In some places wells are sunk for the purpose of accumulating the product in a situation convenient for collection by pumping the water out. The oil exudes on the shores of lakes and lagoons, or rises from springs beneath the beds of rivers. Such are the springs of Baku, in Persia, and the wells of Amiano, in the duchy of Parma, in Italy. The usual geological position of the rocks furnishing this natural product is in the coal measures—but it is by no means confined to this group of rocks, since it has been found in deposits much more recent, and also in those that are older—but in whatever deposits it may occur, it is uniformly regarded as a product of vegetable decomposition. Whether this decomposition has been effected by fermentation only, or by the aid of an elevated temperature, and distilled by heated vapour, is perhaps hardly settled. It is interesting, however, in this connection to remember that the distillation, at an elevated temperature, of certain black, bituminous shales in England and France has furnished large quantities of an oil having many points of resemblance with naphtha, the name given to this colourless oil, which is the usual product of distilling petroleum. The very high boiling point of most of the products of the distillation of the rockoil from Venango County, Pennsylvania, would seem to indicate that it was a pyrogenic (fire-produced) product. Bitumen, asphaltum, mineral pitch, chapapote, etc., etc., are names variously given to the more or less hard, black, resinous substance which is produced usually from the exposure of petroleum to the air, and is found either with or without the fluid naphtha or petroleum. The most remarkable examples of the occurrence of these substances, so intimately connected with the history of rock-oil, are the Lake Asphaltites of the Dead Sea, so memorable in history, the well-known Bitumen Lake of Trinidad, and the deposits of mineral pitch or chapapote in Cuba. In one of the provinces of India, vast quantities of petroleum are annually produced, the chief consumption being local, for fuel and lights, but a portion is also exported to Europe for the production of naphtha. In the United States, many points on the Ohio and its tributaries are noted as producing this oil; nearly all of them within the coal measures. A detailed history of these various localities can be found recorded in books of science, and their repetition here would be out of place. GENERAL CHARACTER OF THE CRUDE PRODUCT