RECORD: Darwin, C. R. Geological diary: Port Famine. (2.1834) CUL-DAR34.125-128 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. 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.


125

(excellent observations)

Port Famine Feb 3d [1834] — Common rock. slate but little fissile on Port St Anna South side (slate 1790) in layers or beds dipping running N. 71 (—23 V) W (=48°) & dip southerbly∠ 56°. — crossed by numerous other lines (forming rhomboids which run NE by E & SW by W (true). —

On other N side of St Anna — exactly same dip

In the first & second little coves the direction is N. 68° W, but dip only 29°. — Here the slate is separated by many grey calcareo harder beds (1791). — I see slight flaws. here by the non-correspondence. of these beds. —

They are traversed by few narrow dykes of earthy fusible matter. trap. (1792) — the sides of these are slightly tortuous. they cross at right angle both previous sorts of beds: in one case 2 more approximate 2 feet apart & enclosed slate — which was not altered. — they approached to each other, then separated & one died away. — In these beds there are nodules of dark calcareous rock. but they are more abundant further on & will be described. — I have shown the bed & side of creek ran about NW & SE. the creek ran about E by N & S by W — on the northern shore I was surprised to find slate, running. N 69° W but dipping to the NE at ∠ 15°. — therefore an anticlinal line runs obliquely across the creek. —

The dip continued to Rocky point, in one place traversed by vertical cleavage line running NE by E & SW by S. —

The former cleavage more resembles beds. The slate is

See Darwin's discussion of Port Famine in South America, pp. 151-2, 156, 265, 267.

125 verso

here more compact & slightly calcareous (1789) it contains very numerous globular & shell shaped concretions of dark coloured limestone: in some of these impressions of siphon shaped [cornu-annonas]. — (1785—1788). —

One of these I measured most perfect, measured in the centre. following the curvatures 21 inches short legs of siphon. 7 inches: head the of do. (& this lower limit was the rather broardest 2.7 inches. = Several of these impressions. =

Conglomerate at Cape. Remarkable; many some blocks of do on beach here

on the salte veins ([illeg] with & across beds) of white carb of lime. — crystallized. — & nodules of iron pyrites

Feb. 7th [1834] — The calcareous concretions are very curious shape sausage— cylinders, stalactiform. occur rather in layers.

At North side of Rocky Point, there is a coarse greenish slate (1811) passing into this greywacke (1812) with small angular fragment of green slate. — in the former there was the remains of some twelve shell.

I omitted to mention that in the slate I found a curious thing organic remains the nature of which I am quite ignorant (1813). also saw a Nautilus such as will be mentioned at Mount Tarn. only three as large. —

126

Port Famine

If the slate is subject to stratification, we shall probably have the puzzle of long distance in direction of dip, with exact same points, high angle & no anticlinal line. —

2d the anticlinal line occurs in a valley. — hills on each side much higher. — It would however well explain form of land & hills: similarity of form of gneiss & slate. — But then it must be remembered we know there is such a thing as highly inclined original cleavage: it is strangely improbable that in the South there should be cleavage running dipping to SSW & have stratification to SW.

Feb. 6th. [1834] Between Port St Anna & rocky Point got following dips.

[the coastline is sketched on the left side of the page] L Rocky P. H G F E D C cx b a K St Anna P. Famine

(a) N 68
23
45
W 25. S.
(b) 70
23
47
22
(c) 55
23
32
30
(c) 60
23
37
  38.  
(c) x 78
23
47
    25  
(d) irregular no decided strata
(E) dip NW ∠ 5. or horizontal
(F)   81 81
23
58
  11 north
(do)   69
23
46
    15 north
(G)   75
23
52
    17 do
(H)   70
23
49
    11 do
(K)   80 dip 78° to S or ┴ staying tortuous 78
23
55
 
L   70
23
47
    45 dip North. dip 78° to S or ┴ staying tortuous

I have only one remark to make. it is very extraordinary the anticline line being at the point where the line commences a mile or two to the mouth. Mt Phillip ([blank]) feet high. —

126 verso

Mount Tarn Feb. 6th. [1834] — The summit only shows rocks. Hence on the side of St: we have a precipitous escarpement — the rock is essentially compact coarse slate; generally blueish sometimes yellowish (1810); parting of seams ferruginous, also contains pyrites: the structure is curious, appearing generally like so many immense common balls of 3 or 4 feet diameter. round which the slate folds. — as is shown by its decomposition. — Some of the rock contains much iron. — I found in one bed not far from summit (height 2600 ft) a univalve shell & bivalve-like Terebratula which I lost. — Some of an Echinus; but these were uncommon there were however numerous fragments of impressions of a shell, somewhat resembling that found North of Pocky Point. — it was special. & flattened like a Nautilus & evidently very common. — 1809). —

It was very curious effect of snow in decomposing rock. — rubble & vegetation at foot. —

Stratification hard to be made out. The highest point dipped at ∠ 28 to a ran N & N. 62. W. — the whole ridge veined from this to 20° & more 23/39 degree less west.

I could see other escarpements to the western resembled this. Hill seemed to run NW by W & SE by E. (compass) But none of these are accentuated. —

NW by 1/2 W to NW by N

127

[Folio 127 missing from the original]

128

Feb 6th. [1834] At foot of Mount Tarn. many boulders of western rocks at highest part of ordinary high water mark

the largest was of Hornblende rock. was a rough [illeg] with convex & rounded, mean height 4ft 6in feet. girth 24 ft. — Many were half this sum & quarter. common 2 in 3 or 2 times as large as the head. — [sketch]

In the sheltered rocks North of P. St Anna. blocks of that peculiar (NW arch of P. [Julian] an granite block girth 15 ft. mean length 2 3 ft 6 feet: [many] 2.6 feet. — Another of conglomerate nearly [illeg] size, generally very few in such these sites

Mem: Alluvial formation: Height?? Origin of Rock M. Philip

A couple of miles north of Rocky point slides nearly [vertical] (or dip northernly). (N. 65 W. comp). & nearer to same point N. 55 W. 23/32 comp. — 23/42 P. St Anna. — strata slightly [illeg]

Bivalve & shell. like a Turritella in a green [conglomerate] pebbles of quartz; blending with the slate: in [irregular] sort of masses or veins: perhaps slightly parallel to [illeg] but very obscure: (Mem argument from stones not [illeg] rounded & at high water mark must both be [illeg] on very limited sense). — Mem. Wickham [illeg]

Blocks of granite &c (2.10 1/2.1) & many other layers & [illeg] in [illeg] of hills 30 & 40 feet above sea. [illeg] Perhaps M. Phillip [illeg] (creek all run NW.) block but smally angular. — coarse hornblendic

128 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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