65

(1)

Falklands Is^ds

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 6^ft 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.

65 verso

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

66

(2)

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 1/20 ^th 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

66 verso

[illeg] : case of 20 yards

[sketch]
20
for

67

(3)

[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

67v

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

68

(4)

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

68 verso

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

isolated hills commence more northerly. —

69

(5)

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). —

69v [blank]

70

(6)

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.—'

70 verso

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

71

(7)

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. —

71 verso

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 ?

72

(8)

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

72v [blank]

73

(9)

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!

73v [blank]