I had a vague wish to read Comte, and so had George, but he has entirely cured us of any such vain wish.
There is another article (229/3. "North British Review," Volume 50, 1869: "Geological Time," page 406. The papers reviewed are Sir William Thomson, "Trans. R. Soc. Edin." 1862; "Phil. Mag." 1863; Thomson and Tait, "Natural Philosophy," Volume I., App. D; Sir W. Thomson, "Proc. R. Soc. Edin." 1865; "Trans. Geol. Soc. Glasgow," 1868 and 1869; "Macmillan's Mag." 1862; Prof. Huxley, Presidential Address, "Geol. Soc. London," February, 1869; Dr. Hooker, Presidential Address, "Brit. Assoc." Norwich, 1868. Also the review on the "Origin" in the "North British Review," 1867, by Fleeming Jenkin, and an article in the "Pall Mall Gazette," May 3rd, 1869. The author treats the last-named with contempt as the work of an anonymous journalist, apparently unconscious of his own similar position.) just come out in last "North British," by some great mathematician, which is admirably done; he has a severe fling at you (229/4. The author of the "North British" article appears to us, at page 408, to misunderstand or misinterpret Sir J.D. Hooker's parable on "underpinning." See "Life and Letters," III., page 101 (note). Sir Joseph is attacked with quite unnecessary vehemence on another point at page 413.), but the article is directed against Huxley and for Thomson. This review shows me--not that I required being shown--how devilish a clever fellow Huxley is, for the reviewer cannot help admiring his abilities. There are some good specimens of mathematical arrogance in the review, and incidentally he shows how often astronomers have arrived at conclusions which are now seen to be mistaken; so that geologists might truly answer that we must be slow in admitting your conclusions. Nevertheless, all uniformitarians had better at once cry "peccavi,"--not but what I feel a conviction that the world will be found rather older than Thomson makes it, and far older than the reviewer makes it. I am glad I have faced and admitted the difficulty in the last edition of the "Origin," of which I suppose you received, according to order, a copy.
LETTER 230. TO J.D. HOOKER. Down, August 7th [1869].
There never was such a good man as you for telling me things which I like to hear. I am not at all surprised that Hallett has found some varieties of wheat could not be improved in certain desirable qualities as quickly as at first. All experience shows this with animals; but it would, I think, be rash to assume, judging from actual experience, that a little more improvement could not be got in the course of a century, and theoretically very improbable that after a few thousands [of years] rest there would not be a start in the same line of variation. What astonishes me as against experience, and what I cannot believe, is that varieties already improved or modified do not vary in other respects. I think he must have generalised from two or three spontaneously fixed varieties. Even in seedlings from the same capsule some vary much more than others; so it is with sub-varieties and varieties. (230/1. In a letter of August 13th, 1869, Sir J.D. Hooker wrote correcting Mr. Darwin's impression: "I did not mean to imply that Hallett affirmed that all variation stopped--far from it: he maintained the contrary, but if I understand him aright, he soon arrives at a point beyond which any further accumulation in the direction sought is so small and so slow that practically a fixity of type (not absolute fixity, however) is the result.")
It is a grand fact about Anoplotherium (230/2. This perhaps refers to the existence of Anoplotherium in the S. American Eocene formation: it is one of the points in which the fauna of S. America resembles Europe rather than N. America. (See Wallace "Geographical Distribution," I., page 148.)), and shows how even terrestrial quadrupeds had time formerly to spread to very distinct regions. At each epoch the world tends to get peopled pretty uniformly, which is a blessing for Geology.