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Darwin Correspondence Project

To Leonard Horner   [23 December 1846 – January 1847]1

Down. Farnborough. Kent.


My dear Mr Horner.

I am truly pleased at your approval of my Book2 & it was very kind of you taking the trouble to tell me so.— I long hesitated whether I would publish it or not, & now that I have done so at a good cost of trouble, it is indeed highly satisfactory to think that my labour has not been quite thrown away.

I entirely acquiesce in your criticism on my calling the Pampean form “recent”; pleistocene wd. have been far better. I object however, altogether on principle (whether I have always followed my principle is another question) to designate any epoch after man. It breaks through all principles of classification to take one mammifer as an epoch. And this is presupposing we know something of the introduction of man: how few years ago all beds earlier than the pleistocene were characterized as being before the monkey epoch. It appears to me, that it may often be convenient to speak of an Historical or Human depoisit in the same way as we speak of an Elephant bed, but that to apply it to an Epoch is unsound.

I have expressed myself very ill, & I am not very sure that my notions are very clear on this subject; except that I know that I have often been made wrath (even by Lyell) at the confidence with which people speak of the introduction of man, as if they had seen him walk on the stage, & as if, in a geological chronological sense, it was more important than the entry of any other mammifer.—

You ask me to do a most puzzling thing to point out what is newest in my volume, & I found myself incapable of doing almost the same for Lyell.— My mind goes from point to point without deciding: what has interested oneself or given most trouble is, perhaps quite falsely thought newest.— The elevation of the land is perhaps more carefully treated than any other subject; but it cannot of course be called new. I have made out a sort of index, which will not take you a couple of minutes to skim over, & then you will perhaps judge, what seems newest.

The summary at end of book wd also serve same purpose.—3

I do not not know where E. de B.4 has lately put forth on the recent elevation of the Cordillera, He “rapported” favourably on d’Orbigny, who in late times fires off a most Royal salute;5 every volcano bursting forth in the Andes at the same time with their elevation, the debacle thus caused depositing all the Pampean mud & all the Patagonian shingle! is not this making Geology nice & simple for beginners?

We have been very sorry to hear of Bunbury’s severe illness; I believe the measles are often dangerous to grown-up-people. I am very glad that your last account was so much better.6

With many thanks | Most truly yours | C. Darwin.

I am astonished that you should have had the courage to go right through my Book. It is quite obvious that most geologists find it far easier to write than to read a book.


Ch.I & II. | Elevation of the land.— equability on E. coast as shown by terraces. p 19— length on W. coast p 53— Height at Valparaiso p 32— number of periods of rest at Coquimbo— p 49. elevation within Human period near Lima greater than elsewhere observed— The discussion p 41 on non horizontality of terraces perhaps one of newest features. on formation of terraces rather newish.—

Ch III p 62. Argument of horizontal elevation of Cordillera I believe new.— I think the connection (p 54) between earthquake shocks & insensible rising important.—

Ch. IV The strangeness of the (as strange as Eocene) mammifers, coexisting with recent shells.—

Ch V. Curious pumice— infusorial mudstone p 118 of Patagonia— climate of old Tertiary period p 134— The subject which has been most fertile in my mind, is the discussion from p. 135 to end of Chapter on the non-ready-accumulation of fossiliferous deposits.7

Ch. VI Perhaps some facts on metamorphism, but chiefly on the layers in mica-slate &c being analagous to cleavage.

Ch VII. The grand up & down movements (& vertical silicified trees) in the Cordillera. see summary p. 204 and p. 240 Origin of the Claystone porphyry formation p. 170

Ch VIII p 224. Mixture of Cretaceous & Oolitic forms— p 226 great subsidence— I think (p 232) there is some novelty in discussion on axes of eruption & injection. p. 247 Continuous volcanic action in the Cordillera. I think the concluding Summary (p 237) wd show what are the most salient features in the Book.


Dated from the reference to Charles James Fox Bunbury’s measles, see n. 6, below. The first possible Wednesday in this period was 23 December.
The concluding pages of chapter eight summarise the entire volume, see South America, pp. 237–48.
Jean Baptiste Louis Léonce Élie de Beaumont.
Élie de Beaumont 1843, one in a series of reports on contemporary geology.
Bunbury recorded the onset of measles on 16 December 1846 and the beginning of his recovery on 18 January 1847 (F. J. Bunbury ed. 1891–3, Middle Life 1: 205).
CD refers to his explanation for the absence of fossiliferous deposits on the coasts of South America, which leads him to discuss the conditions most favourable for the deposition and preservation of geological formations (South America, pp. 135–9).


South America: Geological observations on South America. Being the third part of the geology of the voyage of the Beagle, under the command of Capt. FitzRoy RN, during the years 1832 to 1836. By Charles Darwin. London: Smith, Elder & Co. 1846.


Responds to LH’s comments on South America.

Thinks it unsound to designate a geological epoch after man. Doubts people’s confidence in date of man’s introduction.

Criticises A. D. d’Orbigny’s theory of elevation of the Cordillera.

Lists sections of South America of special interest.

Letter details

Letter no.
Charles Robert Darwin
Leonard Horner
Sent from
Source of text
DAR 145: 138
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 977,” accessed on 24 January 2020,

Also published in The Correspondence of Charles Darwin, vol. 3