If you have not read Bates' book (171/2. Henry Walter Bates, "The Naturalist on the River Amazons," 2 volumes, London, 1863. In a letter to Bates, April 18th, 1863, Darwin writes, "It is the best work of natural history travels ever published in England" ("Life and Letters," II., page 381.), I think it would interest you. He is second only to Humboldt in describing a tropical forest. (171/3. Quoted in "Life and Letters," II., page 381.). Talking of reading, I have never got the "Edinburgh" (171/4. The "Geological Evidence of the Antiquity of Man," by Sir Charles Lyell, and works by other authors reviewed in the "Edinburgh Review." Volume CXVIII., July 1863. The writer sums up his criticism as follows: "Glancing at the work of Sir Charles Lyell as a whole, it leaves the impression on our minds that we have been reading an ingenious academical thesis, rather than a work of demonstration by an original writer...There is no argument in it, and only a few facts which have not been stated elsewhere by Sir C. Lyell himself or by others" (loc. cit., page 294).), in which, I suppose, you are cut up. LETTER 172. TO H. FALCONER. December 26th [1863]. Thank you for telling me about the Pliocene mammal, which is very remarkable; but has not Owen stated that the Pliocene badger is identical with the recent? Such a case does indeed well show the stupendous duration of the same form. I have not heard of Suess' pamphlet (172/1. Probably Suess's paper "Ueber die Verschiedenheit und die Aufeinanderfolge der tertiaren Land-faunen in der Niederung von Wien." "Sitz.-Ber. Wien Akad." XLVII., page 306, 1863.), and should much like to learn the title, if it can be procured; but I am on different subjects just at present. I should rather like to see it rendered highly probable that the process of formation of a new species was short compared to its duration--that is, if the process was allowed to be slow and long; the idea is new to me. Heer's view that new species are suddenly formed like monsters, I feel a conviction from many reasons is false. CHAPTER 1.IV.--EVOLUTION, 1864-1869. LETTER 173. TO A.R. WALLACE. Down, January 1st, 1864.