More Letters of Charles Darwin — Volume 1. Darwin Charles

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СКАЧАТЬ during an equal period — oceanic or continental? For the conversion of sea into land would always equal the turning of much land into sea.

      But all this would be done in a fraction of the Pliocene period; the Glacial shells are barely 1 per cent. extinct species. Multiply this by the older Pliocene and Miocene epochs.

      You also forget an author who, by means of atolls, contrived to submerge archipelagoes (or continents?), the mountains of which must originally have differed from each other in height 8,000 (or 10,000?) feet, so that they all just rose to the surface at one level, or their sites are marked by buoys of coral. I could never feel sure whether he meant this tremendous catastrophe, all brought about by what Sedgwick called "Lyell's niggling operations," to have been effected during the era of existing species of corals. Perhaps you can tell me, for I am really curious to know...(47/3. The author referred to is of course Darwin.)

      Now, although there is nothing in my works to warrant the building up of continents in the Atlantic and Pacific even since the Eocene period, yet, as some of the rocks in the central Alps are in part Eocene, I begin to think that all continents and oceans may be chiefly, if not all, post-Eocene, and Dana's "Atlantic Ocean" of the Lower Silurian is childish (see the Anniversary Address, 1856). (47/4. Probably Dana's Anniversary Address to the "American Association for the Advancement of Science," published in the "Proceedings" 1856.) But how far you are at liberty to call up continents from "the vasty deep" as often as you want to convey a Helix from the United States to Europe in Miocene or Pliocene periods is a question; for the ocean is getting deeper of late, and Haughton says the mean depth is eleven miles! by his late paper on tides. (47/5. "On the Depth of the Sea deducible from Tidal Observations" ("Proc. Irish Acad." Volume VI., page 354, 1853-54).) I shall be surprised if this turns out true by soundings.

      I thought your mind was expanding so much in regard to time that you would have been going ahead in regard to the possibility of mountain-chains being created in a fraction of the period required to convert a swan into a goose, or vice versa. Nine feet did the Rimutaka chain of New Zealand gain in height in January, 1855, and a great earthquake has occurred in New Zealand every seven years for half a century nearly. The "Washingtonia" (Californian conifer) (47/6. Washingtonia, or Wellingtonia, better known as Sequoia. Asa Gray, writing in 1872, states his belief that "no Sequoia now alive can sensibly antedate the Christian era" ("Scientific Papers," II., page 144).) lately exhibited was four thousand years old, so that one individual might see a chain of hills rise, and rise with it, much {more} a species — and those islands which J. Hooker describes as covered with New Zealand plants three hundred (?) miles to the N.E. (?) of New Zealand may have been separated from the mainland two or three or four generations of Washingtonia ago.

      If the identity of the land-shells of all the hundreds of British Isles be owing to their having been united since the Glacial period, and the discordance, almost total, of the shells of Porto Santo and Madeira be owing to their having been separated {during} all the newer and possibly older Pliocene periods, then it gives us a conception of time which will aid you much in your conversion of species, if immensity of time will do all you require; for the Glacial period is thus shown, as we might have anticipated, to be contemptible in duration or in distance from us, as compared to the older Pliocene, let alone the Miocene, when our contemporary species were, though in a minority, already beginning to flourish.

      The littoral shells, according to MacAndrew, imply that Madeira and the Canaries were once joined to the mainland of Europe or Africa, but that those isles were disjoined so long ago that most of the species came in since. In short, the marine shells tell the same story as the land shells. Why do the plants of Porto Santo and Madeira agree so nearly? And why do the shells which are the same as European or African species remain quite unaltered, like the Crag species, which returned unchanged to the British seas after being expelled from them by glacial cold, when two millions (?) of years had elapsed, and after such migration to milder seas? Be so good as to explain all this in your next letter.

      LETTER 48. TO J.D. HOOKER. Down, July 5th {1856}.

      I write this morning in great tribulation about Tristan d'Acunha. (48/1. See "Flora Antarctica," page 216. Though Tristan d'Acunha is "only 1,000 miles distant from the Cape of Good Hope, and 3,000 from the Strait of Magalhaens, the botany of this island is far more intimately allied to that of Fuegia than Africa.") The more I reflect on your Antarctic flora the more I am astounded. You give all the facts so clearly and fully, that it is impossible to help speculating on the subject; but it drives me to despair, for I cannot gulp down your continent; and not being able to do so gives, in my eyes, the multiple creationists an awful triumph. It is a wondrous case, and how strange that A. De Candolle should have ignored it; which he certainly has, as it seems to me. I wrote Lyell a long geological letter (48/2. "Life and Letters," II., page 74.) about continents, and I have had a very long and interesting answer; but I cannot in the least gather his opinion about all your continental extensionists; and I have written again beseeching a verdict. (48/3. In the tenth edition of the "Principles," 1872, Lyell added a chapter (Chapter XLI., page 406) on insular floras and faunas in relation to the origin of species; he here (page 410) gives his reasons against Forbes as an extensionist.) I asked him to send to you my letter, for as it was well copied it would not be troublesome to read; but whether worth reading I really do not know; I have given in it the reasons which make me strongly opposed to continental extensions.

      I was very glad to get your note some days ago: I wish you would think it worth while, as you intend to have the Laburnum case translated, to write to "Wien" (that unknown place) (48/4. There is a tradition that Darwin once asked Hooker where "this place Wien is, where they publish so many books."), and find out how the Laburnum has been behaving: it really ought to be known.

      The Entada is a beast. (48/5. The large seeds of Entada scandens are occasionally floated across the Atlantic and cast on the shores of Europe.); I have never differed from you about the growth of a plant in a new island being a FAR harder trial than transportal, though certainly that seems hard enough. Indeed I suspect I go even further than you in this respect; but it is too long a story.

      Thank you for the Aristolochia and Viscum cases: what species were they? I ask, because oddly these two very genera I have seen advanced as instances (I forget at present by whom, but by good men) in which the agency of insects was absolutely necessary for impregnation. In our British dioecious Viscum I suppose it must be necessary. Was there anything to show that the stigma was ready for pollen in these two cases? for it seems that there are many cases in which pollen is shed long before the stigma is ready. As in our Viscum, insects carry, sufficiently regularly for impregnation, pollen from flower to flower, I should think that there must be occasional crosses even in an hermaphrodite Viscum. I have never heard of bees and butterflies, only moths, producing fertile eggs without copulation.

      With respect to the Ray Society, I profited so enormously by its publishing my Cirrepedia, that I cannot quite agree with you on confining it to translations; I know not how else I could possibly have published.

      I have just sent in my name for 20 pounds to the Linnaean Society, but I must confess I have done it with heavy groans, whereas I daresay you gave your 20 pounds like a light-hearted gentleman...

      P.S. Wollaston speaks strongly about the intermediate grade between two varieties in insects and mollusca being often rarer than the two varieties themselves. This is obviously very important for me, and not easy to explain. I believe I have had cases from you. But, if you believe in this, I wish you would give me a sentence to quote from you on this head. There must, I think, be a good deal of truth in it; otherwise there could hardly be nearly distinct varieties under any species, for we should have instead a blending series, as in brambles and willows.

      LETTER 49. TO J.D. HOOKER. July 13th, 1856.

      What a book a devil's chaplain might write on the clumsy, wasteful, blundering, low, and horribly cruel works of nature! With respect to crossing, from one СКАЧАТЬ