ASPHALTUM, Jew's PITCH, a kind of bitumen, solid, and generally of a brownish black colour. It is somewhat unctuous to the touch, though it does not stain or adhere to the fingers. When laid on hot iron it swells, but does not properly liquefy, and discharges much smoke in combustion. It is easily ignited ; and when the flame is extinguished, a light spongy coal remains behind, which by further combustion leaves a small quantity of ashes.
This substance is found in different parts of the world ; and from what we can collect, there seems to be some difference in its nature according to the place from which it is taken ; for the descriptions of it, as oc curring on the spot, at least so far as concern its exter nal character, are not invariably coincident.
Asphaltum was well known to the ancients. Straho and Diodorus speak of the uses to which that found in the Dead Sea was converted. According to the former, a solid mass, sometimes extending to three acres in size, and at other times less than one, rose on the sur face once a year. Seen at a distance, it resembled a kind of island : and the inhabitants in the neighbour hood having descried it, went out on rafts, which they loaded with asphaltum cut from the mass with hatchets. Its rising was preceded for twenty days by peculiar in dications ; such as a bituminous odour, and noxious va pours disseminated far around. At present, it appears like large lumps of earth floating on the surface, which, when driven on shore, are collected by the Arabs, who divide it with the Paella of Damascus. Their own por tion is also purchased by him, either for money or stuffs useful to them.
Asphaltum is found in large masses at Avlonia, in Albania, and in the island of Barbadoes, where it is call ed Munjack. It is there dug out of strata of earth at different depths, and in a great measure supplies the place of coal. If the veins are either on or near the sur face, scarcely any vegetable grows in the vicinity. It is likewise found in several parts of Europe. There are two large pits on the south side of a mountain near Neuenberg ; and on searching into the opposite side of the mountain, the same substance was found at the like depth.
But one of the most extraordinary collections of as plialtuinmthe whole world, is an entire lake, or rather .
plain of in the island of Trinidad. This is called the Thr Lake by the English, and La Bray by the French, from its resembling common pitch, and supplying its place for shipping. The situation of the lake is to the
leeward side of the island, on a cape or headland pro jecting into the sea, and elevated from 80 to 100 feet above its surface. There is no higher land on the same side of the island ; and on approaching the cape, we are sensible of a strong sulphureous smell even at ten miles distance. Its first aspect is that of a lake of water in colour and appearance ; but when closely viewed, it seems a plain as smooth as glass. As in hot dry wea ther, the surface liquefies to the depth of an inch, it cannot then be walked over, owing to its adhesive quality. The lake is of a circular form, about three miles in circumference, but its depth is not yet ascer tained: no other stratum has hitherto been found be low it. Though it appears perfectly smooth, if viewed in its dry state, some yards from the edge, the surface is intersected by numerous chasms and fissures, all anas tomosing together. Each ridge or undulation of the fissures is from four to six feet asunder from the next, and from two to ten feet deep. Their size continually varies, and one of eight or ten feet to-day may to-mor row be entirely closed up, or others will open where there was a solid mass of pitch. It is thence conjec tured, that the pitch itself floats, or is supported on a lake of water below. The sides of the fissures are con vex, inclining downwards, and they are full of pure water abounding with small fish. The sides incline downwards, and unite at the bottom. The general ap pearance of the whole has been compared to the angular figures on a tortoise shell. The surface of the asphal tum yields only to the blow of an axe ; but at the depth of a foot it is a little softer. An oily substance is con tained in its cells : it is very friable, and when liquid of a jet black. Some-parts of the surface are covered with thin and brittle scoriae. The soil for a considerable dis tance around this lake consists of cinders and burnt earth, and where otherwise, it is strongly argillaceous, and extremely fertile. Every part of the country within thirty miles seems formed by the convulsions of sub tcrraneous fire ; and liquid bitumen is found to the thickness of two inches, in small round holes and fis sures in many parts of the neighbouring woods, as also in places more remote.