STRUCTURE 11.

Garnet rock, interspersed with siderite, felspar, and spangles of brown mica, from Portsoy in Scotland.

It seems essential to this rock that the garnet matter should be dispersed throughout; otherwise gigantic and common garnets are sometimes so closely mingled in mica slate, that the rock might fall under this denomination.

The garnet trap of Saussure, §2258, of a brownish green colour, composed of a mixture of particles of steatite, fibrous hornblende, and mica, including many little garnets of a dull red?

NOME XIII. SHORL ROCK.

This rock is chiefly composed of the common black shorl*, the black tourmaline of Haüy, which, according to Klaproth, contains 22 parts of iron. It is common in granite, gneiss, and other primitive rocks; but is sometimes found to form a rock by itself, or mixed with quartz. It

* The word is original, and not derived from the town of Shorlau, as appears from the term Shirl, used by the Cornish miners in the

same sense.

must not be confounded with the shorl en masse of Saussure, and other French mineralogists, which is siderite.

Shorl rock is not uncommon in Cornwall; the substance being generally, if not always, in small crystals, sometimes disposed in transverse radiations.

STRUCTURE I. ENTIRE.

Shorl rock in small crystals from Cornwall. In very small crystals, elegantly fasciated in various directions, from the same county.

STRUCTURE II. MINGLED.

Shorl rock mingled with quartz, from Cornwall. Dr. Kidd informs us that Roche Castle, near Bodmin, Cornwall, stands on a rock of this description*.

NOME XIV. ACTINOTE ROCK.

Saussure describes, § 2281, entire rocks composed of grey delphinite; a kind of glassy acti

note.

• Outlines, i. 235.

NOME XV. MARBLE OF MAJORCA.

This rock is of a singular and anomalous structure, as the shape of the spots, or concretions, resembles that of almonds. It is black and white, and takes a very fine polish. The natives call it amandrado*. It is found near Alaro, in the island of Majorca.

NOME XVI. MARBLE OF CAMPAN.

This marble, so well known in France, is found in the Pyrenees, not far from Bagneres. It is either red or green; and both colours even occur in a small specimen; but it is greatly contaminated with argil, as before mentioned. It is ranked among the anomalous rocks, because it often presents a singular structure, which may be called guttular, being disposed in oblong drops like icicles. These uncommon forms sometimes become important in a geological point of view. Ramond observed another marble in that vicinity, analogous to that of Campan," that is to say, with a white base, veined with red and

* Laborde's Spain, iii. 448.

green by steatitic clays; it contains a number of conical nodules, in which the different substances which compose it are rolled in a spiral form, and represent so many little distinct whirlpools, as independent of one another, as different from the flexions of the layers which contain them."*

NOME XVII. PHOSPHORITE.

This rock is reported by some to form hills, and by others only thick strata, in the province of Estremadura, in Spain. It is said somewhat to resemble curved laminar barytes; and is of a yellowish white colour, often spotted with yellowish grey. It is a combination of lime, and phosphoric acid, the latter amounting to 34. It is rather soft, and brittle, and translucent on the edges.

Brochant says that its site is at Logrosan near

• Ramond, Voy. au Mont Perdu, p. 99.

Truxillo, in beds mingled with quartz, and in such abundance as to form a hill. It was known for a long time to the inhabitants by its property of yielding a phosphoric light. In 1788, Proust first indicated its nature, in the Journal de Physique*.

NOME XVIII. GLOBULAR ROCK.

This anomaly was discovered by Saussure, in a hill not far from Hyeres, in the South of France. As his important work has never been translated, an extract may be satisfactory.

"On my ascent I observed, in the calcareous rock of the mountain, a hemisphere of 15 or 18 inches diameter, entirely composed of calcareous spar, disposed in concentric layers, and each of these layers formed by an assemblage of needles, converging towards the centre of the mass. I at first thought it was accidental; but, as I proceeded, I saw with much surprise that the whole mountain, to its very summit, is composed of balls of spar, whose structure is nearly the same. Their bulk varies: the largest being two or three feet in diameter; the smallest, two or three

Min. i. 585.