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Darwin Correspondence Project

To David Forbes   11 December [1860]1

Down Bromley Kent.

Dec. 11.

My dear Sir

Your letter has pleased me exceedingly.2 When I saw how much error you detected in d’Orbigny, I said to myself “Good Heavens my turn will come next”.—3

I hope that you will be able to send your observations on Chile &c to Geolog. Soc. before your departure (which I am sorry to hear is so very soon); but of course if not written out already that will be quite impossible.4 On your return if you wish to publish in extenso, your case would be an excellent one for aid from the Government grant to Royal Socy.—5 Pray bear this in mind.— You would get plenty of backers.— Your paper just sent to G. Soc. will at once put you in that position, that you might boldly demand aid.

I am sorry for my blunder about Andesite.6 Have you ever reflected on the subject of plutonic rocks being same character throughout extensive areas at same epoch. I remember this subject treated of by (I think) Keilhau: it seems to me very mysterious & indicating some great unknown class of facts.—7

How curious I shall be at some future time to read about the Uspallata formation.8 I know how busy you are & must be; but it would be a great favour, if you would write literally one line to me to say whether the great mound of detritus at Val del Yeso has any connection with ice-action; because I am preparing new Edition of my Origin of Species, & if you say “no” I will strike out 3 lines; if you say “yes” I will leave them as they now stand.—9 I saw in the valley of Cauquenes boulders which I now think must have had some connexion with Glacial action.—10

When in S. America, would it trouble you to make a few observations on Mules, as by enclosed paper, & some time write me the results?11

With every good wish for your success & prosperity, & with cordial thanks for your letter & kind expressions. Believe me | My dear Sir | Yours very sincerely | C. Darwin


The year is established by the references to Forbes’s paper on the geology of Bolivia and southern Peru (Forbes 1860), which was read before the Geological Society of London on 21 November 1860. A summary of this letter was published in Correspondence vol. 13, Supplement.
Forbes’s letter has not been found. The letter from David Forbes, [November? 1860] (Correspondence vol. 8), which should now be dated [after 11 December 1860], is a reply to this letter.
CD refers to Forbes 1860, in which Forbes challenged many of Alcide Charles Victor Dessalines d’Orbigny’s findings on the geology of South America (Orbigny 1835–47; see Correspondence vol. 8, letter to Charles Lyell, 4 December [1860]). For a summary of the differences between Forbes and Orbigny, see Proceedings of the Geological Society of London 33 (1877): 44–6.
Forbes 1860 was intended as the first part of a memoir that would include two further parts on the geology of Chile and the Argentine (Forbes 1860, p. 62). However, Forbes read no further paper on the geology of South America to the Geological Society.
Forbes did not publish on the geology of Chile and Argentina with the Royal Society of London.
CD had described a volcanic rock that he found in the vicinity of the Beagle Channel as andesite (South America, pp. 154–5 et seq.). Forbes had revised CD’s nomenclature, preferring to call it diorite on account of its similarity to European diorites (Forbes 1860, p. 29).
CD had earlier been impressed by Baltazar Mathias Keilhau’s theory of the origin of rocks by heat-induced crystallisation (see Keilhau 1838–40 and 1844, and Correspondence vol. 3, letter to Adolf von Morlot, 10 October [1844] and n. 7).
CD crossed the Uspallata pass and the Uspallata range in Argentina in 1835 (see Journal of researches 2d ed., pp. 331, 333; see also South America, pp. 60, 175).
CD described the geological features of the Yeso valley, in Chile, in South America, p. 178. This may have been the source for the passage about the ‘vast mound of detritus’ in an Andean valley in Origin, p. 373. After receiving Forbes’s reply (Correspondence vol. 8, letter from David Forbes, [after 12 December 1860] [previously dated [November? 1860]), CD restated his conviction that the mound was due to glacial action (Origin 3d ed., pp. 403–4).
See South America, pp. 64–7. While a small number of boulders near Cauquenes in Chile had previously been described by Adolphe Théodore Brongniart as erratics deposited by glaciers, CD argued that river action and uplift could have displaced them from their original strata (South America, p. 66 and n.).
The enclosure listing questions for Forbes has not been found. By mules, CD probably means hybrids between goats and sheep. For Forbes’s reply, see Correspondence vol. 8, letter from David Forbes, [November? 1860], now redated [after 11 December 1860]. CD cited Forbes on the sheep of Chile in Variation 1: 95, and considered the question of the possible relatedness of sheep to goats in Variation 1: 94, 98–9, and 102.


Encourages Forbes to publish his geological observations on Chile.

Letter details

Letter no.
Charles Robert Darwin
David Forbes
Source of text
DAR 185: 150

Please cite as

Darwin Correspondence Project, “Letter no. 3019F,” accessed on 25 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 18 (Supplement)