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ON 

THE EROSION 

OF 

VALLEYS AND LAKES; 

A 

REPLY TO SIR RODERICK MURCHISON'S 

ANNIVERSARY ADDRESS TO THE GEOGRAPHICAL 
SOCIETY. 

BY 

A. C. RAMSAY, F.R.S. 



EXTRACTED FROM THE PHILOSOPHICAL MAGAZINE FOR 
OCTOBER 18C4. 



LONDON: 
PRINTED BY TAYLOR AND FRANCIS, 

RED LION COURT, FLEET STREET. 

1864. 



ON THE 



EROSION OF VALLEYS AND LAKES. 



AFTER the publication of my memoir '^On the Glacial 
Origin of certain Lakes in the Ice-worn regions of Europe 
and North America/^ several eminent British and Continental 
geologists, and some other persons who have only a general 
literary acquaintance with physical geology, did me the honour, 
in special memoirs, or in letters in newspapers, to express opi- 
nions that my views were deserving of the strongest opposition. 
To none of these opponents have I heretofore made any reply, 
and some of them, I found, were dealt with by men who met 
their arguments more ably perhaps than I could have done 
myself. Besides, I considered that if my theory, as I believe, 
be true, it would be sure in the long run to make its way just 
in the slow and steady manner it seems to me to be now doing. 
We all profess to appeal to nature, and " in nature there is no 
opinion ; there is truth in everything that is in nature ; and in 
man alone is error." To those who are not geologists in any 
practical sense it would never occur to me to reply. Physical 
geology, in the true meaning of the term, does not exist without 
a thorough practical acquaintance with, and experience of, rocks 
of all kinds on a large scale. The man who merely wanders 
about a country and looks curiously at rocks, without a long 
course of severe training, has no more scientific right to form a 
definite opinion as to the causes that brought about the external 
configuration of the land than the father of a family would have 
to decide questions in comparative anatomy, because for half 
his life he had daily carved beef, mutton, pork, fowls, and fish. 

Of late, however, an exceedingly authoritative protest against 
my theory has been entered by Sir Roderick Murchison, in his 
Anniversary Address to the Geographical Society, — an address 
issued indeed to the geologists of Europe ; for the portion that 
bears upon icy phenomena has been printed separately for special 
distribution. It would almost be uncourteous on my part silently 
to pass over the remarks of one who in his own person has 
attained the highest honours in the Geological and the Geogra- 
phical Societies, and who is besides my oldest living geological 
friend. " As a geologist, with wide experience, the President of 



4 Prof. A. C. Ramsay on the Erosion 

the geographers clearly states his conviction"* that my theory 
of the origin of certain lakes and other theories of denudation 
connected therewith, are so opposed to obvious facts, that, if 
his conviction be well founded, the wonder seems to me that 
any man of weight and know^ledge could be found to follow^ me 
at all. I may therefore be pardoned if in this instance I depart 
from the course of leaving the value of my theory to be worked 
out solely by time. 

I have said that Sir Roderick has entered an authoritative 
protest, because, as several persons have remarked to me, so much 
stress has been laid on the argumentum ad fwminem, liberally as 
regards Continental geologists, and more sparingly with Ame- 
rican and English names. Indeed, in reading the Address, I 
was more than once reminded of the observation of one of my 
opponents, who in the ' Reader ' observed to this effect, " that 
Professor Desor entirely disagrees with Professor Ramsay — how 
can he do otherwise ? for Desor has lived among glaciers all his 
life." In like manner Studer and Escher von der Linth, " by 
numerous appeals to nature," Gastaldi, De Mortillet, and many 
more are all arrayed in opposition to the theory, the presumption 
being that the chances are therefore infinitely against it, and I 
must needs be wrong because they are so eminent, and some of 
them have lived so long among the Alps. For, differing from 
them, how is it likely that a man can be right who has only ex- 
plored the Alps five or six times with a special object, even though 
he may have spent*five-and-twenty years on subjects allied to or 
identical with it ? Such is the general impression produced, not 
on myself alone, by many of Sir Roderick's remarks. I have no 
objection to this kind of argument ; it is so old in the history 
of science that its value is understood. To compare great things 
with our small matter, Copernicus and Galileo experienced it, 
Hutton and Playfair knew it well ; the most eminent geologists 
were for long deaf to the voice of William Smith, let him charm 
ever so wasely; and Agassiz himself, in glacial geology, had 
among his chief opponents distinguished seniors, some of whom 
even now only hesitatingly follow him. It is easy to " appeal to 
nature," but the language of her reply is not always to be 
understood merely by long poring on her face ; and it generally 
happens that many an abortive effort is made before some happy 
accident reveals the key. 

In my original memoir, when discussing the origin of the lake- 
basins, I found it necessary in some degree to treat of disturb- 
ances of rocks in general. Accordingly, Sir Roderick very pro- 
perly regards the question as one not merely of lakes, but as 
involving his belief "with the vast majority of practical geologists, 
that the irregularities of the surface of the Alps have been primarily 
* Geological Magazine, No. 3, p. 12". 



of Valleys and Lakes. 5 

caused by dislocations and denudations /^ and again, that " until 
lately geologists seemed so be generally agreed that most of the 
numerous deep openings and depressions which exist in all lofty 
mountains were primarily due to cracks which took place during 
the various movements ivhich each chain has undergone at various 
periods," &c. The meaning of this, I conceive to be, that moun- 
tain valleys lie in lines of curvature, dislocation, and fracture, 
and that the mountains on each side of them are mountains, far 
less because of denudation than by reason of operations of frac- 
ture and dislocation. Therefore important lakes that fill true 
rock-basins lie only in lines of fracture, or else, as in the myriad 
lakes of North America, in hollows of wider dislocation somewhat 
aided by subsequent denudations. 

Every reasoning mind respects authority when it bears ou 
questions that have been reduced to demonstration ; but this is 
precisely what has not been done with respect to the origin of 
S]}ecial Alpine lakes and valleys by those whose main argument 
is disturbance of strata. Assertions and crude ideas in all kinds 
of books and papers are " as plenty as blackberries ; " but for 
clear demonstrations— none are given. Nor does Sir Roderick 
either attempt or point to any when he says that in the Alps he 
" long ago came to the conclusion that the chief cavities, vertical 
precipices, and subtending deep, narrow gorges, have been ori- 
ginally determined by movements and openings of the crust, 
whether arranged in anticlinal or synclinal lines, or not less fre- 
quently modified by great transversal or lateral breaks, at right 
angles to the longitudinal or main folds of elevation or depres- 
sion." Now in my paper I gave six stratigraphical reasons to 
show why the lakes do not lie in hollows of disturbance, and 
then pointed to ice as the only remaining agent by which they 
could be formed, thus attempting to reduce the matter as nearly 
as I could to a demonstration ; and what I want is an attempt 
at demonstration in return. But where is the proof beyond the 
general assertion and impression that craggy-sided mountains 
and valleys prove dislocations which gape, if they were mere 
close or nearly close fractures and denudation did the rest, the 
argument is equally in favour of my view ; for valleys which have 
been scooped out by denudation often necessarily coincide with 
lines of fracture, a proposition obvious to every geologist. But 
I want the proof that the Alpine valleys are dislocations. Let 
any one go into them and prove it in numerous cases, with his 
geological map in his hand, by the arrangement of the rocks on 
either side, and by the fracture or fault visible, or otherwise cer- 
tainly demonstrable in the bottom. Where are these valley faults, 
whose name ought to be legion, marked in the best geological 
maps of Switzerland ? If they exist, they remain yet to be indi- 
cated in definite lines ; for indeed none know better than the 



6 Prof. A. C. Ramsay on the Erosion 

many eminent geologists of Switzerland and the north of Italy, 
for whom and for whose work I have the highest respect, that 
the geological map of their country is as yet but an admirable 
sketch, and in all probability will remain so till their governments 
authorize more general and uniform painstaking surveys. When 
this is done, and when all the faults and curvatures possible are 
actually laid down, and when geological sections on a true scale 
have been run across the Alps, it will then be possible to reason 
with precision on the denudation of the mountains; and it 
will be found (what is well known now) that before the present 
surface of the valleys saw the light, vast piles of strata, as in 
Wales, have been removed by denudation, and the valleys were 
formed long after the latest important disturbances of the strata 
took place. 

And now to prove that 1 also respect authority, let me quote 
from books of immortal repute ; and surely those who reverence 
authority most, will not disdain that of Hutton and Playfair. 
What say the father of physical geology and his great disciple ? 
"If," says Hutton, reasoning on this subject, "the valley was 
made for the rain by any other natural cause, either we should 
tell by what means this work had been performed, or all reason- 
ing on the subject is at end, and fancy substituted in its place. 
If, again, the river be considered as the means employed by 
nature in making this valley, then all the solid parts between 
the bounding mountains must have been removed." Again, 
reasoning on the weathering and erosion that originated the py- 
ramids on and around Mont Elanc, he observes, " It is true, 
indeed, that geologists have everywhere imagined to themselves 
great events, or powerful causes, by which these changes in the 
earth should be brought about in a short space of time ; but they 
are under a double deception ; first, witli regard to time, which 
is unlimited*, whereas they want to explain appearances by a cause 
acting in a limited time; secondly, with regard to operation, 
their supposition of a great debacle is altogether incompetent for 
the end required." Again, arguing on the approximately hori- 
zontal gneissic strata of the neighbourhood of Monte Rosa, he 
shows that the great isolated peaks have been separated by " the 
greatest degradation, in being wasted by the hand of time. . . . 
Here," he says, "is nothing but a truth that may almost every- 
where be perceived " if we had only faculties to perceive it. 

Again, reasoning on strata that correspond on opposite sides 
of valleys, Plaj'fair, in the Huttouian Illustrations, says, "there is 
no man, however little addicted to geological speculations, who 
does not immediately acknowledge that the mountain was once 
continued quite across the place in which the river now flows ; 
and, if he ventures to reason concerning the cause of so wonder- 
* In the original, " limited.". This is an evident misprint. 



of Valleys and Lakes. 7 

ful a change, he ascribes it [in the modern fashion] to some 
great convulsion of nature, which has torn the mountain asunder 
and opened a passage for the waters. It is only the philo- 
sopher, who has deeply meditated on the effects which action 
long continued is able to produce, and on the simplicity of the 
means which nature employs in all her operations, who sees in 
this nothing but the gradual working of a stream, that once 
flowed over the top of the ridge which it now so deeply inter- 
sects, and has cut its course through the rock, in the same way, 
and almost with the same instrument, by which the lapidary 
divides a block of marble or granite/' And in the Alps (p. 122) 
he shows that " the sharp peaks of the granite mountains .... 
but mark so many epochs in the progress of decay," while the 
loftiness of the harder peaks is due not to mere upheaval but to 
the circumstance "that the waste and detritus to which all 
things are subject will not allow soft and weak substances to 
remain long in an exposed and elevated situation." "Thus, 
with Dr. Hutton (p. 126), we shall be disposed to consider those 
great chains of mountains, which traverse the surface of the 
globe, as cut out of masses vastly greater, and more lofty than 
anything that now remains." I could multiply sentences of 
this kind from the writings of these great philosophers ; but 
enough has been said to recall to memory the fact that before 
the present race of " practical geologists " had written a line, 
men of rare knowledge, keen sagacity, and the highest intel- 
lectual powers, by appeals to nature already held those views 
which some of their degenerate descendants have so readily repu- 
diated, but to which a younger school show strong symptoms of 
returning. 1 doubt also if some of the Swiss and Italian geolo- 
gists will be quite content to stand godfathers to the opinion that 
the Alpine valleys generally are apt to lie in lines of mere curva- 
ture or fracture, whether close or gaping; but without further 
authority than that of personal conversation it would be impro- 
per to quote their names. 

Unless I were to write a special elementary treatise on denu- 
dation, enough has now been said to show that the theory of 
formation of great systems of valleys by erosion in which water 
and ice are main agents, is not a mere absurdity, and 1 do not 
therefore care minutely to analyze the assertions that many of 
the Alpine rivers " flow in fissures or deep chasms, . . . which 
water alone never could have opened out;" or again, that the 
Rhine and the Danube "never could have eroded those deep 
abrupt gorges through which they here and there flow, and 
which are manifestly due to original ruptures of the rocks." To 
the neglected and even half-forgotten school of Hutton and 
Playfair, and to many expert geologists of the present day whose 
lives have been spent in practically analyzing the rocky struc- 



8 Prof. A. C. Ramsay on the Erosion 

tures of countries, the manifest nature of such " original rup- 
tures " is anything but evident ; and I for one believe that the 
" ruptures" are only manifest to those who accept such hypotheses 
" without inquiring into what has been the former state of things, 
or what will be the future"*. To this day there is no error so 
common, even among geologists, as that which vaguely attri- 
butes the form and nature of the present surface-outlines of the 
earth chiefly to the operation of violent disturbance in recent 
geological times, not clearly perceiving that the great and small 
outlines of mountain- chains, of valleys, of river-gorges and of 
plains are the combined results of an immense number of opera- 
tions, many of these going back to exceedingly remote periods of 
geological antiquity, and a great proportion of their details being 
lost even to probable conjecture. 

These operations, however, in the production of scenery mainly 
resolve themselves into the following series, the parts of which, 
ever since land and water first existed, may be arranged in any 
possible combination. 

a. Oscillation with respect to the sea-level of rocks that have or 
have not been contorted and metamorphosed, accompanied by pauses 
in oscillation of greater or less duration. 

b. Great plains of marine denudation. 

c. Subaerial denudations of all kinds ; wearing away of sea- 
coasts ; and in the interior of the country, chemical decompositions, 
frost, snow, ice, wind, rain, and rivers; modified by height of land, 
and the various positions, hardness, and other characters of rocks. 

Contortion and metamorphism seem to be essential accompa- 
niments of all great mountain-chains. It may also possibly 
be proved that in intensely contorted regions mountain-chains 
are high or low according to the relative antiquity of disturb- 
ance, while sometimes the irregular protuberances, as in the 
Devonian and other rocks of the Rhine and Moselle, have been 
planed away altogether. 

Plains of marine denudation are sure to be inclined at a very 
low angle if formed during slow depression of the land. 

Further, while the sea helps to make bays, the other agents of 
waste enumerated above cut out all mountain-peaks not volcanic, 
all the minor valleys, in this term including such valleys as those 
of the Alps, the Highlands, Wales, &c., but not such a valley as 
the great one that lies between the Alps and the Jura. 

Fractures and volcanos, in the production of the great scenic 
features of continental pliysical geography, are, as a rule, mere 
subordinate and subsidiary accidents, the first modifying the 
effects of denudation by juxtaposition of different kinds of rocks, 
and the second (which seem to be connected with general elc 
rations) forming accidental mountains, hills, and hilly regions, 
* Hutton, vol. ii. p. 257. 



of Valleys and Lakes. 9 

which, as in the Andes, may form non-essential parts of moun- 
tain-chains. 

I shall now make some remarks on what has been said in the 
Address respecting the action of ice in general, and its share in 
forming lakes that are true rock-basins in particular, taking 
these in connexion with other points at issue. 

" Before entering on the consideration of the new theory of 
the power of moving ice," Sir Roderick gives a brief review of 
the recent progress of Alpine glacial geology, meaning by recent 
principally those twenty-five or thirty years that have elapsed since 
Agassiz began to insist not only on the enormous size of the old 
glaciers of the Alps, but on what is now generally recognized as 
the true glacial theory. " Granting to the land glacialists their full 
demand " for the great size of the old glacier of the Rhone, it is 
stated by Sir Roderick, backed by the authority of Sir Charles 
Lyell, that there is nothing in that fact " which supports the opi- 
nion that the deep cavity in which the lake [of Geneva] lies was 
excavated by ice ;" for among other things it is " to be noticed 
in the case of the Lake of Geneva " that it "trends from £. to 
W., whilst the detritus and blocks sent forth by the old glacier 
of the Rhone have all proceeded to the N. and N.N.W., or in 
direct continuation of the line of march of the glacier which 
issued from the nai'row gorge of the Rhone. By what momen- 
tum, then, was the glacier to be so deflected to the west that it 
could channel or scoop out, on flat ground, the great hollow 
now occupied by the Lake of Geneva ? And, after efi^ecting this 
wonderful operation, how was it to be propelled upwards from 
this cavity on the ascent, to great heights on the slopes of the 
Jura mountains ?" The same argument it is stated holds good 
of the Rhine glacier, which I have attempted to show scooped 
out the shallow hollow of the Lake of Constance. One would 
suppose these questions to be so conclusive, that the mere asking 
is enough, and any opposite views must be absurdities which no 
man of any sound knowledge could entertain ; and yet men are 
found who do entertain them in part or in whole, even authors of 
great authority on geological and physical subjects, not only in 
the three kingdoms, but on the continents of Europe and Ame- 
rica. Now with regard to the great old glacier of the Rhine, the 
sentence bearing on it is so worded that I am unable to make out 
whether it is implied that in the belief of Sir Roderick Murchi- 
son no great glacier issuing from the Upper Rhine valley ever 
overspread the region around the Lake of Constance, or whether 
he and M. Escher von der Linth simply at one time could not 
find signs of a glacier that so " plunged into the flat region on 
the east and north " (of the Hohe Sentis) " as to have scooped 
out the cavity in which the lake lies." If the former, then Sir 



10 Prof. A. C. Ramsay on the Erosion 

Roderick's opinion seems to have been formed a long time ago ; 
for, adopting M, Escher's authority, anyone who cor.sults his 
map of the ancient extension of the Alpine glaciers, will see that 
he draws an enormous glacier, which issuing from the broad flat 
valley of the Rhine, tranquilly overspread the country on all sides 
of the lake, and without the necessity for any plunge, could only 
have been itii by smaller tributary streams of ice that, if such 
existed, descended on the northern slopes of the Hohe Sentis*. 

In like manner. Sir Roderick is of opinion that the basin of 
the Lake of Geneva was not scooped out by ice, because "it 
trends from east to west," or at right angles to the main flow of 
the glacier — because ice, per se, neither has nor has had any 
excavating power" — because (p. 12) "in valleys with a very 
slight descent, .... no erosion whatever takes place, particularly 
as the bottom of the glacier is usually separated from the sub- 
jacent rock or vegetable soil by water arising from the melting 
of the ice," and because even in gorges " whence the largest gla- 
ciers have advanced for ages, we meet with islands of solid rock 
and little bosses still standing out, even in the midst of the val- 
leys down which the icy stream has swept," and "there is no 
proof of wide erosion " — and, yet again, because (p. 15) " ice has 
so much plasticity that it has always moulded itself upon the 
inequalities of the hard rocks over which it passed," and " has 
never excavated the lateral valleys, nor even cleared out their 
old alluvia," and furthermore, in general terms, because ice 
could not have been propelled up an inclination from the bottom 
of a lake, let the angle, I presume, be ever so small. 

Now the east and west course of the lake is here treated as if 
the glacier of the Rhone which overspread it were the only gla- 
cier which helped to cover the area ; but if any one will take the 
trouble to refer to the map which accompanies my memoir, or, 
better still, to M. Escher's, he will see that the mass of ice must 
have been prodigiously swelled by the great tributary glacier of 
Chamouni, which, descending from Mont Blanc, filled a valley 
some fifty miles in length, and joined the Rhone glacier near the 
lower end of the Lake of Geneva. Neither does it require much 
reasoning to see that during the cold of the glacial epoch all the 
higher region south of the lake must have maintained its glaciers 
and filled the valleys that run north ; for even now some of the 

* I have to apologize to my friend M. Escher von der Linth for not 
having used his map of the ancient glaciers as my chief authority when my 
Jlemoir on the Lakes was read. The first time I saw his map, which was 
sent me by Principal Forbes of St. Andrews, was after the publication 
of my memoir. Had I seen it in time, I would certainly have availed my- 
self, in the construction of my sketch map. of the authority of a geologist so 
accurate and distinguished as Escher von der Linth, 



of Valleys and Lakes. 1 1 

peaks are tipped with perpetual snow. The Rhone glacier had 
therefore no lack of tributaries to maintain its mass over all the 
area of the Lake of Geneva, though towards the west, where the 
glacier thinned away, that mass would be less than over the 
eastern half of the lake, where weight and grinding-power must, 
I believe, on that account have necessarily been greater. But 
the main flow of the ice, after escaping from the Rhone valley, 
was necessarily of a mixed nature, partly to the N.W., and also 
to a great extent to the N.E. and S. W., simply because the N. W. 
face of the glacier abutted on the Jura. For it requires no pro- 
found knowledge of physics to perceive that any body, whether 
actually plastic like pitch, or of a modified plasticity that may be 
fractured and reunite hke^e/Zy*, or that by " fracture and regela- 
tion " behaves like a plastic body, — I say it requires no profound 
knowledge of physics to understand that such a body, constantly 
renewed and pressed on from behind, w^hen opposed by a high 
impassable barrier (like the Jura), will spread itself out in the 
direction of least resistance, that direction in the case of the 
Rhone glacier having been at right angles to the general pres- 
sure, or N.E. and S.W., whence I believe the general form and 
trend of the Lake of Neuchatel. 

But, in the second place, is there indeed no proof that ice 
" neither has nor has had any excavating power," whether in val- 
leys of large or of low inclination, narrow or broad ? Then why 
is it that all the rivers that flow from glaciers, great and small, 
are so muddy ? Surely no one will contend that all " the flour 
of rocks " that gives to the rivers a pipeclay colour has been 
washed in by streams from the surface. Alpine club men who 
drink (rarely) of the brooks that run on the surface of the ice 
will repudiate the idea ; those who fancy they see in the Loess 
of the Rhine the old glacier-ground mud of the Alps will shrink 
from it ; and many, if not all the Alpine geologists versed in ice 
whom I have conversed with in Italy and Switzerland, will, I ven- 
ture to say, still hold that glaciers by erosion seriously affect 
their beds. What else is the meaning of the striation and deep 
grooving, the mammillation and the glassy polish, even of quartz, 
and of all the Alpine rocks, whether hard or soft ? The mud of 
the rivers is chiefly derivedfrom this incessant ice-waste; and that 
is why it is so unearthy, so clean, fresh, and impalpable. Were it 
merely or chiefly surface-wash, derivedfrom the hills and washed 
underneath and carried forward below the glaciers, the sediment 
in great part would be dirty, torrential, and coarse enough, espe- 
cially if, as is stated, glaciers do not seriously grind along their 
rocky floors. So far from a glacier exercising only a trifling grind- 
ing-power, " because it is usually separated from the subjacent 
* I have obtaineil this comparison from the Master of the Mint. 



12 Prof. A. C. Ramsay on the Erosion 

rock or vegetable soil by water arising from the melting of the 
ice/^ the grinding power is so immense, that in unweathered 
ground comparatively recently covered by a glacier, every foot 
of surface is often polished and striated. If, indeed, water usually 
separates ice from the rock so that it does not press upon it, 
a glacier, whether 30 or 3000 feet thick, would need to be 
trciited in the main as a floating body; and it is well known 
that with floating ice there is some eight or ten times as much 
ice below as above the water. 

As for bosses " still standing out in the midst of the valleys " 
proving that glaciers have no erosive power, the reader unlearned 
in theories of denudation will easily understand that the same 
kind of argument might be applied to the pillars of earth left 
for a time in the midst of a railway-cutting the actual exca- 
vation of which he had not seen ; or because Goat Island still 
stands in the middle of the falls, the Niagara has not cut its 
gorge ; or because other low islands lie higher up, the river has 
not worn out a channel on either side of them and will not 
destroy them ; or in marine denudation, that the chalk between 
Old Harry and his Wife and the mainland of Swanage Bay, and 
that between the Needles and the Isle of Wight, has not been 
washed away by the sea, because the islets still stand in the 
midst. If, however, it be said that the glacier-islets are the 
result of old subaerial denudations before the glacier began to 
flow, I might perhaps doubt it, but, for evident reasons, for the 
purpose of this argument, I will not quarrel with it. If they 
have not been left prominent either by streams or ice, then, 
according to the hypothesis which accounts for these valleys by 
disturbance, the bosses in the midst of the glaciers are the result 
of a process of dislocation of which I should like to see the spe- 
cial proof. 

The peculiarity and in part the amount of this wearing action 
of ice is indeed due to that very " plasticity " which enables ice to 
mould " itself upon the inequalities of the hard rock." And it is 
just therein that its excavating power diff'ers from that of water. 
Still water cannot excavate a large basin-shaped hollow, and in 
the depths of a lake water is still; but glacier- ice, having 
" moulded itself upon the inequalities of the hard rocks over 
which it passed," can even move right over a barrier of rock and 
grind it into ruches moutonnees. The very fact that a roche mou- 
tonnee has, as stated by Sir Roderick, a "Stoss-Seite," is indeed 
proof that with sufficient pressure behind, a glacier can to some 
extent pass uphill ; and those who remember the great size and 
height of many of these barriers in Switzerland, as, for instance, 
the Kirchet and the hill behind the Grimsel, will be prepared to 
follow the arguments urged in my original paper — and, for dif- 



of Valleys and Lakes. 13 

ferent reasons, also held by De Mortillet — viz. that a glacier of 
sufficient thickness could not only fill a lake, but could flow up 
the low angle of the ascent towards the outflow and escape 
beyond its bounds*. 

If a glacier can round, polish, and cover with striations the 
rocks over which it passes — if, flowing from its caverns, it can 
charge rivers thickly with the finest mud, then it can wear away 
its rocky floor and sides. Here indeed an appeal to nature may 
safely be made, and the answer will be easily obtained ; for, 
standing on the surface of scores of glaciers, such as those of the 
Aar, and casting the eye upward, the whole mountain-sides are 
moutonnes, and parallel striations running along and down the 
valley are universal ; and not there alone, but miles and miles 
below the end of the puny glaciers of today the signs of the 
same wearing actions of grander ice-streams are visible both in 
and thousands of feet above the present bottoms of the valleys. 
It needs no subtle argument to prove it. Nature proclaims it ; 
we have but to open our eyes and look upon it to see that ice 
grinds, and has ground and planed away the surface of rocks, as 
surely as a planing machine cuts ii'on, and for much the same 
cause. "What more," says Hutton, writing of analogous waste, 
" what more is required ? Nothing but time. It is not any part 
of the process that will be disputedf ; but after allowing all the 
parts the whole will be denied ; and for what ? only because 
we are not disposed to allow that quantity of time which the 
ablution of so much wasted mountain might I'equire." " Time," 
says Playfair, " performs the office of integrating the infinitesimal 
parts of which this progression is made up ;" and though I have 
in this Magazine formerly attempted to show, for purely geolo- 
gical reasons, that the greater valleys in the Alps existed before the 
so-called glacial period, yet I know perfectly well, not only that 
since that time glaciers have worn a vast quantity of matter out 
of them, but that, given sufficient time, a glacier of itself might 
scoop out a valley of any depth, just as running water may do 
the same, or as surely as that, given sufficient time, the sea will 
wear away any island, soft or hard, large or small, that rises 
amidst its waves. 

In further proof of the assertion that glacier-ice can have no 
serious effiect in wearing away its bottom, great stress is laid on 
the well-known fact that such short and steep glaciers as those 

* Unless I am much mistaken, geologists will some day be much sur- 
prised at the size and kind of hills that they will be obliged to allow that 
glaciers have travelled over. 

t Things, however, that he co nsidered almost self-evident are now dis- 
puted every day. The tendency of opinion begins to set in the opposite 
direction. 



14 Prof. A. C. Ramsay on the Erosion 

of the Brenva and Miage ride over their moraines. I know these 
glaciers well, and the statement that they do ride on their 
moraines is perfectly true ; but few geologists, and probably no 
physical philosopher will rest his reputation on the assertion 
that, if those glaciers were to increase till they attained their 
ancient size, when as mere tributary sources they helped to swell 
the enormous mass that ploughed all down the Val d'Aosta to 
beyond Ivrea, — will anyone, I say, rest his reputation on the 
belief that these moraine heaps would lie where they now do, 
underneath a thousand or thousands of feet of ice, unmoved to 
all eternity, or at least till the complete decline of the glaciers 
permitted the loose material to be attacked by running water? 
If so, again, whence the muddy glacier rivers, and whence the 
scratched stones that come from under the glaciers ? Tyndall will 
not believe in their immobility, nor De Mortillet, nor Gastaldi, 
nor Darwin, who was the first to show that the larger glaciers of 
"Wales had ploughed the drift out of some of the greater valleys 
of the country ; and many other geologists of weight will equally 
shrink from the idea. Has ice no weight ? Do the huge glaciers 
of Victoria-land and of Greenland exert no pressure on the ground 
over which they flow ? and are there no stones and no powder of 
rocks beneath to help the grinding-power ? Rub iron with your 
finger often and long enough, and it will wear a channel in the 
metal ; for the skin, like the passing glacier, will be renewed, 
while the iron has no means of restoration. If yielding water 
can wear out a channel, which few people will deny, far more, 
then, must the weight of a thick glacier exercise a prodigious 
abrading-power ; for surely no one on reflection will be so bold 
as to assert that 50 feet, or one, two, or three thousand vertical 
feet of ice with a specific gravity of nearly 0-92 will everywhere, 
or nearly everywhere, be separated from its floor by a stra- 
tum of water so complete that the glacier rarely touches the bot- 
tom. If Agassiz, Forbes, and Tyndall, backed by Studer, 
Escher, and Gastaldi, were to tell me so (and they would not 
dream of it), my reverence for authority (and it is great) could 
not persuade me to believe them. 

If, then, glaciers can waste rocks and deepen valleys, is it 
possible that the great old glaciers under favourable circum- 
stances have excavated lake-basins, when rocks of unequal hard- 
ness came in their course, or when from special causes the 
pressure of ice was unusually great on certain areas ? Or were 
they apt to do so by a combination of these causes, when, ceas- 
ing to flow through valleys of great or of moderate inc ination, 
they descended into regions that are comparatively level ? 

I will not repeat what I have elsewhere printed about the 
effect of ice passing over rocks of unequal hardness, nor yet what 



of Valleys and Lakes. 15 

I have said of the confluence of immense glaciei-s like those that 
once united in the valley of the Lago Maggiore at what are now 
the Borromean Isles. But it seems to me that to any one who 
allows any excavating power to a glacier, it will be evident that 
when the general inclination of a valley was comparatively steep, 
a glacier could have had no opportunity of cutting for itself any 
special basin-shaped hollows. Its coui'se, with a difference, is 
like that of a torrent. But in a flat-bottomed part of a valley, 
or in a comparative plain that lies at the base of a mountain- 
range, the case is not the same. For instance, to take an ex- 
treme case, if a glacier tumble over a slope of 45°, no one would 
dream of the ice-flow producing any special effect, except that 
in the long run, the upper edge of the rock that forms the cata- 
ract being worn away, its average angle would be lowered. And 
so of minor slopes ; if the ice flowing fast (for a glacier) rendered 
the rocky surface undei-neath unequal, such inequalities could not 
become great and permanent ; for the rapidly flowing ice would 
attack the projecting parts with greater power and effect than the 
minor hollows, and so preserve an approximate uniformity, or an 
average angle of moderate inclination. But when a monstrous 
glacier descended into a comparative plain, or into a low, flat 
valley, the case was different. There, to use homely phrases, 
the ice had time to select soft places for excavation, and there, if, 
from the confluence of large glaciers, or for other reasons, the 
downward pressure of the ice was of extra amount, the excavating 
effect, I contend, must have been unusually great in special areas, 
and have resulted in the formation of rock-bound hollows. And 
though the glacier of Ivrea has been constantly quoted as a case 
that completely proves the absurdity of my theory, this merely 
shows the unwariness of those who quote it ; for not only are 
there a great many rock-basins full of water above Ivrea in 
among the vast roches moutonnees near the opening of the plain, 
but, where beyond this point the glacier spread out so wide on 
the Pliocene plain, it has scooped away so much material that 
parts of that plain are below the average level of the plains of 
Piedmont that lie outside the great moraine. Given sufficient 
time and extension of the glacier, and more matter still would 
have gone away. The same argument equally applies to the 
case on the Lake of Zurich, where glacier debris is said to lie on 
alluvial detritus. In reply to the question why in the actual 
valley of Aosta there are no lake-basins, I might with equal 
propriety say, Many contorted regions are much faulted, and 
there is often an evident connexion between contortion and faults ; 
but in some contorted regions there are few or no faults, and 
the reason of their absence remains to be accounted for. I have 
attempted to explain why the rock-basins are present, and not 



16 Prof. A. C. Ramsay on the Erosion 

why they are absent. It may be that some of the alluvial flats 
of the valley are lake-hollows filled up. 

But another statement urged by Sir Roderick against my 
theory is^ that the scooping-out of such hollows by ice is im- 
possible, because ice cannot flow up an inclined plane. If so, I 
repeat, what is the meaning of the " Sioss-Seife" or upper side 
of a roche moutonnee that bars a wide glacier valley, through 
which barrier perhaps a mere narrow river gorge passes — as, for 
instance, in the case of the Kirchet so well known to Alpine 
men, or, on a smaller scale, of the roches moutonnees near the 
slate-quarries in Nant Francon ? In both cases the barrier re- 
mained intact till the drainage of the glacier- formed lakes cut 
gorges through them — or, if Sir Roderick prefer it, till convul- 
sions made gorges. Its moutonnee form will convince every 
accomplished glacialist that the ground was once covered by 
ice. The strike of the rocks will be enough for ordinary geolo- 
gists ; for no man can suppose who sees the corresponding forms 
of the roches moutonnees on either side of the narrow gorge of 
the Aar, that that gorge existed before the period of the great 
glacier, and that the glacier flowed entirely between the walls of 
the narrow passage. If I am right in this, then the great old 
glacier of the Aar flowed right over the hill, from bottom to top, 
and away into regions far beyond, in the manner I have imper- 
fectly shown in my little book on the old glaciers of Switzerland 
and North Wales, and equally so whether the gorge was formed 
by sudden violence or by water. 

In the existence, therefore, of " Stoss-Seiten," and in their 
upward striations, both in small and large roches moutonnees, 
there is proof that the belief that glaciers cannot flow over 
hillocks, and even hills of considerable size, is a mere assertion 
founded on prejudice : to me the wonder is, that any one can 
ever have believed it who has truly observed phenomena in the 
Alps, or who is familiar even with the ancient glaciation of our 
own country. And if this be so, I see no difficulty in accepting 
the hypothesis that the length and inclination of the slope 
which the bottom of a glacier may ascend depend simply on 
the thickness of the ice, and on the amount of the propelling 
power behind, that power being due to the weight and mass of 
the descending ice, and the average angles of the valley behind 
the point whence the upward ascent begins*. 

Now, in dealing with this question, most of the geologists 
who have opposed me have treated the larger lake-hollows much 
as they do Time. Unconsciously they seem to me to be afraid both 
of it and of them. "Look,'' they seem to say, "at these mountains, 

* I think it might be possible to make a very good approximate calcula- 
tion on this point, and I hope it may yet be done. 



of Valleys and Lakes. 1 7 

how awfully high and rugged they are ; can any amount of time, 
aided by weather, torrents, rivers, and glaciers produce such 
eflFects ? Old writers, like Hutton and Playfair, and a few 
modern observers (some of whom, both in America and Europe, 
have great familiarity with rocks), say they can; but we know that 
rending and fracture is the chief agent, and denudation is in com- 
parison quite a trifling affair. Look, again, at the hollows of the 
lakes, how awfully deep they are ! How is it possible for a glacier 
ever to have slid up a hill from a depth so profound ? " In 
treating the slopes as great, consists the viciousness of this sup- 
posed argument. Unconsciously, some of the arguers are draw- 
ing exaggerated diagrams in their minds. They foreshorten the 
slope, increase in their mind's eye its steepness, and forget 
their trigonometry altogether. But let me beg of them to try 
to realize the real state of the case, and see how small by com- 
parison the depth really is, and how gentle the slope. Were 
the bottom of the Lago jMaggiore not undulated (for I believe 
the islands to be mere roches moutonnees) , this slope from the 
deepest part of the lake (2600 feet) to its outflow would only 
be 2° 21' in a distance of about 12 miles, a slope so gentle that, 
were a man standing on it, by the eye he would barely be able 
to tell whether he was on an inclined plane or not*. Again, 
take the Lake of Geneva from the place where it is nearly a 
thousand feet deep to Geneva, the average slope is only about 
25', an angle so small that any geologist looking at it would be 
apt to consider the surface as horizontal. The question, then, 
as regards the lakes resolves itself into this : Is it possible that 
the ice of the great old glaciers could ever have travelled up 
these exceedingly small inclinations for a distance, say of 12 
miles in the one case and 20 to 25 miles in the other ? 

And now, in connexion with this point, I could wish that Sir 
Roderick had expressed an opinion whether or not he agrees 
with the old geologists, that (p. 7) " the Lakes of Geneva and 
Neufchatel were so filled up with snow and ice that the advancing 
glaciers travelled on them as bridges of ice, the foundations of 
which occupied the cavities." If this were so, then, in other 
words, the lower strata of ice in the hollow of what is now a 
lake remained in a condition of static equilibrium, and over this 
ice the advancing part of the glacier slipped or was propelled. 
Strictly speaking, it is evident that this state of static equilibrium 
is impossible ; for all the ice of a glacier a little below the sur- 
face being, even in winter, in a melting state, the lower strata 
above alluded to must have been destroyed and renewed over 
and over again ; and as glacier-ice is practically anything but a 

* In my original paper on the glacial excavation of certain lakes, I 
made an unfortunate error in calculation, stating that the angle is about 5°. 
In an able article in the ' Reader,' Professor Jukes corrected the error, and 
made the slope 2°. 



18 Prof. A. C. Ramsay on the Erosion 

rig:id body, I think it would be easy to show that, just as in Arc- 
tic regions in winter the more rapid flow of the lower strata of 
ice, with a temperature of about 32°, shatters the more rigid 
and slowly-moving upper layers which have a temperature far 
below that point, so, for other reasons, the motion of some 2000 
vertical feet of ice sliding over the basin, would be communicated 
to the lower strata ; for pressure in ice produces adhesion of parts. 
I for one cannot conceive a horizontal fracture of 40 miles in length 
over the area of the Lake of Geneva, clearly dividing two bodies 
of ice, the lower of which was, where thickest, nearly 1000 feet, 
and the upper and sliding stratum must have been nearly 3000 
feet thick. It is, in fact, a piece of mere elementary knowledge 
that any heavy body passing steadily across any other body, the 
parts of which are moveable, will communicate motion to the 
parts over which it passes, whether one or both of those bodies 
be viscid or plastic, or of some other compound character ; and 
when I wrote my original paper it never occurred to me that 
there was any need of mentioning a point so obvious. But in a 
glacier that tills a lake-basin, this is by no means the only, and 
perhaps not the principal, cause of motion. A glacier does not 
throughout all its course move on simply by virtue of gravity. 
Pressure from behind has a great deal to do with it ; as, for 
instance, in the case of the Rhone glacier, familiar to so many, 
and cited by Professor Merian and Dr. Tyndall. There, at the 
cataract, the ice fractures and slides down comparatively rapidly 
in masses, but at the base, where it moves slowly, pressure from 
behind causes the masses to touch and reunite, and the whole 
slides on, a re-formed mass, into the lower valley, the inclination of 
which is small. So, in the case of the lakes, the depths of which 
seem so appalling, but the real angles of the beds of which are so 
small, there seems to me nothing either impossible or remarkable 
in the idea that the long and enormous onflowing inclined 
mass of the glacier of the Rhone pushed before it in the plain 
(for such it is) its own more sluggish continuation up a slope of 
25' for a distance of 20 or 25 miles. I believe that the same 
argument is equally applicable to the Lago Maggiore. where the 
already vast glacier, swelled by the mighty tributary of the Val 
d^Ossola, was thus enabled to push along the low average slope 
of 2° 21' for a distance about half as great. The very islands in 
many a lake once filled with ice help to prove this ; for, as in 
the case of Loch Lomond, they are mere roches moutonnees, and 
I for one cannot conceive that the mammillation ceases imme- 
diately below the surface of the water. 

Having got thus far, I will not repeat my arguments to show 
that (as I attempted to prove in my original memoir) the Alpine 
and other ice-worn lakes known to me do not lie in areas of 
special subsidence, nor in gaping fractures, nor in simple synclinal 



of Valleys aad Lakes. 1 9 

basins, nor in hollows of watery erosion. If any one who reads 
this is curious about them, he must refer to that memoir*; but 
this at least I may be permitted to say : I used at all events 
arguments, even somewhat elaborate, and not mere statements, 
and whether these arguments are fated to be successful time 
alone will show. That they were at all events of some value, the 
names of the distinguished geologists who have accepted my 
theory helps to show ; and 1 could add to these other names as 
high as the very highest of those on whose authority Sir Roderick 
so much depends, did propriety permit me to quote from letters 
and commit men to opinions which they have not expressed in 
print. 

But before leaving the subject, let me say a little more about 
the possibility of these lakes lying in fractures. For this pur- 
pose let us take some of those that lie on the north side of the 
Alps, partly in the region of the Miocene strata. If they lie in 
lines of gaping fracture, nearly as wide as the present lakes, 
then on the hills, say between the Lake of Lucerne and Thun, 
and between Thun and the Lake of Zurich, the Miocene strata 
would be crumpled up in zigzag lines across the average line of 
strike, to an amount corresponding to the distance between the 
severed strata in the spaces now overlooking and occupied by the 
lakes. This is not the case. Again, if the fractures were mere 
narrow cracks, then the amount of denudation that took place 
so as to form the wide valleys has been enormous, and within a 
mere fraction of what I require, especially when we consider 
that the great denudation necessary to widen the fractures would 
have filled up the lake-basins. The theory of the chief forma- 
tion of Alpine valleys having been effected by weather, water, 
and ice, would therefore still hold good. 

I might continue these arguments, and discuss in detail what 
Sir Roderick has said about Scandinavia, North America, and 
other regions, and among other things show how unprecise is 
the knowledge that we actually possess respecting the details of 
the boulder-beds that overspread some of them, and how unsafe 
it is to conclude, because a country is not actually mountainous, 
and does not now lie high above the sea-level, that it was never 
covered by glacier-ice in motion, and may not at one time 
have lain much higher. In spite of Agassiz^s memoirs, it is not 
long since all the lower Till of Scotland was considered not to 
be ordinary moraine-matter at all, but to have been formed 
solely in the sea by the transporting agency of icebergs. Let 
those who still believe it refer for proof to the contrary to Mr. 
Geikie's admii'able work ' On the Phenomena of the Glacial Drift 
of Scotland.' I know enough of the superficial strata in North 

* They are also given in ' The Physical Geology and Geography of 
Great Britain.' 



20 On the Erosion of Valleys and Lakes. 

America to foresee that the erratic deposits there will some day 
also be divided into terrestrial and marine series, and I am 
pretty sure that Sir William Logan will not deny the proba- 
bility. For the vast size of the ancient glaciers of that con- 
tinent, I would refer to Professor Dana's admirable Manual of 
American Geology. It is a mistake to suppose that the stria- 
tions there merely run from north to south, for Sir William 
Logan, who has mapped them, proves that they often conform 
to the bends of the valleys. 

As regards the great lakes of that continent, so far from being 
" cavities originally due to a combination of ruptures and denu- 
dations of the rocks,'' it is impossible intimately to know the 
country and believe it. There the Silurian strata, amid which 
the lakes lie, are arranged so tranquilly and at angles so low, 
that the flattest chalk of Great Britain may be almost said to be 
tumultuous in comparison ; and the forthcoming sections of Sir 
William Logan conclusively prove that around the lakes there 
is no trace of dislocation to help to form the hollows, nor yet do 
they lie in hollows of special subsidence. Only Lake Superior 
covers a faint synclinal curve; and Lake Ontario, so far from 
occupying an area of special depression, actually lies on a very 
low anticlinal bend of soft strata, the top of which has been 
denuded away. That Sir William, who has been called the best 
stratigraphical geologist in America, believes that ice has some- 
thing to do with the scooping out of rock-basins, any one 
may see who refers to his late masterly report on the geology of 
Canada ; and Professor Newberry, whom Sir Roderick knows as a 
physical geologist and geographer, adheres strongly tothatopinion. 

As for the observation of my friend M. de Verneuil, that the 
oi'ographic hollows in Spain are precisely those that " a theorist " 
might "attribute to excavation by ice," I decline to be judged 
by it, till I have seen them and declared that opinion. I object, 
both for myself and my supporters, that we should be judged in 
a manner so vague. And further, I think I appeal to Nature 
to some purpose when, neither for the first nor the second time, 
I ask philosophers to consider why it is that not only drift- and 
moraine-dammed lakes, but striated rock-basins of all sizes occur 
in such prodigious numbers in America, Scandinavia, the High- 
lands, and in all other rocky temperate regions, high or low, that 
have been glaciated, while in tropical and subtropical regions 
they are so rare as to be quite exceptional elsewhere than in 
mountain areas that now or once maintained their glaciers. 

Several other points raised by Sir Roderick in that part of his 
Address that relates to physical geology, glaciers, and icebergs 
remain to be discussed. I liave entered, however, on this argu- 
ment with great reluctance, and, unless circumstances again con- 
strain me, I shall leave the remaining questions untouched.