Asphaltum, or solid bitumen, is much harder than pitch, brittle, and of a brownish-black colour. It burns freely, and leaves but little residue. In Judea, it is found on the waters of the Dead sea, or the lake of Asphaltes. It is also called _Jews' pitch_. It was employed by the Egyptians for embalming under the name of _mumia mineralis_. Both maltha and asphaltum were used by the ancients as a cement. The walls of Babylon were cemented with these substances, as obtained from the river Is, which falls into the Euphrates. It may be observed, that those countries, which yield bitumen, contain salt springs, and it frequently accompanies pyrites. Limestone, particularly the black, contains it, and the colour is often owing to its presence. The _stink stone_, or bituminous carbonate of lime, is of this kind. The retinasphaltum, a combination of bitumen and earth, having a yellow colour, burns with a bright flame, and fragrant odour, which at last becomes bituminous. Many stones, and particularly some of the black marbles, owe their colour to bitumen; hence they burn white. The bituminous schistus, or bituminous shale, sometimes contains so much of this substance as to burn in the fire. Jet is a mineral of a black colour, and resembles the cannel coal. It is inflammable, producing a green flame, with a strong bituminous odour. With respect to bitumens, we may observe, that they all possess one character, that of being inflammable; and that they are more or less so in proportion as they partake of the principle of naphtha; or, at least, the rapidity of their combustion depends upon the presence of this oil. The following additional facts, therefore, with respect to naphtha, may be interesting: Certain liquids have the property of uniting with naphtha, which has also the property of dissolving and combining with solid substances, of which the following examples may be stated: At the degree of ebullition, it dissolves sulphur, which, on cooling, is in part deposited in needle-form crystals. At the same temperature, it also dissolves phosphorus, part of which is again separated. It unites also with iodine. With camphor, it also combines, and in large quantity. It takes up a much larger proportion of pitch. In the cold, its action on wax is feeble, but assisted by heat, it unites with it in all proportions. On lac and copal, its action is feeble. In the cold, it does not dissolve caoutchouc; but when assisted by heat, it dissolves this substance, though not completely. These facts may determine its action in certain mixtures. According to Theodore de Saussure's Analysis, (_Bibliot. Universelle_, iv, p. 116), it appears, that naphtha is composed of 87.60 carbon, and 12.78 hydrogen. _Sec. XIII. Of Oil of Spike._