To Charles Lyell   26 April [1858]1

Moor Park, Farnham | Surrey

Ap. 26th

My dear Lyell

I have come here for a fortnights hydropathy, as my stomach had got from steady work into a horrid state. I am extremely much obliged to you for sending me Hartungs interesting letter.2 The erratic boulders are splendid. It is a grand case of floating ice versus Glaciers.—3 He ought to have compared northern & southern shores of the islands. It is eminently interesting to me, for I have written a very long chapter on subject, collecting briefly all the geological evidence of glacial action in different parts of world, & then at great length, (on the theory of species changing) I have discussed the migration & modification of plants & animals in sea & land over a large part of world.4 To my mind it throws a flood of light on whole subject of distribution, if combined with the modification of species. Indeed I venture to speak with some little confidence on this, for Hooker about a year ago kindly read over my chapter,5 though he then demurred gravely to the general conclusion, I was delighted to hear a week or two ago, that he was inclined to come round pretty strongly to my views of distribution & change during the glacial period.6

I had a letter from Thompson of Calcutta the other day, which helps me much, as he is making out for me what heat our temperate plants can endure.—7 But it is too long a subject for a note; & I have written this only because Hartungs note has set the old subject afloat in my mind again. But I will write no more for my object here is to think about nothing, bathe much walk much, eat much & read much novels.—

Farewell, with many thanks & very kind remembrances to Lady Lyell.—8 | Ever yours | C. Darwin

1
Dated by the relationship to the preceding letter and by CD’s visit to Moor Park from 20 April to 4 May 1858 (‘Journal’; Appendix II).
2
Georg Hartung’s letter to Lyell has not been located. Lyell’s reply to Hartung, dated 22 April 1858, mentions the erratic boulders on the Azores (K. M. Lyell ed. 1881, 2: 283–4). CD’s notes on the letter are in DAR 50 (ser. 5): 17.
3
CD had long believed that many of the geological phenomena associated with the former cold period had been produced by floating ice rather than by glaciers (see Correspondence vols. 2 and 3).
4
Much of CD’s evidence for the existence of a former worldwide cold period was based on the distribution of erratic boulders. For the importance of the cold period for his theory of the geographical distribution of animals and plants, see Natural selection, pp. 534–66.
5
Joseph Dalton Hooker had read the manuscript of CD’s chapter on geographical distribution in the autumn of 1856 (see Correspondence vol. 6).
6
See the letter to J. D. Hooker, 10 April [1858], in which similar topics are discussed.
7
Thomas Thomson was superintendent of the Calcutta botanic garden, 1854–61. His letter to CD has not been found. CD had directed the same query to other botanists late in 1857 (see Correspondence vol. 6, letter to F. J. H. von Mueller, 8 December [1857], and letter from Charles Moore, 11 August 1858).

Manuscript Alterations and Comments

1.8 changing)] parenthesis over comma
1.12 though] after del ‘&’
1.12 then] interl
1.13 inclined] after del ‘he was’
2.5 walk] before omitted point

Please cite as “DCP-LETT-2262,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-2262