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. In different parts of the globe the trunks of trees, which have been long buried, have passed into the state of jet; and, in almost all these trees may be traced the distinctive characters of the species to which they belong. They are more or less brittle, more or less unctuous, according to the species, the degree of alteration, and the nature of the soil. All of them have a smooth and glassy fracture, but all are not adapted for the tool of the workman. When, for instance, the texture of the tree presents only a mass of dry fibres, the jet obtained is dry and brittle; and cannot be used in the forming of trinkets. But, if the texture be unctuous the fibre acquires a considerable degree of softness, is susceptible of being properly wrought, and receives a perfect and beautiful polish. A fictitious kind of jet is made of glass; and several varieties of mineral pitch, and cannel coal, are imposed upon ignorant purchasers for jet. When jet is once set on fire it burns with a green flame, and continues to burn for a considerable time, exhaling a strong bituminous smell. If the heat be rendered greater, it melts. GRAPHITE FAMILY. 223. _BLACK LEAD, or PLUMBAGO, is an inflammable mineral, which consists of carbon, or charcoal (48), combined with iron, in the proportion of about nine parts of the former to one of the latter._ _It is of dark iron─grey colour, with a strong metallic lustre, and so soft that it is easily scratched with a knife. To the touch it is soft and greasy; and, when handled, it stains the fingers. In weight it is about twice as heavy as water._