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Darwin Correspondence Project

To Charles Lyell   [1 November 1849]1

[Down]

Thursday

My dear Lyell

I have been deeply interested in your letter, & so far at least worthy of the time it must have cost you to write it.— I have not much to say: I look at the whole question as settled, Santorin2 is splendid; it is conclusive—it is perfect.— You have read Dufrenoy3 in a hurry, I think, & added to difficulty; it is the whole hill or “colline” which is composed of tuff with cross stratification; the central boss or “monticule” is simply trachyte.— Now I have described one tuff crater at Galapagos (p. 108).4 [DIAGRAM HERE] tuff basalt which has broken through a great solid sheet of basalt; why should not an irregular mass of trachyte have been left in middle after the explosions & emission of mud which produced the overlying tuff— Or again I see no difficulty in a mass of trachyte being exposed by subsequent dislocations & bared or cleaned by rain.— At Ascension, p. 40, subsequent to the last great aeriform explosion, which has covered the country with fragments, there have been dislocations & a large circular subsidence.— As far as size of Astroni5 is concerned it is nothing— do not quote Banks’ cove (for there has been some denudation there) but the “elliptic one”6 (p. 105) which is 1500 yards (34 of naut: mile) in internal diameter, & therefore larger than Astroni; & is the very one, the inclination of whose mud=streams or tuff strata I measured (before I had ever heard the name Dufrenoy) & found varying from 25o to 30o.—

Albemarle Isld instead of being a Crater of Elevation as Von Buch foolishly guessed7 is formed of 4 great sub-aerial, basaltic volcanos, (p. 103) of one of which, you might like know, the external diameter of the summit or crater was above 3 nautical miles— There are no “Craters of Denudation” at Galapagos;.

I hope you will allude to Mauritius;8 I think this is the instance on largest scale of any known,—though imperfectly known. If I were you, I wd give up consistency (or at most only allude in note to your old Editions) & bring out the Craters of Denudation as a new view which it essentially is, & you cannot, I think, give it prominence as a novelty, & yet keep to consistency & passages in old Editions.— I shd. grudge this new view being smothered in your Address, & shd. like to see a separate Paper.—9

The one great channel to Santorin & Palma &c. &c.—is just like the one main chanel being kept open in atolls & encircling barrier reefs, & on same principle of water being driven in, through several shallow breaches.—

I of course utterly reprobate very wild notion of circular elevation: it is a satisfaction to me to think that I perceived there was a screw loose in old view, & so far I think I was of some service to you.—10

Depend on it, you have for ever smashed, crushed & abolished Craters of Elevations.— There must be Craters of engulfment & of explosion mere modifications of craters of Eruption—but Craters of Denudation are the ones which have given rise to all the discussions

Ever yours | C. Darwin

Pray give my best thanks to Lady Lyell for her translation11 which was as clear as daylight to me, including “leglessness”

I shall be up on Wednesday12 & want to speak one word to you about Royal Medals,13

Footnotes

Dated by CD’s reference to visiting London, presumably for the council meeting of the Geological Society, on Wednesday 7 November 1849. The minute book records that CD attended the meeting (Council Minute Books, Geological Society Archives). There is a pencil endorsement on the letter, ‘6 ?8 Nov 1849’, but since CD did not attend another council meeting in November, this is probably incorrect.
Also called Thera, in the Greek Aegean islands. The island was selected by Christian Leopold von Buch as an excellent example of a ‘crater of elevation’, hence CD’s praise of Lyell’s successful demonstration of an alternative explanation based on denudation. Lyell used new charts of the island to show that the original volcanic cone had been eroded during a period of subsidence (C. Lyell 1850a, pp. 215–21).
Ours Pierre Armand Dufrénoy. Annotated copies of volumes three (1836) and four (1838) of Dufrénoy and élie de Beaumont 1830–8 are in the Darwin Library–CUL. CD’s reference is to Lyell’s discussion of the islands of Somma and Monte Nuovo, in the bay of Naples. Lyell appears to have incorporated CD’s suggestions, see C. Lyell 1850a, pp. 223–7.
Volcanic islands, pp. 107–8.
A crater near Naples, mentioned in C. Lyell 1850a, p. 227.
Volcanic islands, p. 105: ‘About a mile southward of Banks’ Cove, there is a fine elliptic crater [of tuff], about 500 feet in depth, and three quarters of a mile in diameter.’
Buch 1836, p. 376.
Volcanic islands, pp. 93–4. Mauritius is given the briefest mention in C. Lyell 1850a, p. 211.
CD’s advice was followed in C. Lyell 1850a. The ‘old editions’ refer to Principles of geology, of which Lyell was preparing an eighth edition (C. Lyell 1850c). The ‘Address’ refers to Lyell’s presidential address (C. Lyell 1850b) delivered at the next anniversary meeting of the Geological Society, 15 February 1850, in which Lyell did not mention his own work on ‘craters of denudation’.
In Volcanic islands, pp. 93–6, there is a discussion of the basaltic mountains of St Helena, St Jago, and Mauritius, the formation of which CD felt could not be explained by either Lyell’s earlier theory or by that of Jean Baptiste Armand Louis Léonce élie de Beaumont. See also letter to Charles Lyell, [2 September 1849].
The translation of Lovén 1844. See letter to M. E. Lyell, [24 October 1849].
Probably for the council meeting of the Geological Society (see n. 1, above).
CD was a member of the Royal Society’s sectional committee of mineralogy and geology, which was due to propose candidates for the Royal Medal at a meeting on 16 November 1849. See letter to Charles Lyell, [18 November 1849], n. 5, for an account of the voting.

Summary

Discusses CL’s refutation of CD’s concept of "craters of elevation" and CL’s new concept of "craters of denudation". Mentions examples of such craters. Admits that his own concept of these craters was unsatisfactory. Urges CL to publish article ["On craters of denudation", Q. J. Geol. Soc. Lond. 6 (1850): 207–34].

Letter details

Letter no.
DCP-LETT-1264
From
Charles Robert Darwin
To
Charles Lyell, 1st baronet
Sent from
Down
Source of text
American Philosophical Society (Mss.B.D25.83)
Physical description
6pp

Please cite as

Darwin Correspondence Project, “Letter no. 1264,” accessed on 23 September 2019, https://www.darwinproject.ac.uk/letter/DCP-LETT-1264.xml

Also published in The Correspondence of Charles Darwin, vol. 4

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