My dear M^r Darwin

I have just returned from a two months residence in Poland and on Tuesday 21^st. am to give my lecture on the Aymara Indians—¹ It would give me profound pleasure to see you there if your health would permit you, for I believe I shall bring forward some very important points in support of your views— I took all my notes with me to Poland and accomplished there what I am sure I should not have done here, ie a somewhat complete memoir on the subject— I think it will be about 90 pages or so of 8^vo print—and if I am not overrating its importance, I believe it contains some rather important data in fact I was surprised myself at the number of observations when I came to string them together. My intention was if time had allowed it to have placed the MS in your hands before the lecture but I have only just got back and find I have to copy out fair, some of it and fill in some references &c which I had not with me—so I shall not be able to do so— the measurements are all put in proper form and I have made out a sketch so as to compare them with other Nations. black & white—proving I think the case about the altitude &c completely & several other differences for which I at present can assign no reason²

M^r Squeer the Nicaraguan–Peruvian traveller is now in Paris and comes over the morning of my lecture expressly for it & has sent already a number of illustrations which will assist me—and I think that there will be others who can speak on the subject.—³ I shall of course only give an abstract of the more interesting and important conclusions vivâ voce—or otherwise it would take up far too much time—

I do not know whether your book is as yet so far advanced that it is too late to supply you with any data but now that I have got this matter off my hands at last—I think you will find in my MS. better or rather more correct data than what you noted down in the course of our conversation when I had to trust mainly to recollections⁴

Trusting that your health is better now that we have such fine weather | I remain my dear M^r Darwin | Yours most sincerely | David Forbes