More Letters of Charles Darwin, vol 2 | Page 6

trust to such facts as yours (and others) about seeds of the same species from mountains and plains having acquired a slightly different climatal constitution. I know all that I have said will excite in you savage contempt towards me. Do not answer this rigmarole, but attack me to your heart's content, and to that of mine, whenever you can come here, and may it be soon.
LETTER 383. J.D. HOOKER TO CHARLES DARWIN. Kew, 1870.
(383/1. The following extract from a letter of Sir J.D. Hooker shows the tables reversed between the correspondents.)
Grove is disgusted at your being disquieted about W. Thomson. Tell George from me not to sit upon you with his mathematics. When I threatened your tropical cooling views with the facts of the physicists, you snubbed me and the facts sweetly, over and over again; and now, because a scarecrow of x+y has been raised on the selfsame facts, you boo-boo. Take another dose of Huxley's penultimate G. S. Address, and send George back to college. (383/2. Huxley's Anniversary Address to the Geological Society, 1869 ("Collected Essays," VIII., page 305). This is a criticism of Lord Kelvin's paper "On Geological Time" ("Trans. Geolog. Soc. Glasgow," III.). At page 336 Mr. Huxley deals with Lord Kelvin's "third line of argument, based on the temperature of the interior of the earth." This was no doubt the point most disturbing to Mr. Darwin, since it led Lord Kelvin to ask (as quoted by Huxley), "Are modern geologists prepared to say that all life was killed off the earth 50,000, 100,000, or 200,000 years ago?" Mr. Huxley, after criticising Lord Kelvin's data and conclusion, gives his conviction that the case against Geology has broken down. With regard to evolution, Huxley (page 328) ingeniously points out a case of circular reasoning. "But it may be said that it is biology, and not geology, which asks for so much time--that the succession of life demands vast intervals; but this appears to me to be reasoning in a circle. Biology takes her time from geology. The only reason we have for believing in the slow rate of the change in living forms is the fact that they persist through a series of deposits which, geology informs us, have taken a long while to make. If the geological clock is wrong, all the naturalist will have to do is to modify his notions of the rapidity of change accordingly.")
LETTER 384. TO J.D. HOOKER. February 3rd [1868].
I am now reading Miquel on "Flora of Japan" (384/1. Miquel, "Flore du Japon": "Archives Neerlandaises" ii., 1867.), and like it: it is rather a relief to me (though, of course, not new to you) to find so very much in common with Asia. I wonder if A. Murray's (384/2. "Geographical Distribution of Mammals," by Andrew Murray, 1866. See
Chapter V.
, page 47. See Letter 379.) notion can be correct, that a [profound] arm of the sea penetrated the west coast of N. America, and prevented the Asiatico-Japan element colonising that side of the continent so much as the eastern side; or will climate suffice? I shall to the day of my death keep up my full interest in Geographical Distribution, but I doubt whether I shall ever have strength to come in any fuller detail than in the "Origin" to this grand subject. In fact, I do not suppose any man could master so comprehensive a subject as it now has become, if all kingdoms of nature are included. I have read Murray's book, and am disappointed--though, as you said, here and there clever thoughts occur. How strange it is, that his view not affording the least explanation of the innumerable adaptations everywhere to be seen apparently does not in the least trouble his mind. One of the most curious cases which he adduces seems to me to be the two allied fresh-water, highly peculiar porpoises in the Ganges and Indus; and the more distantly allied form of the Amazons. Do you remember his explanation of an arm of the sea becoming cut off, like the Caspian, converted into fresh-water, and then divided into two lakes (by upheaval), giving rise to two great rivers. But no light is thus thrown on the affinity of the Amazon form. I now find from Flower's paper (384/3. "Zoolog. Trans." VI., 1869, page 115. The toothed whales are divided into the Physeteridae, the Delphinidae, and the Platanistidae, which latter is placed between the two other families, and is divided into the sub-families Iniinae and Platanistinae.) that these fresh-water porpoises form two sub- families, making an extremely isolated and intermediate, very small family. Hence to us they are clearly remnants of a large group; and I cannot doubt we here have a good instance precisely like that of ganoid fishes, of a large ancient marine group,