686

1835 Geological notes made from Capt Fitz Roy Specimens collected on the coast of Peru

Cobija

3207 ... 3212
At Cobija there is one specimen of a close grained ferruginous imperfect Syenite: we also have dark grey compact stone Porphyritic Lava with white Feldspar. & red harsh, altered stone, which sometimes contains Cryst specks of Carb of Lime. The latter clearly belong to the Porph. Breccia formation: the former is either one of the old subaqueous Lavas or injected rock..— There is much salt on the whole surface. —

Arica

3213: 14 At Arica the rock on the beach is an impure stink-stone Lava stone containing black cherty concretions. 3215 — Also a stratified rock which it is very difficult to say exact nature: 3217 I believe a sediment of broken crystals &c are blended by subsequent metamorphic action. — There is also some of the true Plate Porphyry 3216. containing black crystals. —

Here we may suppose at at Iquique. the escarpement of Porph. Breccia. comes close to the Beach. — At Cobija it could not have been far distant. —

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687

1835

Arica

The whole surrounding country by Capt. FitzRoys account is either covered. by a singular rather hard dark brown stone 3218. abounding with salts. on the outer surface of which. pieces project as if in a Breccia. — But on first fracture, it would rather appear to be a Pseudo-Breccia. Such occurs on the high neighbouring hills. On the hard layer of pure semi-transparent salt: which has on its superior surface another soft opake saline substance. 1264 Tin Label — Here we see a close similarity with the alluvial covering of Iquique. The brown stone perhaps corresponds to the concretions in the Tisa. — May we conjecture saliferous sandstone is here present?

This supposition may possibly though throw some light on the very doubtful origin of the salt & nitrate of soda. It would appear that this saline covering extends the whole distance from between Arica to & Cobija (270 miles)

Islay. 3205 3206

At Islay the commonest rock appears very close grained syenitic granitic crystals almost blending together. — & anothe some gneiss. — Whole soil granitic. — In patches, there are layers of white very fine volcanic ashes with black mica & little fragments of Trachyte. —

687 verso

RN p. 102 abstract

Lesson describes grand tertiary form of Payta

Sowerby has shells

M^r Bollaert says seam of Hucilagaya run NE by E & SW by W.

William Bollaert (1807-1876) writer, chemist, geographer, and ethnologist, Bollaert worked as an assayer in the silver-mining province of Tarapacá and later surveyed for the Peruvian government.