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Lowes. Harbor 8^th. [January 1835] —

All the rocks are mica slate (like 2489), with great layers of quartz, as before; which alternates & passes into phyllade ampellite (2488), & a green talcose slate (2487) without order. — the two latter varieties being the most abundant. —

Laminae. slightly tortuous but dip with great regularity ∠ 40°-50° to WSW 1/2 S. —

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Lowes Harbor 9^th. — (6

These are cliffs of tertiary formation, about 300 ft high: composed of blackish hardened mud, with various sized scattered pebbles mostly rounded, some only partly so. —

Exactly same as at E. coast of Chiloe. There were beds of even, thinly laminated sandy=clay, also as at Chiloe. — I found one layer of loose sand, with particles of comminuted marine shells: mineralogical nature of which very different from the true Tertiary strata begin with [dislocations]. — The upper bed almost composed of pebbles in lines: also some small subordinate plains of do. —

On the beach. Block of scoricae. —

The mica slate chiefly with plates of quartz, also much ampellite dip to W by S. about

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Lowes H. (7

∠45. — The mean with yesterday WSW. — (NB. 2 or 3 or 4 miles East of ship): — At point the mica slate was traversed by dykes & masses of crystalline am rocks in a most extraordinary degree. — The word example simile will more truly explain appearance, than a thousand explanations. it is the thin crust of a tart broken in & the fruit & syrup mingling with it. — The cleavage of the gneiss has had a great influence in the form of the dykes: hence where best seen they are not vertical but inclined. — The sizes junctions are quite distinct, but contorted in every direction; veins & masses of the rock of dyke from the fringe has penetrated the slate, & fragments of the latter are entangled within the dyke: The cleavage is bent & twisted dips in every directions amongst

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Lowes H (8

those pieces, which appear to have been lifted up on the surface of the melted rock. — In other places layer are quite parallel to the slate & even have a few lines planes parallel to the slate; close inspection will always show, that the dyke fills up irregularities & sends off little obtuse veins, where the qualities of two rocks to the last point of contact are quite distinct. — The parallelism will in a short distance be suddenly quite destroyed. —

[sketch] vertical section
dyke slate S

oth

There is some pyrite in the schists

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Fig. 2 Horizontal section

9 ft dyke
S N
The included slate with usual dip

x
N
dyke

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Fig 2 represents dyke about 90 yards wide, with (x) bed 7 yards wide of slate thus traversed & cut off; also (z) mass of slate, traversing these bands parallel to cleavage of the dyke-rock. —

The system of dyke is very large, & forms a chain of islands & low hills: from resisting decomposition. — There is first one of 60 y^ds, there is a creek of water, of about 100 80 y^ds wide, perhaps contains at bottom slate, we then have the 90 y^ds dyke & beyond this there is another smaller dyke. These have same direction as far as this can be made out, which is same with cleavage, or perhaps 2 or 3 points to the East of North. How does this differ from an axis of elevation? (a) it is same in nature with the granite range

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(a) The band of disturbance in which the schists might only be considered as entangled pieces is at least more than 200 y^ds wide:

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Lowes H. (10

[illeg]

Yet the cleavage is only affected in the fragments which absolutely adhaere to sides of dyke. — We here see the mechanical effects of cleavage. — I suspect the tendency of upburst ran NNE & SSW. — The rock of dykes varied much in nature: the changes were in no determinate order: a fine greenish black (conch-fract) base with crystals of feldspar is the commonest (2489): there is much euritic rock 90: which passes by every shade into a white & variegated rock 90: 91 is also abundant, as is 92 with numerous grains of quartz: 2493 is not very common & is a beautiful white trappy feldspathic rock with crystals of do grains of quartz & specks of pyrite: there are others splintery hornstones: the order expresses their comparative abundance in dykes: they occur in great angular masses: —

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Mellamoy.¹ an active volcano. — regular cone, rim of broken craters; looks table topped from some points. —

Peleña (four tops, not volcano. —

There is other great cone to South of Mellamoy. —

¹ Melimoyu.

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Lowes H. — Jan^y 10^th. — (11

Examined some states a mile to the W of Tent point. — which from dyke Is^d makes a distance of [blank] miles; the in nearly all of which the dip is exactly the same — here it is WSW ∠40°. — Therefore argument not upheaved. — Rock here chiefly this green chloritic slate — found bed parallel to cleavage of a mixture of chlorite epidote & white feldspar (2498) well crystallized in some specimens: this passed into the schist & gradually assumed the laminated structure. —

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Lowes Harbor. Jan. 15^th. — (12

(day of sailing)

To the westward. —— Usual, WSW dip; some nearly vertical. — transitions from one rock to the other generally gradual. — Saw some layers of regular white feldspar. —

Where enormous veins were freq of quartz, running in irregular direction, were frequent: cleavage contorted as if by violent intrusion:

Yet the quartz in places rather formed lens-shaped masses, than veins & in other places was intimately connected with the surrounding: this was well seen. where the mica slate. contained numerous crystals, placed in waving lines of feldspar? which formed, from weathering a curious external surface:

at [little Potalos] Is^d mica slate ampelite in regular. laminae, with but little of the red patches of crystals, dipped W by S. 30°.

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(13

was traversed by dyke of greenish. homogenous feldspathic rock (2511): which to the depth of several inches was turned red. —

Fig.3

[sketch]

rather irregular
cleavage NNW NE by E C E
WNW A B
F X D

Their form of dyke shows that originally there was the line of fissure AB & CD, which were stretched open by injected stone: E & F gave way: & dykes became united, craters of each following its own coarse or fissure. —