More Letters of Charles Darwin Volume II

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LETTER 502. TO C. LYELL.
Down, May 8th [1855].

The notion you refer to was published in the "Geological Journal" (502/1.
"on the Transportal of Erratic Boulders from a lower to a higher Level."
By C. Darwin.), Volume IV. (1848), page 315, with reference to all the
cases which I could collect of boulders apparently higher than the parent
rock.

The argument of probable proportion of rock dropped by sea ice compared to
land glaciers is new to me. I have often thought of the idea of the
viscosity and enormous momentum of great icebergs, and still think that the
notion I pointed out in appendix to Ramsay's paper is probable, and can
hardly help being applicable in some cases. (502/2. The paper by Ramsay
has no appendix; probably, therefore Mr. Darwin's notes were published
separately as a paper in the "Phil. Mag.") I wonder whether the "Phil.
Journal [Magazine?.]" would publish it, if I could get it from Ramsay or
the Geological Society. (502/3. "On the Power of Icebergs to make
rectilinear, uniformly-directed grooves across a Submarine Undulatory
Surface." By C. Darwin, "Phil. Mag." Volume X., page 96, 1855.) If you
chance to meet Ramsay will you ask him whether he has it? I think it would
perhaps be worth while just to call the N. American geologists' attention
to the idea; but it is not worth any trouble. I am tremendously busy with
all sorts of experiments. By the way, Hopkins at the Geological Society
seemed to admit some truth in the idea of scoring by (viscid) icebergs. If
the Geological Society takes so much [time] to judge of truth of notions,
as you were telling me in regard to Ramsay's Permian glaciers (502/4. "On
the Occurrence of angular, sub-angular, polished, and striated Fragments
and Boulders in the Permian Breccia of Shropshire, Worcestershire, etc.;
and on the Probable Existence of Glaciers and Icebergs in the Permian
Epoch." By A.C. Ramsay, "Quart. Journ. Geol. Soc." Volume XI., page 185,
1855.), it will be as injurious to progress as the French Institut.

LETTER 503. TO J.D. HOOKER.
Cliff Cottage, Bournemouth, [September] 21st [1862].

I am especially obliged to you for sending me Haast's communications.
(503/1. "Quart. Journ. Geol. Soc." Volume XXI., pages 130, 133, 1865;
Volume XXIII., page 342, 1867.) They are very interesting and grand about
glacial and drift or marine glacial. I see he alludes to the whole
southern hemisphere. I wonder whether he has read the "Origin."
Considering your facts on the Alpine plants of New Zealand and remarks, I
am particularly glad to hear of the geological evidence of glacial action.
I presume he is sure to collect and send over the mountain rat of which he
speaks. I long to know what it is. A frog and rat together would, to my
mind, prove former connection of New Zealand to some continent; for I can
hardly suppose that the Polynesians introduced the rat as game, though so
esteemed in the Friendly Islands. Ramsay sent me his paper (503/2. "On
the Glacial Origin of certain Lakes in Switzerland, etc." "Quart. Journ.
Geol. Soc." Volume XVIII., page 185, 1862.) and asked my opinion on it. I
agree with you and think highly of it. I cannot doubt that it is to a
large extent true; my only doubt is, that in a much disturbed country, I
should have thought that some depressions, and consequently lakes, would
almost certainly have been left. I suggested a careful consideration of
mountainous tropical countries such as Brazil, peninsula of India, etc.; if
lakes are there, [they are] very rare. I should fully subscribe to
Ramsay's views.

What presumption, as it seems to me, in the Council of Geological Society
that it hesitated to publish the paper.

We return home on the 30th. I have made up [my] mind, if I can keep up my
courage, to start on the Saturday for Cambridge, and stay the last few days
of the [British] Association there. I do so hope that you may be there
then.

LETTER 504. TO J.D. HOOKER.
November 3rd [1864].

When I wrote to you I had not read Ramsay. (504/1. "On the Erosion of
Valleys and Lakes: a Reply to Sir Roderick Murchison's Anniversary Address
to the Geographical Society." "Phil. Mag." Volume XXVIII., page 293, 1864)
How capitally it is written! It seems that there is nothing for style like
a man's dander being put up. I think I agree largely with you about
denudation--but the rocky-lake-basin theory is the part which interests me
at present. It seems impossible to know how much to attribute to ice,
running water, and sea. I did not suppose that Ramsay would deny that
mountains had been thrown up irregularly, and that the depressions would
become valleys. The grandest valleys I ever saw were at Tahiti, and here I
do not believe ice has done anything; anyhow there were no erratics. I
said in my S. American Geology (504/2. "Finally, the conclusion at which I
have arrived with respect to the relative powers of rain, and sea-water on
the land is, that the latter is by far the most efficient agent, and that
its chief tendency is to widen the valleys, whilst torrents and rivers tend
to deepen them and to remove the wreck of the sea's destroying action"
("Geol. Observations," pages 66, 67).) that rivers deepen and the sea
widens valleys, and I am inclined largely to stick to this, adding ice to
water. I am sorry to hear that Tyndall has grown dogmatic. H. Wedgwood
was saying the other day that T.'s writings and speaking gave him the idea
of intense conceit. I hope it is not so, for he is a grand man of science.

...I have had a prospectus and letter from Andrew Murray (504/3. See
Volume II., Letters 379, 384, etc.) asking me for suggestions. I think
this almost shows he is not fit for the subject, as he gives me no idea
what his book will be, excepting that the printed paper shows that all
animals and all plants of all groups are to be treated of. Do you know
anything of his knowledge?

In about a fortnight I shall have finished, except concluding chapter, my
book on "Variation under Domestication"; (504/4. Published in 1868.) but
then I have got to go over the whole again, and this will take me very many
months. I am able to work about two hours daily.

LETTER 505. TO J.D. HOOKER.
Down [July, 1865].

I was glad to read your article on Glaciers, etc., in Yorkshire. You seem
to have been struck with what most deeply impressed me at Glen Roy (wrong
as I was on the whole subject)--viz. the marvellous manner in which every
detail of surface of land had been preserved for an enormous period. This
makes me a little sceptical whether Ramsay, Jukes, etc., are not a little
overdoing sub-aerial denudation.

In the same "Reader" (505/1. Sir J.D. Hooker wrote to Darwin, July 13th,
1865, from High Force Inn, Middleton, Teesdale: "I am studying the
moraines all day long with as much enthusiasm as I am capable of after
lying in bed till nine, eating heavy breakfasts, and looking forward to
dinner as the summum bonum of existence." The result of his work, under
the title "Moraines of the Tees Valley," appeared in the "Reader" (July
15th, 1865, page 71), of which Huxley was one of the managers or
committee-men, and Norman Lockyer was scientific editor ("Life and Letters
of T.H. Huxley," I., page 211). Hooker describes the moraines and other
evidence of glacial action in the upper part of the Tees valley, and speaks
of the effect of glaciers in determining the present physical features of
the country.) there was a striking article on English and Foreign Men of
Science (505/2. "British and Foreign Science," "The Reader," loc. cit.,
page 61. The writer of the article asserts the inferiority of English
scientific workers.), and I think unjust to England except in pure
Physiology; in biology Owen and R. Brown ought to save us, and in Geology
we are most rich.

It is curious how we are reading the same books. We intend to read Lecky
and certainly to re-read Buckle--which latter I admired greatly before. I
am heartily glad you like Lubbock's book so much. It made me grieve his
taking to politics, and though I grieve that he has lost his election, yet
I suppose, now that he is once bitten, he will never give up politics, and
science is done for. Many men can make fair M.P.'s; and how few can work
in science like him!

I have been reading a pamphlet by Verlot on "Variation of Flowers," which
seems to me very good; but I doubt whether it would be worth your reading.
it was published originally in the "Journal d'Hort.," and so perhaps you
have seen it. It is a very good plan this republishing separately for sake
of foreigners buying, and I wish I had tried to get permission of Linn.
Soc. for my Climbing paper, but it is now too late.

Do not forget that you have my paper on hybridism, by Max Wichura. (505/3.
Wichura, M.E., "L'Hybridisation dans le regne vegetal etudiee sur les
Saules," "Arch. Sci. Phys. Nat." XXIII., page 129, 1865.)

I hope you are returned to your work, refreshed like a giant by your huge
breakfasts. How unlucky you are about contagious complaints with your
children!

I keep very weak, and had much sickness yesterday, but am stronger this
morning.

Can you remember how we ever first met? (505/4. See "Life and Letters,"
II., page 19.) It was in Park Street; but what brought us together? I
have been re-reading a few old letters of yours, and my heart is very warm
towards you.

LETTER 506. TO C. LYELL.
Down, March 8th [1866].

(506/1. In a letter from Sir Joseph Hooker to Mr. Darwin on February 21st,
1866, the following passage occurs: "I wish I could explain to you my
crude notions as to the Glacial period and your position towards it. I
suppose I hold this doctrine: that there was a Glacial period, but that it
was not one of universal cold, because I think that the existing
distribution of glaciers is sufficiently demonstrative of the proposition
that by comparatively slight redispositions of sea and land, and perhaps
axis of globe, you may account for all the leading palaeontological
phenomena." This letter was sent by Mr. Darwin to Sir Charles Lyell, and
the latter, writing on March 1st, 1866, expresses his belief that "the
whole globe must at times have been superficially cooler. Still," he adds,
"during extreme excentricity the sun would make great efforts to compensate
in perihelion for the chill of a long winter in aphelion in one hemisphere,
and a cool summer in the other. I think you will turn out to be right in
regard to meridional lines of mountain-chains by which the migrations
across the equator took place while there was contemporaneous tropical heat
of certain lowlands, where plants requiring heat and moisture were saved
from extinction by the heat of the earth's surface, which was stored up in
perihelion, being prevented from radiating off freely into space by a
blanket of aqueous vapour caused by the melting of ice and snow. But
though I am inclined to profit by Croll's maximum excentricity for the
glacial period, I consider it quite subordinate to geographical causes or
the relative position of land and sea and the abnormal excess of land in
polar regions." In another letter (March 5th, 1866) Lyell writes: "In the
beginning of Hooker's letter to you he speaks hypothetically of a change in
the earth's axis as having possibly co-operated with redistribution of land
and sea in causing the cold of the Glacial period. Now, when we consider
how extremely modern, zoologically and botanically, the Glacial period is
proved to be, I am shocked at any one introducing, with what I may call so
much levity, so organic a change as a deviation in the axis of the
planet...' (see Lyell's "Principles," 1875, Chapter XIII.; also a letter to
Sir Joseph Hooker printed in the "Life of Sir Charles Lyell," Volume II.,
page 410.))

Many thanks for your interesting letter. From the serene elevation of my
old age I look down with amazement at your youth, vigour, and indomitable
energy. With respect to Hooker and the axis of the earth, I suspect he is
too much overworked to consider now any subject properly. His mind is so
acute and critical that I always expect to hear a torrent of objections to
anything proposed; but he is so candid that he often comes round in a year
or two. I have never thought on the causes of the Glacial period, for I
feel that the subject is beyond me; but though I hope you will own that I
have generally been a good and docile pupil to you, yet I must confess that
I cannot believe in change of land and water, being more than a subsidiary
agent. (506/2. In Chapter XI. of the "Origin," Edition V., 1869, page
451, Darwin discusses Croll's theory, and is clearly inclined to trust in
Croll's conclusion that "whenever the northern hemisphere passes through a
cold period the temperature of the southern hemisphere is actually
raised..." In Edition VI., page 336, he expresses his faith even more
strongly. Mr. Darwin apparently sent his MS. on the climate question,
which was no doubt prepared for a new edition of the "Origin," to Sir
Charles. The arrival of the MS. is acknowledged in a letter from Lyell on
March 10th, 1866 ("Life of Sir Charles Lyell," II., page 408), in which the
writer says that he is "more than ever convinced that geographical
changes...are the principal and not the subsidiary causes.") I have come
to this conclusion from reflecting on the geographical distribution of the
inhabitants of the sea on the opposite sides of our continents and of the
inhabitants of the continents themselves.

LETTER 507. TO C. LYELL.
Down, September 8th [1866].

Many thanks for the pamphlet, which was returned this morning. I was very
glad to read it, though chiefly as a psychological curiosity. I quite
follow you in thinking Agassiz glacier-mad. (507/1. Agassiz's pamphlet,
("Geology of the Amazons") is referred to by Lyell in a letter written to
Bunbury in September, 1866 ("Life of Sir Charles Lyell," II., page 409):
"Agassiz has written an interesting paper on the 'Geology of the Amazons,'
but, I regret to say, he has gone wild about glaciers, and has actually
announced his opinion that the whole of the great valley, down to its mouth
in latitude 0 deg., was filled by ice..." Agassiz published a paper,
"Observations Geologiques faites dans la Vallee de l'Amazone," in the
"Comptes Rendus," Volume LXIV., page 1269, 1867. See also a letter
addressed to M. Marcou, published in the "Bull. Soc. Geol. France," Volume
XXIV., page 109, 1866.) His evidence reduces itself to supposed moraines,
which would be difficult to trace in a forest-clad country; and with
respect to boulders, these are not said to be angular, and their source
cannot be known in a country so imperfectly explored. When I was at Rio, I
was continually astonished at the depth (sometimes 100 feet) to which the
granitic rocks were decomposed in situ, and this soft matter would easily
give rise to great alluvial accumulations; I well remember finding it
difficult to draw a line between the alluvial matter and the softened rock
in situ. What a splendid imagination Agassiz has, and how energetic he is!
What capital work he would have done, if he had sucked in your "Principles"
with his mother's milk. It is wonderful that he should have written such
wild nonsense about the valley of the Amazon; yet not so wonderful when one
remembers that he once maintained before the British Association that the
chalk was all deposited at once.

With respect to the insects of Chili, I knew only from Bates that the
species of Carabus showed no special affinity to northern species; from the
great difference of climate and vegetation I should not have expected that
many insects would have shown such affinity. It is more remarkable that
the birds on the broad and lofty Cordillera of Tropical S. America show no
affinity with European species. The little power of diffusion with birds
has often struck me as a most singular fact--even more singular than the
great power of diffusion with plants. Remember that we hope to see you in
the autumn.

P.S.--There is a capital paper in the September number of "Annals and
Magazine," translated from Pictet and Humbert, on Fossil Fish of Lebanon,
but you will, I daresay, have received the original. (507/2. "Recent
Researches on the Fossil Fishes of Mount Lebanon," "Ann. Mag. Nat. Hist."
Volume XVIII., page 237, 1866.) It is capital in relation to modification
of species; I would not wish for more confirmatory facts, though there is
no direct allusion to the modification of species. Hooker, by the way,
gave an admirable lecture at Nottingham; I read it in MS., or rather, heard
it. I am glad it will be published, for it was capital. (507/3. Sir
Joseph Hooker delivered a lecture at the Nottingham meeting of the British
Association (1866) on "Insular Floras," published in the "Gardeners'
Chronicle," 1867. See Letters 366-377, etc.)

Sunday morning.

P.S.--I have just received a letter from Asa Gray with the following
passage, so that, according to this, I am the chief cause of Agassiz's
absurd views:--

"Agassiz is back (I have not seen him), and he went at once down to the
National Academy of Sciences, from which I sedulously keep away, and, I
hear, proved to them that the Glacial period covered the whole continent of
America with unbroken ice, and closed with a significant gesture and the
remark: 'So here is the end of the Darwin theory.' How do you like that?

"I said last winter that Agassiz was bent on covering the whole continent
with ice, and that the motive of the discovery he was sure to make was to
make sure that there should be no coming down of any terrestrial life from
Tertiary or post-Tertiary period to ours. You cannot deny that he has done
his work effectually in a truly imperial way."

LETTER 508. TO C. LYELL.
Down, July 14th, 1868.

Mr. Agassiz's book has been read aloud to me, and I am wonderfully
perplexed what to think about his precise statements of the existence of
glaciers in the Ceara Mountains, and about the drift formation near Rio.
(508/1. "Sur la Geologie de l'Amazone," by MM. Agassiz and Continho,
"Bull. Soc. Geol. France," Volume XXV., page 685, 1868. See also "A
Journey in Brazil," by Professor and Mrs. Louis Agassiz, Boston, 1868.)
There is a sad want of details. Thus he never mentions whether any of the
blocks are angular, nor whether the embedded rounded boulders, which cannot
all be disintegrated, are scored. Yet how can so experienced an observer
as A. be deceived about lateral and terminal moraines? If there really
were glaciers in the Ceara Mountains, it seems to me one of the most
important facts in the history of the inorganic and organic world ever
observed. Whether true or not, it will be widely believed, and until
finally decided will greatly interfere with future progress on many points.
I have made these remarks in the hope that you will coincide. If so, do
you think it would be possible to persuade some known man, such as Ramsay,
or, what would be far better, some two men, to go out for a summer trip,
which would be in many respects delightful, for the sole object of
observing these phenomena in the Ceara Mountains, and if possible also near
Rio? I would gladly put my name down for 50 pounds in aid of the expense
of travelling. Do turn this over in your mind. I am so very sorry not to
have seen you this summer, but for the last three weeks I have been good
for nothing, and have had to stop almost all work. I hope we may meet in
the autumn.

LETTER 509. TO JAMES CROLL.
Down, November 24th, 1868.

I have read with the greatest interest the last paper which you have kindly
sent me. (509/1. Croll discussed the power of icebergs as grinding and
striating agents in the latter part of a paper ("On Geological Time, and
the probable Dates of the Glacial and the Upper Miocene Period") published
in the "Philosophical Magazine," Volume XXXV., page 363, 1868, Volume
XXXVI., pages 141, 362, 1868. His conclusion was that the advocates of the
Iceberg theory had formed "too extravagant notions regarding the potency of
floating ice as a striating agent.") If we are to admit that all the
scored rocks throughout the more level parts of the United States result
from true glacier action, it is a most wonderful conclusion, and you
certainly make out a very strong case; so I suppose I must give up one more
cherished belief. But my object in writing is to trespass on your kindness
and ask a question, which I daresay I could answer for myself by reading
more carefully, as I hope hereafter to do, all your papers; but I shall
feel much more confidence in a brief reply from you. Am I right in
supposing that you believe that the glacial periods have always occurred
alternately in the northern and southern hemispheres, so that the erratic
deposits which I have described in the southern parts of America, and the
glacial work in New Zealand, could not have been simultaneous with our
Glacial period? From the glacial deposits occurring all round the northern
hemisphere, and from such deposits appearing in S. America to be as recent
as in the north, and lastly, from there being some evidence of the former
lower descent of glaciers all along the Cordilleras, I inferred that the
whole world was at this period cooler. It did not appear to me justifiable
without distinct evidence to suppose that the N. and S. glacial deposits
belonged to distinct epochs, though it would have been an immense relief to
my mind if I could have assumed that this had been the case. Secondly, do
you believe that during the Glacial period in one hemisphere the opposite
hemisphere actually becomes warmer, or does it merely retain the same
temperature as before? I do not ask these questions out of mere curiosity;
but I have to prepare a new edition of my "Origin of Species," and am
anxious to say a few words on this subject on your authority. I hope that
you will excuse my troubling you.

LETTER 510. TO J. CROLL.
Down, January 31st, 1869.

To-morrow I will return registered your book, which I have kept so long. I
am most sincerely obliged for its loan, and especially for the MS., without
which I should have been afraid of making mistakes. If you require it, the
MS. shall be returned. Your results have been of more use to me than, I
think, any other set of papers which I can remember. Sir C. Lyell, who is
staying here, is very unwilling to admit the greater warmth of the S.
hemisphere during the Glacial period in the N.; but, as I have told him,
this conclusion which you have arrived at from physical considerations,
explains so well whole classes of facts in distribution, that I must
joyfully accept it; indeed, I go so far as to think that your conclusion is
strengthened by the facts in distribution. Your discussion on the flowing
of the great ice-cap southward is most interesting. I suppose that you
have read Mr. Moseley's recent discussion on the force of gravity being
quite insufficient to account for the downward movement of glaciers (510/1.
Canon Henry Moseley, "On the Mechanical Impossibility of the Descent of
Glaciers by their Weight only." "Proc. R. Soc." Volume XVII., page 202,
1869; "Phil. Mag." Volume XXXVII., page 229, 1869.): if he is right, do
you not think that the unknown force may make more intelligible the
extension of the great northern ice-cap? Notwithstanding your excellent
remarks on the work which can be effected within the million years (510/2.
In his paper "On Geological Time, and the probable Date of the Glacial and
the Upper Miocene Period" ("Phil. Mag." Volume XXXV., page 363, 1868),
Croll endeavours to convey to the mind some idea of what a million years
really is: "Take a narrow strip of paper, an inch broad or more, and 83
feet 4 inches in length, and stretch it along the wall of a large hall, or
round the walls of an apartment somewhat over 20 feet square. Recall to
memory the days of your boyhood, so as to get some adequate conception of
what a period of a hundred years is. Then mark off from one of the ends of
the strip one-tenth of an inch. The one-tenth of an inch will then
represent a hundred years, and the entire length of the strip a million of
years" (loc. cit., page 375).), I am greatly troubled at the short duration
of the world according to Sir W. Thomson (510/3. In a paper communicated
to the Royal Society of Edinburgh, Lord Kelvin (then Sir William Thomson)
stated his belief that the age of our planet must be more than twenty
millions of years, but not more than four hundred millions of years
("Trans. R. Soc. Edinb." Volume XXIII., page 157, 1861, "On the Secular
Cooling of the Earth."). This subject has been recently dealt with by Sir
Archibald Geikie in his address as President of the Geological Section of
the British Association, 1899 ("Brit. Assoc. Report," Dover Meeting, 1899,
page 718).), for I require for my theoretical views a very long period
BEFORE the Cambrian formation. If it would not trouble you, I should like
to hear what you think of Lyell's remark on the magnetic force which comes
from the sun to the earth: might not this penetrate the crust of the earth
and then be converted into heat? This would give a somewhat longer time
during which the crust might have been solid; and this is the argument on
which Sir W. Thomson seems chiefly to rest. You seem to argue chiefly on
the expenditure of energy of all kinds by the sun, and in this respect
Lyell's remark would have no bearing.