My dear Lyell

I am very much obliged for your long letter,² which has interested me much. But before coming to the volcanic Cosmogony! I must say that I cannot gather your verdict as judge and jury (and not as advocate) on the continental extensions of late authors, which I must grapple with, and which as yet strikes me as quite unphilosophical, in as much as such extensions must be applied to every oceanic island, if to any one, as to Madeira; and this I cannot admit, seeing that the skeletons at least of our continents are ancient, and seeing the geological nature of the oceanic islands themselves. Do aid me with your judgment; if I could honestly admit these great extensions, they would do me good service.

With respect to active volcanic areas being rising areas, which looks so pretty on the coral-map,³ I have formerly felt “uncomfortable” on exactly same grounds with you, viz; maritime position of volcanos. And still more from the immense thicknesses of Silurian &c volcanic strata; which thickness at first impresses the mind with idea of subsidence; if this could be proved, the theory would be smashed;⁴ but in deep oceans, though the bottom were rising great thicknesses of submarine lava might accumulate. But I found after writing coral-book cases in my notes of submarine vesicular lava-streams in the upper masses of the Cordillera, formed as I believe during subsidence, which staggered me greatly. With respect to the maritime position of volcanos, I have long been coming to conclusion that there must be some law, causing areas of elevation, (consequently of land) and of subsidence to be paralell (as if balancing each other) and closely approximate: I think this from the form of continents with deep ocean on one side,—from coral-map,—and especially from conversations with you on immense subsidences of the carboniferous &c periods, and yet with continued great supply of sediment: if this be so, such areas with opposite movements would probably be separated by sets of paralell cracks, and would be the seat of volcanos and tilts, and consequently volcanos and mountains would be apt to be maritime: but why volcanos should cling to the rising edge of the cracks I cannot conjecture.— That areas with extinct volcanic archipelagos may subside to any extent, I do not doubt.

Your view of bottom of Atlantic long sinking with continued volcanic outburst and local elevations at Madeira, Canaries &c grates (but of course I do not know how complex the phenomena are, which are thus explained) against my judgment: my general ideas strongly lead me to believe in elevatory movements being widely extended. The notion of local subsidence under great volcanic piles (from shrinking &c) I think receives support from very frequent coincidence of volcanic tertiary streams and lakes or Fresh Water beds,—an idea which, I think, you might work into something, if it be not already, in your Encyclopedic Principles.— One ought, I think, never to forget that when a volcano is in action, we have distinct proof of an action from within outwards.— Nor should we forget, as I believe follows from Hopkins,⁵ and as I have insisted in my Earthquake Paper,⁶ that volcanos and mountain-chains are mere accidents resulting from the elevation of an area, and as mountain-chains are generally long so should I view areas of elevation as generally large.

Your old original view that great oceans must be sinking areas, from there being causes making land and yet there being little land, has always struck me, till lately, as very good. But in some degree this starts from assumption that within periods of which we know anything, there was either a continent in such areas, or at least a sea-bottom of not extreme depth. But my vague ideas on this head are worth absolutely nothing. By the way this letter from brevity of expression may appear as if my notions were dogmatic, which Heaven knows is far from the case.

I am delighted that I may say (with absolute truth) that my essay is published at your suggestion;⁷ but I hope it will not need so much apology as I at first thought; for I have resolved to make it nearly as complete as my present materials allow. I cannot put in all which you suggest, for it would appear too conceited. I shall not attempt history of subject, but in one page devoted to two or three leading and opposed authorities, I had already, after a few remarks on the Principles, ventured on the words—“and with a degree of almost prophetic caution which must excite the admiration &c &c.” But I shall hereafter beg you to look at what I say on Principles in this one respect.⁸

With hearty thanks | Your’s most truly | Ch. Darwin

I wrote this so badly that I have had it copied to facilitate your reading, & I am sure it deserves facilitation.—