a black inflammable substance of the bituminous kind, harder than asphaltum, and susceptible of a good polish. It becomes electrical by rubbing, attracting light bodies like yellow amber. It swims on water, so that its specific gravity must be less than 1000; notwithstanding which, it has been frequently confounded with the lapis obsidianus, the specific gravity of which, according to Kirwan, is no less than 1744. It also resembles cannel-coal extremely in its hardness, receiving a polish, not foiling the fingers, &c., so that it has also been confounded with this. The distinction, however, is easily made betwixt the two; for cannel-coal wants the electrical properties of jet, and is likewise so heavy as to sink in water; its specific gravity being no less than 1273; whereas that of jet, as has already been said, is less than 1000.

Mr. Magellan is of opinion that jet is a true amber, differing from the yellow kind only in the mere circumstance of colour, and being lighter on account of the great quantity of bituminous matter which enters into its composition. When burning it emits a bituminous smell. It is never found in strata or continued masses like fossil stones; but always in separate and unconnected heaps like the true amber. Great quantities of it have been dug up in the Pyrenean mountains; also near Batalka, a small town of Portugal; and in Galicia in Spain. It is found also in Ireland, Sweden, Prussia, Germany, and Italy. It is used in making small boxes, buttons, bracelets, mourning jewels, &c. Sometimes also it is employed in conjunction with proper oils in making varnishes. When mixed with lime in powder, it is said to make very hard and durable cement.

**Jet d'Eau**, a French term, frequently also used with us, for a fountain that calls up water to a considerable height in the air.