Чарльз Дарвин
More Letters of Charles Darwin — Volume 2
Having burnt my own fingers so consumedly with the Wealden, I am fearful for you, but I well know how infinitely more cautious, prudent, and far-seeing you are than I am; but for heaven's sake take care of your fingers; to burn them severely, as I have done, is very unpleasant.
Your 2 1/2 feet for a century of elevation seems a very handsome allowance. can D. Forbes really show the great elevation of Chili? I am astounded at it, and I took some pains on the point.
I do not pretend to say that you may not be right to judge of the past movements of Europe by those now and recently going on, yet it somehow grates against my judgment, — perhaps only against my prejudices.
As a change from elevation to subsidence implies some great subterranean or cosmical change, one may surely calculate on long intervals of rest between. Though, if the cause of the change be ever proved to be astronomical, even this might be doubtful.
P.S. — I do not know whether I have made clear what I think probable, or at least possible: viz., that the greater part of Europe has at times been elevated in some degree equably; at other times it has all subsided equably; and at other times might all have been stationary; and at other times it has been subjected to various unequal movements, up and down, as at present.
LETTER 492. TO C. LYELL. Down, December 4th {1860}.
It certainly seems to me safer to rely solely on the slowness of ascertained up-and-down movement. But you could argue length of probable time before the movement became reversed, as in your letter. And might you not add that over the whole world it would probably be admitted that a larger area is NOW at rest than in movement? and this I think would be a tolerably good reason for supposing long intervals of rest. You might even adduce Europe, only guarding yourself by saying that possibly (I will not say probably, though my prejudices would lead me to say so) Europe may at times have gone up and down all together. I forget whether in a former letter you made a strong point of upward movement being always interrupted by long periods of rest. After writing to you, out of curiosity I glanced at the early chapters in my "Geology of South America," and the areas of elevation on the E. and W. coasts are so vast, and proofs of many successive periods of rest so striking, that the evidence becomes to my mind striking. With regard to the astronomical causes of change: in ancient days in the "Beagle" when I reflected on the repeated great oscillations of level on the very same area, and when I looked at the symmetry of mountain chains over such vast spaces, I used to conclude that the day would come when the slow change of form in the semi-fluid matter beneath the crust would be found to be the cause of volcanic action, and of all changes of level. And the late discussion in the "Athenaeum" (492/1. "On the Change of Climate in Different Regions of the Earth." Letters from Sir Henry James, Col. R.E., "Athenaeum," August 25th, 1860, page 256; September 15th, page 355; September 29th, page 415; October 13th, page 483. Also letter from J. Beete Jukes, Local Director of the Geological Survey of Ireland, loc. cit., September 8th, page 322; October 6th, page 451.), by Sir H. James (though his letter seemed to me mighty poor, and what Jukes wrote good), reminded me of this notion. In case astronomical agencies should ever be proved or rendered probable, I imagine, as in nutation or precession, that an upward movement or protrusion of fluidified matter below might be immediately followed by movement of an opposite nature. This is all that I meant.
I have not read Jamieson, or yet got the number. (492/2. Possibly William Jameson, "Journey from Quito to Cayambe," "Geog. Soc. Journ." Volume XXXI., page 184, 1861.) I was very much struck with Forbes' explanation of n{itrate} of soda beds and the saliferous crust, which I saw and examined at Iquique. (492/3. "On the Geology of Bolivia and Southern Peru," by D. Forbes, "Quart. Journ. Geol. Soc." Volume XVII., page 7, 1861. Mr. Forbes attributes the formation of the saline deposits to lagoons of salt water, the communication of which with the sea has been cut off by the rising of the land (loc. cit., page 13).) I often speculated on the greater rise inland of the Cordilleras, and could never satisfy myself...
I have not read Stur, and am awfully behindhand in many things...(492/4. The end of this letter is published as a footnote in "Life and Letters," II., page 352.)
(FIGURE 5. Map of part of South America and the Galapagos Archipelago.)
LETTER 493. TO C. LYELL. Down, July 18th {1867}.
(493/1. The first part of this letter is published in "Life and Letters," III., page 71.)
(493/2. Tahiti (Society Islands) is coloured blue in the map showing the distribution of the different kinds of reefs in "The Structure and Distribution of Coral Reefs," Edition III., 1889, page 185. The blue colour indicates the existence of barrier reefs and atolls which, on Darwin's theory, point to subsidence.)
Tahiti is, I believe, rightly coloured, for the reefs are so far from the land, and the ocean so deep, that there must have been subsidence, though not very recently. I looked carefully, and there is no evidence of recent elevation. I quite agree with you versus Herschel on Volcanic Islands. (493/3. Sir John Herschel suggested that the accumulation on the sea-floor of sediment, derived from the waste of the island, presses down the bed of the ocean, the continent being on the other hand relieved of pressure; "this brings about a state of strain in the crust which will crack in its weakest spot, the heavy side going down, and the light side rising." In discussing this view Lyell writes ("Principles," Volume II. Edition X., page 229), "This hypothesis appears to me of very partial application, for active volcanoes, even such as are on the borders of continents, are rarely situated where great deltas have been forming, whether in Pliocene or post-Tertiary times. The number, also, of active volcanoes in oceanic islands is very great, not only in the Pacific, but equally in the Atlantic, where no load of coral matter...can cause a partial weighting and pressing down of a supposed flexible crust.") Would not the Atlantic and Antarctic volcanoes be the best examples for you, as there then can be no coral mud to depress the bottom? In my "Volcanic Islands," page 126, I just suggest that volcanoes may occur so frequently in the oceanic areas as the surface would be most likely to crack when first being elevated. I find one remark, page 128 (493/4. "Volcanic Islands," page 128: "The islands, moreover, of some of the small volcanic groups, which thus border continents, are placed in lines related to those along which the adjoining shores of the continents trend" {see Figure 5}.), which seems to me worth consideration — viz. the parallelism of the lines of eruption in volcanic archipelagoes with the coast lines of the nearest continent, for this seems to indicate a mechanical rather than a chemical connection in both cases, i.e. the lines of disturbance and cracking. In my "South American Geology," page 185 (493/5. "Geological Observations on South America," London, 1846, page 185.), I allude to the remarkable absence at present of active volcanoes on the east side of the Cordillera in relation to the absence of the sea on this side. Yet I must own I have long felt a little sceptical on the proximity of water being the exciting cause. The one volcano in the interior of Asia is said, I think, to be near great lakes; but if lakes are so important, why are there not many other volcanoes within other continents? I have always felt rather inclined to look at the position of volcanoes on the borders of continents, as resulting from coast lines being the lines of separation between areas of elevation and subsidence. But it is useless in me troubling you with my old speculations.
LETTER 494. TO A.R. WALLACE. March 22nd {1869}.
(494/1. The following extract from a letter to Mr. Wallace refers to his "Malay Archipelago," 1869.)
I have only one criticism of a general nature, and I am not sure that other geologists would agree with me. You repeatedly speak as if the pouring out of lava, etc., from volcanoes actually caused the subsidence of an adjoining area. I quite agree that areas undergoing opposite movements are somehow connected; but volcanic outbursts must, I think, be looked at as mere accidents in the swelling up of a great dome or surface of plutonic rocks, and there seems no more reason to conclude that such swelling or elevation in mass is the cause of the subsidence, than that the subsidence is the cause of the elevation, which latter view is indeed held by some geologists. I have regretted to find so little about the habits of the many animals which you have seen.
LETTER 495. TO C. LYELL. Down, May 20th, 1869.
I have been much pleased to hear that you have been looking at my S. American book (495/1. "Geological Observations on South America," London, 1846.), which I thought was as completely dead and gone as any pre-Cambrian fossil. You are right in supposing that my memory about American geology has grown very hazy. I remember, however, a paper on the Cordillera by D. Forbes (495/2. "Geology of Bolivia and South Peru," by Forbes, "Quart. Journ. Geol. Soc." Volume XVII., pages 7-62, 1861. Forbes admits that there is "the fullest evidence of elevation of the Chile coast since the arrival of the Spaniards. North of Arica, if we accept the evidence of M. d'Orbigny and others, the proof of elevation is much more decided; and consequently it may be possible that here, as is the case about Lima, according to Darwin, the elevation may have taken place irregularly in places..." (loc. cit., page 11).), with splendid sections, which I saw in MS., but whether "referred" to me or lent to me I cannot remember. This would be well worth your looking to, as I think he both supports and criticises my views. In Ormerod's Index to the Journal (495/3. "Classified Index to the Transactions, Proceedings and Quarterly Journal of the Geological Society."), which I do not possess, you would, no doubt, find a reference; but I think the sections would be worth borrowing from Forbes. Domeyko (495/4. Reference is made by Forbes in his paper on Bolivia and Peru to the work of Ignacio Domeyko on the geology of Chili. Several papers by this author were published in the "Annales des Mines" between 1840 and 1869, also in the "Comptes Rendus" of 1861, 1864, etc.) has published in the "Comptes Rendus" papers on Chili, but not, as far as I can remember, on the structure of the mountains. Forbes, however, would know. What you say about the plications being steepest in the central and generally highest part of the range is conclusive to my mind that there has been the chief axis of disturbance. The lateral thrusting has always appeared to me fearfully perplexing. I remember formerly thinking that all lateral flexures probably occurred deep beneath the surface, and have been brought into view by an enormous superincumbent mass having been denuded. If a large and deep box were filled with layers of damp paper or clay, and a blunt wedge was slowly driven up from beneath, would not the layers above it and on both sides become greatly convoluted, whilst those towards the top would be only slightly arched? When I spoke of the Andes being comparatively recent, I suppose that I referred to the absence of the older formations. In looking to my volume, which I have not done for many years, I came upon a passage (page 232) which would be worth your looking at, if you have ever felt perplexed, as I often was, about the sources of volcanic rocks in mountain chains. You have stirred up old memories, and at the risk of being a bore I should like to call your attention to another point which formerly perplexed me much — viz. the presence of basaltic dikes in most great granitic areas. I cannot but think the explanation given at page 123 of my "Volcanic Islands" is the true one. (495/5. On page 123 of the "Geological Observations on the Volcanic Islands visited during the Voyage of H.M.S. 'Beagle,'" 1844, Darwin quotes several instances of greenstone and basaltic dikes intersecting granitic and allied metamorphic rocks. He suggests that these dikes "have been formed by fissures penetrating into partially cooled rocks of the granitic and metamorphic series, and by their more fluid parts, consisting chiefly of hornblende oozing out, and being sucked into such fissures.")
LETTER 496. TO VICTOR CARUS. Down, March 21st, 1876.
The very kind expressions in your letter have gratified me deeply.
I quite forget what I said about my geological works, but the papers referred to in your letter are the right ones. I enclose a list with those which are certainly not worth translating marked with a red line; but whether those which are not thus marked with a red line are worth translation you will have to decide. I think much more highly of my book on "Volcanic Islands" since Mr. Judd, by far the best judge on the subject in England, has, as I hear, learnt much from it.
I think the short paper on the "formation of mould" is worth translating, though, if I have time and strength, I hope to write another and longer paper on the subject.
I can assure you that the idea of any one translating my books better than you never even momentarily crossed my mind. I am glad that you can give a fairly good account of your health, or at least that it is not worse.
LETTER 497. TO T. MELLARD READE. London, December 9th, 1880.
I am sorry to say that I do not return home till the middle of next week, and as I order no pamphlets to be forwarded to me by post, I cannot return the "Geolog. Mag." until my return home, nor could my servants pick it out of the multitude which come by the post. (497/1. Article on "Oceanic Islands," by T. Mellard Reade, "Geol. Mag." Volume VIII., page 75, 1881.)
As I remarked in a letter to a friend, with whom I was discussing Wallace's last book (497/2. Wallace's "Island Life," 1880.), the subject to which you refer seems to me a most perplexing one. The fact which I pointed out many years ago, that all oceanic islands are volcanic (except St. Paul's, and now this is viewed by some as the nucleus of an ancient volcano), seems to me a strong argument that no continent ever occupied the great oceans. (497/3. "During my investigations on coral reefs I had occasion to consult the works of many voyagers, and I was invariably struck with the fact that, with rare exceptions, the innumerable islands scattered through the Pacific, Indian, and Atlantic Oceans were composed either of volcanic or of modern coral rocks" ("Geological Observations on Volcanic Islands, etc." Edition II., 1876, page 140).) Then there comes the statement from the "Challenger" that all sediment is deposited within one or two hundred miles from the shores, though I should have thought this rather doubtful with respect to great rivers like the Amazons.
The chalk formerly seemed to me the best case of an ocean having extended where a continent now stands; but it seems that some good judges deny that the chalk is an oceanic deposit. On the whole, I lean to the side that the continents have since Cambrian times occupied approximately their present positions. But, as I have said, the question seems a difficult one, and the more it is discussed the better.
LETTER 498. TO A. AGASSIZ. Down, January 1st, 1881.
I must write a line or two to thank you much for having written to me so long a letter on coral reefs at a time when you must have been so busy. Is it not difficult to avoid believing that the wonderful elevation in the West Indies must have been accompanied by much subsidence, notwithstanding the state of Florida? (498/1. The Florida reefs cannot be explained by subsidence. Alexander Agassiz, who has described these reefs in detail ("Three Cruises of the U.S. Coast and Geodetic Survey Steamer 'Blake,'" 2 volumes, London, 1888), shows that the southern extremity of the peninsula "is of comparatively recent growth, consisting of concentric barrier-reefs, which have been gradually converted into land by the accumulation of intervening mud-flats" (see also Appendix II., page 287, to Darwin's "Coral Reefs," by T.G. Bonney, Edition III., 1889.)) When reflecting in old days on the configuration of our continents, the position of mountain chains, and especially on the long-continued supply of sediment over the same areas, I used to think (as probably have many other persons) that areas of elevation and subsidence must as a general rule be separated by a single great line of fissure, or rather of several closely adjoining lines of fissure. I mention this because, when looking within more recent times at charts with the depths of the sea marked by different tints, there seems to be some connection between the profound depths of the ocean and the trends of the nearest, though distant, continents; and I have often wished that some one like yourself, to whom the subject was familiar, would speculate on it.
P.S. — I do hope that you will re-urge your views about the reappearance of old characters (498/2. See "Life and Letters," III., pages 245, 246.), for, as far as I can judge, the most important views are often neglected unless they are urged and re-urged.
I am greatly indebted to you for sending me very many most valuable works published at your institution.
2. IX.II. ICE-ACTION, 1841-1882. LETTER 499. TO C. LYELL. {1841.}
Your extract has set me puzzling very much, and as I find I am better at present for not going out, you must let me unload my mind on paper. I thought everything so beautifully clear about glaciers, but now your case and Agassiz's statement about the cavities in the rock formed by cascades in the glaciers, shows me I don't understand their structure at all. I wish out of pure curiosity I could make it out. (499/1. "Etudes sur les Glaciers," by Louis Agassiz, 1840, contains a description of cascades (page 343), and "des cavites interieures" (page 348).)
If the glacier travelled on (and it certainly does travel on), and the water kept cutting back over the edge of the ice, there would be a great slit in front of the cascade; if the water did not cut back, the whole hollow and cascade, as you say, must travel on; and do you suppose the next season it falls down some crevice higher up? In any case, how in the name of Heaven can it make a hollow in solid rock, which surely must be a work of many years? I must point out another fact which Agassiz does not, as it appears to me, leave very clear. He says all the blocks on the surface of the glaciers are angular, and those in the moraines rounded, yet he says the medial moraines whence the surface rocks come and are a part {of}, are only two lateral moraines united. Can he refer to terminal moraines alone when he says fragments in moraines are rounded? What a capital book Agassiz's is. In {reading} all the early part I gave up entirely the Jura blocks, and was heartily ashamed of my appendix (499/2. "M. Agassiz has lately written on the subject of the glaciers and boulders of the Alps. He clearly proves, as it appears to me, that the presence of the boulders on the Jura cannot be explained by any debacle, or by the power of ancient glaciers driving before them moraines...M. Agassiz also denies that they were transported by floating ice." ("Voyages of the 'Adventure' and 'Beagle,'" Volume III., 1839: "Journal and Remarks: Addenda," page 617.)) (and am so still of the manner in which I presumptuously speak of Agassiz), but it seems by his own confession that ordinary glaciers could not have transported the blocks there, and if an hypothesis is to be introduced the sea is much simpler; floating ice seems to me to account for everything as well as, and sometimes better than the solid glaciers. The hollows, however, formed by the ice-cascades appear to me the strongest hostile fact, though certainly, as you said, one sees hollow round cavities on present rock-beaches.
I am glad to observe that Agassiz does not pretend that direction of scratches is hostile to floating ice. By the way, how do you and Buckland account for the "tails" of diluvium in Scotland? (499/3. Mr. Darwin speaks of the tails of diluvium in Scotland extending from the protected side of a hill, of which the opposite side, facing the direction from which the ice came, is marked by grooves and striae (loc. cit., pages 622, 623).) I thought in my appendix this made out the strongest argument for rocks having been scratched by floating ice.
Some facts about boulders in Chiloe will, I think, in a very small degree elucidate some parts of Jura case. What a grand new feature all this ice work is in Geology! How old Hutton would have stared! (499/4. Sir Charles Lyell speaks of the Huttonian theory as being characterised by "the exclusion of all causes not supposed to belong to the present order of Nature" (Lyell's "Principles," Edition XII., volume I., page 76, 1875). Sir Archibald Geikie has recently edited the third volume of Hutton's "Theory of the Earth," printed by the Geological Society, 1899. See also "The Founders of Geology," by Sir Archibald Geikie; London, 1897.)
I ought to be ashamed of myself for scribbling on so. Talking of shame, I have sent a copy of my "Journal" (499/5. "Journal and Remarks," 1832-36. See note 2, page 148.) with very humble note to Agassiz, as an apology for the tone I used, though I say, I daresay he has never seen my appendix, or would care at all about it.
I did not suppose my note about Glen Roy could have been of any use to you — I merely scribbled what came uppermost. I made one great oversight, as you would perceive. I forgot the Glacier theory: if a glacier most gradually disappeared from mouth of Spean Valley {this} would account for buttresses of shingle below lowest shelf. The difficulty I put about the ice-barrier of the middle Glen Roy shelf keeping so long at exactly same level does certainly appear to me insuperable. (499/5. For a description of the shelves or parallel roads in Glen Roy see Darwin's "Observations on the Parallel Roads of Glen Roy, etc." "Phil. Trans. R. Soc." 1839, page 39; also Letter 517 et seq.)
What a wonderful fact this breakdown of old Niagara is. How it disturbs the calculations about lengths of time before the river would have reached the lakes.
I hope Mrs. Lyell will read this to you, then I shall trust for forgiveness for having scribbled so much. I should have sent back Agassiz sooner, but my servant has been very unwell. Emma is going on pretty well.
My paper on South American boulders and "till," which latter deposit is perfectly characterised in Tierra del Fuego, is progressing rapidly. (499/6. "On the Distribution of the Erratic Boulders and on the Contemporaneous Unstratified Deposits of South America," "Trans. Geol. Soc." Volume VI., page 415, 1842.)
I much like the term post-Pliocene, and will use it in my present paper several times.
P.S. — I should have thought that the most obvious objection to the marine-beach theory for Glen Roy would be the limited extension of the shelves. Though certainly this is not a valid one, after an intermediate one, only half a mile in length, and nowhere else appearing, even in the valley of Glen Roy itself, has been shown to exist.
LETTER 500. TO C. LYELL. 1842.
I had some talk with Murchison, who has been on a flying visit into Wales, and he can see no traces of glaciers, but only of the trickling of water and of the roots of the heath. It is enough to make an extraneous man think Geology from beginning to end a work of imagination, and not founded on observation. Lonsdale, I observe, pays Buckland and myself the compliment of thinking Murchison not seeing as worth nothing; but I confess I am astonished, so glaringly clear after two or three days did the evidence appear to me. Have you seen last "New Edin. Phil. Journ.", it is ice and glaciers almost from beginning to end. (500/1. "The Edinburgh New Philosophical Journal," Volume XXXIII. (April-October), 1842, contains papers by Sir G.S. Mackenzie, Prof. H.G. Brown, Jean de Charpentier, Roderick Murchison, Louis Agassiz, all dealing with glaciers or ice; also letters to the Editor relating to Prof. Forbes' account of his recent observations on Glaciers, and a paper by Charles Darwin entitled "Notes on the Effects produced by the Ancient Glaciers of Carnarvonshire, and on the Boulders transported by Floating Ice.") Agassiz says he saw (and has laid down) the two lowest terraces of Glen Roy in the valley of the Spean, opposite mouth of Glen Roy itself, where no one else has seen them. (500/2. "The Glacial Theory and its Recent Progress," by Louis Agassiz, loc. cit., page 216. Agassiz describes the parallel terraces on the flanks of Glen Roy and Glen Spean (page 236), and expresses himself convinced "that the Glacial theory alone satisfies all the exigencies of the phenomenon" of the parallel roads.) I carefully examined that spot, owing to the sheep tracks {being} nearly but not quite parallel to the terrace. So much, again, for difference of observation. I do not pretend to say who is right.
LETTER 501. TO J.D. HOOKER. Down, October 12th, 1849.
I was heartily glad to get your last letter; but on my life your thanks for my very few and very dull letters quite scalded me. I have been very indolent and selfish in not having oftener written to you and kept my ears open for news which would have interested you; but I have not forgotten you. Two days after receiving your letter, there was a short leading notice about you in the "Gardeners' Chronicle" (501/1. The "Gardeners' Chronicle," 1849, page 628.); in which it is said you have discovered a noble crimson rose and thirty rhododendrons. I must heartily congratulate you on these discoveries, which will interest the public; and I have no doubt that you will have made plenty of most interesting botanical observations. This last letter shall be put with all your others, which are now safe together. I am very glad that you have got minute details about the terraces in the valleys: your description sounds curiously like the terraces in the Cordillera of Chili; these latter, however, are single in each valley; but you will hereafter see a description of these terraces in my "Geology of S. America." (501/2. "Geological Observations," pages 10 et passim.) At the end of your letter you speak about giving up Geology, but you must not think of it; I am sure your observations will be very interesting. Your account of the great dam in the Yangma valley is most curious, and quite full; I find that I did not at all understand its wonderful structure in your former letter. Your notion of glaciers pushing detritus into deep fiords (and ice floating fragments on their channels), is in many respects new to me; but I cannot help believing your dam is a lateral moraine: I can hardly persuade myself that the remains of floating ice action, at a period so immensely remote as when the Himalaya stood at a low level in the sea, would now be distinguishable. (501/3. Hooker's "Himalayan Journals," Volume II., page 121, 1854. In describing certain deposits in the Lachoong valley, Hooker writes: "Glaciers might have forced immense beds of gravel into positions that would dam up lakes between the ice and the flanks of the valley" (page 121). In a footnote he adds: "We are still very ignorant of many details of ice action, and especially of the origin of many enormous deposits which are not true moraines." Such deposits are referred to as occurring in the Yangma valley.) Your not having found scored boulders and solid rocks is an objection both to glaciers and floating ice; for it is certain that both produce such. I believe no rocks escape scoring, polishing and mammillation in the Alps, though some lose it easily when exposed. Are you familiar with appearance of ice-action? If I understand rightly, you object to the great dam having been produced by a glacier, owing to the dryness of the lateral valley and general infrequency of glaciers in Himalaya; but pray observe that we may fairly (from what we see in Europe) assume that the climate was formerly colder in India, and when the land stood at a lower height more snow might have fallen. Oddly enough, I am now inclined to believe that I saw a gigantic moraine crossing a valley, and formerly causing a lake above it in one of the great valleys (Valle del Yeso) of the Cordillera: it is a mountain of detritus, which has puzzled me. If you have any further opportunities, do look for scores on steep faces of rock; and here and there remove turf or matted parts to have a look. Again I beg, do not give up Geology: — I wish you had Agassiz's work and plates on Glaciers. (501/4. "Etudes sur les Glaciers." L. Agassiz, Neuchatel, 1840.) I am extremely sorry that the Rajah, ill luck to him, has prevented your crossing to Thibet; but you seem to have seen most interesting country: one is astonished to hear of Fuegian climate in India. I heard from the Sabines that you were thinking of giving up Borneo; I hope that this report may prove true.
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.
