RECORD: Darwin, C. R. Geological diary: Dark Harbor. (12.1835) CUL-DAR35.286-287 Transcribed by Kees Rookmaaker, edited by John van Wyhe. (Darwin Online, http://darwin-online.org.uk/)
REVISION HISTORY: Transcribed by Kees Rookmaaker, corrections by John van Wyhe 5.2011. RN1
NOTE: Editorial symbols used in the transcription:
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Reproduced with permission of the Syndics of Cambridge University Library.
December 28th.  — At Cone Harbor, read all this
Dark Harbor (rocked up now).
Rock all micaceous schists, much & regularly laminated, dipping within a point of WSW. ∠ very various often about 40° have seen it 20° & nearly ┴°
Rock (2437) grey, quartzose micaceous schist: which often containing numerous grains (2441) of quartz & occasional side of silvery mica
To the North of Cone Harbor, form of land perhaps point at considerable extent of the volcanic formation
Ynche Isd December 30th. —
Inqui Island. — N. of N. point of Tres Montes Peninsula all the rock either the same as (2447), a quartzose grey rock with grains of quartz (2442): or it passes into a finer grained variety with semi-conchoidal fracture & which is closely connected (2443) with these feldspatic
X Mem: Granite at Cone Harbor
The age of the rock there are hence unquestionably the same, with the whole of Chonos. Archipel:
؟ Is not the direction of outer coast of P. Tres Montes NNW (true): ∴ // to cleavage? —
Dykes not abundant here or at Dark Harbor, only near seat of volcanic action: & at Midship Isd. —
rock of Cone Harbor, which were described as containing specks of quartz. — The rock here differs from Dark Harbor in form not being laminated but rather divided by numerous smooth extensive planes of fracture, which intersect each other at about angle 45°. — Hence every outlying point is ornamented with numerous
fe pyramids. (this is the striking character of the coast & on a great scale perhaps accounts for such hills as the "Cone".
By gradual & perfect mineralogical transition we can trace micaceous slates into the slaty quartzose rock & this again into one which closely corresponds in every respect to what I have called "altered slates", & which the included breccia (at Cone Hill) seem render highly probable. — The dip where they have been ascertained have been similar: It is interesting as showing to what origin mica slate may be attributed. —
287 verso [blank]
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Citation: John van Wyhe, editor. 2002-. The Complete Work of Charles Darwin Online. (http://darwin-online.org.uk/)
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