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Darwin Correspondence Project

To Roderick Impey Murchison   [before 30 May 1849]1


I feel most entirely convinced that floating ice and glaciers produce effects so similar, that at present there is, in many cases, no means of distinguishing which formerly was the agent in scoring and polishing rocks. This difficulty of distinguishing the two actions struck me much in the lower parts of the Welsh valleys.2


This extract from a letter CD wrote to Murchison was printed in a note to Murchison’s paper on glacial detritus in the Alps (Murchison 1849, p. 67 n.), which was read at the Geological Society on 30 May 1849.
Murchison argued in his paper that the striæ found on the rocks of the gorge of St Maurice were produced by vast rafts of floating ice. He appended CD’s remarks with the note that ‘Mr. Charles Darwin, in a recent letter to the author, adheres to his old opinions on this point, derived from observations in America’ (Murchison 1849, p. 67 n.). For CD’s views on the action of floating ice, see ‘Notes on the effects produced by the ancient glaciers of Caernarvonshire, and on the boulders transported by floating ice’ (Collected papers 1: 163–71).


CD believes that floating ice and glaciers produce indistinguishable effects in actions such as scoring or polishing rocks.

Letter details

Letter no.
Charles Robert Darwin
Roderick Impey Murchison, 1st baronet
Sent from
Source of text
Murchison 1849, p. 67 n.

Please cite as

Darwin Correspondence Project, “Letter no. 1241A,” accessed on 13 December 2018,

Also published in The Correspondence of Charles Darwin, vol. 4