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Darwin Correspondence Project

From David Forbes   [after 12 December 1860]1

and is about finished—

The question you ask me about the glacial action I can only answer as follows—2

From Lat. 13o to lat 30o there is a plateau or rather indistinct remains of one at about 12000 feet elevation composed of debris such as would generally be ascribed to ice action— the rocks are in many parts especially lat 15o 16o. 17o. 18o S. strongly furrowed & grooved similar to those of Norway.3 the grooves have a general direction and the debris from the plateau in question contains rolled and marked or grooved & scratched pebbles— down where you observed the mass of debris in question,4 the remains of the plateau is only distinct in spots evidently from the river action, but only some 15 leagues north of same I found it grandly developed—and could not explain it at all untill my later examination of the chain of the Andes northward up to Lat 13. showed me at spots (barometrical measurements) a similar development connecting same with the great Eastern Andean plateau of Silurian debris, described in section—   I was informed that a little south of Cauquenes, there exist real glaciers in the Andes—but I found none north of same—   my information was tolerably reliable

As I believe fully in your theory of the origin of species I shall be glad to do anything for you in advancing same and shall attend to the questions you send me and send you answers as soon as possible    If you have more points I shall attend to them if you drop me a line—   The question you ask me about the Chilean breed of sheep—I can in part answer now—5

I was also struck with this and at 2 haciendas I staid at endeavoured to come to the bottom of this but not satisfactorily.— The prevalent opinion is that the race was originally derived from an intermixture of sheep & goat but as far as I could discover, it is nowhere now produced from this source—and the flocks at all the haciendas I saw are only ofspring of similar sheep and not artificially produced as the mules—   One Haciendado at Mendoza stated that, altho if I asked every other Haciendado—in the province they would tell me it was a cross he never knew such a case to have actually occurred & stated his belief that they were a distinct race of sheep

One would think it had been easy to have sifted such a simple question but I did not succed—   would an examination (microscopic) of the hair be of service—   I could send you some as I have a saddle cover here in Birmingham of this article.—6

There is one point I would direct your attention to    it is the horse— The horse of S America was originally Spanish or Andalusian—but now presents 3 wonderfully different variety

1. Chilian—exactly same as true Andalusian

2. Pampa horse    you know

3. Puno horse—a most strange sort of small horse, slender narrow chested & very peculiar altogether—evidently owing to the rarified atmosphere—7 I believe I can prove a great change from same cause in the Puno Indians (Aymara) whom I found to be structurally different. for example femur longer than tibia, &c.8

Yours very truly | David Forbes

CD annotations

3.1 From … reliable 3.14] ‘Glacial Action’ added brown crayon
4.1 As I … Forbes 8.1] crossed pencil
5.1 I was … sheep 5.9] ‘Hybrid Sheep—’ added brown crayon
7.1 There is … atmosphere— 7.7] ‘Horsesadded brown crayon


The date is based on the reading of Forbes’s paper on the geology of Bolivia and Peru (D. Forbes 1861) at a meeting of the Geological Society on 21 November 1860. Forbes, who had travelled widely in the western regions of South America, visited England in 1860. He returned to Bolivia in 1861 ( DNB).
In his paper on the geology of the Andes (D. Forbes 1861), Forbes did not discuss the possible effects of glacier action. His predominant concern was rather the identification of the primary and secondary rocks and their mineral veins. CD included Forbes’s information in Origin 3d ed., p. 403.
Forbes had geologised in Norway during his employment as superintendent of the mining and metallurgical works at Espedal, 1847–57. See Quarterly Journal of the Geological Society of London 33 (1877): 42.
The reference is to CD’s description of the western coast of South America in South America.
CD cited Forbes’s information on the sheep of Chile in Variation 1: 95. This chapter was completed by 20 March 1861 (Correspondence vol. 9, ‘Journal’; Appendix II).
Forbes had entered into partnership with a Birmingham nickel-smelting firm before leaving for South America in 1857 (DNB).
CD cited Forbes on this point in Variation 1: 52.
Forbes read a paper on the Aymaro Indians of Bolivia and Peru before the Ethnological Society in 1870 (D. Forbes 1870).


Glacial action in the Andes.

Origin of Chilean sheep.

Varieties of S. American horses.

Letter details

Letter no.
David Forbes
Charles Robert Darwin
Sent from
Source of text
DAR 164: 150
Physical description
2pp inc †

Please cite as

Darwin Correspondence Project, “Letter no. 2621,” accessed on 20 August 2018,

Also published in The Correspondence of Charles Darwin, vol. 8