To Charles Lyell   4 December [1849]

My dear Lyell

This letter requires no answer, & I write solely from exuberance of vanity. Dana has sent me the Geolog. of U.S. Expedition & I have just read the Coral Part.—¹ To begin with a modest speech, I am astonished at my own accuracy!! if I were to rewrite now my coral book, there is hardly a sentence I sh^d. have to alter—except that I ought to have attributed more effect to recent volcanic action in checking growth of coral.— When I say all this, I ought to add, that the consequences of the theory on areas of subsidence are treated in a separate chapter to which I have not come, & in this I suspect we shall differ more.—² Dana talks of agreeing with my theory in most points; I can find out not one in which he differs.— Considering how infinitely more he saw of Coral Reefs than I did, this is wonderfully satisfactory to me; though really I think it some little reflection on him, that he did find other & new points to observe. He treats me most courteously.— There now my vanity is pretty well satisfied.

I am now reading the volcanic part, which is excellent & much very original: I do not know whether you have seen it, but I think you ought.— I remember in my last letter talking very big about dikes never being connected directly (ie rectangularly) with lava-streams; but it is clear that such occur frequently at the Sandwich Is^ds. without any cones.— I think, however, that there can be no doubt that this is a rare exceptional case; I do not quite perceive why in some cases there are cones with scoriæ, & in other cases not. I sh^d. suppose Etna could not come into same predicament with the Sandwich Vents, for if I understood you, there were beds of scoriæ between the streams of lava.— But perhaps you have read Dana & all I write is superfluous—³

I c^d. of course lend you my copy,⁴ if you have not one of your own—though I believe there is one in Geolog. Soc.— Dana discusses the great Australian valleys; & thinks they have been formed by running fresh water; his arguments are very ingenious, but I am not at all converted by them; indeed I doubt whether he saw the more striking cases: he allows the valleys are valleys of denudation.—⁵ I looked with some trepidation to Craters of Elevation in index, but there was nothing (as far as I c^d see in casual glance) which concerned you.—

I am bound to state that now that I have read Dana, I believe there are cases at Galapagos, of streams proceeding from dikes without cones, which I saw at a distance, near summit of great craters but did not ascend to.— I remember being surprised at not seeing a cone, but slurred the difficulty over: the great craters at Galapagos, as I have remarked in Book,⁶ are singular from having evolved so little scoriæ.

I shall be up on 19^th.—⁷

Farewell— My boasting has done me a deal of good | Your’s Ever | C. Darwin