My dear Lyell

Many thanks for Hooker’s letter.² It is a real pleasure to me to read his letters, they are alway written with such spirit. I quite agree that Agassiz could never mistake weathered-blocks & glacial action;³ though the mistake has, I know, been made in 2 or 3 quarters of the world. I have often fought with Hooker about the Physicists putting their veto on the world having been cooler; it seems to me as irrational, as if, when Geologists first brought forward some evidence of elevation & subsidence, a former Hooker had declared that this c^d not possibly be admitted until Geologists c^d explain what made the earth rise & fall.⁴ It seems that I erred greatly about some of the plants on the Organ M^ts.,⁵ but I am very glad to hear about Fuchsia &c. I cannot make out what Hooker does believe, he seems to admit the former cooler climate, & almost in the same breath, to spurn the idea. To retort Hooker’s words “It is inexplicable to me” how he can compare the transport of seeds from the Andes to the Organs M^ts. with that from a continent to an island: not to mention the much greater distance, there are no currents of water from one to the other, & what on earth sh^d make a bird fly that distance without resting many times.⁶ I do not at all suppose that nearly all tropical forms were exterminated during the cool period, but in somewhat depopulated areas, into which there c^d be no migration, probably many closely allied species will have been formed since this period. Hooker’s paper in Nat. Hist. Rev. is well worth studying; but I cannot remember that he gives good grounds for his conviction that certain orders of plants c^d not withstand a rather cooler climate, even if it came on most gradually.⁷ We have only just learnt under how cool a temperature several tropical Orchids can flourish.⁸ I clearly saw Hookers difficulty about the preservation of tropical forms during the cool period, & tried my best to retain one spot after another as a hot-house for their preservation; but it w^d not hold good, & it was a mere piece of truckling on my part when I suggested that longitudinal belts of the world were cooled one after the other.⁹ I shall very much like to see Agassiz’ letter whenever you receive one.¹⁰

I have written a long letter; but a squabble with or about Hooker always does me a world of good, & we have been at it many a long year. I cannot quite understand whether he attacks me as a Wriggler or a Hammerer but I am very sure that a deal of wriggling has to be done.¹¹

With many thanks | yours affectionately | Charles Darwin