Unlike most other kinds of coal, this occurs both in stratified masses, and in lumps, nested in clay. It is found in several countries of the Continent, in Wales, Scotland, and near Kilkenny in Ireland.
When laid on burning coals, it becomes red hot, emits a blue lambent flame in the same manner as charcoal; and is, at length, slowly consumed, leaving behind a portion of red ashes. No smoke nor soot is produced from this coal; but, on the contrary, it whitens the places where the fume is condensed; and the effluvia which it gives out are extremely suffocating.
This coal is chiefly used in the drying of malt.
221. BOVEY COAL, BROWN COAL, or BITUMINOUS WOOD, is of brown colour, and in shape exactly resembles the stems and branches of trees, but is usually compressed. It is soft, somewhat flexible, and so light as nearly to float when thrown into water.
The greatest abundance of this coal occurs at Bovey, near Exeter, from which place it derives its name. The lowest stratum is worked at the depth of seventy-five feet beneath the surface of the earth. It is also found in Scotland, Ireland, and Germany.
As fuel, the Bovey coal is used only by the poorest classes of the community, as, notwithstanding its burning with a clear flame, it emits a sweetish but extremely disagreeable sulphureous gas, which is injurious to the health of the inhabitants. It is principally used for the burning of lime, and for the first baking of earthen ware.
222. JET, or PITCH COAL, is a solid, black, and opaque mineral, harder than coal, and found in detached masses from an inch to seven or eight feet in length, having a fine or regular structure, and a grain resembling that of wood.
It has sometimes been confounded with cannel coal ([219]), but it is easily distinguished by its superior hardness: Jet cannot without difficulty be scratched with a knife, whilst cannel coal may be marked by the simple pressure of the nail.
The name of jet has been derived from Gages, a river of Lycia, whence the ancients are said to have obtained this substance. It is frequently cast ashore on the eastern coasts of England, together with pieces of amber and curious pebbles, particularly near Lowestoft in Suffolk, and in some parts of Yorkshire, where many persons employ their leisure in searching for it, and forming it into various kinds of trinkets. Jet is found in several countries of the Continent.
It is stated that in the district of Aude, in France, there are more than 1,000 persons constantly employed in the fabrication of jet into rosaries, buttons, ear-rings, necklaces, bracelets, snuff-boxes, and trinkets of different kinds. Near fifty tons weight of it are annually used for this purpose; and articles to the value of 18,000 livres are said to be sold in Spain alone. In Prussia the amber diggers call it black amber, because it is found accompanying that substance; and because, like amber, it is faintly electric, or attracts feathers and other light objects when rubbed. They manufacture it into various ornamental articles, and sell these to ignorant persons, as black amber, at a great price.