To Charles Lyell   [3 March 1866]1

Down

Saturday

My dear Lyell

I returned the memorial this morning & hope it may be successful.—2

I wish I had earlier known how interested you were on mundane cool period, for perhaps I could have given you additional facts.3 I worked in some new facts in last German Edit. of Origin & they will appear in the new Eng. Edit, but this will be too late for you.4 There is one rather important consideration, as it seems to me, viz that it can be proved that individuals of the same plant, growing N. & S, or growing on mountains & plains, certainly become acclimatised & transmit different constitutional powers of withstanding cold to their seedlings; & this would come into play with the slowly advancing glacial period.—5

You must have given up already so much time to subject that I do not suppose my M.S., which I wrote some ten years ago, would be worth your reading: it is at your service & is well copied out but long, viz 47 Pages folio.— —6 Do not answer on this account.—

It is curious how, I find, facts turning up in support of same view: but the other day I read a paper on the representative closely allied Petrels of N. & S. oceans.—7

Very many thanks for your note.—8

Ever yours | C. Darwin

1
The date is established by the relationship between this letter and the letter from Charles Lyell, 1 March 1866. In 1866, 3 March was the first Saturday after 1 March.
3
Lyell altered the text of the tenth edition of Principles of geology (C. Lyell 1867–8) to include detailed discussion of former climate changes, and in particular the effect of glaciation on climate. For a comparison with the ninth edition, and a summary of the changes and extensive additions incorporated into chapters 10 to 13 of the tenth edition, see C. Lyell 1867–8, p. iv.
4
CD refers to Bronn trans. 1863, and to the fourth edition of Origin, published in November 1866 (Publishers’ Circular 1866). CD’s additions about glaciation in Bronn trans. 1863 are listed in Correspondence vol. 10, Appendix VIII, pp. 718–20; the majority of these were incorporated by CD in his revision of chapter 11, ‘Geographical distribution’, in the fourth edition of Origin. Lyell finished work on the tenth edition of Principles of geology in November 1866 (C. Lyell 1867–8, 1: vi). Lyell referred to the fourth edition of Origin in C. Lyell 1867–8, 1: 264, but not in connection with the mundane cold period.
5
In Origin 4th ed., p. 448, CD wrote: ‘Nor must it be overlooked that, as the cold will have come on very slowly, it is almost certain that many of the inhabitants of the tropics will have become in some degree acclimatised; in the same manner as the same species of plant when living on lowlands and highlands certainly transmit to their seedlings different constitutional powers of resisting cold.’ Lyell included a similar passage on acclimatisation in the chapter on natural selection in the tenth edition of Principles of geology (C. Lyell 1867–8, 2: 319–40).
6
CD’s manuscript and notes for chapter 11 of his ‘big book’ on species, ‘Geographical distribution’, were written in 1856. The manuscript CD refers to is in the Darwin Archive–CUL, DAR 14: D1–47 (see Natural selection, pp. 534–66).
7
CD apparently refers to his theory of migration during the glacial period, on which Lyell had commented in his letter of 1 March 1866, and to Hutton 1865 (‘Notes on some of the birds inhabiting the southern ocean’). Frederick Wollaston Hutton noted a close resemblance between species of petrel inhabiting the northern hemisphere and distinct species inhabiting the southern hemisphere; Hutton termed these similar species ‘analogues’ and suggested that they had originated when southern species migrated northwards during the glacial period and subsequently became isolated. There is an annotated presentation copy of Hutton 1865 in the Darwin Pamphlet Collection–CUL.

Manuscript Alterations and Comments

2.1 earlier] interl
2.2 new facts] interl
2.3 they] ‘th’ over ‘&’
2.7 to … seedlings] interl
3.3 but … folio.—-] interl

Please cite as “DCP-LETT-5025,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-5025