RECORD: Darwin, C. R. Geological diary: At C. Espirito Santo, high cliffs commence. CUL-DAR34.194-195 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.


194

At C. Espirito Santo, high cliffs commence which abound with horizontal lines. & are white & brown & fine grained with much worn darker superior bed. — these end about Lat 52°. 48, where there are curved darker lines as at Cape Virgins — 4 miles more to the South no lines. — former cliffs lofty. —

Feb 17th. [1834] St Sebastian bay. SE. side. cliffs. 200 - 300 feet. — composed of earthy sandstone, tolerably hard, more or less pure. contains very few small pebbles of quartz slate & granitic rock in some places small beds of pebbles. — in lines Pholas, Turritellae — Venus not common) remains of Cancer & very numerous impressions.

Beech leaves & pieces of wood (1847 .. 1851). — leaves former seams In some parts there was much detritus & gravel & in upper parts, but generally this soft earthy sandstone (there are layers of hard sandstone (1848) or rather — semi-bed-semi concretion). — (concretions always are an attempt to form a bed)

The beds are generally inclined & slightly curvilinear, never remain for 20 yards the same; common dip

194 verso

to South ∠ 20°. — the upper beds which are more ferruginous, have repeatedly cut away & replaced the lower in with basin strata: — The inclination of these strata is entirely owing to currents. — (∴ lower are horizontal where upper contorted). On the ground above were blue Mytili. — (some of the ground in the neighbourhead must be near 400 feet high). — I should conjecture, that this bay & useless had once been joined?). —

These beds are clearly of same age with Magellan St alluvium, but the finer substances only deposited & more stratified. — I should think it must have been a bay, where a stream entered; muddy from the Pholades: (∴ quiet, not subject to regular current) yet such occasionally happened (during floods?). — It is interesting to see the leaves of the Fagus & still more to find so hard a

195

sandstone in alluvium (1848).

The Beagle Channel & Sts of Magellan (& probably Useless Bay) [afformed] main exit for this alluvium intermediate [span] protected by C. Monmouth & Hose Peak, produced this deposit;

When the Sts of Magellan were cut through this filled of detritus, the low land which connects St. Sebastian & Useless bay (in line) was cut through & (even if the water has not b even lately been joined). —

On the SE coast were some immense blocks of crystalline rocks, perhaps deposited at this period. — One of syenite hard. mean height above the sand of 5 feet. (shape oblong, with roof like a barn), in circumference 47 feet. (How much below sand!?). — Several others were half & 2/3 of this great size. — They clearly do not come from the alluvial cliffs & here this bay is not exposed.

These cliffs give argument that Magellan beds were deposited under ordinary circumstances. —

195 verso

[sketch]
Ferruginous
more inclined ∠ 20°

current cleavage:

There were heads, dung, immense numbers & holes of Toco Toco. excellent connecting animal

from dead leaves. some slate of vegetation during present elevation

This geology interesting as extensive & very modern section of ocean bottom:

18th [February 1834] Between C. Sebastian & Penas; country very undulating; the higher land tab being nearly 1000 feet high & part wooded. I should think all alluvium: — Where there are cliffs it is rather browner & without many lines. —

19th. [February 1834] Cape Ines. Wood brown. St. Ju[lian] porphyry pebbles brought up by lead! — Cliffs. much the same, rather darker & harder. — lines not quite horizontal. — The Porphyry pebble at bottom are universal in Lat. 54° 22', but they are coarser & more siliceous than Port St Julian. Yet general same color. — Lat 54.22' looking same there were hills 5 or 6 miles evidently slate. — there were alluvial cliffs which extend for some miles further & then die away. — There were small ones near <two words missing?>. —


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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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