A fluid bitumen, of somewhat greater consistence than naphtha, of a black, brown, or sometimes dingy green colour. By exposure to the air, it assumes the consistence of tar, and is then called mineral tar. This substance exudes spontaneously from the earth, or from clefts of rocks, and is found nearly in all countries. Near Rangoon, in Pegu, there are several hundred wells of. petroleum, which are carefully preserved, and yield annually 400,000 hogsheads. At Colebrook-dale, in Shropshire, there is a considerable spring of petroleum, from which large iron pipes are employed to convey it into pits sunk to receive it. From these pits it is conveyed into caldrons, in which it is boiled until it attains the consistence of pitch. Since the first discovery of this substance, three different springs of it have broken out: one of these is near the celebrated iron bridge, and the fluid which issues from it is almost pellucid, but, at the same time, thicker than treacle. Petroleum easily takes fire, and in burning yields a strong, sharp, and somewhat unpleasant odour; a thick and disagreeable smoke. In cold weather it congeals in the open air.
It is used instead of oil for lamps in some places; also, when combined with various matters, in painting timber, and is supposed to check and prevent the future ravages of the worm upon the bottoms of ships coated with it.