c  — 
8.328  A,  both  ±0.3  per  cent,  c/a- 0.8338, 
in  agreement  with  Bannister's  results. 

Another  portion  of  the  sample  was  used 
for  powder  work  on  the  Norelco  diffrac- 
tometer;  it  gave:  a"  =  9.985,  c"  =  8.372  A, 
both  ±0.05  per  cent,  c/a  =  0.8385.  Even 
though  d  =  a"  within  the  limits  of  error, 
it  can  be  concluded  that  the  sample  con- 
tains two  phases,  for  the  difference  in  c 
exceeds  the  uncertainty  of  the  measure- 
ments. The  phase  detected  as  a  single 
crystal  must  exist  in  the  sample  in  very 
small  quantity,  as  its  effect  on  the  powder 
pattern  is  not  noticeable.  Its  cell  dimen- 
sions are  those  obtained  for  samples  of 
sodium  nepheline  synthesized  by  Schairer 
(see  above),  with  less  than  0.20  potassium 
atom  per  cell  (*<0.20). 

It  is  interesting  to  note  that  Cesaro 
(1920)  made  a  careful  goniometric  study 
of  small  perfect  crystals  from  Monte 
Somma,  in  which  he  was  able  to  measure 
the  angle  (1010)  :  (1011)  to  2  or  3  minutes 
of  arc.  The  lowest  c/a  ratio  he  records  is 
0.8358.  This  value  is  lower  than  the  c/a 
ratio  0.8381,  which  is  the  smallest  value 
found  by  X  rays  in  the  low-potassium  re- 
gion (0.20 <#< 2.00).  Cesaro  too  seems 
to  have  encountered  a  specimen  of  sodium 
nepheline  in  his  Monte  Somma  material. 

In  conclusion,  the  chemical  formula 
given  above  cannot  represent  any  one  of 
the  specimens  used  for  single-crystal  work, 
although  it  may  approximate  the  composi- 
tion of  the  powder  sample. 

Bannister  had  already  shown,  by  means 
of  optical  measurements,  that  the  chemical 
composition  of  the  material  occasionally 
changes  from  grain  to  grain  in  one  hand 
specimen.  Such  variability  in  composition 
has,  of  course,  long  been  recognized  in 
mineralogy;  it  must  be  reckoned  with  in 
any  attempt  to  determine  chemical  com- 
position from  cell  dimensions.  It  can  only 
be  hoped  that  careful  sampling  and  grind- 
ing of  the  sample  will  yield  a  representa- 
tive  powder,    whose    X-ray   pattern   will 


242        CARNEGIE  INSTITUTION  OF  WASHINGTON 


show  broadened  peaks,  each  peak  being 
smeared  over  an  angular  range  that  cor- 
responds to  the  range  in  composition. 

SOLID  SOLUTION 

Under  this  heading  last  year's  report 
(Year  Book  55,  p.  205)  gave  an  account 
of  the  variation  of  cell  dimensions  of  syn- 
thetic nephelines  with  different  kinds  of 
solid  solutions.  One  of  the  conclusions 
was  that  neither  omission  solid  solution, 
Nas-yUlyAls-ySis+yOsz,  nor  substitution- 
omission  solid  solution,  Nas^CazDzAls- 
Si8032,  changes  the  cell  dimensions  in 
either  a  or  c.  Further  work  has  shown  that 
this  conclusion  must  be  amended. 

When  the  work  was  repeated  on  newly 
prepared  samples  (see  Synthetic  Nephe- 
lines, above),  the  a  value  had  to  be  cor- 
rected from  9.971  to  9.986  A,  and  the  c 
value  from  8.362  to  8.331  A;  the  cell  vol- 
ume, however,  changed  only  slightly,  from 
720.0  to  719.5  A3.  The  numerical  values 
given  in  last  year's  report  are  indeed  the 
cell  dimensions  of  crystals  of  the  high- 
temperature  form  obtained  by  quenching. 
The  new  data  pertain  to  the  low-tempera- 
ture form,  into  which  the  samples  inverted 
on  cooling.  By  a  curious  coincidence  these 
same  cell  dimensions  are  found  on  crystals 
which  represent  the  limit  of  solid  solution 
by  substitution-omission,  and  they  also  ap- 
proximate those  of  the  low-potassium  sub- 
stitution solid  solution  near  #=0.3. 

PHOSPHATES 

The  question  of  stereoisomerism  of  tetra- 
metaphosphate  has  been  raised  by  Drs.  R.  J. 
Gross  and  J.  W.  Gryder  (Johns  Hopkins 
University).  The  existence  of  two  stereo- 
isomers of  P4O12,  namely  a  ring  form  and 
a  boat  form,  was  postulated  by  them  on 
the  basis  of  chemical  evidence.  The  two 
forms  can  be  isolated  only  in  the  solid 
state;  by  single-crystal  work  they  were 
proved  to  be  distinct  crystalline  species. 
Preliminary  results  were  reported  jointly 
to  the  American  Chemical  Society. 

Work  on  the  crystallography  of  alkali 
phosphates  has  been  continued  with  Drs. 


J.  W.  Gryder  and  Helen  M.  Ondik.  A 
compound  reported  in  the  literature  as 
Na2H2P40i2  was  found  to  be  surprisingly 
insoluble  in  water  for  a  metaphosphate, 
and  its  fibrous  habit  was  intriguing  (Grif- 
fith, 1956) .  The  compound  was  synthesized 
by  Griffith's  procedure,  and  its  identity 
was  checked  by  comparing  its  powder  pat- 
tern with  that  of  material  kindly  furnished 
by  Dr.  Griffith.  The  transparent,  colorless 
product  is  found  to  consist  of  two  distinct 
crystalline  forms  intimately  intergrown. 

Form  I  comprises  approximately  10  per 
cent  by  weight  of  the  sample,  as  estimated 
from  the  relative  intensities  of  powder 
lines.  It  consists  of  crystals  of  thick  tabular 
habit  and  average  dimensions  0.3  X  0.05  X 
0.02  mm.  They  are  monoclinic,  elongated 
[010],  with  cell  dimensions  #  =  30.7,  b  = 
6.77,  c=7.12  A,  all  ±0.5  per  cent,  (3  =  94°  6' 
±l(f,  V=W6  A3.  A  pronounced  pseudo- 
repeat  a=a/2  is  evident.  Because  it  proved 
impossible  to  separate  a  sufficient  amount 
of  phase  I  for  accurate  density  determina- 
tion, we  can  report  only  that  its  density 
is  2.62  g/cm3  or  greater  as  determined  by 
the  flotation  method  using  a  mixture  of 
bromoform  and  toluene  as  the  inert  liquid. 
For  the  same  reason  a  chemical  analysis  of 
this  phase  was  not  possible.  The  space 
group  is  uniquely  determined  as  P2i/a  by 
the  systematic  absences  hOl  with  h  odd  and 
0^0  with  \  odd.  Only  the  forms  {100} 
and  {001}  are  observed,  the  larger  faces 
being  those  of  {100}.  As  cleavage  is  ex- 
tremely fibrous  along  b,  good  single  crys- 
tals are  difficult  to  obtain.  No  further 
work  on  this  form  is  contemplated. 

Form  II,  the  bulk  of  the  material,  con- 
sists of  thin  to  thick  rectangular  plates 
which  grow  up  to  5  mm  in  length.  Only 
cleavage  fragments  can  be  removed  from 
the  matrix  of  the  melt,  and  therefore 
morphology  gives  no  clue  concerning  the 
point-group  symmetry.  Cell  dimensions 
were  determined  on  precession  films  taken 
with  MoKa  radiation:  #=18.74,  £  =  14.79, 
<r  =  7.03  A,  all  ±0.3  per  cent,  3  =  90°  0'±5', 
F  =  1948  A3.  Parallel  to  {100}  the  cleavage 
is  very  easy  and  very  good;  parallel  to 


GEOPHYSICAL  LABORATORY        243 


{010}  it  is  easy  and  fairly  good;  and  paral- 
lel to  {110}  it  is  fairly  easy  and  good.  The 
four  cleavage  directions  result  in  platy  to 
fibrous  fragments. 

The  cell  is  monoclinic  but  markedly 
pseudo-orthorhombic.  Although  the  zero- 
level  net  (010)  #  shows  symmetry  111,  paral- 
lel upper  levels  show  that  a*  and  c*  are 
not  symmetry  directions.  The  pseudo- 
orthorhombic  character  is  emphasized  by 
the  optical  orientation — the  principal  axes 
of  the  index  ellipsoid  lie  along  the  crystallo- 
graphic  axes  within  experimental  error. 
The  optical  character  is  biaxial  positive 
with  the  plane  of  the  optic  axes  parallel 
to  (100)  and  the  acute  bisectrix  along 
[001].  The  indices  are  na=  1.485 ±0.005, 
^=1.510 ±0.005,  ny=  1.545 ±0.001  (deter- 
mined by  J.  D.  H.  Donnay).  Since  the  sys- 
tematic absences  are  h\l  with  h  +  1  odd  and 
hOl  with  h  and  /  both  odd,  the  space  group 
is  Blja  or  Ba.  The  5-centered  lattice  is 
used  to  bring  out  the  pronounced  pseudo- 
symmetry  with  pseudo  space  group  Bmam, 
Bma2,  or  Blam.  The  test  for  pyroelec- 
tricity  with  liquid  nitrogen  gave  negative 
results. 

Because  form  II  is  present  in  much  larger 
amounts  than  form  I,  its  density  could 
be  determined  more  accurately.  The  low- 
est density  obtained  by  the  pycnometric 
method  using  toluene  as  the  inert  liquid 
is  2.34  ±0.02  g/cm3.  The  flotation  method 
using  a  mixture  of  bromoform  and  toluene 
indicates  that  the  density  of  fragments  of 
the  crystal  intergrowth  varies  from  2.34 
to  2.62  g/cm3. 

Using  2.34  g/cm3  as  the  density  and 
Griffith's  formula,  we  calculate  7.54  ±0.08 
formula  units  per  cell.  The  space  groups 
Blja  and  Ba  permit  only  an  even  number 
of  Na2H2P40i2  units  per  cell;  consequently 
the  observed  density  must  be  compared  to 
the  calculated  densities  of  1.86  for  6  and 
2.48  for  8  units  per  cell.  These  values  lie 
well  outside  the  limits  of  experimental  er- 
ror. If  one  molecule  of  water  is  subtracted 
from  the  empirical  formula,  the  result  is 
Na2P40n.  For  8  such  formula  units  per 
cell  the  calculated  density  is  2.36  g/cm3, 


within  the  limits  of  error  of  the  experi- 
mental value.  Knowing  that  the  phos- 
phorus atom  surrounds  itself  tetrahedrally 
by  oxygen  atoms,  we  conclude  from  the 
formula  that  some  of  the  P04  tetrahedra 
must  share  more  than  two  corners.  Fol- 
lowing van  Wazer's  terminology  (1955), 
the  material  is  therefore  an  ultraphosphate. 
It  is  the  first  crystalline  ultraphosphate  on 
record. 

DISORDER  IN  CRYSTALS 

Present-day  interest  in  crystal  structures 
has  shifted  from  the  regularity  to  the  im- 
perfections of  the  interatomic  arrangement. 
Considerable  attention  has  already  been 
devoted  to  the  study  of  mistakes  that  occur 
during  crystal  growth  or  form  the  very 
mechanism  of  growth,  such  as  screw  dis- 
locations. Order-disorder  studies  in  recent 
years  have  had  a  profound  impact  on 
mineralogy,  particularly  on  our  knowledge 
of  layer  minerals  and  of  feldspars.  A  study 
of  disorder  by  means  of  optical  diffraction 
has  been  initiated  in  this  laboratory 
(Chayes).  In  view  of  the  growing  im- 
portance of  this  field,  new  types  of  crystal 
disorder  are  of  special  interest. 

Such  a  new  type  has  been  encountered 
in  sodium  ultraphosphate  form  II  (with 
Gryder  and  Ondik;  see  Phosphates, 
above).  The  experimental  evidence  is  as 
follows.  On  the  precession  patterns  con- 
taining reflections  hlfl,  hf([f  and  ^3,  all 
reflections  with  /  even  are  sharp,  while 
those  with  /  odd  appear  as  diffuse  circles. 
The  c-axis  rotation  pattern  consists  of  odd 
layer  lines  which  are  diffuse  streaks  and  of 
even  layer  lines  which  contain  sharp  spots, 
the  width  of  the  two  types  of  layer  lines 
being  the  same.  It  follows  that  the  reflec- 
tions with  /  odd  are  diffuse  circular  disks 
oriented  normal  to  the  <r#  axis.  This  con- 
clusion is  confirmed  by  Weissenberg  photo- 
graphs. The  intensity  distribution  within 
the  streaky  layer  lines  varies  from  crystal 
to  crystal.  The  radius  of  the  disk  was 
measured  for  one  of  the  specimens  and 
was  found  to  be  0.021  ±0.001  A"1. 

These  observations  indicate  that  the  crys- 


244        CARNEGIE  INSTITUTION  OF  WASHINGTON 


tal  structure  is  disordered  by  random  dis- 
placements of  structural  elements  through 
a  distance  of  c/2  in  the  z  direction.  The 
bonds  parallel  to  the  c  direction  must  be 
very  much  stronger,  indeed  of  a  different 
order  of  magnitude,  than  the  bonds  paral- 
lel to  (001).  Such  requirements  are  met 
by  a  chain  structure  with  chain  axes 
parallel  to  c. 

Additional  evidence  leads  to  the  hy- 
pothesis that  rings  of  four  phosphate  tetra- 
hedra  are  linked  into  chains  by  the  sharing 
of  an  oxygen  atom  between  consecutive 
rings.  The  cell  height  being  equal  to  the 
height  of  one  such  ring,  the  disordered 
crystal  consists  of  chains  displaced  by  half 
a  link  with  respect  to  one  another.  An  ex- 
pression relating  the  observed  diffuse  in- 
tensities to  the  probability  of  chain  dis- 
placement has  been  derived;  the  theoretical 
treatment  is  similar  to  that  given  by  Wil- 
son for  layer  displacements. 

POLYMORPHISM  VERSUS  ISOMERISM 

When  a  chemical  compound  exists  in 
more  than  one  crystalline  modification,  it 
is  usually  a  case  of  polymorphism,  in 
which  each  of  the  polymorphic  forms  is 
stable  in  a  definite  region  of  the  P-T  dia- 
gram. If  the  crystal  structure  of  the  com- 
pound is  of  the  molecular  type,  poly- 
morphic forms  differ  in  the  way  identical 
molecules  pack  in  the  crystal,  whereas 
isomeric  forms  differ  in  the  molecular 
configuration  itself  and  separate  on  crystal- 
lizing from  a  solution  in  which  they  co- 
exist in  equilibrium.  To  discriminate 
between  polymorphism  and  isomerism, 
organic  chemistry  usually  must  come  to 
the  rescue  of  crystallography  unless  the 
crystal  structure  is  first  completely  deter- 
mined. The  working  crystallographer, 
however,  may  have  occasion  to  suspect 
the  existence  of  isomerism  in  the  crystals 
he  studies,  and  can  draw  the  chemist's  at- 
tention to  the  problem.  One  such  oppor- 
tunity came  to  us  this  year. 

Dr.  F.  W.  Barnes,  of  the  Johns  Hopkins 
Hospital,  had  given  us  hollow  crystals  of 
5,5-diethylbarbituric  acid    (barbital,  vero- 


nal), grown  at  low  temperature  in  his 
laboratory.  These  crystals  turned  out  to 
be  rhombohedral,  thus  different  from  the 
monoclinic  pseudo-orthorhombic  barbital 
described  in  the  chemical  and  crystallo- 
graphic  compendia.  Mr.  William  Seip  then 
referred  us  to  a  paper  by  Fischer  and 
Kofler,  that  appeared  in  the  Archiv  der 
Pharmazie  in  1932,  in  which  three  forms 
of  barbital,  described  as  polymorphic 
forms,  had  been  studied  optically  with  the 
polarizing  microscope.  A  crystallographic 
re-examination  of  these  forms  was  under- 
taken (jointly  with  J.  D.  H.  Donnay). 

New  data  were  obtained  on  the  rhombo- 
hedral form.  It  occurs  in  elongated  crystals 

composed  of  trigonal  prisms:    1120,  2110, 

3030,  0330,  4150,  and  1540,  in  order  of  de- 
creasing size.  Several  easy  cleavages  are 
parallel  to  the  c  axis.  Cleavage  fragments 
were  used  for  X-ray  work.  Cell  dimensions 
are:  tf=26.97±0.09,  r=6.85±0.02  A;  18 
molecules  per  cell  give  a  calculated  density 
of  1.276  g/cm3,  as  compared  with  the 
measured  value  of  1.26  (by  M.  Crute). 
The  space  group  determined  by  X  rays  is 

R3  or  R3;  a  pyroelectric  test  in  liquid 
nitrogen  was  negative,  but  R3  is  the  more 
probable  in  view  of  the  morphological  de- 
velopment. A  powder  pattern  was  taken 
and  indexed.  The  indices  of  refraction 
determined  by  Fischer  and  Kofler  were 
confirmed  to  0.001. 

Crystal  data  on  the  monoclinic  form  of 
barbital  go  back  to  Hertel  (1930,  1935). 
In  the  pseudo-orthorhombic  description 
(1930),  Hertel  had  given  an  incorrect 
space  group,  Cmcm  instead  of  Ccmm,  for 
0=7.11,  £  =  14.4,  c=9.7  kX.  The  morpho- 
logical development  of  the  crystals  was 
found  to  be  incompatible  with  the  space 
group  on  record;  re-examination  by  X 
rays  gave  the  correct  space  group.  The 
monoclinic  description  (1935)  with  space 
group  C2/c  or  Cc  and  interchange  of  a 
and  b  was  confirmed  by  indexing  a  powder 
pattern.  The  optical  data  of  Fischer  and 
Kofler  (1932)  were  confirmed;  the  indices 
agree  within  ±0.003.  These  two  authors 


GEOPHYSICAL  LABORATORY        245 


observed  the  c  axis  to  be  polar;  the  prob- 
able space  group  is  accordingly  Cc. 

Preliminary  data  on  the  triclinic  form 
confirm  the  values  of  the  indices  of  refrac- 
tion measured  by  Fischer  and  Kofler  on 
twinned  crystal  plates.  More  work  is 
needed  before  the  triclinic  character  can 
be  confirmed  and  cell  dimensions  reported. 

The  following  evidence  indicates  that 
the  three  forms  of  barbital  are  not  poly- 
morphs, but  isomers.  On  melting  either 
the  monoclinic  or  the  rhombohedral  form, 
and  letting  it  recrystallize  from  the  melt, 
we  always  retrieve  the  original  form. 
Whereas  Fischer  and  Kofler  report  the 
rhombohedral  form  as  the  form  stable  at 
high  temperature,  the  rhombohedral  crys- 
tals we  studied  were  obtained  at  low  tem- 
perature and  were  accompanied  by  only 
very  small  amounts  of  the  other  two  forms. 
Fischer  and  Kofler  report  that  all  three 
forms  usually  occur  together  in  their  prepa- 
rations; occasionally  only  two  forms  were 
found  by  us. 

DIGENITE 

The  work  on  digenite  was  continued. 
In  view  of  the  impossibility  of  producing 
true  single  crystals,  it  was  decided  to  at- 
tempt a  determination  of  the  crystal  struc- 
ture from  the  data  obtained  from  twins.  It 
was  necessary  to  analyze  the  data  with  a 
view  to  finding  which  reflections  were  con- 
tributed by  the  several  crystals  of  the  twin 
to  the  cubically  indexed  diffraction  spectra 
on  the  X-ray  photographs. 

A  tentative  crystal  structure  has  been 
arrived  at,  on  the  basis  of  space  group 

R3m.  All  atoms  lie  along  the  threefold 
axis  of  the  rhombohedral  cell  described  in 
last  year's  report  (Year  Book  55,  p.  204). 
The  sulfur  atoms  are  placed  at  ;r=0,±%, 
±%,  and  lead  to  an  S-S  distance  of 
3.92  A.  The  sulfur  sites  correspond  to  the 
face  centers  of  the  small  cube,  which  was 
the  cell  reported  by  Rahlfs  (1936).  One 
copper  atom  is  located  at  x=Y2,  and  is 
octahedrally  co-ordinated  to  sulfur  atoms. 
The  other  copper  atoms  are  found  at 
#=±~0.060  in  tetrahedral  co-ordination, 


but  displaced  from  the  center  toward  one 
face  of  the  sulfur  tetrahedron;  at  x  — 
±0.133,  in  triangular  co-ordination;  at 
#=±0.250  and  ±0.350,  in  regular  tetra- 
hedral co-ordination.  The  Cu-S  distance 
ranges  from  2.26  A  for  the  triangular  co- 
ordination to  2.77  A  for  the  octahedral  one. 
This  structure  leads  to  satisfactory  agree- 
ment between  calculated  and  observed  in- 
tensities for  the  superstructure  reflections, 
which  are  the  reflections  that  appear  on  a 
powder  pattern.  For  the  weak  reflections, 
observed  only  on  "single-crystal"  patterns, 
the  agreement  still  leaves  much  to  be 
desired. 

Powder  patterns  were  taken  at  high  tem- 
perature at  the  National  Bureau  of  Stand- 
ards, on  the  heating  camera  designed  by 
Mr.  F.  A.  Mauer,  who  kindly  agreed  to 
help  us  with  this  task.  The  sample  was 
heated  in  a  helium  atmosphere  to  prevent 
oxidation.  The  temperature  was  slowly 
raised  to  -500°  C.  Between  60°  and  65° 
the  weak  reflections  disappear,  indicating 
the  existence  of  a  transition  above  which 
the  small  cubic  pseudocell  becomes  the 
true  cell. 

The  electrical  conductivity  of  digenite 
was  tested  by  Dr.  A.  Franklin,  at  the  Na- 
tional Bureau  of  Standards.  He  reports 
that  digenite  is  an  unusually  good  con- 
ductor, even  at  room  temperature;  there 
is  no  sharp  change  in  conductivity  at  the 
transition  temperature. 

CRYSTALLOCHEMICAL  ANALYSIS 

Identification  of  small  amounts  of  crys- 
talline material  is  a  problem  that  is  always 
with  us.  A  number  of  methods  are  well 
established;  for  instance,  determination 
may  be  made  by  means  of  the  polarizing 
microscope,  by  the  powder  technique  of 
X-ray  diffraction,  by  microchemical  tests, 
by  spectroscopic  analysis.  When  single 
crystals  are  available,  identification  may  be 
based  on  the  determination  of  the  cell  di- 
mensions by  X  rays,  a  method  that  has 
become  possible  only  recently,  after  the 
necessary  determinative  tables  of  crystal 
data  were  published.   It  was  thus  a  chal- 


246        CARNEGIE  INSTITUTION  OF  WASHINGTON 


lenge  to  devise  a  practical  determinative 
procedure  that  could  be  applied  by  scien- 
tists not  specially  trained  in  X-ray  crystal- 
lography. Such  a  procedure  has  been 
worked  out  for  each  of  the  crystal  systems, 
and  for  all  kinds  of  crystals,  euhedral,  sub- 
hedral,  or  anhedral.  It  requires  only  a 
precession  camera  and  a  two-circle  goni- 


ometer. It  can  be  applied  in  a  routine 
fashion,  with  a  minimum  of  interpretation, 
although  some  judgment  remains  indis- 
pensable. 

The  method  has  been  written  up  as  a 
chapter  for  the  coming  third  edition  of 
Physical  Methods  of  Organic  Chemistry, 
edited  by  A.  Weissberger. 


APPLICATION  OF  THE  "MOREY-SCHREINEMAKERS' 
THEOREM  OF  COINCIDENCE" 

G.  W.  Morey 


A  large  part  of  the  experimental  work 
of  the  Geophysical  Laboratory  has  been 
the  determination  of  the  melting  points 
and  other  phase-equilibrium  relations  of 
the  oxides  and  their  mixtures  and  com- 
pounds which  make  up  the  earth's  crust. 
This  work  has  been  guided  by  the  theo- 
retical precepts  developed  by  the  great 
American  physicist  and  mathematician, 
J.  Willard  Gibbs.  The  greater  part  of  our 
studies  have  dealt  with  nonvolatile  oxides, 
in  which  the  only  experimental  variables 
needing  consideration  are  the  temperature 
and  the  compositions  of  matter  under  con- 
sideration. There  is,  however,  increasing 
interest  in  systems  in  which  volatile  sub- 
stances such  as  water  and  carbon  dioxide 
are  introduced  as  components.  This  in- 
creasing interest  is  manifest  not  only  in  the 
work  of  this  Laboratory  but  also  in  other 
laboratories  interested  in  experimental  geo- 
chemistry, and  to  a  rapidly  increasing  ex- 
tent in  the  chemical  industries,  which  see 
the  possibilities  of  radically  new  methods 
of  manufacture  resulting  from  high-pres- 
sure reactions.  Such  reactions  require 
simultaneous  consideration  not  only  of  the 
composition  variables  but  also  of  pressure 
and  temperature,  and  involve  complica- 
tions resulting  from  critical  phenomena 
and  significant  solubility  of  solids  in  gases. 
The  theoretical  consideration  of  such  sys- 
tems is  little  known  and  is  not  ordinarily 
treated  in  textbooks. 

The  fundamental  considerations  devel- 
oped by  Gibbs  are  competent  guides  to  the 
most  complicated  of  these  systems,  but 
their  detailed  application  leads  to  phase- 


equilibrium  relations  difficult  to  under- 
stand and  expound  because  of  their  com- 
plexity. One  aspect  of  such  relations, 
namely  the  course  of  the  pressure-tempera- 
ture curves  of  univariant  equilibria  in 
which  such  P-T  curves  follow  each  other 
around  an  invariant  point,  can  be  devel- 
oped and  applied  in  a  comparatively  sim- 
ple manner.  The  treatment  of  this  problem 
is  based  on  a  theorem  deduced  rigorously 
by  Morey  and  Williamson,  and  from  gen- 
eral considerations  by  Schreinemakers,  and 
called  by  Prigogine  the  "Morey-Schreine- 
makers'  Theorem  of  Coincidence."  This 
is  a  powerful  tool,  applicable  to  all  types 
of  P-T  curves,  and  simple  to  apply,  but 
since  it  is  not  included  in  textbooks  it  is 
not  generally  known.  By  application  of 
this  theorem  it  is  possible  not  only  to  de- 
termine the  sequence  of  P-T  curves  around 
an  invariant  point  in  a  system  of  many 
components,  but  also  to  fix  the  phase  as- 
semblages that  can  have  stable  coexistence 
in  the  divariant  regions  between  the  P-T 
curves,  even  though  the  points  in  such 
regions  are  projections  on  the  P-T  plane  of 
an  ^-dimensional  hyperprism.  A  paper 
recently  published  gives  a  detailed  exposi- 
tion of  how  this  theorem  may  be  applied 
to  the  various  types  of  invariant  points  in 
a  ternary  system,  and  of  the  various  types 
of  P-T  curves  proceeding  from  these  in- 
variant points,  using  as  an  example  the 
ternary  system  water-Na20  ^1203*25102 
(nepheline)-Na20  ■  AI2O3  *  6S1O2  (albite), 
in  which  the  compounds  Na20*Al203' 
4Si02*2H20  (analcite)  and  Na20  ■  AI2O3  ■ 
4Si02  (jadeite)  are  formed. 


GEOPHYSICAL  LABORATORY        247 


MISCELLANEOUS  ADMINISTRATION 


PENOLOGISTS'  CLUB 

The  Petrologists'  Club  met  at  the  Labo- 
ratory on  six  occasions  this  year.  After 
rather  rapid  growth  in  the  previous  few 
years,  the  membership  has  leveled  off  at 
about  150  active  participants. 

The  following  papers  were  presented: 

"Gravity  and  continental  structure,"  by 
H.  E.  Tatel  (Department  of  Terrestrial  Mag- 
netism). 

"Equilibrium  texture  in  rocks,"  by  J.  B. 
Thompson,  Jr.  (Harvard  University). 

"Origin  of  spilites,"  by  G.  D.  Nicholls 
(University  of  Manchester). 

"The  1955  eruption  of  Kilauea,"  by  G.  A. 
MacDonald  (U.  S.  Geological  Survey). 

"Oxidation  and  reduction  in  metamor- 
phism,"  by  H.  P.  Eugster,  J.  R.  Smith,  and 
W.  G.  Ernst  (Geophysical  Laboratory),  and 
H.  James  (U.  S.  Geological  Survey). 

"Origin  of  lamprophyres  associated  with 
granitic  plutons,"  by  C.  A.  Hopson  (Johns 
Hopkins  University). 

SEMINARS 

The  Laboratory  continued  its  weekly 
series  of  seminars,  in  which  papers  con- 
cerned primarily  with  work  in  progress 
were  presented  largely  by  staff"  members. 
Several  talks  were  given  by  guest  speakers 
from  outside  the  Laboratory,  including : 

"The  origin  of  lamprophyres,"  by  C.  A. 
Hopson  (Johns  Hopkins  University). 

"An  attempt  to  limit  the  possible  composi- 
tion of  the  ore-forming  fluid,"  P.  B.  Barton, 
Jr.  (U.  S.  Geological  Survey). 

"Recent  developments  in  X-ray  fluores- 
cence," I.  Adler  (U.  S.  Geological  Survey). 

"Phase  relations  in  the  system  gold-silver- 
tellurium,"  N.  Markham  (University  of  Ade- 
laide, South  Australia). 

"Systems  involving  ferrous  and  ferric  ox- 
ide," A.  Muan  (Pennsylvania  State  Univer- 
sity). 

"Recent  studies  on  silica,"  R.  Roy  (Penn- 
sylvania State  University). 

SYMPOSIUM  ON  HIGH  PRESSURES 

On  June  12,  1957,  a  one-day  symposium 
on  high  pressures  was  held  at  the  Geo- 
physical Laboratory.  The  morning  session 


was  devoted  to  formal  talks  by  Professor 
H.  Tracy  Hall,  Director  of  Research, 
Brigham  Young  University,  on  "Chemistry 
at  high  pressures  and  high  temperatures," 
and  by  Professor  Harry  G.  Drickamer, 
Head,  Chemical  Engineering  Department, 
University  of  Illinois,  on  "The  effect  of 
high  pressures  on  optical  properties  of  ma- 
terials." After  a  buffet  luncheon,  the  first 
session  of  the  afternoon  was  devoted  to 
general  discussion  of  phase  changes  in- 
duced by  pressure  and  their  relation  to 
geophysical  problems,  with  Professor  Birch, 
of  Harvard,  contributing  notably.  The 
final  portion  of  the  day  was  devoted  to 
apparatus  design,  with  discussion  led  by 
Professor  Hall. 

The  group  attending  the  symposium  in- 
cluded: L.  H.  Adams  (National  Bureau 
of  Standards),  L.  T.  Aldrich  (Department 
of  Terrestrial  Magnetism),  Charles  W. 
Beckett  (National  Bureau  of  Standards), 
Francis  Birch  (Harvard  University),  E.  H. 
Carnevale  (Naval  Ordnance  Laboratory), 
Harry  G.  Drickamer  (University  of  Illi- 
nois), Abraham  Friedman  (Atomic  En- 
ergy Commission), Irving  Friedman  (U.  S. 
Geological  Survey),  H.  R.  Gault  (Lehigh 
University),  John  W.  Graham  (Depart- 
ment of  Terrestrial  Magnetism),  H.  J. 
Hadow  (United  Kingdom  Scientific  Mis- 
sion), H.  Tracy  Hall  (Brigham  Young 
University),  Joseph  Hilsenrath  (National 
Bureau  of  Standards),  Francis  T.  McClure 
(Applied  Physics  Laboratory),  Donald 
Newhall  (Harwood  Engineering  Com- 
pany), Thomas  B.  Nolan  (U.  S.  Geologi- 
cal Survey),  Donna  Price  (Naval  Ord- 
nance Laboratory),  Sidney  G.  Reed,  Jr. 
(Office  of  Naval  Research),  A.  E.  Ring- 
wood  (Harvard  University),  Eugene  Rob- 
ertson (U.  S.  Geological  Survey),  William 
W.  Rubey  (U.  S.  Geological  Survey), 
Paul  A.  Scherer  (Carnegie  Institution  of 
Washington),  H.  E.  Tatel  (Department 
of  Terrestrial  Magnetism),  Dudley  Taylor 
(Naval  Ordnance  Laboratory),  M.  A. 
Tuve  (Department  of  Terrestrial  Magnet- 
ism),  Alvin   van   Valkenburg,   Jr.    (Na- 


248        CARNEGIE  INSTITUTION  OF  WASHINGTON 


tional  Bureau  of  Standards),  Charles  E.  posium  to  the  Washington  Crystal  Col- 
Weir    (National    Bureau    of   Standards),  loquium. 

George  W.  Wetherill  (Department  of  Ter-  H.  P.  Eugster  served  as  Lecturer  in  the 

restrial  Magnetism),  and  Samuel  Zerfoss  Department  of  Geology,  Johns  Hopkins 

(National  Bureau  of  Standards).  University,  each  Friday  during  the  aca- 

In  addition  to  the  above,  the  following  demic  year  1956-1957.  He  also  lectured  at 

staff  members  and  guest  investigators  of  the  fall  meeting  of  the  National  Academy 

the   Geophysical  Laboratory   were  in   at-  of  Sciences. 

tendance:  P.  H.  Abelson,  R.  G.  Arnold,  J.  W.  Greig  served  as  Visiting  Research 
H.  L.  Barnes,  P.  B.  Barton,  Jr.  (U.  S.  Geo-  Associate  at  the  College  of  Mineral  Indus- 
logical  Survey),  F.  R.  Boyd,  Jr.,  S.  P.  tries,  Pennsylvania  State  University,  from 
Clark,  Jr.,  G.  L.  Davis,  J.  L.  England,  November  1956  through  March  1957.  Dur- 
W.  G.  Ernst,  H.  P.  Eugster,  J.  W.  Greig,  ing  this  period  he  gave  a  series  of  lectures 
G.  Kullerud,  E.  H.  Roseboom,  J.  F.  on  various  aspects  of  phase  equilibria  in 
Schairer,  J.  R.  Smith,  D.  B.  Stewart  (U.  S.  ternary  systems,  which  were  attended  by 
Geological  Survey),  D.  R.  Wones,  H.  S.  staff  members  and  graduate  students  of 
Yoder,  Jr.,  and  E.  G.  Zies.  five  departments:  Mineralogy  and  Petrol- 
ogy, Geophysics  and  Geochemistry,  Geol- 
lectures  0gy5  Metallurgy,  and  Ceramic  Technology. 

During  the  report  year  staff  members  G.  W.  Morey  gave  a  series  of  three  lec- 

were  invited  to  present  lectures  as  follows :  tures  before  the  Inorganic  Chemical  Di- 

P.  H.  Abelson  lectured  at  the  National  vision  of  Monsanto  Chemical  Company  at 

Academy  of  Sciences;  the  Annual  Meeting  Dayton,  Ohio. 

of  the  Trustees  of  the  Carnegie  Institution  J-  F-  Schairer  delivered  the  Presidential 
of  Washington;  the  New  York  Academy  Address,  "The  crystallization  of  rock-form- 
of  Sciences-A.A.A.S.  Symposium  on  Mod-  in£  minerals  from  magmas  and  the  nature 
ern  Ideas  on  Spontaneous  Generation;  a  o£  the  residual  liquid,"  at  the  annual  meet- 
graduate  seminar  at  Catholic  University;  mS  o£  the  Geological  Society  of  Wash- 

the  Pittsburgh  Section  of  the  American  m§;05;  ™        ,            ,        ,     ^     , 

nu^^;^\  c^;~«-  ,.  „  n  n       •        •     t?    .u  (j.  K.  1  llton  lectured  at  the  Gordon  Re- 

Cnemical  society    a  Colloquium  in  Earth  ,     ~     r               ^                     TT  . 

c  •             .   .i      -xr         i      \^    T      .           c  search  Conference;   Georgetown   Univer- 

bciences  at  the  Massachusetts  Institute  of  ^     r                  xt    i       -n 

rr,    ,      i             ,       XT.       iT.-1-i  sity;  a  Conference  on  Nuclear  Processes  in 

lechnology;     the    National    Biophysical  ^ J  \     .    c  ...          _  ^    .            A     ^  ,• 

r>     r                i      tt    o    ttt     i       ^  Geologic  Settings  at  Boston ;  and  a  1  ektite 

Conference;  the  U.  S.  Weather  Bureau:  n     r  °              °        ju.-ut^---         c 

,      T          . '     .  .       .    .      _^                      '  Conrerence  sponsored  by  the  Division  or 

the  Journal  Club  of  the  Department  of  Earth  Sciences>  National  Research  CoundL 

Geology,    Johns    Hopkins    University;    a  H.  S.  Yoder,  Jr.,  lectured  at  the  Depart- 

Symposium  on  Isotope  Separation  spon-  ment  o£  Geol         Columbia  University;  a 

sored  by  the  Netherlands  Physical  Society  Basak  Conference  sponsored  by  the  Di- 

and  the  International  Union  of  Pure  and  vision   o£   Earth   Sciences,   National   Re- 

Apphed  Physics  at  Amsterdam;  and  the  search  Council;  and  the  Institute  on  Lake 

National  Bureau  of  Standards.  Superior  Geology,  Michigan  State  Univer- 

F.  R.  Boyd,  Jr.,  lectured  at  the  National  sity.  He  also  gave  a  series  of  two  lectures 
Academy  of  Sciences;  the  Washington  each,  at  the  Department  of  Geology,  Uni- 
Junior  Academy  of  Sciences;  and  the  versity  of  Wisconsin;  the  Department  of 
Physics  Department,  Howard  University.  Geology,  University  of  Chicago;  and  the 

G.  Donnay  addressed  the  Point-Group  Department  of  Geology,  University  of 
Seminar,  Physics  Department,  Polytechnic  Illinois. 

Institute  of  Brooklyn.   Together  with  G.  

Kullerud  and  J.  D.  H.  Donnay  (of  Johns  The  "Summary  of  Published  Work"  be- 

Hopkins  University)  she  presented  a  sym-  low  briefly  describes  the  papers  published 


GEOPHYSICAL  LABORATORY        249 


in  scientific  journals  during  the  report  year. 
In  addition,  the  following  papers  are  now 
prepared  for  publication :  H.  L.  Barnes  and 
G.  Kullerud,  "Relations  between  composi- 
tion of  ore  minerals  and  ore  solutions"; 
F.  R.  Boyd,  Jr.,  "Geology  of  the  Yellow- 
stone rhyolite  plateau";  F.  Chayes  and 
W.  S.  MacKenzie,  "Experimental  error  in 
determining  certain  peak  locations  and  dis- 
tances between  peaks  in  X-ray  (powder) 
dinractometer  patterns";  G.  Donnay,  J.  D. 
H.  Donnay,  and  G.  Kullerud,  "Crystal 
and  twin  structure  of  digenite,  Cu9S5"; 
J.  W.  Gryder,  H.  Ondik,  and  G.  Donnay, 
"Disorder  in  a  crystalline  condensed  phos- 
phate"; W.  S.  MacKenzie,  "The  crystal- 


line modifications  of  NaAlSisOs";  G.  W. 
Morey,  "The  system  water-nepheline-al- 
bite:  A  theoretical  discussion";  G.  W. 
Morey,  "The  transition  between  the  low- 
and  the  high-temperature  form  of  sodium 
tripolyphosphate";  J.  F.  Schairer,  "Melting 
relations  of  the  common  rock-forming  ox- 
ides"; G.  R.  Tilton,  G.  L.  Davis,  G.  W. 
Wetherill,  and  L.  T.  Aldrich,  "Isotopic 
ages  of  zircon  from  granites  and  pegma- 
tites"; O.F.  Tuttle  and  N.L.  Bowen,"The 
origin  of  granites  in  the  light  of  experi- 
mental studies  in  the  system  NaAlSi308- 
KAlSisOs-SiOs-H^O";  H.  S.  Yoder  and 
Th.  G.  Sahama,  "Olivine  X-ray  determina- 
tive curve." 


SUMMARY  OF  PUBLISHED  WORK 


(1255) 


Variations  in  X-ray  powder  diffraction 
patterns  of  plagioclase  feldspars.  J.  R. 
Smith  and  H.  S.  Yoder,  Jr.  Am.  Min- 
eralogist, 41,  632-647  (1956). 

The  angular  separation  between  the  (131) 


(1256)     Paleobiochemistry.    P.  H.  Abelson. 
American,  195,  83-92  (1956). 


Sci. 


A  variety  of  types  of  organic  substances 
have  been  preserved  in  their  original  form  or 
in  only  slightly  altered  state  for  many  mil- 
and  (131)  reflection  in  X-ray  difTractometer  lions  of  years.  Some  of  these  occurrences  are 
patterns  of  66  chemically  analyzed  natural  described,  and  their  significance  to  potential 
plagioclases,  1 1  plagioclases  synthesized  in  the  knowledge  of  past  living  forms  is  pointed  out. 
dry  way,  and  4  plagioclases  synthesized  hy- 


drothermally  has  been  measured  and  plotted 
against  composition.  By  this  criterion,  plagio- 
clases synthesized  in  the  dry  way  and  natural 
plagioclases  from  thick  stratiform  mafic  intru- 


(1257) 


Petrographic  modal  analysis.  F.  Chayes. 
New  York,  John  Wiley  &  Sons,  Inc. 
x+113pp.     1956. 

A  manual,  intended  for  graduate  students 


sions  constitute  two  distinctly  different  series,  and  advanced  undergraduates,  outlining  the 

each  of  which  is  closely  defined  by  a  single  geometrical  basis  of  the  procedure,  describing 

curve.     Natural    plagioclases    from    volcanic  experimental  studies  of  various  kinds  of  ana- 

and   hypabyssal   rocks   and   plagioclases   syn-  lytical  and  sampling  errors,  and  discussing  a 

thesized  hydrothermally  are  intermediate  be-  method  of  estimating  and  controlling  the  ef- 

tween  the  two  series.    Other  natural  plagio-  feet  of  grain  size  on  experimental  error  in 

clases,  some  of  which  have  been  assumed  by  studies  of  two-feldspar  granites, 
other  workers  to  belong  to  a  "low-tempera- 


ture" series,  do  not  belong  to  either  of  the 
series  mentioned  above,  and  cannot  be  repre- 
sented by  any  single  curve.  It  is  concluded 
that  composition  determinations  cannot  be 
made  by  means  of  the  available  curves  based 
on  the  variation  of  reflection  separations,  be- 


(1258)  The  Holmes  effect  and  the  lower  limit 
of  modal  analysis.  F.  Chayes.  Mineral. 
Mag.,  31,  276-281  (1956). 

Thin-section  analysis  is  essentially  an  areal 
measurement,  the  measurement  area  usually 
being  the  upper  surface  of  the  section.  If 
cause  there  is  no  a  priori  way  of  knowing  transmitted  light  is  used  for  the  measurement, 
how  closely  a  given  plagioclase  is  represented  the  apparent  areas  of  opaque  grains  are  in 
by  a  particular  curve.  Given  the  composition  general  somewhat  larger  than  their  true  areas 
of  a  plagioclase,  however,  the  curves  are  use-  on  the  measurement  surface.  For  strictly 
ful  for  making  an  estimate  of  its  degree  of  spherical  opaque  particles  in  a  transparent 
inversion  toward  some  undefined  low-tem-  matrix  the  expected  excess  of  apparent  over 
perature  state.  true   area   is   shown   to  be    (jtr2^)/(2r  +  ^), 


250        CARNEGIE  INSTITUTION  OF  WASHINGTON 


where  r  is  the  spherical  radius  and  \  is  the 
thickness  of  the  thin  section.  A  table  shows 
the  relation  between  true  and  apparent  area 
as  a  function  of  r/\. 

(1259)  Pressure-temperature  curves  in  some 
systems  containing  water  and  a  salt. 
G.  W.  Morey  and  W.  T.  Chen.  /.  Am. 
Chem.  Soc,  78,  4249-4252  (1956). 

A  novel  method  for  the  determination  of 
vapor  pressures  of  saturated  solutions  has 
been  applied  to  binary  systems  containing 
water  and  the  salts  LiF,  NaF,  KF,  NaCl,  KC1, 
RbCl,  CsCl,  PbCl2,  Li2S04,  Na2S04,  K2S04, 
T12S04,  Na2C03,  K2C03,  Na204B203, 
Na4P207,  and  K4P207  at  some  or  all  of  the 
temperatures  374°,  400°,  500°,  600°,  and 
700°  C. 

(1260)  Experimental  and  theoretical  studies  of 
the  mica  polymorphs.  J.  V.  Smith  and 
H.  S.  Yoder,  Jr.  Mineral.  Mag.,  31,  209- 
235  (1956). 

An  experimental  and  theoretical  study  has 
been  made  in  order  to  determine  the  number 
and  the  structure  of  the  possible  polymorphs, 
and  the  structural  relations  between  them. 
The  simplest  structures  are  1M,  2Ml5  2M2, 
3T,  20,  and  6H  polymorphs,  and  more  com- 
plicated types  can  be  developed.  Some  of  the 
previously  described  polymorphs  were  not 
contained  in  the  theoretical  list  and  were  re- 
examined. The  6M  structure  was  found  to  be 
a  2M2  polymorph,  the  6-layer  triclinic  type 
was  found  to  be  a  2  Mi  polymorph,  and  the 
3M  structure  was  shown  to  be  a  3T  type. 
The  24-layer  triclinic  structure  could  be  de- 
scribed on  a  simpler  8-layer  cell.  This  type 
together  with  a  new  12-layer  monoclinic 
structure,  as  well  as  other  structures  of  higher 
periodicity,  presumably  consists  of  complex 
stacking  and  results  from  spiral-growth 
mechanism.  Two  extreme  types  of  layer- 
disordered  crystals  may  be  built,  and  a  dis- 
order of  individual  ions  may  also  occur.  Sin- 
gle stacking  faults  result  in  twinned  crystals. 
A  new  twin  relation  (180°  rotation  about 
the  [100]  axis)  has  been  recognized.  Twenty 
specimens  from  extreme  geological  environ- 
ments have  been  examined  to  evaluate  the 
control  of  environment  on  the  stacking.  The 
type  of  stacking  could  not  be  attributed  solely 
to  the  influence  of  pressure  and  temperature. 
Composition  seems  to  play  a  dominant  role 


in  the  type  of  stacking,  and  semiquantitative 
structural  arguments  appear  to  support  this 
contention.  The  influence  of  growth  mecha- 
nism is  discussed.  A  scheme  for  the  identifi- 
cation of  the  mica  polymorphs  by  X-ray 
powder  and  single-crystal  methods  is  given. 

(1261)  The  chemical  formula  of  empressite. 
G.  Donnay,  F.  C.  Kracek,  and  W.  R. 
Rowland,  Jr.  Am.  Mineralogist,  41, 
722-723  (1956). 

Ag5Te3  is  synthetic  empressite.  Ag5_a.Te3 
is  the  formula  deduced,  for  the  mineral,  from 
cell  dimensions  and  density  of  analyzed 
crystals. 

(1262)  A  provisional  reclassification  of  granite. 

F.  Chayes.  Geol.  Mag.,  94,  58-68 
(1957). 

The  term  "granite"  could  be  usefully  re- 
served for  massive  or  weakly  oriented  plu- 
tonic  rocks  of  color  index  less  than  20  per  cent 
and  quartz  content  between  20  and  40  per 
cent  by  volume.  A  symbolic  classification  of 
rocks  meeting  these  requirements  is  pre- 
sented. The  various  classes  are  based  on  the 
relative  proportions  of  plagioclase  and  alkali 
feldspar,  and  subclasses  based  on  the  ternary 
dominance  ratio  quartz-alkali  feldspar-plagio- 
clase  are  also  proposed.  The  symbols  are 
simple  and  easily  remembered.  A  few  of  the 
common  names  now  in  use  are  retained  for 
class  designations. 

(1263)  Organic  constituents  of  fossils.  P.  H. 
Abelson.  Geol.  Soc.  Am.  Mem.  67,  pp. 
87-92  (1957). 

This  chapter  describes  the  occurrence  of 
amino  acids  in  recent  shells  and  in  a  variety 
of  fossils  as  old  as  360  million  years.  These 
findings  are  correlated  with  laboratory  tests  of 
the  thermal  stability  of  alanine. 

(1264)  High-order  transitions  in  (Na,K)  AlSi04. 

G.  Donnay.  Third  International  Meet- 
ing on  Reactivity  of  Solids,  Madrid, 
April  1956.    1957. 

According  to  Ehrenfest's  definition,  a  high- 
order  transition  corresponds  to  a  discontinuity 
in  any  one  of  the  derivatives  of  the  Gibbs  free 
energy  G.  The  order  of  the  transition  is  set 
equal  to  the  order  of  the  lowest  derivative  of 
G  that  shows   a  discontinuity.    High-order 


GEOPHYSICAL  LABORATORY        251 


transitions  are  usually  detected  by  observing 
an  anomalous  change  in  specific  heat  with 
temperature  for  a  given  composition.  Nephe- 
line,  Na8_a;Ka;Al8Si8032,  is  an  example  of  a 
low-temperature  phase  in  which  changes  of 
the  composition  a:  in  a  solid-solution  range 
result  in  high-order  transitions  at  x=^lA 
and  x  =  2.00.  A  singularity  in  the  curve  of 
cell  volume  V  against  x  corresponds  to  a  dis- 
continuity in  (dV/dx)^  which  is  equal  to 
(d2G/dPdx)T.  Such  a  transition  is  therefore 
of  the  second  order. 

(1265)  Annual  report  of  the  Director  for  1955- 
1956. 

(1266)  Optical  analyzer.  G.  Donnay  and  J.  D. 
H.  Donnay.  Rev.  Sci.  Instr.,  28,  145 
(1957). 

Two  Polaroids,  coupled  for  synchronous 
rotation,  are  mounted  between  glass  plates 
and  placed  one  at  the  top,  the  other  at  the 
bottom  of  a  brass  cylinder,  which  can  rotate 
in  a  brass  sleeve.  The  crystal  on  the  goniom- 
eter head  can  be  introduced  into  the  cylin- 
der through  a  hole  in  the  sleeve  and  a  cor- 
responding one  in  the  cylinder.  The  crystal 
can  thus  be  observed  between  crossed  Pola- 
roids while  it  is  rotated  about  the  axis  of  the 
goniometer  head. 

(1267)  The  nepheline-kalsilite  system:  I.  X- 
ray  data  for  the  crystalline  phases.    J.  V. 


Smith  and  O.  F.  Tuttle.     Am.  J.  Sci., 
255,  282-305  (1957). 

X-ray  data  are  given  for  the  following 
phases:  high-  and  low-  carnegieite,  high- 
and  low-nepheline,  kalsilite,  orthorhombic 
KAlSi04,  synthetic  kaliophilite,  natural  kali- 
ophilite,  anomalous  natural  kaliophilite,  tetra- 
kalsilite,  and  02.  Comparison  of  the  cell 
dimensions  indicates  that  the  structures  of  all 
the  phases  except  carnegieite  are  based  on  a 
tridymite-type  framework.  Synthetic  natural 
and  anomalous  natural  kaliophilite  are  not 
identical,  but  comparison  of  their  X-ray  prop- 
erties indicates  that  they  are  structurally  re- 
lated. The  variation  of  the  cell  dimensions 
of  nepheline  and  kalsilite  solid  solutions  has 
been  determined.  Discontinuities  in  the 
curves  of  composition  versus  cell  dimensions 
are  discussed  in  terms  of  the  known  crystal