RECORD: Darwin, C. R. Geological diary: Chiloé. (1.1835) CUL-DAR35.341-342 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online,

REVISION HISTORY: Transcribed by Kees Rookmaaker, corrections and editing by John van Wyhe 5.2011. RN1

NOTE: This document, part of the largest scientific document composed by Darwin during the voyage of the Beagle, is written mostly in ink. Marginal notes are here integrated into the text. See a map of Chiloe from Narrative 2. Darwin's time in Chiloé is described in the Beagle diary pp. 280-6.

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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.


Feb. 1st [1835] — Chiloe. —

Pebbles in Chevereas creek are contained in the true tertiary formation. — At the head there is an East dip: which probably belongs to the troubled band. — I see there is yellow carb. of lime crystallized in the fissures. — Sphaerical hard concretions follow on each side lines of fissure. —

Proceeding along the straight coast South of Huapi Lacuy. (We first find some pebbles imbedded lying unconformably on common strata) there is a West dip, it is the line of strike of the Huepacho shoal. — Then we have some little horizontal. Then the dip appears to diverge from a curve [sketch] NE E
Ne being the more common one: & dipping directly from the line of inland hill. —

The anticlinal band point is beautifully distinct, the strike is N 6° W & the dip from each side quite regular & well seen from the infinite number of beds in the cliffs which are about 200 ft high. — The dip is from 10° to 20°. — A valley separates the dips (one of elevation) about 300 yds wide. —

The appearance of this The line is parallel to the point of Huechucucuy, composed of mica slate. — The appearance of these cliffs is decidedly that of upheaval: Yet the occasional dips from a cause centre: the almost universality extent of this inclination inclined strata: and the following appearance which may sometimes ne seen, show in patches that the strata have been inclined from original [sketch]

341 verso [blank]


deposition. —Many reefs of mica slate, which we know runs in a N & S direction lie beneath & cause this apparent lines of elevation & opposite dip. — I cannot myself conceive hundred of thin beds preserving their thickness on a slope of 25°. — Neither can I believe that a sloping plane, would cause the deposits for many hundred yards of either side to retain that dip, this [sketch] in a great breadth of strata the same dip. — Again we do not see any dykes, where rocks are visible: on the other hand valley of elevation.

Some way on this side of P. Huechucucuy the presence of [illeg] rock is announced by hard breccia of such rocks & lava pebbles;

The mica slate is such as often mentioned: dip not very regular, where best W 17 S. high angle. — Much however dipped to East & even E by S. — Direction within 17 degrees of N & S. — Few boulders in all places. —

342 verso

Peninsula of Lacuy


Jan.y 1835

Generally in Chiloe alternations of sandstone & greenish slaty clay

Wood probably converted into iron pyrites. — in patches. — small siliceous veins stem with iron pyrites
(Spec 2543)

formerly land parallel to shells Huechucucuy not horizontal

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

File last updated 2 July, 2012