RECORD: Darwin, C. R. Geological diary: East Falkland Island (appendix). (3.1834) CUL-DAR32.133-150 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online, http://darwin-online.org.uk/)

REVISION HISTORY: Transcribed from the microfilm by Kees Rookmaaker, corrections against the manuscript and editing by John van Wyhe 7.2010. 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.

This document contains the amusing note by Darwin 'I cannot draw', 134 verso.

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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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1834 March E. Falkland Isd (appendix)

I reexamined & hammered, during this years visit, every inch of the passage (described Page 106) between the Quartz rock & the slate: it is described quite accurately. —

W
  1895
like
1893
like
M L H
  1897 1896 1893
like
1895 1893
like
1895
(like)
G F E D C B A

E

(N B. By "like" I mean specimen so resembled that number as not to be worth bringing home. the simple numbers mean that the specimen was obtained from that very locality). —

Series of changes on coast walking from E to W 1/2 a mile Johnson Harbour

A  To a crystalline granular quartz rock with the aluminous particles in its interstices; evidently the same, with the common hill rock. —

(B) Earthy ferruginous Quartz, subject to much variation

(c) Again it becomes purer; then earthy (D), which most insensibly becomes finer & finer, till in ¼ of a mile we have (E); which shortly shows seams of compact blue slate (F): There is then for some miles greenish coarse slates (G): after this, the earthy quartz, the passage rock, (H) is seen; again becomes purer (L) & rather suddenly passes into Pale Slate, which extends for several miles:

in a distance of 20 yards

All these specimens passed by the finest gradations into each other: & as here seen are only steps in the series

Stratification of Transition P 112

In another part of the coast, near the settlement I found the specimen (1893), overlying & alternating with a coarse blue slate in nearly horizontal beds: again & then it would pass insensibly passes into it: in other places again it passed into a sandstone, such as contains the Terebratula (itself in one spot contained fragments of shell): it was very curious to see, when the passage was completed the sandstone assume, a most fine, even, laminated

Stratification of Transition P 112] added pencil in margin.

a few pencil insertions on this page.

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the laminae of clay slate, these are included ['included' is on facing recto]

But on the beach, when a considerable thickness of the

When a considerable horizontal thickness

Where, a considerable thickness of the sandstone inclined beds were visible exposed

page in pencil referring to facing page.

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1834 March E. Falkland Isd appendix. —

1894 structure (1894): the laminae had the usual direction of the slate W by N & E by S & were nearly vertical. — Hence it is certain that the pure granular, crystalline, quartz rock, which forms all the ridges of hills & the main chain (20 or 30 miles long. 4 or 5 broard & about 1200 to 1600 feet high) passes by now lateral & very gradual changes in its nature & structure to the fossiliferous slate & sandstone of the intermediate low country. —

In a valley, between the main central quartz range & a smaller one to the north, I observed the following appearance fact: In an extent of some hundred yards, there was found a common blue slate with the usual strike dipping N by ½ E, ∠ 50°-60°; within this there were included numerous parallel layers of varying thickness, of a sandstone, precisely similar in every respect, except in not containing remains to the fossiliferous kind strata at the town; it had the same the layer were of various thickness the had the exact (of course became necessarily from being parallel) dip with the slate:

In vertical direction I could not see ,(. owing to lowness of the cliff ) the sandstone for more than 10 to 20 feet. — xxx Where the inclined beds were thick horizontal waving irregular ferruginous water lines might be seen. traversing in a nearly horizontal line the inclined layers they were however obscure:

Anyone happening whatever should If anyone was to see this section without considering any other facts he would be convinced; that the even layers of slate & sandstone had been once horizontally deposited. & were now tilted up by a force from below into their present highly inclined position. — On close examination, however, at parts on shore of the arm of Berkeley Sound

Another section line of crust (near the town 10 or 12 miles distant) showed a somewhat similar, but more curious appearance: in the first case, the same sort kinds of slate & sandstone

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134 verso

P.3

[sketch]
Sandstone
Slate
Slate
Sandstone
Slate

This is not an exact representation of nature (I cannot draw) only an illustration of what takes place. —

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(X)

the first plan occurred in highly inclined between & parallel laminae layers, running in their usual direction W by N. E by S. — in other places close to these were seen at a short distance irregular horizontal beds of sandstone only at a short mile apart were covered from above & beneath by the same laminae of laminated slate;
V. drawing opposite Page
& lastly in more than one section, I saw the extremities of the highly inclined layers of sandstone bending at their lower extremities & joining on the horizontal. — or it might be described, that the horizontal sandstone thinned out & the extremities of the beds were caught up between the inclined layers of slate. —

Now, it must be remembered (last & this year) that the finely laminated pale slate with its usual dip direction & ┴° dip has been seen above & beneath extensive nearly horizontal beds of fossiliferous sandstone: Therefore the slate has not been tilted up into this position: Therefore neither have the layers of sandstone which occur with the slate in the very same direction & position: Hence it is certain that the "power of cleavage" has separated the constituent parts of slate of sandstone, from the fluid water in which they were suspended; & formed them ito even, parallel, bes beds & laminae & there they it has deposited in an inclined position of 50° & upwards. (a) — I formerly stated that the sandstone dipped irregularly & to between to S & SW; whilst the slate between S. & SSW. this is easily explained by the 2d section, where the SSW & NNE highly inclined beds of sandstone passing into horizontal would give rise to irregularities yet t to a general dip of between (S. & SW). & (N & NE). —

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[section crossed through] (a) that the inclined laminae of slate has not been deposited by current is clear because at AA they occur vertically over horizontal foss beds (B) of fossiliferous sandstone
[sketch] A B A

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1834 March E. Falkland Isd Appendix

considering my former observations, & those I now more extensively made, I think the nearest point of (a) compass to which the strata of quartz dip is S by W or the opposite point N by E. But this is difficult to ascertained, because, as will be shown, the ridges of hills are not regularly anticlinal, but have points of elevation, with slight dip in the very direction of the range; hence an observation taken at any spot excepting the very top (not summit of hill) of these points of elevation, may be erroneous to the extent of a point or two, without the cause being seen. — It is certain the slate dips almost invariably to the S by W or N by E; but the quartz strata are inclined generally from 30° to 45° whilst the laminae of slate, are as generally from a greater angle than this to vertical. We have explained the cause of irregularities in the sandstone & shown why it varies from the S by W dip, when loosing its laminated structure. —

The facts connected with the stratification of the Quartz are very complicated. — I will detail what is met with in an irregular & N S line, which crosses the head of Berkeley Sound. —

P. 110 We have seen that the north of this bay there are many parallel low crests, which all dip to the S by W at an angle from 40° to 50° After crossing Berkeley Sound, which is fringed on each side by slates, sandstones, & the "passage rock". —

We then come to an E & W range of hills, in which the "oblong of upheaval" P 110 (pretty accurately described during last year) occurs: it is high up. & its structure is seen by a transverse break in the range

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(Z)

1 30° 40° many crests, dipping at about ∠. 45 generally to S by W.: — Hills running more or less nearly E & W. —
2 Berkeley Sound much broarder; fringed with slates (& subordinate sandstone. of laminae running W by N & E by S. ┴ or dipping to S by W or N by E
3 45° 3 or 4° This range. runs E & W; all these dips being included in it: the "oblong of upheaval" is the centre & top; the SSE dip (marked with ? I had no time to follow out. —
4 Great valley of fragments Perhaps caused by mixture of the two image dips towards its centre
5 hill 960 feet W by S. small range: hill 90 2 ft anticlinal sides dipping to the SSE & NNW. —
6 small valley of fragments  
7 summit horizontal
strata
base of hill
main great central chain. 3 or 4 miles broard. & 200 feet high (?): this section running W by S or WSW & N by E &c: this section is a few miles to the West of the others
8 40° at the W extremity of this range 20 miles distant where the chain bends up is a NW by W line
  Slates & sandstone with usual dip

(a) This applies only to the eastern half of the island where the central S by W chain extends. perhaps a S by E (or even SSE) dip is prevalent. —

The table contains many arrows indicating direction of dip which have not been transcribed.

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[sketch] ESE E WNW A B D

A longitudinal section, would show the strata folding over as here drawn, but not so much arched; the line CB represents the manner in which one end has been removed by the transverse valley so that in ascending by that end, you walk up an inclined doom, dipping on the right & left hand & behind you; & occasionally step up on another higher, but similar layer; if the hill had remained perfect, the envelope would have been as C E D. —

[sketch] ESA NNE SSW L N M K G P H

This is a sort of view of the transverse section showing by the line of break (C D). — This is a most curious scene of natural architecture
K is the nearest curved doom way. M & N retreating, one behind the other: they are flanked by straight beds, dipping from each side; G & P being furthest back, where (C) is. —

I do not know whether the above is intelligible; a slice of flattened oval [sketch] formed of concentric layers, with one end obliquely broken off. would represent what I intend to express. — The line from which on all sides, there is the greatest dip runs in a WNW. ESE, whilst the range runs W & E: hence on the summit looking ESE the strata run horizontal whilst on each side, there is a small dip V P 210. — I have in several

The most remarkable circumstance is, that within (at base of range) 300 or 400 yards of (G), we have beds dipping to the hills at a very small angle & at 1/4 of mile distant at an angle of 45°; — diagram (2) V diagram (2)(3) & (x) a sort of plan of hills & dips

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1834 March E. Falkland Isd (appendix)

The arched strata are much fractured; & the convex surface of all both high & low, the dooms are traversed in innumerable, straight thread like veins, of quartz, which generally form a net work crossing each other at right angles. —

This will subsequently be mentioned. —V Diagrams At the southern foot of these hills this range, we have strata dipping to the hill, as was the case at its northern base. — We then cross a valley & come to a short W by S range, which is parallel to the great central chain. —

In [Eastward] dip to point. hence, [illeg]

Measured Barometrically

The principal hills is 96 (2) feet high: it presents on its north & south slope anticlinal strata; the rock of the summit is exceedingly broken has undergone extreme violence; & hence perhaps we see little of curvilinear beds. — Proceeding along this same ridge to the Westward, we meet at the lower part or dip on its southern side & low down a dip of 70 degree to S 1/2 W 10°: This probably was the bottom of an archway; the breaking up of which has filled a small transverse valley with fragments: passing this we come to a low flat hill, the summit being broard & having horizontal strata & some longitudinal dip, the northern slope dipping dipped to N by W ∠ 47. & the southern to the south. — Another small transverse valley separates this hill from a much higher one, yet not so high as the 960 ft the first perhaps its height is 700 ft maybe
at its SE base, there are strata, dipping to the SSE ∠ 59°; the summits of the strata were curiously folded back on themselves Fig.2

[sketch] NNW ?? SSE ∠ 59° 60°
This probable some such curvature surmounted the 70° dip just noticed in a similar relative position. —

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1834 March E. Falkland Isd (appendix)

The summit of the 900 ft hill is composed of several crests the strata of which dip very regularly at angle 50°-50° to to N by E to or NNE ∠ 50°-55° Some of the Southern ones coastal strata, had the very their bare superior upper extremities of the strata. a little arched curved towards the South.
[sketch] S E ∠ 50°

They were excessively broken: I saw one mass quadrant shaped, the section of a long arch-way (V Fig 1). it was detached block, but evidently very nearly in situ, just beneath the top of the broken curves: it had evidently formed a part some-what similar to AB (Fig. 2): The base 6 ft: 9 inches; & the arch-way of which it is a section 12 feet long: following the Southern crest other such pieces more or less perfect might be seen. — The curvature is perhaps near that of even oblate spheroid, or as drawn: The surface of the arch-way is perfectly smooth & regular: internally there are obscure parallel lines of curvature, forming highly curved layers. —

The block is very compact, with the exception of one great vertical rent & some smaller oblique ones: these rents have destroyed the continuity of the curve: by following with the eye, the curvature Z. X, it is certain the mass (B) has subsided, from its true position shown by dotted lines. Before this was made, the curve must have been solid & perfect for 90° degrees. calling (T) the centre of the circle. — The surface of the arch-way is smooth; on close inspection, these will be seen at intervals from 1/2 to two inches, parallel longitudinal veins, ranging in breadth from 1/10th to 1/30th of inch; these are partially nearly filled with crystallized

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1834 March E. Falkland Isd (appendix)

quartz (lines at right angles or transversally to the veins): these veins thin out at the extremities; where close above or beneath it, another commences. —

There were other veins but at wider intervals at right angles to the above, & parallel to (ZX). — The whole surface is thus interlaced by delicate veins. — I examined many of the fragments of much curved strata & found these all in this state these veins to occur in all.

Ocean wall

Now it is clear that no stratum with parallel sides, of hard rock could bear such bending, as here shown, without being splintered into a thousand fragments: — the mass must have been soft, yet sufficiently consolidated, for the curvature to cause numerous parallel, thin vents:
mud even would crack with such a twist
for from these being filled with quartz, the whole mass. must likewise have been permeable to water, holding silex in solution. — The origin of the longitudinal veins is evident; that of the transverse ones. (parallel to Z X.) is probably owing to these hills not being elevated by a line but an ellipse of upheaval. — V. P. 5: —

Generally

The summit of all the hills, (where generally frequently these curved strata frequently occur) present a scene of great violence; they are covered by with great blocks & dislocated by fissures. — Yet I am certain from close examination, there is no intimate connection between this violence & the curvature of the strata: many of the [illeg] the shaped fragments I have already said remarked very likely
the most curved pieces. were compact & Fig. 1 is a proof, in that individual case & not caused by the fissures: Every where the quartz rock, has been so violently shaken; perhaps the curved show strata

Ocean wall] added pencil.

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it most, from the partially filled & numerous veins rendering the stone more brittle.

P.7 I have said, that on North side of hill the strata dip to N by E ∠ 50°, & that the more central ones have their superior extremities arched: about About 50 yards to the South of this & about 50 20 feet lower down on: the Southern slope again we see meet the strata dipping on the san [illeg] to N by E ∠ 50°. —

In these strata intermediate narrow space between these to are some strata which dipping dip at small angle to the South & the highly curved pieces such as (Fig. 1): & so form the Southern slope of the crest.

Now in (Fig. 2), what i actually saw is represented by those lines which have no dots beneath them. I think however these strata figure must appear it cannot be doubted however that the original curvature howe was somewhat like (the line L D H). — Presently other instances will be given of similar forms. —

If the summit of the hill was more cut off (as much has been) 100 feet lower, we should only have probably a mass of strata dipping to the N by E. — shown by dotted. horizon: line. —

The range, in which the those foregoing last described hills occur is three or four miles long: it may be observed the doom occurs at three very different elevations, [that in each a short range] [illeg] was perspective, although [2 words illeg] & that the dips are not solely. (but chiefly) on the North & South, but likewise laterally: Hence, we may suppose, the summit of the line of elevation has been undulating (I use this hypothetical expression, to explain my measuring

(fig 6) [sketch] A 1200 1160 B C 960
Geological section at below 2 & 3 miles long
960 2-3 miles corner

Summarize by

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[two faint pencil sketches- page not microfilmed]

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1834 March E. Falkland Isd (appendix)

not the cause). This line expresses the relative height of the dooms. — (A) being the 1960 ft hill: (B) the broard topped one: & (C) the one of which (Fig 2) is presumed section: 962 —

There probably are many other curves in this line, which I did not see in my short examination. —

Valley of slate
Mica
M. Simon

I will now pass on to the broarder, higher central. W by S range of hills. — I crossed this only in one place to the West of the line of foregoing sections. — On the northern side there is a pretty general dip to the north; with common ∠°; The summit is irregular & 2 or 3 ? miles broard, in the its central & southern part we see much the strata coming are horizontal strata: being generally much of these being much fractured & torn, they often show showed resemblances to old ancient walls & buildings:

At On the very southern edge of the range sum there were the strata are vertical strata (a) the extremities of some of which them were are so curved, so as to give the idea of joining having been joined on to the horizontal strata ones, which were are only a few yards distant (& these perhaps to the northern dip). — [sketch]

I could see for some distance: on edge of the hill such a curvature to be from an apparent fact: a The above dips give a sort of anticlinal line. (b) — Descending the southern slope; nearly at foot we meet vertical strata & a little further on, at the base, of steep side a small regular archway. with upright sides. [sketch] This is a strong instance of different height of arch-ways

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142 verso

(a) Some of the unbroken pieces, curved as represented were 2 or 3 feet thick & 4 or 5 long.

(b) The anticlinal line

(fig. 7) [sketch] S. N

The section of this range may be composed of many undulations, as here shown by dotted lines in the place of one. & this, I think, most probable. — The breadth S to N is so out of proportion to the vertical height of the sides. —

This main chain is composed of granular crystalline quartz with specks of imperfect mica. —

96: 70 : : 81 : V

70
96 5670 .59
480
870
768
102 4

7 816
116
10

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in a transverse section of a ridge; we have already shown it to be the case in a longitu= section of another ridge. — The line of upheaval (speaking for explanation sake) must have resembled the swell of the ocean; where in a line there are points of different height & where in any one wave, the outline is undulation. —

section ceases Country with South stratificature N & S. cleavage

In the western part of the Island (distance of 15 or 20 miles?) this main chain sinks, & near its extremity turns upwards in a NW by W line. In the low country below, the direction of the laminae slate (a) changed in a corresponding manner. — Also some beds of quartz dipped to the SW by W (a still greater change from the S or S by E dip) at an angle of 40°. —

Fig. (8) [sketch] H K B
Sw by W. ∠. 40°: A to B 20 yards: brought together here:

I there found two events, 20 (measured) yards apart, both with same dip. The S. Western one had some of its basal strata, arched as at (K): those at (B) perfectly straight: there must have been some arrangement, as represented by dots. A line about (H) would obliterate all traces of this arch-way. in as much as the inclined beds (b) & the superior arched ones are of the same thickness. Who would not at f then be convinced that the groups A & B only 20 yards apart, had once formed a horizontal mass of strata, wh subsequently been simply tilled into present position. —

143 verso

(a) This is a very strong instance, how the laminae of slate, beds, of quartz & range of hills, follow each others movements. —

(b)
[sketch] K A A E H B B D

A Diagram will render this manifest: if A & B are 20 10 feet apart & the strata are all or if same thickness one foot thick: the lowest curve (H) will be half 10 feet, below the highest (E). — Therefore a section at K D will show nothing of this arch-way. —

From curvature of quartz found elevation one action.

Coincidence [shl] & cleavage

change K quartz to sandstone

[sketch] [sketch]

Explain reasons for no supposition.— no branch transverse sections [sketch]

When [ridge] change so does the cleavage

From curvature...so does the cleavage] added pencil.

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x N of Berk. S. there is so much breadth in mass of the three ridges: [Beechey] saw equal 3/5 about of do & good how counts S of main range

Considering the various cases of curvature, described & especially this latter one, it appears to me most probable, that whenever, (as N. of Berkeley Sound) there are many crests dipping at one point they formerly possessed arched summits. — On this supposition, the N & S section, already described, at P. 5: would present the following appearance, where the dotted lines are imaginary.
X There is a line omitted.

Breadth must be exaggerated.

Fig. 9 [sketch]
S Main chain NB+ Hab. Sandstone 960. Hill (B) B.Gr.valley of fragments (V) oblong upheaval hill (A) A. Berkeley Sound x remain N

Before coming to any general conclusions, I must mention, that all the hills are of quartz, & that this quartz attains a much greater elevation than the intermediate slates: The main chain, must been be nearly 1000 feet above any slate. — Proofs will subsequently be given, that this island has been ravaged by earthquakes of the greatest violence, & that, when at a lower level, the sea has destroyed much, of the softer rocks, such as slates & sandstone, which are easily disintegrated. —

Any one reading over these notes. would say, an E & W line of elevation (a) has forced up the horizontal strata of quartz. whilst they were yet soft, though superincumbent slate. —

Against this, theory it appears to me there are the strongest arguments. —

1st. This is certain the strata of quartz were soft when so twisted ? How could they remain soft during the immense period, during which the slates, with their thick seams of shells were formed? & how could. water charge with silex, penetrate, though such

x N of Berk. S. ... S of main range] added pencil in margin.

Breadth must be exaggerated.] added pencil in margin.

Part of the sketch is in pencil, and the long lines and some of the captions are drawn in black ink.

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(a) Do not Geologists use this odd coincidence of elevation, just subsequent to formation, too often?

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a mass, so as to fill up the veins, caused in all the strata (this being curved? —

2d What force, from below, could impress the curves figured at P. 7 & 11; where at no great distance beneath the surface (at P 11 in at most in 10 yards) the curvature ceases. — This argument applies still stronger; if it is stated, that during the formation & consolidation of the successive beds of quartz, a succession of elevations took place; in this case the upper arches, were formed by a force acting through the solid layers of inferior quartz. — ? It may also be asked, how does it happen that a succession of elevations, should act in the very same line?. —

3.d The coincidence in direction & point of dip, between the quartz strata & the laminae of slate: the latter, we know, be to have been deposited in somewhat near its present position. —

I will now state what the facts seem to prove, neglecting the absurdity of the conclusions. —

1.st We have seen lines of cleavage & mineralogical changes, are identical or parallel: (In Tierra del Fuego. — Clay slate & feldspathic rock. — Variations in clay. slate. — Clay slate & Mica slate. — At. M. Video chloritic slate & gneiss. — Gneiss & layers of quartz: ? at Rio de Jan: Gneiss & mica slate) we must suppose, whatever cause has effected caused the one has effected the other: Here then, the cause which gave the W by N & E by S. direction to the laminae of slate (b) separated great parallel masses of quartz: It is a strong corroboration of this, that in

145 verso

(a) Following out this hypothesis (which I cannot agree to although the most probable of its kind) it may be said, that after the quartz ranges after being been elevated by successive undulatory movements, the slate was deposited in the valleys; & that the transition rocks are owing to the silex yet being abundantly precipitated. — It is odd in this case the transition being lateral & not one over the other! —

Belongs to P 12

Again each arch-way, when so narrow, must be have been the effect of one movement; it is impossible such a coincidence to happen as two lines of elevation. exactly to be parallel & coincide; in this case the lowermost strata must have been moved time after time through an angle of nearly 90°. — Yet the inferior archways are not more broken than the upper ones. —

(b) In recent chemico-mechanical beds we see the an attraction of particulars acting at considerable distances; forming concretionary masses. V. S. Cruz. —

(a) On reading 3d Vol. of Mr. Lyell:1 another Hypothesis strikes me: the quartz beds are inferior, altered (hence mica) sandstone beds; upheaved through the rocks which form a passage between it & the unaltered, & thus have been contorted: Against this we have oddness of curvature (common to every hypothesis): absence of all evidence of superposition: but chiefly the strange coincidence of line of upheaval with cleavage of slate: (it is clear that vertical laminae must be tilted in two 4 directions, & not have the strike altered, but this by no means accounts for the coincidence, although it may allow of subsequent movements): However, these hypotheses may be settled the curious facts respecting cleavage. remain the same. —

1 Lyell 1830-3, vol. 3.

Belongs to P 12] added pencil in margin.

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the place of even finding a super-position of the slate on the quartz, there was a gradual & lateral. transition. —

2.d We have seen in T. del Fuego, a mica-slate with a cleavage. running in the usual direction, yet all the layers very serpentine. —

The irregular & [strange] curvatures in the quartz are of similar origin, but on a most gigantic scale

3.d We have seen, that the same cleavage is impressed on the slate after periods intervals of some duration; in the same manner, the curvatures which occur at different heights is have been formed at successive periods, when the strata were soft & permeable to water. —

no, because any time before consolidation [true], but probably yes

4th The relative position of the land is solely owing to the degradation of the softer beds, carried on by powerful agents, during a great length of time. (an ancient. transition formation)

5th A mass of land has been raised from the bottom of the sea. (as in Patagonia in recent times), since which its external form, so its internal bays & its ridges of hills have been modeled, on the principle of the hardest rock, notwithstanding longest the effects of air & water; Hence the forms are roughly parallel to the direction of the cleavage. —

Analogy from neighbouring continent connected with soundings

It is important to observe, that the power which causes cleavage (a) is so far of a mechanical nature. as to bend & stretch the strata of quartz. — ؟ To it a Vibration??. — Are the lines of mineral change, owing to lines of electrical intensity, or difference??! & therefore of heat!!??? — (b)

no, because... probably yes] added pencil in margin.

Analogy...soundings] added pencil in margin.

146 verso

(a) That in the sandstone layers, the power of cleavage has sometimes been overcome & instead of inclined beds, parallel to the slate, we have horizontal ones traversing it. — This seems to take place where the sandstone. was abundant, & where organic remains were present.
The sandstone is of a more mechanical origin than the slate. —

Hence perhaps in finely laminated slate, we seldom meet fossils, because if present the slate would not have had this structure ??!. —

(b) There is no harm in conjectures: do the electrical currents which circulate at the surface & are supposed to cause polarity: act with such intensity beneath the surface as to melt & alter rocks?!!!!!! X [sketch]

Recapitulation

Where cause horizontal, hence absence of [sofar] in C. — Contest with specific gravity. —

The cleavage must take place when very soft to separate ingredients (?a matter from shell remains at the period?). & therefore after intervals: also because [inclined] different layers seen up 20 ft — Mem Lord Mulgrave mud is it in Playfair

Arguments in favour of real waves in fluid mass

Recapitulation... in fluid mass] added pencil.

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1834 March E. Falkland Isd (appendix)

In very many parts of the island, the bottom of valleys are partly filled with up with an astonishing number of large angular blocks fragments of quartz; (b) These are so excessively numerous, that I am at a loss to describe the appearance presented by them. — The blocks vary in size from a mans chest to 10 or 20 times, that size; & of course occasionally much larger; they must in many places form a mass of considerable depth; the water is often heard trickling deep below. & of course in the centre of the valleys it would soon fill up the crevices of the blocks & thus raise its bed. The Peat on each side is daily deminishing the apparent breadth, which must vary from a few hundred yards to more than a mile; In the great "valley of fragments" as we called a valley it is necessary to cross by jumping from band stone to stone an uninterrupted band of about half a mile. But the most curious circumstance is the very little inclination of these streams of blocks; (if less even) a mail coach would not alter its speed to in ascending the inclination). — The more inclined beds on sides of hills I saw dipping at 10°; but in the broard flat valleys in many places they are only impercep just more than imperceptibly inclined. — They can often be traced to the crest of hills, where masses as large as churches have been arrested in their course: the curved plates f the arch-ways lie in immense quantities at the very source; (a) the scene is like a ruined castle, which formerly commanded the pass. — For the

which by the act of was here been blown into

More inexplicable, than any part of Cordilleras)

Perhaps beneath the sea

Pernety was a traveller & capable of judging of this phenomena

More inexplicable...judging of this phenomena] added pencil in margin.

which by the act of was here been blown into] added pencil.

147 verso

(a) On a hill, almost 700 feet high, at the very summit, I saw a large arched fragment, lying on its convex surface. — Therefore this piece must have been pitched up & turned or more probably another part of the hill anterior to these convulsions was higher than the present. —

(b) Mr Kent1 has accurately described to me immense streams of blocks, as occurring at W. Point (the N W Point of W Island): also at Swan Island. & Port Egmont. — Fragments very large & angular. — The phenomenon. then extends over the whole group of island. —

These are described in Pernetys Voyage2

The insertion of Quartz an epoch of uncommon violence equalled by that of the fragments—

It caught by shower of rain [protection]

like the fragments, bound about like sand on Paper: of [Campestro] it was thought a wonderful thing.

distinct from [columns] of liquid quartz

[sketch] No

Anaology with neighbouring continental movements

Height of quartz

probably [added] by probably degredation

1 William Kent (d. 1862) joined the expedition as Assistant surgeon in September 1833. Darwin refers to the Beagle's tender on the second voyage, Adventure, not the ship of the same name under Captain King of the first voyage. With thanks to Simon Keynes for information on Kent.

2 Pernety 1770.

These are described...probably degredation] added pencil.

148

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1834 March E. Falkland Isd (appendix)

valleys of little inclination, another simile, will give a very faithful idea of the appearance: it is, as if from every point in the mountains great streams of white trachytic Lava had burst forth & that these had subsequently been torn into a myriad fragments. — Every one talks of the "streams of blocks." — I never saw, any-where else such a scene of violence & desolation; it is perhaps rendered the more striking, by the low & nearly rounded form of the mountains. The hills are in many places traversed by fissures. —

Pat

The convulsions (b) to which these appar facts are to be attributed, must chiefly have taken place, since the elevation of the land. — The blocks are angular, with only their points blunted (caused by their fall). & the interstices are not filled up; if this had once happened, it would have remained, so for in this climate Peat immediately protects soil even on the side of hills. — The volcanic focus of these earthquakes (a), may perhaps be connected with the antarctic islands. —

I do not think curved elevation of quartz strata only kind of elevation.

Clay beneath Peat

No map exists, which pretends to follow all the every windings of the many creeks amongst these islands: if there did, it would represent a Medusa's head. — These arms cut through the low slate county on both N & S side Of the very base of the valleys of the central backbone of quartz. —

Their channels are from 20. to 50 feet, & sides

I do not think curved...kind of elevation.] added pencil.

Clay beneath Peat] in pencil in margin.

There are a few pencil insertions on this page.

148 verso

(a). A Mendoza Gaucho told me he during the few years he had been here, had never felt the slightest movement. —

(b) How immense must the force have been which could have caused great angular blocks. to have flowed like a liquid, down very gentle inclinations, & probably, out when above the water. —

One would suspect that the tops of the hills had been (subsequent to their consolidation) blown up, like the walls of a castle with gunpowder. —

149

17

1834 March E. Falkland Isd (appendix)

steep. — Here alone, excepting on the crests of the hills naked rock is seen. — They are generally shallow & silted up with much mud, their heads being converted into dry land: the water is so still & motionless, that it does not carry away decomposing matter & hence supports scarcely any living creatures: it is quite impossible that the water, as now circumstanced could have cut these channels: But raise sink the sea land (according to Mr Lyell theory) 100 feet & there is an efficient cause. — (a) On this supposition the N E. peninsula of of the island would itself be an island; & the stream then running from Berkeley S. to St Salvador bay. would excavate & that great valley account for the latter being a valley transverse to the general order. — When I saw these canals in the slate valleys, between the quartz; from the first it struck me, how little an increase of duration would have amply been sufficient of excavating the whole (conjectured) mass between the slate quartz hills.

I ought to have stated that streams of running water have very little influence on the surface; the sides & even bottom (where not very much inclined) being protected by a thick covering of Peat. —

With respect to general geology I have but little to add. — I may notice, that in the Eastern parts of this Island quartz is the prevailing rock; that the slate wedges in between the hills. & in the western parts from

149 verso

(a) In this NE Peninsula, I found at some elevation above the sea, a small flat plain with steepish side, which as it appeared had certainly once formed a bay:

V. P. 114 At some such period the beds of white clay beneath the peat were probably deposited. —

150

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1834 March E. Falkland Isd (appendix)

much of the land on both sides of the central chain. — This latter must be about 1200 feet high, is composed of pure or ferruginous. granular quartz rock. 1892. which in many places for includes specks of imperfect mica. — From these hills the country to the south appears like a plain, but in truth it is remarkably undulatory like the waves of the sea (a); these valleys are generally parallel to main chain; but they are oftentimes intersected by winding arms of the sea. — The rock is coarse blue slate, sandstone & much transition rock: the cleavage. is speaking roughly E & W: in very many cases it is hard to say whether the rock is divided by cleavage laminae, in stratification, so confused is the structure:

The schooner brought me a specimen of coarse blue slate from Eagle Island. South coast:

At the western extremity of the central chain. the laminae of slate ran NW by W. & ... nearly vertical on N. dip, this was in the plain, the hills above of quartz changed in a corresponding line: V. P. 11. but the quartz dipped to SW by W. 40° (I have given reason. why it is difficult at one point to know exact dip of quartz). Having crossed this chain we again find slate &c &c. here it dipped at high angle to the SSW. —

M. Simon lies in this part; it is the highest hill in the country, 1500 1600? does not belong to any very regular chain. —

150 verso

(a) According to my hypothesis, lines of mineralogical change, might be expected parallel to these valleys. — hence, when the surface. was beneath the sea, the softer parts would be scooped out in these lines. — At present the bottoms are lined with thick bed of Peat. —


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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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