To Charles Lyell [3 October 1846]
My dear Lyell
I have been much interested with Ramsay;1 but have no particular suggestions to offer: I agree with all your remarks made the other day.2 My final impression is, that the only argument against him, is to tell him to read & reread the Principles, & if not then convinced to send him to Pluto.— Not but what he has well read the Principles! & largely profited thereby.— I know not how carefully you have read this paper, but I think you did not mention to me, that he does p. 327 believe that the main part of his great denudation was effected during a vast (almost gratuitously assumed) slow Tertiary subsidence & subsequent Tertiary oscillating slow elevation.— So our high-cliff argument is inapplicable. He seems to think his great subsidence only favourable for great denudation, I believe, from the general nature of the off-shores sea’s bottoms, that it is almost necessary: do look at two pages p. 25 of my S. American Vol. on this subject, when out next week.—3
The foundation of his views viz of one great sudden upheaval,4 strikes me as threefold.— 1st to account for the great dislocations; this strikes me as the odder, as he admits that a little northwards, there were many & some violent dislocations at many periods during the accumulation of the palæozoic series.—5 If you argue against him allude to the cool assumption that petty forces are conflicting:6 look at Volcanos; look at recurrent similar earthquakes at same spots; look at repeatedly injected intrusive masses. In my paper on Volc. Phæn. in Geolog. Transact, I have argued (& Lonsdale thought well of the argument, in favour, as he remarked, of your original doctrine) that if Hopkins views are correct, viz that mountain-chains are subordinate consequences to changes of level in mass, then, as we have evidence of such horizontal movements in mass having been slow, the formation of mountain chains (differing from volcanos only in matter being injected instead of ejected) must have been slow.—7
Secondly, Ramsay has been influenced, I think, by his alpine insects: but he is wrong in thinking that there is any necessary connection of Tropics & large insects; videlicet Galapagos. Arch. under the Equator. Small insects swarm in all parts of Tropics, though accompanied generally with large ones.—8
Thirdly, he appears influenced by the absence of newer deposits on the old area, blinded by the supposed necessity of sediment accumulating somewhere near (as no doubt is true) & being preserved;—an example, as I think, of the common error, on which I wrote to you about. The preservation of sedimentary deposits being, as I do not doubt, the exception, when they are accumulated during periods of elevation or of stationary level; & therefore the preservation of newer deposits would not be probable, according to your view that Ramsay’s great palæozoic masses were denuded, whilst slowly rising — Do pray look at end of II. Chapt at what little I have said on this subject in my S. American volume.9
I do not think you can safely argue that whole surface was probably denuded at the same time to the level of the lateral patches of Magnesian conglomerate.—
The latter part of paper strikes me as good, but obvious. I shall send him my S. American Vol. for it is curious on how many similar points we enter, & I modestly hope it may be a half oz: weight towards his conversion to better views. If he wd but reject his great sudden elevations, how sound & good he wd be.— I doubt whether this letter will be worth the reading.
Ever your’s | C. D.
Discusses A. C. Ramsay’s article ["On the denudation of South Wales", Mem. Geol. Surv. G. B. 1 (1846)]. Mentions his own paper ["Volcanic phenomena in South America", Collected papers 1: 53–86]. Emphasises that sedimentary deposits are not ordinarily preserved.
Please cite as
Darwin Correspondence Project, “Letter no. 1004,” accessed on 26 September 2016, http://www.darwinproject.ac.uk/DCP-LETT-1004