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Darwin Correspondence Project

To Charles Lyell   7 February [1866]1


Feb 7.

My dear Lyell

I am very much obliged for your note & the extract which have interested me extremely.2 I cannot disbelieve for a moment Agassiz on Glacial action after all his experience, as you say, & after that capital book with plates which he early published;3 as for his inferences & reasoning on the valley of the Amazon that is quite another question; nor can he have seen all the regions to which Mrs A. alludes.4

Her letter is not very clear to me & I do not understand what she means by “to a height of more than 3000 ft”.5 There are no erratic boulders (to which I particularly attended) in the low country round Rio. It is possible or even probable that this area may have subsided; for I cd detect no evidence of elevation or any tertiary formations or volcanic action.6

The Organ Mts. are from 6000 to 7000 ft in height & I am only a little surprized at their bearing the marks of glacial action.7 For some temperate genera of plants viz Vaccineum, Andromeda, Gaultheria, Hypericum, Drosera, Habenaria, inhabit these Mts. & I look at this almost as good evidence of a cold period as Glacial action.8 That there are not more temperate plants can be accounted for by the isolated position of these Mountains.

There are no erratic boulders on the Pacific coast North of Chiloe & but few glaciers in the Cordillera; but it by no means follows I think that there may not have been formerly gigantic glaciers on the Eastern & more humid side.9

In the 3rd Ed. of the Origin p 403, you will find a brief allusion, on authority of Mr D. Forbes, on the former much lower extension of glaciers in the equatorial Cordillera.10 Pray also look at p 407 at what I say on the nature of Tropical vegetation (which I could now much improve) during the glacial period.11 I feel a strong conviction that soon every one will believe that the whole world was cooler during the glacial period.12

Remember Hooker’s wonderful case recently discovered of the identity of so many temperate plants on the summit of Fernando Po & on the Mts. of Abyssynia:13 I look at as certain that these plants crossed the whole of Africa from E. to W. during this same period. I wish I had published a long chapter written in full & almost ready for the press on this subject which I wrote ten years ago.14 It was impossible in the Origin to give a fair abstract.15

My health is considerably improved, so that I am able to work nearly 2 hours a day & so make some little progress with my everlasting book on domestic varieties.16

You will have heard of my sister Catherine’s easy death last Friday morning.17 She suffered much, & we all look at her death as a blessing for there was much fear of prolonged & greater suffering. We are uneasy about Susan, but she has hitherto borne it better than we cd have hoped.18

Emma joins me in love to Lady Lyell19 & believe me dear Lyell | yours affectionately | Charles Darwin

Remember glacial action of Lebanon, when you speak of no glacial action in S. & on Himalaya & in S.E. Australia.—20

P.S. I have been very glad to see Sir C. Bunbury’s letter.21 If the genera which I name from Gardner are not considered by him, as usually temperate forms, I am of course silenced;22 but Hooker looked over the M.S chapter some ten years ago & did not score out my remarks on them,23 & he is generally ready enough to pitch into my ignorance, & snub me as I often deserve.— My wonder was how any, even so few, temperate forms reached the mountains of Brazil; & I supposed they travelled by the rather high land & ranges (name forgotten) which stretch from the Cordillera towards Brazil— Cordillera genera of Plants have, also, somehow reached the Silla of Caraccas.24

When I think of the vegetation of N. Zealand & W. coast of S. America, where glaciers now descend to, or very near, to the sea, I feel it rash to conclude that all Tropical forms wd be destroyed by a considerably cooler period under the Equator.—25


The year is established by the reference to the death of Emily Catherine Langton (Catherine; see n. 17, below).
The letter from Lyell has not been found; the extract was probably part of a letter from Elizabeth Cabot Cary Agassiz to Mary Elizabeth Lyell, describing the progress of Louis Agassiz’s expedition to Brazil (see n. 4, below, and letter from C. J. F. Bunbury to Charles Lyell, 3 February 1866 and n. 2).
CD refers to J. L. R. Agassiz 1840b; Louis Agassiz was among the first to formulate a theory of ancient glaciation (see, for example, Imbrie and Imbrie 1979, pp. 30–1). CD read J. L. R. Agassiz 1840b and expressed his admiration of it in his letter to Louis Agassiz, 1 March [1841] (Correspondence vol. 2).
Agassiz’s view that glacial action had created the valley of the Amazon was apparently conveyed in the letter from E. C. C. Agassiz to M. E. Lyell (see n. 2, above). For more on Agassiz’s interest in former glacial action in South America and its implications, see the letter from C. J. F. Bunbury to Charles Lyell, 3 February 1866 and nn. 7 and 8. For a narrative of Agassiz’s Brazilian expedition, and its scientific findings, see J. L. R. Agassiz and Agassiz 1868. In the tenth edition of Principles of geology (C. Lyell 1867–8, 1: 468–9), Lyell said that Agassiz had failed to discover proofs of former glaciation in the Amazon basin.
Elizabeth Agassiz apparently referred to the altitude of certain features around Rio de Janeiro in her letter (see n. 2, above), but see also n. 7, below. See also the letter from C. J. F. Bunbury to Charles Lyell, 20 February 1866 and n. 9.
CD had explored the area around Rio de Janeiro, Brazil, in 1832 while on the Beagle voyage (Journal of researches, pp. 21–43). CD wrote that erratic boulders were not found on the intertropical plains of South America, including the valley of the Amazon (ibid., pp. 288–9). However, Agassiz claimed to have found drift and erratic boulders on the sides of the valley at Tijuca, near Rio (Hartt 1870, pp. 27–30; see also J. L. R. Agassiz and Agassiz 1868, pp. 399–401). Agassiz also noted that, while elevation was consistent with the physical geography of certain parts of the Brazilian coast, the Amazon basin appeared to have subsided and showed no evidence of deposits of marine origin (J. L. R. Agassiz 1866b, pp. 450–3).
The Serra dos Orgãos, or Organ Mountains, are a coastal range in central Rio de Janeiro state; the highest peaks just exceed 7000 ft (Columbia gazetteer of the world), although Agassiz estimated their height at between 2000 and 3000 ft (J. L. R. Agassiz and Agassiz 1868, pp. 46, 69). Agassiz’s description of the Organ Mountains, including reference to ‘glacial phenomena’, is given in J. L. R. Agassiz and Agassiz 1868, pp. 492–3, and Hartt 1870, pp. 15–18. CD referred to these mountains in the fourth and later editions of Origin (for example, Origin 4th ed., pp. 444–5); only in the fourth edition did he mention Agassiz’s reported discovery of marks of glacial action.
CD believed that temperate plants retreated to mountains in the tropics at the end of a former ice age, as warmer temperatures returned (see also letter from C. J. F. Bunbury to Charles Lyell, 3 February 1866 and nn. 8 and 9). George Gardner had recorded the presence of Andromeda, Drosera, Gaultheria, Habenaria, Hypericum, and Vaccinium in the Organ Mountains (Gardner 1846b, pp. 281–4).
CD gave an account of the glaciers of South America in Journal of researches, pp. 279–90, and speculated on the relationship between former climate and the range of certain tender plant species in that continent (ibid., pp. 268–71, 291).
In Origin 3d ed., pp. 403–4, CD wrote: Mr. D. Forbes … informs me that he found in the Cordillera, from lat. 13o to 30o S., at about the height of 12,000 feet, strongly-furrowed rocks, resembling those with which he was familiar in Norway, and likewise great masses of detritus, including grooved pebbles. See also Correspondence vol. 13, Supplement, letter to David Forbes, 11 December [1860] and n. 8, and Correspondence vol. 8, letter from David Forbes, [November? 1860] (now redated to [after 11 December 1860]).
In Origin 3d ed., p. 407, CD wrote: As the cold came slowly on, all the tropical plants and other productions will have retreated from both sides towards the equator.... The tropical plants probably suffered much extinction; how much no one can say; perhaps formerly the tropics supported as many species as we see at the present day crowded together at the Cape of Good Hope, and in parts of temperate Australia.... But the great fact to bear in mind is, that all tropical productions will have suffered to a certain extent.
CD’s belief that the non-glaciated parts of the earth experienced a cooler climate during the glacial period is expressed in Origin, pp. 369–80 (see also, for example, Correspondence vol. 6, letter to Charles Lyell, 8 July [1856], and Correspondence vol. 11, letter to J. D. Hooker, 26 [March 1863]). Lyell, however, believed that the earth was formerly hotter (Fleming 1998, p. 163) and resisted arguments in favour of a glacial period (Boylan 1998). Later, CD modified his views on geographical distribution to allow for former periods of warmer climate during glaciation in alternate hemispheres (Origin 5th ed., pp. 451–9). For more on contemporary publications that influenced CD’s position on former climate change, see the letter to J. D. Hooker, [28 February 1866] and n. 7.
CD refers to J. D. Hooker 1861; CD’s annotated copy is in his collection of unbound journals in the Darwin Library–CUL. Abyssinia is now Ethiopia; Fernando Po, an island off the coast of West Africa in the Gulf of Guinea, is now known as Bioko (Columbia gazetteer of the world). Joseph Dalton Hooker concluded that a close relationship existed between the temperate flora of Fernando Po, growing above 5000 feet on Clarence Peak, and that of Abyssinia, situated 1800 miles away on the other side of the continent.
CD refers to the chapter ‘Geographical distribution’ in his ‘big book’ on species (Natural selection, pp. 534–66). In that chapter, CD had also proposed that plants migrated during a recent ice age from Abyssinia to Cape Province (now part of the Republic of South Africa), that is from north-east to south-west Africa (ibid., pp. 551–2). See also n. 13, above.
Chapters 11 and 12 of Origin, pp. 346–410, were devoted to geographical distribution. In chapter 11, CD considered dispersal during the glacial period and mentioned the occurrence on mountains in Abyssinia of species otherwise found in Europe or the Cape of Good Hope (now part of the Republic of South Africa) (Origin, p. 375).
CD refers to Variation. On CD’s health and his resumption of work on Variation, see the letter to H. B. Jones, 3 January [1866] and n. 5.
The date of death of CD’s younger sister, Catherine, was registered as Thursday 1 February 1866 (see also letter from J. D. Hooker, 4 February 1866 and n. 1).
Susan Elizabeth Darwin, CD’s sister, had suffered distress and loneliness during Catherine’s final illness (see letter from E. C. Langton to Emma and Charles Darwin, [6 and 7? January 1866]).
For Hooker’s report of former glacial action on the mountains of Lebanon, see Correspondence vol. 8, letter to T. H. Huxley, 1 November [1860] and n. 4; see also J. D. Hooker 1862, pp. 12 and 17. CD’s lightly annotated copy of J. D. Hooker 1862 is in his unbound journals in the Darwin Library–CUL. CD added Hooker’s information on Lebanese glaciation to Origin 4th ed., p. 442 (see also Peckham ed. 1959, pp. 591–2). CD referred to former glaciation in the Himalayas and south-east Australia in Origin, p. 373 (see also Correspondence vol. 7, letter from J. D. Hooker, 25 January 1859 and n. 9). The evidence for glaciation in Australia was provided by William Branwhite Clarke, though it was not attributed to him by name (see Correspondence vol. 9, letter from W. B. Clarke, [August 1861] and nn. 4 and 5); an attribution of the information to Clarke was added in the fourth and later editions of Origin (Origin 4th ed., p. 443).
In his letter to Lyell (see n. 21, above), Charles James Fox Bunbury maintained that the flora of the Organ mountains was Brazilian rather than northern in character. CD refers here to the temperate genera listed in the third paragraph of the present letter. See also n. 8, above. These genera were cited by CD in Natural selection, p. 551 (see also Origin, p. 374).
Hooker had commented on the manuscript of Natural selection, without criticising CD’s use, on page 551, of Gardner’s information to argue that ‘Those few temperate forms which were able to penetrate the lowlands of Tropical America during the Glacial epoch, would be most of all modified, & when the climate again became hot, could only survive on high land’ (see Correspondence vol. 6, letter from J. D. Hooker, 9 November 1856 and n. 2). CD argued similarly in Origin, pp. 378–9.
For CD, the Cordillera included all the mountain ranges that run parallel to the west coast of South America (see Journal of researches, p. 237). Silla de Caracas is a mountain in the coastal range near Caracas, Venezuela, close to the Caribbean Sea (Columbia gazetteer of the world). Citing information from the German naturalist Alexander von Humboldt, CD wrote of plant species that are found both on the Silla de Caracas and in the lower latitudes of the Cordillera in Natural selection, p. 551; see also Origin, pp. 374–5. This information came from Humboldt and Bonpland 1822, pp. 491–9, CD’s annotated copy of which is in the Darwin Library–CUL (see Marginalia 1: 417).
Examples of South American glaciers descending to the sea in the proximity of tropical vegetation are given in Journal of researches, pp. 282–7. For Julius von Haast’s evidence of subtropical vegetation growing beside a glacier near the New Zealand coast, see J. F. J. von Haast 1864; see also Correspondence vol. 12, letter from J. D. Hooker, 15 June 1864 and n. 10. CD marked Haast’s observation of this phenomenon in his unbound copy of J. F. J. von Haast 1864, p. 475, which is in the Darwin Library–CUL.


Agassiz, Louis. 1839. Remarks on glaciers. Edinburgh New Philosophical Journal 27: 383–90.

Agassiz, Louis. 1840c. Études sur les glaciers. Neuchâtel: Jent and Gassmann.

Agassiz, Louis. 1866b. Aperçu du cours de l’Amazone. Bulletin de la Société de Géographie 12: 433–57.

Agassiz, Louis and Agassiz, Elizabeth. 1868. A journey in Brazil. Boston: Ticknor and Fields.

Columbia gazetteer of the world: The Columbia gazetteer of the world. Edited by Saul B. Cohen. 3 vols. New York: Columbia University Press. 1998.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Fleming, James Rodger. 1998. Charles Lyell and climatic change: speculation and certainty. In Lyell: the past is the key to the present, edited by Derek J. Blundell and Andrew C. Scott. London: Geological Society.

Gardner, George. 1846b. The vegetation of the Organ mountains of Brazil. Journal of the Horticultural Society of London 1: 273–86.

Haast, John Francis Julius von. 1864f. Glacial deposits in New Zealand. Natural History Review n.s. 4: 474–6.

Hartt, Charles Frederick. 1870. Thayer Expedition: scientific results of a journey in Brazil by Louis Agassiz and his travelling companions: geology and physical geography of Brazil. Boston, Mass.: Fields, Osgood, & Co.

Hooker, Joseph Dalton. 1861b. On the vegetation of Clarence Peak, Fernando Po; with descriptions of the plants collected by Mr Gustav Mann on the higher parts of that mountain. [Read 7 March 1861.] Journal of the Proceedings of the Linnean Society (Botany) 6 (1862): 1–23.

Hooker, Joseph Dalton. 1862a. On the cedars of Lebanon, Taurus, Algeria, and India. Natural History Review n.s. 2: 11–18.

Humboldt, Alexander von and Bonpland, Aimé Jacques Alexandre. 1822. Personal narrative of travels to the equinoctial regions of the new continent, during the years 1799–1804. Volume 3. Translated by Helen Maria Williams. 2d edition. London: Longman, Hurst, Rees, Orme, & Brown.

Imbrie, John and Imbrie, Katherine Palmer. 1979. Ice Ages: solving the mystery. London and Basingstoke: Macmillan Press.

Journal of researches: Journal of researches into the geology and natural history of the various countries visited by HMS Beagle, under the command of Captain FitzRoy, RN, from 1832 to 1836. By Charles Darwin. London: Henry Colburn. 1839.

Lyell, Charles. 1867–8. Principles of geology or the modern changes of the earth and its inhabitants considered as illustrative of geology. 10th edition. 2 vols. London: John Murray.

Marginalia: Charles Darwin’s marginalia. Edited by Mario A. Di Gregorio with the assistance of Nicholas W. Gill. Vol. 1. New York and London: Garland Publishing. 1990.

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Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Discussion of Mrs Agassiz’s letter [to Mary Lyell, forwarded to CD] regarding S. American glacial action,

with comments on Bunbury’s letter on temperate plants.

Refers to opinions of Agassiz, David Forbes, Hooker, and CD on glacial period and glaciers.

Wishes he had published a long chapter on glacial period [Natural selection, pp. 535–66] written ten years ago.

Tells of death of his sister, Catherine, and other family matters.

Letter details

Letter no.
Charles Robert Darwin
Charles Lyell, 1st baronet
Sent from
Source of text
American Philosophical Society (Mss.B.D25.312)
Physical description
LS(A) 10pp

Please cite as

Darwin Correspondence Project, “Letter no. 4999,” accessed on 19 April 2024,

Also published in The Correspondence of Charles Darwin, vol. 14