Dear Sir

Having just read your excellent memoir on Denudation,¹ I have taken the liberty to send you a copy of my volume on S. America, finding that we have discussed some related questions.— I wish I had profited by your memoir before publishing my volume.— I see that we entirely agree on the sea’s great power compared with ordinary alluvial action, & likewise on the frequency of grand oscillations of level & on several other points. If you had time to read parts of my volume, I should much like to discuss with you many cases, such as my notion of subsidence being necessary for the formation of high sea-cliffs, as inferred from the nature of the sea’s bottom off them,² likewise the horizontal elevation of the Cordillera, as inferred from the sloping gravel fringes in the valleys³ —on the non-horizontality of lines of escarpments round old bays, &c &c—⁴

I grieve to see how diametrically opposite our views are (I being a follower of Lyell) on the probability of great & sudden elevations of mountain-chains: I cannot but think, that you would have estimated existing forces, as more than “petty” & entertained some doubt about their being “conflicting”⁵ had you inspected with your own eyes the wide area of recently elevated & similarly affected districts in S. America. There is much which I could say on this head, but I will not intrude on you. May I ask, whether you do not admit M^r Hopkin’s views of mountain-chains being the subordinate effects of fractures consequent on changes of level in the surrounding areas;⁶ & does not all the evidence, which we possess, tend to show that widely-extended elevations are slow, & may we not infer from this that the formation of mountain-chains is likewise probably slow.— I cannot see any difficulty, after a line of fracture has been once formed, in fluidifyed rock being pumped in by as many strokes, as it is pumped out in a common volcano, & yet producing a symmetrical effect.—

But I much fear that I have cause to apologise for having written at such unreasonable length: the interest excited in me by your Memoir, must plead my excuse, & trusting that you will forgive the liberty I have taken | I remain, dear Sir | Yours faithfully | C. Darwin