Чарльз Дарвин
More Letters of Charles Darwin — Volume 2
(554/4. In a letter to Sir Joseph Hooker, October 6th, 1847, Mr. Darwin, in referring to the origin of Coal, wrote: "...I sometimes think it could not have been formed at all. Old Sir Anthony Carlisle once said to me gravely that he supposed Megatherium and such cattle were just sent down from heaven to see whether the earth would support them, and I suppose the coal was rained down to puzzle mortals. You must work the coal well in India.")
LETTER 555. TO J.D. HOOKER. Down, May 22nd, 1860.
Lyell tells me that Binney has published in Proceedings of Manchester Society a paper trying to show that Coal plants must have grown in very marine marshes. (555/1. "On the Origin of Coal," by E.W. Binney, "Mem. Lit. Phil. Soc. Manchester," Volume VIII., 1848, page 148. Binney examines the evidence on which dry land has been inferred to exist during the formation of the Coal Measures, and comes to the conclusion that the land was covered by water, confirming Brongniart's opinion that Sigillaria was an aquatic plant. He believes the Sigillaria "grew in water, on the deposits where it is now discovered, and that it is the plant which in a great measure contributed to the formation of our valuable beds of coal." (Loc. cit., page 193.)) Do you remember how savage you were long years ago at my broaching such a conjecture?
LETTER 556. TO L. HORNER. Down {1846?}.
I am truly pleased at your approval of my book (556/1. "Geological Observations on South America," London, 1846.): it was very kind of you taking the trouble to tell me so. I long hesitated whether I would publish it or not, and now that I have done so at a good cost of trouble, it is indeed highly satisfactory to think that my labour has not been quite thrown away.
I entirely acquiesce in your criticism on my calling the Pampean formation "recent" (556/2. "We must, therefore, conclude that the Pampean formation belongs, in the ordinary geological sense of the word, to the Recent Period." ("Geol. Obs." page 101).); Pleistocene would have been far better. I object, however, altogether on principle (whether I have always followed my principle is another question) to designate any epoch after man. It breaks through all principles of classification to take one mammifer as an epoch. And this is presupposing we know something of the introduction of man: how few years ago all beds earlier than the Pleistocene were characterised as being before the monkey epoch. It appears to me that it may often be convenient to speak of an Historical or Human deposit in the same way as we speak of an Elephant bed, but that to apply it to an epoch is unsound.
I have expressed myself very ill, and I am not very sure that my notions are very clear on this subject, except that I know that I have often been made wroth (even by Lyell) at the confidence with which people speak of the introduction of man, as if they had seen him walk on the stage, and as if, in a geological chronological sense, it was more important than the entry of any other mammifer.
You ask me to do a most puzzling thing, to point out what is newest in my volume, and I found myself incapable of doing almost the same for Lyell. My mind goes from point to point without deciding: what has interested oneself or given most trouble is, perhaps quite falsely, thought newest. The elevation of the land is perhaps more carefully treated than any other subject, but it cannot, of course, be called new. I have made out a sort of index, which will not take you a couple of minutes to skim over, and then you will perhaps judge what seems newest. The summary at the end of the book would also serve same purpose.
I do not know where E. de B. {Elie de Beaumont} has lately put forth on the recent elevation of the Cordillera. He "rapported" favourably on d'Orbigny, who in late times fires off a most Royal salute; every volcano bursting forth in the Andes at the same time with their elevation, the debacle thus caused depositing all the Pampean mud and all the Patagonian shingle! Is not this making Geology nice and simple for beginners?
We have been very sorry to hear of Bunbury's severe illness; I believe the measles are often dangerous to grown-up people. I am very glad that your last account was so much better.
I am astonished that you should have had the courage to go right through my book. It is quite obvious that most geologists find it far easier to write than to read a book.
Chapter I. and II. — Elevation of the land: equability on E. coast as shown by terraces, page 19; length on W. coast, page 53; height at Valparaiso, page 32; number of periods of rest at Coquimbo, page 49; elevation within Human period near Lima greater than elsewhere observed; the discussion (page 41) on non-horizontality of terraces perhaps one of newest features — on formation of terraces rather newish.
Chapter III., page 65. — Argument of horizontal elevation of Cordillera I believe new. I think the connection (page 54) between earthquake {shocks} and insensible rising important.
Chapter IV. — The strangeness of the (Eocene) mammifers, co-existing with recent shells.
Chapter V. — Curious pumiceous infusorial mudstone (page 118) of Patagonia; climate of old Tertiary period, page 134. The subject which has been most fertile in my mind is the discussion from page 135 to end of chapter on the accumulation of fossiliferous deposits. (556/3. The last section of Chapter V. treats of "the Absence of extensive modern Conchiferous Deposits in South America; and on the contemporaneousness of the older Tertiary Deposits at distant points being due to contemporaneous movements of subsidence." Darwin expresses the view that "the earth's surface oscillates up and down; and...during the elevatory movements there is but a small chance of durable fossiliferous deposits accumulating" (loc. cit., page 139).)
Chapter VI. — Perhaps some facts on metamorphism, but chiefly on the layers in mica-slate, etc., being analogous to cleavage.
Chapter VII. — The grand up-and-down movements (and vertical silicified trees) in the Cordillera: see summary, page 204 and page 240. Origin of the Claystone porphyry formation, page 170.
Chapter VIII., page 224. — Mixture of Cretaceous and Oolitic forms (page 226) — great subsidence. I think (page 232) there is some novelty in discussion on axes of eruption and injection. (page 247) Continuous volcanic action in the Cordillera. I think the concluding summary (page 237) would show what are the most salient features in the book.
LETTER 557. TO C. LYELL. Shrewsbury {August 10th, 1846}.
I was delighted to receive your letter, which was forwarded here to me. I am very glad to hear about the new edition of the "Principles," (557/1. The seventh edition of the "Principles of Geology" was published in 1847.), and I most heartily hope you may live to bring out half a dozen more editions. There would not have been such books as d'Orbigny's S. American Geology (557/2. "Voyage dans l'Amerique meridionale execute pendant les Annees 1826-37." 6 volumes, Paris, 1835-43.) published, if there had been seven editions of the "Principles" distributed in France. I am rather sorry about the small type; but the first edition, my old true love, which I never deserted for the later editions, was also in small type. I much fear I shall not be able to give any assistance to Book III. (557/3. This refers to Book III. of the "Principles" — "Changes of the Organic World now in Progress.") I think I formerly gave my few criticisms, but I will read it over again very soon (though I am striving to finish my S. American Geology (557/4. "Geological Observations on South America" was published in 1846.)) and see whether I can give you any references. I have been thinking over the subject, and can remember no one book of consequence, as all my materials (which are in an absolute chaos on separate bits of paper) have been picked out of books not directly treating of the subjects you have discussed, and which I hope some day to attempt; thus Hooker's "Antarctic Flora" I have found eminently useful (557/5. "Botany of the Antarctic Voyage of H.M.S. 'Erebus' and 'Terror' in the Years 1839-43." I., "Flora Antarctica." 2 volumes, London, 1844-47.), and yet I declare I do not know what precise facts I could refer you to. Bronn's "Geschichte" (557/6. "Naturgeschichte der drei Reiche." H.E. Bronn, Stuttgart, 1834-49.) which you once borrowed) is the only systematic book I have met with on such subjects; and there are no general views in such parts as I have read, but an immense accumulation of references, very useful to follow up, but not credible in themselves: thus he gives hybrids from ducks and fowls just as readily as between fowls and pheasants! You can have it again if you like. I have no doubt Forbes' essay, which is, I suppose, now fairly out, will be very good under geographical head. (557/7. "On the Connection between the Distribution of the existing Fauna and Flora of the British Isles, and the Geological Changes which have affected their Area, especially during the Epoch of the Northern Drift," by E. Forbes. "Memoirs of Geological Survey," Volume I., page 336, 1846.) Kolreuter's German book is excellent on hybrids, but it will cost you a good deal of time to work out any conclusion from his numerous details. (557/8. Joseph Gottlieb Kolreuter's "Vorlaufige Nachricht von eininigen das Geschlecht der Pflanzen betreffenden Versuchen und Beobachtungen." Leipzig, 1761.) With respect to variation I have found nothing — but minute details scattered over scores of volumes. But I will look over Book III. again. What a quantity of work you have in hand! I almost wish you could have finished America, and thus have allowed yourself rather more time for the old "Principles"; and I am quite surprised that you could possibly have worked your own new matter in within six weeks. Your intention of being in Southampton will much strengthen mine, and I shall be very glad to hear some of your American Geology news.
LETTER 558. TO L. HORNER. Down, Sunday {January 1847}.
Your most agreeable praise of my book is enough to turn my head; I am really surprised at it, but shall swallow it with very much gusto... (558/1. "Geological Observations in S. America," London, 1846.)
E. de Beaumont measured the inclination with a sextant and artificial horizon, just as you take the height of the sun for latitude.
With respect to my Journal, I think the sketches in the second edition (558/2. "Journal of Researches into the Natural History and Geology of the Countries visited during the Voyage of H.M.S. 'Beagle.'" Edition II. London, 1845.) are pretty accurate; but in the first they are not so, for I foolishly trusted to my memory, and was much annoyed to find how hasty and inaccurate many of my remarks were, when I went over my huge pile of descriptions of each locality.
If ever you meet anyone circumstanced as I was, advise him not, on any account, to give any sketches until his materials are fully worked out.
What labour you must be undergoing now; I have wondered at your patience in having written to me two such long notes. How glad Mrs. Horner will be when your address is completed. (558/3. Anniversary Address of the President ("Quart. Journ. Geol. Soc." Volume III., page xxii, 1847).) I must say that I am much pleased that you will notice my volume in your address, for former Presidents took no notice of my two former volumes.
I am exceedingly glad that Bunbury is going on well.
LETTER 559. TO C. LYELL. Down, July 3rd {1849}.
I don't know when I have read a book so interesting (559/1. "A Second Visit to the United States of North America." 2 volumes, London, 1849.); some of your stories are very rich. You ought to be made Minister of Public Education — not but what I should think even that beneath the author of the old "Principles." Your book must, I should think, do a great deal of good and set people thinking. I quite agree with the "Athenaeum" that you have shown how a man of science can bring his powers of observation to social subjects. (559/2. "Sir Charles Lyell, besides the feelings of a gentleman, seems to carry with him the best habits of scientific observation into other strata than those of clay, into other 'formations' than those of rock or river-margin." "The Athenaeum," June 23rd, 1849, page 640.) You have made H. Wedgwood, heart and soul, an American; he wishes the States would annex us, and was all day marvelling how anyone who could pay his passage money was so foolish as to remain here.
LETTER 560. TO C. LYELL. Down, {December, 1849}.
(560/1. In this letter Darwin criticises Dana's statements in his volume on "Geology," forming Volume X. of the "Wilkes Exploring Expedition," 1849.)
...Dana is dreadfully hypothetical in many parts, and often as "d — d cocked sure" as Macaulay. He writes however so lucidly that he is very persuasive. I am more struck with his remarks on denudation than you seem to be. I came to exactly the same conclusion in Tahiti, that the wonderful valleys there (on the opposite extreme of the scale of wonder {to} the valleys of New South Wales) were formed exclusively by fresh water. He underrates the power of sea, no doubt, but read his remarks on valleys in the Sandwich group. I came to the conclusion in S. America (page 67) that the main effect of fresh water is to deepen valleys, and sea to widen them; I now rather doubt whether in a valley or fiord...the sea would deepen the rock at its head during the elevation of the land. I should like to tour on the W. coast of Scotland, and attend to this. I forget how far generally the shores of fiords (not straits) are cliff-formed. It is a most interesting subject.
I return once again to Coral. I find he does not differ so much in detail with me regarding areas of subsidence; his map is coloured on some quite unintelligible principle, and he deduces subsidence from the vaguest grounds, such as that the N. Marianne Islands must have subsided because they are small, though long in volcanic action: and that the Marquesas subsided because they are penetrated by deep bays, etc., etc. I utterly disbelieve his statements that most of the atolls have been lately raised a foot or two. He does not condescend to notice my explanation for such appearances. He misrepresents me also when he states that I deduce, without restriction, elevation from all fringing reefs, and even from islands without any reefs! If his facts are true, it is very curious that the atolls decrease in size in approaching the vast open ocean S. of the Sandwich Islands. Dana puts me in a passion several times by disputing my conclusions without condescending to allude to my reasons; thus, regarding S. Lorenzo elevation, he is pleased to speak of my "characteristic accuracy" (560/2. Dana's "Geology" (Wilkes expedition), page 590.), and then gives difficulties (as if his own) when they are stated by me, and I believe explained by me — whereas he only alludes to a few of the facts. So in Australian valleys, he does not allude to my several reasons. But I am forgetting myself and running on about what can only interest myself. He strikes me as a very clever fellow; I wish he was not quite so grand a generaliser. I see little of interest except on volcanic action and denudation, and here and there scattered remarks; some of the later chapters are very bald.
LETTER 561. TO J.D. DANA. Down, December 5th, 1849.
I have not for some years been so much pleased as I have just been by reading your most able discussion on coral reefs. I thank you most sincerely for the very honourable mention you make of me. (561/1. "United States Exploring Expedition during the Years 1839-42 under the Command of Charles Wilkes, U.S.N." Volume X., "Geology," by J.D. Dana, 1849.) This day I heard that the atlas has arrived, and this completes your munificent present to me. I have not yet come to the chapter on subsidence, and in that I fancy we shall disagree, but in the descriptive part our agreement has been eminently satisfactory to me, and far more than I ever ventured to anticipate. I consider that now the subsidence theory is established. I have read about half through the descriptive part of the "Volcanic Geology" (561/2. Part of Dana's "Geology" is devoted to volcanic action.) (last night I ascended the peaks of Tahiti with you, and what I saw in my short excursion was most vividly brought before me by your descriptions), and have been most deeply interested by it. Your observations on the Sandwich craters strike me as the most important and original of any that I have read for a long time. Now that I have read yours, I believe I saw at the Galapagos, at a distance, instances of those most curious fissures of eruption. There are many points of resemblance between the Galapagos and Sandwich Islands (even to the shape of the mound-like hills) — viz., in the liquidity of the lavas, absence of scoriae, and tuff-craters. Many of your scattered remarks on denudation have particularly interested me; but I see that you attribute less to sea and more to running water than I have been accustomed to do. After your remarks in your last very kind letter I could not help skipping on to the Australian valleys (561/3. Ibid., pages 526 et seq.: "The Formation of Valleys, etc., in New South Wales."), on which your remarks strike me as exceedingly ingenious and novel, but they have not converted me. I cannot conceive how the great lateral bays could have been scooped out, and their sides rendered precipitous by running water. I shall go on and read every word of your excellent volume.
If you look over my "Geological Instructions" you will be amused to see that I urge attention to several points which you have elaborately discussed. (561/4. "A Manual of Scientific Enquiry, prepared for the use of Her Majesty's Navy, and adapted for Travellers in General." Edited by Sir John F.W. Herschel, Bart. London, 1849 (Section VI., "Geology." By Charles Darwin).) I lately read a paper of yours on Chambers' book, and was interested by it. I really believe the facts of the order described by Chambers, in S. America, which I have described in my Geolog. volume. This leads me to ask you (as I cannot doubt that you will have much geological weight in N. America) to look to a discussion at page 135 in that volume on the importance of subsidence to the formation of deposits, which are to last to a distant age. This view strikes me as of some importance.
When I meet a very good-natured man I have that degree of badness of disposition in me that I always endeavour to take advantage of him; therefore I am going to mention some desiderata, which if you can supply I shall be very grateful, but if not no answer will be required.
Thank you for your "Conspectus Crust.," but I am sorry to say I am not worthy of it, though I have always thought the Crustacea a beautiful subject. (561/5. "Conspectus Crustaceorum in orbis terrarum circumnavigatione, C. Wilkes duce, collectorum." Cambridge (U.S.A.), 1847.)
LETTER 562. TO C. LYELL. {Down, March 9th, 1850.}
I am uncommonly much obliged to you for your address, which I had not expected to see so soon, and which I have read with great interest. (562/1. Anniversary Address of the President, "Quart. Journ. Geol. Soc." Volume VI., page 32, 1850.) I do not know whether you spent much time over it, but it strikes me as extra well arranged and written — done in the most artistic manner, to use an expression which I particularly hate. Though I am necessarily pretty well familiar with your ideas from your conversation and books, yet the whole had an original freshness to me. I am glad that you broke through the routine of the President's addresses, but I should be sorry if others did. Your criticisms on Murchison were to me, and I think would be to many, particularly acceptable. (562/2. In a paper "On the Geological Structure of the Alps, etc." ("Quart. Journ. Geol. Soc." Volume V., page 157, 1849) Murchison expressed his belief that the apparent inversion of certain Tertiary strata along the flanks of the Alps afforded "a clear demonstration of a sudden operation or catastrophe." It is this view of paroxysmal energy that Lyell criticises in the address.) Capital, that metaphor of the clock. (562/3. "In a word, the movement of the inorganic world is obvious and palpable, and might be likened to the minute-hand of a clock, the progress of which can be seen and heard, whereas the fluctuations of the living creation are nearly invisible, and resemble the motion of the hour-hand of a timepiece" (loc. cit., page xlvi).) I shall next February be much interested by seeing your hour-hand of the organic world going.
Many thanks for your kindness in taking the trouble to tell me of the anniversary dinner. What a compliment that was which Lord Mahon paid me! I never had so great a one. He must be as charming a man as his wife is a woman, though I was formerly blind to his merit. Bunsen's speech must have been very interesting and very useful, if any orthodox clergyman were present. Your metaphor of the pebbles of pre-existing languages reminds me that I heard Sir J. Herschel at the Cape say how he wished some one would treat language as you had Geology, and study the existing causes of change, and apply the deduction to old languages.
We are all pretty flourishing here, though I have been retrograding a little, and I think I stand excitement and fatigue hardly better than in old days, and this keeps me from coming to London. My cirripedial task is an eternal one; I make no perceptible progress. I am sure that they belong to the hour-hand, and I groan under my task.
LETTER 563. C. LYELL TO CHARLES DARWIN. April 23rd, 1855.
I have seen a good deal of French geologists and palaeontologists lately, and there are many whom I should like to put on the R.S. Foreign List, such as D'Archiac, Prevost, and others. But the man who has made the greatest sacrifices and produced the greatest results, who has, in fact, added a new period to the calendar, is Barrande.
The importance of his discoveries as they stand before the public fully justify your choice of him; but what is unpublished, and which I have seen, is, if possible, still more surprising. Thirty genera of gasteropods (150 species) and 150 species of lamellibranchiate bivalves in the Silurian! All obtained by quarries opened solely by him for fossils. A man of very moderate fortune spending nearly all his capital on geology, and with success.
E. Forbes' polarity doctrines are nearly overturned by the unpublished discoveries of Barrande. (563/1. See note, Letter 41, Volume I.)
I have called Barrande's new period Cambrian (see "Manual," 5th edition), and you will see why. I could not name it Protozoic, but had Barrande called it Bohemian, I must have adopted that name. All the French will rejoice if you confer an honour on Barrande. Dana is well worthy of being a foreign member.
Should you succeed in making Barrande F.R.S., send me word.
LETTER 564. TO J.D. HOOKER. June 5th {1857}.
(564/1. The following, which bears on the subject of medals, forms part of the long letter printed in the "Life and Letters," II., page 100.)
I do not quite agree with your estimate of Richardson's merits. Do, I beg you (whenever you quietly see), talk with Lyell on Prestwich: if he agrees with Hopkins, I am silenced; but as yet I must look at the correlation of the Tertiaries as one of the highest and most frightfully difficult tasks a man could set himself, and excellent work, as I believe, P. has done. (564/2. Prof. Prestwich had published numerous papers dealing with Tertiary Geology before 1857. The contributions referred to are probably those "On the Correlation of the Lower Tertiaries of England with those of France and Belgium," "Quart. Journ. Geol. Soc." Volume X., 1854, page 454; and "On the Correlation of the Middle Eocene Tertiaries of England, France, and Belgium," ibid., XII., 1856, page 390.) I confess I do not value Hopkins' opinion on such a point. I confess I have never thought, as you show ought to be done, on the future. I quite agree, under all circumstances, with the propriety of Lindley. How strange no new geologists are coming forward! Are there not lots of good young chemists and astronomers or physicists? Fitton is the only old geologist left who has done good work, except Sedgwick. Have you thought of him? He would be a brilliant companion for Lindley. Only it would never do to give Lyell a Copley and Sedgwick a Royal in the same year. It seems wrong that there should be three Natural Science medals in the same year. Lindley, Sedgwick, and Bunsen sounds well, and Lyell next year for the Copley. (564/3. In 1857 a Royal medal was awarded to John Lindley; Lyell received the Copley in 1858, and Bunsen in 1860.) You will see that I am speculating as a mere idle amateur.
LETTER 565. TO S.P. WOODWARD. Down, May 27th {1856}.
I am very much obliged to you for having taken the trouble to answer my query so fully. I can now be at rest, for from what you say and from what little I remember Forbes said, my point is unanswerable. The case of Terebratula is to the point as far as it goes, and is negative. I have already attempted to get a solution through geographical distribution by Dr. Hooker's means, and he finds that the same genera which have very variable species in Europe have other very variable species elsewhere. This seems the general rule, but with some few exceptions. I see from the several reasons which you assign, that there is no hope of comparing the same genus at two different periods, and seeing whether the tendency to vary is greater at one period in such genus than at another period. The variability of certain genera or groups of species strikes me as a very odd fact. (565/1. The late Dr. Neumayr has dealt, to some extent, with this subject in "Die Stamme des Thierreichs," Volume I., Wien, 1889.)
I shall have no points, as far as I can remember, to suggest for your reconsideration, but only some on which I shall have to beg for a little further information. However, I feel inclined very much to dispute your doctrine of islands being generally ancient in comparison, I presume, with continents. I imagine you think that islands are generally remnants of old continents, a doctrine which I feel strongly disposed to doubt. I believe them generally rising points; you, it seems, think them sinking points.
LETTER 566. TO T.H. HUXLEY. Down, April 14th {1860}.
Many thanks for your kind and pleasant letter. I have been much interested by "Deep-sea Soundings,", and will return it by this post, or as soon as I have copied a few sentences. (566/1. Specimens of the mud dredged by H.M.S. "Cyclops" were sent to Huxley for examination, who gave a brief account of them in Appendix A of Capt. Dayman's Report, 1858, under the title "Deep-sea Soundings in the North Atlantic.") I think you said that some one was investigating the soundings. I earnestly hope that you will ask the some one to carefully observe whether any considerable number of the calcareous organisms are more or less friable, or corroded, or scaling; so that one might form some crude notion whether the deposition is so rapid that the foraminifera are preserved from decay and thus are forming strata at this profound depth. This is a subject which seems to me to have been much neglected in examining soundings.
Bronn has sent me two copies of his Morphologische Studien uber die Gestaltungsgesetze." (H.G. Bronn, "Morphologische Studien uber die Gestaltungsgesetze der Naturkorper uberhaupt und der organischen insbesondere": Leipzig, 1858.) It looks elementary. If you will write you shall have the copy; if not I will give it to the Linnean Library.
I quite agree with the letter from Lyell that your extinguished theologians lying about the cradle of each new science, etc., etc., is splendid. (566/2. "Darwiniana, Collected Essays," Volume II., page 52.)
LETTER 567. TO T.H. HUXLEY. May 10th {1862 or later}.
I have been in London, which has prevented my writing sooner. I am very sorry to hear that you have been ill: if influenza, I can believe in any degree of prostration of strength; if from over-work, for God's sake do not be rash and foolish. You ask for criticisms; I have none to give, only impressions. I fully agree with your "skimming-of-pot theory," and very well you have put it. With respect {to} contemporaneity I nearly agree with you, and if you will look to the d — d book, 3rd edition, page 349 you will find nearly similar remarks. (567/1. "When the marine forms are spoken of as having changed simultaneously throughout the world, it must not be supposed that this expression relates to the same year, or to the same century, or even that it has a very strict geological sense; for if all the marine animals now living in Europe, and all those that lived in Europe during the Pleistocene period (a very remote period as measured by years, including the whole Glacial epoch), were compared with those now existing in South America or in Australia, the most skilful naturalist would hardly be able to say whether the present or the Pleistocene inhabitants of Europe resembled most closely those of the Southern hemisphere." "Origin," Edition VI., page 298. The passage in Edition III., page 350, is substantially the same.) But at page 22 of your Address, in my opinion you put your ideas too far. (567/2. Anniversary Address to the Geological Society of London ("Quart. Journ. Geol. Soc." Volume XVIII., page xl, 1862). As an illustration of the misleading use of the term "contemporaneous" as employed by geologists, Huxley gives the following illustration: "Now suppose that, a million or two of years hence, when Britain has made another dip beneath the sea and has come up again, some geologist applies this doctrine {i.e., the doctrine of the Contemporaneity of the European and of the North American Silurians: proof of contemporaneity is considered to be established by the occurrence of 60 per cent. of species in common}, in comparing the strata laid bare by the upheaval of the bottom, say, of St. George's Channel with what may then remain of the Suffolk Crag. Reasoning in the same way, he will at once decide the Suffolk Crag and the St. George's Channel beds to be contemporaneous; although we happen to know that a vast period...of time...separates the two" (loc. cit., page xlv). This address is republished in the "Collected Essays," Volume VIII.; the above passage is at page 284.) I cannot think that future geologists would rank the Suffolk and St. George's strata as contemporaneous, but as successive sub-stages; they rank N. America and British stages as contemporaneous, notwithstanding a percentage of different species (which they, I presume, would account for by geographical difference) owing to the parallel succession of the forms in both countries. For terrestrial productions I grant that great errors may creep in (567/3. Darwin supposes that terrestrial productions have probably not changed to the same extent as marine organisms. "If the Megatherium, Mylodon...had been brought to Europe from La Plata, without any information in regard to their geological position, no one would have suspected that they had co-existed with sea shells all still living" ("Origin," Edition VI., page 298).); but I should require strong evidence before believing that, in countries at all well-known, so-called Silurian, Devonian, and Carboniferous strata could be contemporaneous. You seem to me on the third point, viz., on non-advancement of organisation, to have made a very strong case. I have not knowledge or presumption enough to criticise what you say. I have said what I could at page 363 of "Origin." It seems to me that the whole case may be looked at from several points of view. I can add only one miserable little special case of advancement in cirripedes. The suspicion crosses me that if you endeavoured your best you would say more on the other side. Do you know well Bronn in his last Entwickelung (or some such word) on this subject? it seemed to me very well done. (567/4. Probably "Untersuchungen uber die Entwickelungsgesetze der organischen Welt wahrend der Bildungszeit unserer Erdoberflache," Stuttgart, 1858. Translated by W.S. Dallas in the "Ann. and Mag. Nat. Hist." Volume IV., page 81.) I hope before you publish again you will read him again, to consider the case as if you were a judge in a court of appeal; it is a very important subject. I can say nothing against your side, but I have an "inner consciousness" (a highly philosophical style of arguing!) that something could be said against you; for I cannot help hoping that you are not quite as right as you seem to be. Finally, I cannot tell why, but when I finished your Address I felt convinced that many would infer that you were dead against change of species, but I clearly saw that you were not. I am not very well, so good-night, and excuse this horrid letter.
