The whole subject is so new and vast that I suppose you hardly expect anyone to be at once convinced, but that he should keep your view before his mind and 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 and earth. Your whole paper seems to me admirably clear and well put. I may remark that Rütimeyer has shown that several wild mammals in Switzerland since the neolithic period have had their dentition and, I _think_, general size _slightly_ modified. I cannot believe that the Isthmus of Panama has been open since the commencement of the glacial period; for, notwithstanding the fishes, so few shells, crustaceans, and, according to Agassiz, not one echinoderm is common to the sides. I am very glad you are going to publish all your papers on Natural Selection: I am sure you are right, and that they will do our cause much good. But I groan over Man--you write like a metamorphosed (in retrograde direction) naturalist, and you the author of the best paper that ever appeared in the _Anthropological Review_! Eheu! Eheu! Eheu!--Your miserable friend, C. DARWIN. * * * * * _Down, Beckenham, Kent. March 31, 1870._ My dear Wallace,--Many thanks for the woodcut, which, judging from the rate at which I crawl on, will hardly be wanted till this time next year. Whether I shall have it reduced, or beg Mr. Macmillan for a stereotype, as you said I might, I have not yet decided. I heartily congratulate you on your removal being over, and I much more heartily condole with myself at your having left London, for I shall thus miss my talks with you which I always greatly enjoy. I was excessively pleased at your review of Galton, and I agree to every word of it. I must add that I have just re-read your article in the _Anthropological Review_, and _I defy_ you to upset your own doctrine.--Ever yours very sincerely, CH. DARWIN * * * * * _Down, Beckenham, Kent. April 20, [1870]._ My dear Wallace,--I have just received your book ["Natural Selection"][81] and read the preface. There never has been passed on me, or indeed on anyone, a higher eulogium than yours. I wish that I fully deserved it. Your modesty and candour are very far from new to me. I hope it is a satisfaction to you to reflect--and very few things in my life have been more satisfactory to me--that we have never felt any jealousy towards each other, though in one sense rivals. I believe that I can say this of myself with truth, and I am absolutely sure that it is true of you. You have been a good Christian to give a list of your additions, for I want much to read them, and I should hardly have had time just at present to have gone through all your articles.