RECORD: Darwin, C. R. Geological diary: T: del Fuego (appendix). (11.1835) CUL-DAR34.177-178 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online, http://darwin-online.org.uk/)
REVISION HISTORY: Transcribed by Kees Rookmaaker, corrections and editing by John van Wyhe 4.2011. 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.
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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.
1835 November Appendix. p 94. — T: del Fuego
I have coloured a chart to represent form of land & directions of mountain chains & laminated structure of the slates. — The blue band indicates, as far as I have been able to form any judgment, the separation between the hard rocks & the horizontal strata of the tertiary formations on the East side. —
(1) The red lines represent the ascertained cleavage
(2) The black lines with shade ([sketch]) the ascertained
mountain principal lines of mountain ridges: where cleavage is known, red with do. —
(3) Simple black lines. on the land, supposed mountain ridges. — on the sea, show the point of compass being parallel to the neighbouring ones. —
There are four sets of lines, each set having a certain direction. — Where the mountain chains are supposed, they are clearly indicated by the directions of the channels. —
There manifestly is in all cases a strict parallelism of outer coast. extent of formation band of mountains &
177 verso [blank]
channels. — In the only part which I visited, (viz. the southern) to the above must be added
ch ridges of principal chains of mountains & cleavage of the slates. —
It is impossible to resist the conclusion, from the nature of things, that these two last fact, however they may stand with respect to each other, act as cause to effect on the
tha former. —
I have also attempted to color T. del Fuego & East Patagonia. The map is applicable to the paper on recent formations of "East coast of T. del Fuego." — Where grounds for division 5 & 6 will be found. — Looking at Southern S. America generally I believe porphyry & trappean rocks 2 & 3 are allied in age, although here distinct in general characters. — The granitic formation (1)
likewise on the contrary is generally distinct, whilst here is difficult to distinguish from the trappean & porphyritic &c (2). — In Chili slate (4) & granitic rocks are hard to desr
In T. del Fuego, the axis
of a or principal one of the mountain ranges, if judged from dimensions lies in the granitic division (1). — I suspect, in a geological point of view, the trappean rocks (2) ought to be considered as the prolongation of the central true Cordilleras of Chili. —
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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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