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).