To Daniel Sharpe [19 January 1847]1
Down Farnborough | Kent
My dear Sir
I do not know whether you look at the Edin. New. Phil. Journal, but if not, do read a very short letter from Studer at p. 186 of last Number.2 I have been pleased with it, as it confirms my facts & views on the “foliation” of gneiss &c. being quite distinct from stratification: Studer does not seem to have perceived that foliation is only much developed cleavage.—
I often think over what little I was able to understand of your Paper,3 & I anxiously look forward to read it in extenso.—4 [DIAGRAM HERE] cleavage A cleavage A cleavage A
When non=cleaving beds intervene between those with cleavage, have you ever noticed very carefully the lines of junction? do the edges of the cleavage planes ever indent in ever so small a degree the bases or tops of the intercalated non=cleaved beds. If you have time to send me one single line, just inform me on this head—
believe me | Yours very truly | C. Darwin
Comments on letter by Bernhard Studer ["Remarks on the geological relations of the gneiss of the Alps", Edinburgh New Philos. J. 42 (1846–7): 186] and on article by DS ["On slaty cleavage", J. Geol. Soc. Lond. 3 (1847): 74–105]. Discusses geological cleavage and foliation.