My dear Lyell

Very many thanks for your two notes¹ & especially for Maury’s map:² also for Books which you are going to lend me.

I am sorry you cannot give any verdict on continental extensions; & I infer that you think my arguments of not much weight against such extensions: I know I wish I could believe.—

I have been having a good look at Maury (which I once before looked at)³ & in respect to Madeira & co, I must say that the chart seems to me against land-extension explaining introduction of organic beings. Madeira, the Canaries & Azores are so tied together that I sh^d. have thought that they ought to have been connected by some bank if changes of level had been connected with their organic relation. The azores ought too to have shown, more connection with America. I had sometimes speculated whether icebergs could account for the greater number of European plants & their more northern character on the Azores compared with Madeira; but it seems dangerous until boulders are found there.⁴

One of the most curious points in Maury, as it strikes me, is the little change, which about 9000 feet of sudden elevation would make in the continent visible, & what a prodigious change 9000 feet subsidence would make! Is this difference due to denudation during elevation? Certainly 12,000 feet elevation would make a prodigious change.—⁵

I have just been quoting you in my essay on ice carrying seeds in S. hemisphere;⁶ but this will not do in all the cases.— I have had a week of such labour in getting up the relations of all the antarctic floras from Hooker’s admirable works. Oddly enough I have just finished in great detail giving evidence of coolness in Tropical regions during the glacial epoch, & the consequent migration of organisms through the Tropics. There are a good many difficulties, but upon the whole it explains much. This has been a favourite notion with me almost since I wrote on erratic boulders of the south.—⁷ It harmonises with the modification of species, & without admitting this awful postulate the glacial epoch in the south & Tropics does not work in well. About Atlantis, I doubt whether the Canary islands are as much more related to the continent as they ought to be if formerly connected by continuous land.—

Yours most truly | C. Darwin

Hooker with whom I have formerly discussed the notion of the world or great belts of it having been cooler, though he at first saw great difficulties (& difficulties there are great enough) I think is much inclined to adopt the idea. With modification of specific forms it explains some wondrous odd facts in distribution.

But I shall never stop if I get on this subject, on which I have been at work, sometimes in triumph & sometimes in despair, for the last month.