RECORD: Darwin, C. R. Geological diary: Rat Island / The Mount. (7-8.1832) CUL-DAR34.1 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online,

REVISION HISTORY: Transcribed by Kees Rookmaaker, corrected and edited by John van Wyhe 10.2011. RN1

NOTE: This document, part of the largest scientific document composed by Darwin during the voyage of the Beagle, is written mostly in ink. See the Beagle diary pp. 199, 212.

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Reproduced with the permission of the Syndics of Cambridge University Library and William Huxley Darwin.

See the introduction to the Geological Diary by Gordon Chancellor.


Rat island. 27th

Mica slate. — coarse granular

beds & cleavage running E by N

plans of fracture dipping to E SE (differing in contrary vary from schist) ∠ 12°. — there not regular even dipping SSW

containing in imbedded portions chloritic schist. these are penetrated by veins of quartz & mica. from which penetrated smaller much twisted vary most of granular quartz are sent off so that the whole schist is this entangled. (specimen 649). — I may observe that the schist has same planes of cleavage & fracture as mica slate, so that it is same formation. —

The Mount 28th

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Citation: John van Wyhe, editor. 2002-. The Complete Work of Charles Darwin Online. (

File last updated 22 March, 2013