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1832 Feb. 20^th Fernando Noronha (230 miles from C. St. Roque) 26

As far as I was enabled to observe during the seven hours I was on this island, its geological formation appears very uniform. — Fernando really consists of several small islands. — but they may be considered as one in as far as relates to their Natural History. The extreme length is about 9 miles & 3 in breadth. — The most remarkable feature is a lifting a peak hill on the north end of the main island. — Tot height is about 1000 feet. — the base is not very steep & thickly wooded, but the peak whether seen at a distance or near is of a most singular appearance. — it is about 400 feet high. & shaped irregularly conical. The southern side overhangs. the others are nearly perpendicular:
255...258 Phonolite Humboldt? (Petro siliceous ? Leucostini Dec: Class: Trachyte. Daubeny
The rock of which it the whole hill is composed consists of numerous crystals of villous feldspar & a few acicular ones of hornblende in a greenish feldspathic base. — it is brittle, very sonorous, & divided into columns. — Whilst viewing the group of Islands from the highest accessible point. viz. the base of the peak. — other cones are seen. of a less height. but doubt certainly of the same formation. — Immediately on seeing them. one is inclined to attribute their origin to mass of rocks partially softened by heath & protruded from beneath. —

[in margin, position unclear] D^r Webster in the Chanticleer Voyage¹ says the peak is composed of a greenstone of felspar, quartz & Hornblende; the quartz the great component part! embedded masses of siliceous schist: surely glossy felspar is mistaken for quartz !! & this writer criticises Playfair & other geologist. —

The coast near the Town. presents a type of the lower parts of the island. — Here

¹ Webster 1834 2: 327.

39 verso

(a) This cleavage appears to be owing to scales of vitreous feldspar arranged in the same planes.

(b) The Phonolite occurs on each side of the mass of Tufa & its accompanying basaltic dykes. — As these dykes are of ordinary appearance I suppose are of course injected from below an inferior mass of basalt. — Therefore the Basalt Phonolite alternates (& is superior (?)) to the Basalt — which is in direct opposition to what Humboldt says more is the case. — (This is a mere conjecture). —

(c) The rock & soil being much the same I was much surprised at the much greater fertility of this island compared to St. Jago. — I should conceive this latter island to be (as it now exists) of a much later origin than Fernando & therefore the soil rocks are not so much decomposed. but I chiefly attribute the difference of to the prevailing winds at the two places. At St Jago the NE trade blows during the whole year & coming off the coast of Africa must be very dry; at Fernando the prevailing wind is SE & of course passing over so large a track of ocean must be loaded with moisture. — In a Tropical country, where rain does not fall for so many months the state of the air must have a most considerable effect on the vegetation.

I should conceive from the appearances of the rocks that the island owes its origin to about the same period as central parts of St. Jago. — The projections are reversed in St Jago. the Basaltic far preponderate. in Fernando the Trachyte — in both, the latter is in conical projecting masses

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is seen the same Feldspathic rock, although in places it has a slaty structure 259 & 260, cleaving in direction NW. — With Near this, there occur large beds of white Tufa (a), through which numerous dykes run. varying in thickness from 8 feet to a few inches. —

Mem. D^r Webster says there is limestone ∴ ? tufa?

These are composed of two rocks; one black basalt amygdaloidal with carb: & Lime & containing numerous crystals of Augite 261...263; the other with a white & coarser base slightly vesicular containing minute vitreous crystalline feldspar & Augite 264. — This latter also occurs in beds. — In this part of the coast, numerous large blocks of basalt (with olivine?) are scattered 265...268. it is quite evident that they come from above. — & at a distance in another part I saw a black mass of columns, in all probability of same nature. — (b)

The pebbles on the coast are cemented together. — The whole island is covered with trees, & from a height looks like one single wood, with a few spots cleared for cultivation. — The soil which results from the decomposition (c) of the Feldspathic rock is a pale clay. with containing unaltered crystals. although exceedingly dry, it appears to be very favourable to vegetation. — On the hills Leechens & mosses covered the rocks. & I there remarked a grass. — I could not help being surprised at the almost entire absence rarity of monocotyledonous

[in margin:] D^r Webster says Isl^d not volcanic because no scoriae. Overlooks amygdaloidal dykes! forget that scoriae could be remote.

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1832 Feb. 20^th Fernando Noronha 28

plants, excepting those cultivated by the inhabitants. — Large masses of the columnar rock shaded by laurels & ornament[ed] by a leafless tree covered with fine pink flowers like Dystachis, only of more [delicate] colour, gave to the nearer parts of the scenery a beautiful effect. — & the bright sight of a tropical scene could not fail to render the more distant islands & wild outline of the coast exceedingly striking. — The woo[ds] were full of birds, but not of many sorts. — doves & a bird. like the english willow wren were very common: I was surprised to see Terns settling on the trees in flocks. — Both boobys noddys & a most graceful little tern of a snow-white colour when disturbed from the branches, hovered in great numbers round our heads. like little angels — I did not observe any hawks or ravens; which is curious. considering the number of birds that would serve for prey. & the secure building place the rocks would afford. them: compared to St Jago it is quite inexplicable.

How can birds of preys catch others in a Wood?!

Mice & Lizards are in great profusion, as I believe is always the case in a hot dry country. — The commonest animal is a little ant. — which builds a nest often 3 feet high & 2 thick, round the stems of trees. It is formed of tough dark brown substance & is full of irregular cavities, disposed without any order. — from the bottom a broard covered way goes to the ground, & from the top small ones branch off along the boughs of the tree. —