My dear Wallace

I have been very much struck, by your whole article (returned by this post), especially on the rate of denudation, for the still glaciated surfaces have of late much perplexed me.² Also especially on the lesser mutations of climate during the last 60,000 years; for I quite think with you no cause so powerful in inducing specific changes through the consequent migrations. Your argument w^d be somewhat strengthened about organic changes having been formerly more rapid, if Sir W. Thompson is correct that physical changes were formerly more violent & abrupt.³

The whole subject is so new & vast, that I suppose you hardly expect anyone to be at once convinced, but that he sh^d. keep your view before his mind & let it ferment. This, I think, everyone will be forced to do.— I have not as yet been able to digest the fundamental notion of the shortened age of the sun & Earth. Your whole paper seems to me admirably clear & well put.— I may remark that Rütimeyer has shown that several wild mammals in Switzerland since neolithic period have had their dentition & I think general size slightly modified.⁴ I cannot believe that Isthmus of Panama has been open since commencement of Glacial period; for notwithstanding the Fishes so few shell, crustacean & according to Agassiz not one echinoderm is common to the sides.—⁵ I am very glad you are going to publish all your papers on Nat Selection: I am sure you are right, & that they will do our cause much good.

But I groan over Man— you write like a metamorphosed (in retrograde direction) naturalist, & you the author of the best paper that ever appeared in Anth. Review!⁶

Eheu Eheu Eheu⁷ | Your miserable friend | C. Darwin