Ɛpsilon

To Archibald Geikie   27 December [1871]1

Down, | Beckenham, Kent.

Dec. 27th

My dear Sir

I am truly obliged for your paper which I have read with greatest possible interest.2 You put whole case with admirable clearness. I did not know whether you will care to hear what I am about. I formerly observed the action of earth-worms, & lately I have ascertained the amount which they annually bring to surface & (for even figures) it is over area of 10 acres no less than 161 tons of dry earth in the finest condition for being washed away.3 This is generally perched on the blades of grass, & if long or heavy rain falls soon, it flows (as I have ascertained) a little down even a gentle slope. I can not enter here into full details.— Now some 30 years ago, when I blundered so finely over Glen Roy, I remember thinking that slopes covered with turf could not be degraded, even during thousands of years.4 This I now see is a complete error. The roots of plants which secrete so much carbonic acid, & the humic acid, are known to disintegrate some rocks,5 & then earth-worms bring the finer particles to the surface, & they will be washed a little downwards; again buried in the roots, & again brought up, & again washed a little down.— As I have been in old days a great sinner about sub-aerial denudation, it wd. please me much to throw even smallest ray of light on subject.—6 I lately thought of one great difficulty, & you refer to it; viz the persistence of ridges & furrows on old pasture lands, ploughed centuries ago.7 I remember some 40 years ago having seen such with surprise in N. Wales.—8 Have you ever observed any such cases? I want very much to know whether the ridges & furrows run down the slopes, or transversely. If up & down the slopes, all that I shd. expect would be that they would be less well defined at the lower than at the upper parts of the sloping surface. Of course you will not think of answering this note, unless you can kindly give me any information about old grass-covered ploughed land.—

I have forgotten to thank you for your volcanic paper. which I read with interest in our Journal.—9 Excepting your personal friends, I believe no one was more sorry to hear of the fever which spoiled your Italian tour, than I was, as I felt sure that you wd. have done excellent work—10

Pray believe me | Yours very sincerely | Ch. Darwin

Will you excuse me for saying how much I admire the manner in which you give fair praise to Ramsay, Croll (whose paper I formerly read) & Whitaker.11 How can Elie de Beaumont pretend to say that old tumuli & fortifications are now as steep & lofty as they once were?—12 I am trying to get observations made by Dr H. Johnson at Wroxeter, viz how much fine earth is now heaped over narrow walls.—13

Forgive me for scribbling at such length.—

1
The year is established by the relationship between this letter and the letter from Archibald Geikie, 24 December 1871.
2
CD refers to Geikie’s paper on modern denudation (Geikie 1868b).
3
CD had read a paper on the activity of earthworms before the Geological Society of London in 1837 (‘Formation of mould’). CD’s calculation was drawn from measurements made at Leith Hill Common by Lucy Caroline Wedgwood (see Earthworms, pp. 165–9, and letter from L. C. Wedgwood, 20 November [1871] and n. 2).
4
In 1861, CD had concluded that one of his earliest geological papers, ‘Parallel roads of Glen Roy’, was ‘one long gigantic blunder’, and that his theory to account for the geological phenomena described in it was completely erroneous (see Correspondence vol. 9, letter to T. F. Jamieson, 6 September [1861]). In this paper, CD had written (p. 76): if we look at a convex slope of soil clothed with turf, and drained on each side by rivulets, we can see no reason, as long as the vegetation is persistent, why such a slope (with the exception of any spot where a waterspout might burst, or a stroke of lightning fall) should not last for as many thousand centuries as the obelisks of Egypt shall remain entire. He used the argument that turf-covered ground would suffer little erosion to support the case that the upper roads might have been formed much earlier than the lower roads without suffering substantially greater denudation.
6
In Origin, p. 287, CD had estimated that it would have taken three hundred million years for the Kentish Weald to be eroded. After this estimate was derided (the age of the crust of earth was then often estimated to be one hundred million years), CD reduced it in the second edition, and removed it altogether from the third and subsequent editions. See Herbert 2005, pp. 350–4; see also Correspondence vol. 17, letter from A. C. Ramsay, 2 February 1869, and letter to A. C. Ramsay, 3 February [1869].
7
Geikie mentioned the persistence of furrow marks in land that had not been ploughed for a long time as one of Léonce Elie de Beaumont’s arguments for the insignificance of the atmosphere as a cause of denudation (Geikie 1868b, p. 171; see also Earthworms, p. 290).
8
CD spent time in North Wales regularly between 1826 and 1831 (Correspondence vol. 1, Appendix I).
9
Geikie’s paper ‘On the tertiary volcanic rocks of the British Islands’ was published in the Quarterly Journal of the Geological Society of London (Geikie 1871).
10
Geikie travelled to Italy in 1870 to study the volcanic districts of the south, but succumbed to a fever that lasted some weeks and was forced to return home (Geikie 1924, pp. 131–40).
11
CD refers to Andrew Crombie Ramsay, James Croll, and William Whitaker, all of whom were mentioned in Geikie 1868b. Geikie cited two papers by Croll, ‘On the excentricity of the earth’s orbit’ (Croll 1876c) and ‘On geological time, and the probable date of the glacial and the upper Miocene period’ (Croll 1868). There is an annotated copy of Croll 1868 in the Darwin Pamphlet Collection–CUL.
12
See Geikie 1868b, p. 171.

Manuscript Alterations and Comments

1.5 for … away. 1.6] added; ‘for’ over point
1.7 (as … ascertained)] interl
1.8 I can not] ‘not’ added
1.8 here] interl
1.10 , even … years.] added, comma over point
1.12 some] interl
1.14 again washed] ‘again’ interl
1.16 lately] above del ‘formerly’
1.17 old] interl
1.19 very] interl
1.21 at the] interl
4.1 the] after del ‘your’

Please cite as “DCP-LETT-8122F,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-8122F