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Darwin Correspondence Project

To Francis Darwin   6 January 1872

Down, | Beckenham, Kent.

Jan 6. 1872

My dear Frank

Very many thanks for all the trouble you have taken. I do not quite understand one or 2 points. You speak of ridges running down the slope; therefore I suppose your wavy line A is a horizontal section of the surface; but if so, how can yr Red letters D & E represent an upper & lower part of the same slope?1 Lastly, I do not feel sure whether the difference in thickness of the slope between top & bottom (where I have put 2 blue crosses) refers to the ridges & furrows, or to the upper & lower part of the slope.

Please to answer this at your leisure & return the enclosed & I am very much obliged for the trouble you have taken | yours affectly | Ch. Darwin

CD annotations

1.2 I suppose … surface; 1.3] ‘Yes’ added above, ink
1.3 but if so, … same slope? 1.4] ‘D & E are only to show that the 2 trenches were not cut across the same furrow’ added above, ink
1.5 difference … between] ‘No texture & color only’ added above, ink
1.6 upper & lower part of the slope. 1.7] ‘No to the top & bottom of trenches only’ added below, ink


Francis’s letter and diagram have not been found in the Darwin Archive–CUL. CD’s notes for Earthworms are in DAR 63–5. Francis wrote his answers to CD’s questions between the lines of the letter; see Francis Darwin’s annotations, at the end of the letter.


Earthworms: The formation of vegetable mould through the action of worms: with observations on their habits. By Charles Darwin. London: John Murray. 1881.


Asks FD questions about his sketch [missing] of ridges and furrows. [FD’s answers are interlined.]

Letter details

Letter no.
Charles Robert Darwin
Francis Darwin
Sent from
Source of text
Natural History Museum (General Manuscripts MSS DAR 29)
Physical description
2pp †

Please cite as

Darwin Correspondence Project, “Letter no. 8147,” accessed on 16 May 2021,

Also published in The Correspondence of Charles Darwin, vol. 20