in Mineralogy (Mineral Pitch, Asphaltum, Erdpech), the most perfectly inflammable mineral known. Of this there are three varieties, elastic, earthy, and sluggy; the first is distinguished by its softness and elasticity, which, however, it partly loses on exposure to the air; the second, by its dull earthy appearance, and softness sufficient to take an impression from the nail; and the third, from its more or less conchooidal fracture, corresponding to the degrees of lustre it possesses. The component parts of these, however, are the same; and except in appearance and consistency, they do not differ from the naphtha, petroleum, or mineral-oil, a fine colourless fluid, which is first inspissated, becomes brown, and is then changed into mineral pitch by exposure to the air. Bitumen is usually of a black or brownish hue, is easily inflammable, and burns with a bituminous smell, much smoke, and a clear flame; some varieties even melt at a higher temperature. In specific gravity it varies considerably, from 0.828 to 1.160, according to its density; and in composition it is principally made up of bituminous oil, hydrogen gas, and charcoal. The elastic variety has been found principally in the Odin mine at Castleton, in Derbyshire; and from its property of taking up the traces of a pencil in the same manner as Indian rubber, it has obtained the appellation of mineral caoutchouc. The earthy species abounds in Trinidad, where it forms a lake said to be three miles in circumference, and where, when mixed with grease or common pitch, it is used for paying the bottoms of ships. It has also been met with in Persia, in Dalmatia, and in the Hartz. The sluggy variety, again, occurs, forming nodules in the lead mines of Matlock in Derbyshire, at Hurlet near Paisley, imbedded in sandstone in Albania, and in many parts of the continent. The more liquid varieties of this mineral admit of considerable application for illuminating, for fuel, in the manufacture of varnish, &c.; and some of the harder kinds may be cut into ornaments, in the same way as jet.