RECORD: Darwin, C. R. Geological diary: Falkland Islands. [3.1833] CUL-DAR34.65-73 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 3.2011, corrections by Gordon Chancellor 5.2011. RN2

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.

Editorial symbols used in the transcription:
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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.


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Falklands Isds

Wednesday. [6 March 1833]1 A hill which I ascended was very interesting, its summit consisted of several crests. which dipped from N by E to NNE. ∠ 50°-55°.

The Southern crest had its top arched: the tops alone of the plates being arched:

They were excessively broken: I saw one mass the quadrant shaped. the section of a long arch way. — the base 6ft 9". — V drawing. — it appeared to be most resembling a quadrant of an oblate spheroid going of at a tangent. it was traversed by one great vertical rent. which has destroyed the continuity of the curve: the surface of the arch was perfectly smooth & regular. & before this crack had been so for nearly 90°. —

The block was very fine from fissure — excepting this main one; which when the curve was formed. could not have existed: because the curvature of the subsided mass B corresponds to A. When in the position of dotted lines

1 6 March 1833 was a Wednesday. See Darwin's entry in the Falkland notebook, pp. 9a-10a.

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Till I saw Fig 1 I never doubted cracks helped to make curves

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There was line of parallel curvature in blocks

The fragment of cylinder, was about 12 feet long. — the surface was traversed at every 2. 1. inch or 1/2 inch distance by longitudinal parallel veins. for 1/10 to 1/20th of inch in thickness; tapering any at points. — & probably ribbed by crystallized but not filling up the entire vein. —

There were also. fewer. layer but much more distant as in a transverse direction

longitudinal

Now these veins most clearly are owing to the sketching of the half consolidated rock, during its curvature, & proof it is affected whilst quartz was dissolved in circumambient fluid. — M

These veins evidently are not sufficient to account for a curvature impressed on horizontal strata:

The northern curvature dipped at angle above 50°. — but the southern dipped at very much smaller angle to the South. Yet at about 50 yard in this direction. I met straight plains dipping as before; at same angle northerly

therefore shape of the cleavage strata must

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[illeg]: case of 20 yards

[sketch]
20
for

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[sketch]
N 40 S N ∠ 50

I. think it must have been some such fissure > from the almost curvature. in Fig. 1. & that the southern crest 40 yards apart was about 50 feet below the upper. & little dip of Southern curves. — all of which are shown in this figure; even the fragment Fig 1 was found in its relative position:

The whole top of hill. was covered with fragments. I do not think the arch-way was much more broken than the plates: these endless fragments lying about of curved & arched plates of quartz. & which together with other shapeless blocks commenced the lava like streams. already described. — They resembled the ruin of some great building its walls. arching & passages: —

The streams which have filled up the valley

67 verso

The same power which separate gneiss from slate: feldspathic rock & slate: chloritic slate gneiss: laminae of [gum] from gneiss: has separated the quartz from the slate & impressed on both the same cleavage

degradation has altered their levels —

As we have seen in mica slate quartz tortuous yet general say same cleavage, so here on a most gigantic scale the same thing occurred: — (if the same tendency had occurred to form curves in the slate: they could not have retained them): we have seen common cleavage recurs after intervals, so has this; hence down at different elevations & all permeable to water: there is proof of mechan[ism] ageing in veins of downs has been caused by a Distraction & if so is all cleavage caused by such vibrations; (from subterraneous earth quartz — perhaps more constitute than generally supposed

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must have been a mile wide: composed of fragments, with mainly their points broken: & varying from the size of a mans chest to four 9 or 10 times that size. —

I noticed on one summit of a crest an great inverted archway. I imagine the violence which must have pitched & turned round such masses or fallen from above. — This great period of violence must be quite distinct from the curved strata: & perfected. when upheaving from beneath the water: because stones with crevices not filled up or rotten:

Is this Andes — Georgia? — centre of violence

I have stated there were some veins in a traverse direction or parallel to (Z X). These seem owing to the mountain being an oblong of elevation on a grand scale & not a ridge. — I cannot explain it better than by comparing the range of hills to a swell, when there are higher points in same line; the sides of which waves, mainly dip

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This range of hills runs W by S. & is parallel to main range:

isolated hills commence more northerly. —

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to & from point of swell. also slightly laterally: —

Accordingly at E point of hill is valley. we have a doom dipping to SSW ∠ 59°. —

The next eastern hill is lower (according to general shape of swell). the strata on top are broader & flatter, but sides dip to their respective points. north side (to N by W. 47°) —

We then have a great valley of fragments & the next rock we see is S 1/2 W. 70°. — The bottom of an arch way. —

We then come to the highest hill. (= to main range) This dips, very regularly on each side. — (Wave longer): more anticlinal lines. than in other cases: from rupture of summit: crater-like look: great masses like churches coming into the main Sout North valley of fragments. very little inclination (4 or 5°): one extraordinary scene: — mail coach g could. gallop up it in the W & E range: — We then meet N. dip (I fancy the S. dip of curve. has chiefly carried caused great valley). —

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there the southerly dip pertaining to curious section.—

[sketch with many arrows]
N 45° Berkeley S. small ∠ 45 46° ? valley of fragments This returns to W of [shaft] line

& Perhaps to the S. a N. dip is prevalent (Usborne) at small angle. —

In old notes my description of (curious section) is generally good it is a most wonderful scene. — strata all curved. in balanced with fine thread-like veins. (thus not taking place only in outer doom. but in all: showing general softness). —

this page written lengthwise after 'there the southerly dip pertaining to curious section.—'

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N. B. the line of wave & hills are not exactly parallel (?)

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line of greatest curvature dips to this point: to ESE. on top I could see scarcely any or no dip. — I imagine the wave was this

[sketch] ESE ESE WNW

if there had been no excisement. sta [go] would ascend on such a curved doom, but being such you ascend stem by stem. to a higher & higher curved strata. till you reach the nearly flat summit (further I could not go). —

[sketch] a Bow like this being forced up through soft pap beds. —

the great well. traveled E & W.

[sketch] W N E not seen to the North because lower

but of such a figure as to tilt generally to S. —

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It is curious. the regular SSW crest crest dip occurs with very small angle, beneath & within 200 300 or 400 yards of this dune.

This valley at best a mile wide:

origin of Peat ?

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on the Hypothetical motion of a great swell [illeg] in a remaining in the Quartz. We explain points or ovals of upheavals: the tops of wavves: slight differences between cleaveage of hills & direction. owning to lateral dip of wave: — on this idea the swell N of Berkeley sound had a W & E (?) lines. then the same South of it. — then throwing up a small W by S line, it formed the great main W by S range; broard & equal throwing up the strata on each side:

in the northern part & tilling up the strata to the south, then turning them over & [marrow] and ways & lastly elevating them. —

[sketch] S a n 3 [waves] N

In central of Island. one of two big waves: & point of W by S range. a sudden change, was effected on the line: This line is identical. with cleavage of slate: How come it, that high & low part of mountains were soft. so as to take curvature

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If the quartz was inferior & protruded through slates, so much more time during organic remains. for it to harden: Also to obtain much quartz for its veins. when slate was forming:

This is on the supposition that the transition rocks overlies the quartz: —

We have seen same cleavage appear after period of organic life. Could contorted cleavage do so?

The SW dip of sandstone is to be doubted because cleavage & she drams up beds. —

If the transition rocks are latent: probably then were of same height: degradation is sufficient: — then we have cleavage power placing materials in lines, giving one a curved another a flat cleavage: — allowing sandstone to form a bed & turning it up into inclined planes. —

If so. parallel veins in doom. prove. mechanical form. perhaps an undulation is not then all cleavage some such force? — Recurs after periods! in same time!

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