To Charles Lyell [on or before 20 January 1847]
My dear Lyell
That you may not suppose that I have been overrash in generalising my conclusion, I copy following passage, p. 167.1
“As in some cases it appears that where a fissile rock has been exposed to partial metamorphic action, for instance from the irruption of granite,, the foliation has supervened on the already existing cleavage-planes; so, perhaps in some instances, the foliation, of a rock may have been determined by the original planes of deposition or of oblique current-laminæ; I have, however, myself never seen such a case, & I must maintain that in most extensive metamorphic areas, the foliation is the extreme result of that process, of which cleavage is the first effect.”2 &c &c
Ever yours | C. D.
Quotes from South America [p. 167] on the foliation of metamorphic rocks.
Please cite as
Darwin Correspondence Project, “Letter no. 1053,” accessed on 7 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-1053