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.
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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.
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.
Till I saw Fig 1 I never doubted cracks helped to make curves
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
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
[illeg]: case of 20 yards
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
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
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
This range of hills runs W by S. & is parallel to main range:
isolated hills commence more northerly. —
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). —
69 verso [blank]
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.—'
N. B. the line of wave & hills are not exactly parallel (?)
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. —
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 ?
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
72 verso [blank]
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!
73 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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