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BITUMEN 



BITTER SPAS. A carbonate of lime and carbonate of magnesia. See DOLO- 

 MITE. 



BITUMEN. (Bitume, Fr. ; Erdpech, Ger.) This term, as commonly applied, 

 comprises a number of solid viscid and liquid substances, resembling pitch, tar, 

 naphtha and the like, and consisting mainly of native hydrocarbons, more or less 

 oxygenated. Most of these appear to be too variable in composition to take rank as 

 distinct mineralogical species, and our knowledge of the chemical constitution of many 

 of them is still very imperfect. Professor Dana, in the last edition of his ' System of 

 Mineralogy' (1868), has proposed a valuable scientific classification of the numerous 

 hydrocarbons occurring in nature. It seems convenient, however, for practical 

 purposes to adhere to the older and more popular, if less philosophical arrangement. 



Bitumen comprises several distinct varieties, of which the two most important are 

 asphaltum and naphtha. 



Asphaltum or mineral pitch is solid, and of a black, or brownish-black, colour, 

 with a conchoidal brilliant fracture. It is sometimes called Bitumen of Judea, from 

 its occurrence on the Dead Sea, or Lake Asphaltites. See ASPHALT. 



Naphtha. Liquid and colourless when pure, with a bituminous odour. Sea 

 NAPHTHA. The darker-coloured varieties are fully described under PETROLEUM. 



Springs, of which the waters contain a mixture of petroleum, and the various 

 minerals allied to it as bitumen, asphaltum, and pitch are very numerous, and are, 

 in many cases, undoubtedly connected with subterranean heat, by the agency of which 

 organic remains undergo some of those remarkable changes which ultimately result 

 in the formation of coal. Within a few years many discoveries have been made of 

 sources of fluid bitumen and petroleum in both the Old and New Worlds. The im- 

 portance of these natural products renders it advisable to comprehend a description of 

 them under one general head. In one locality there are said to be 520 wells, which 

 yield annually 400,000 hogsheads of petroleum. See PETROLEUM. 



Fluid bitumen is seen to ooze from the bottom of the sea on both sides of the island 

 of Trinidad, and to rise up to the surface of the water. It is stated that, about 

 seventy years ago, a spot of land on the western side of Trinidad, nearly half-way 

 between the capital and an Indian village, sank suddenly, and was immediately 

 replaced by a small lake of pitch. In this way, probably, was formed the celebrated 

 Great Pitch Lake. Sir Charles Lyell remarks : ' The Orinoco has for ages been 

 rolling down great quantities of woody and vegetable bodies into the surrounding sea, 

 where, by the influence of currents and eddies, they may be arrested and accumulated 

 in particular places. The frequent occurrence of earthquakes, and other indications 

 of volcanic action in those parts, lend countenance to the opinion that these vegetable 

 substances may have undergone, by the agency of subterranean fire, those trans- 

 formations or chemical changes which produce petroleum ; and this may, by the same 

 causes, bo forced up to the surface, where, by exposure to the air, it becomes inspissated, 

 and forms the different varieties of pure and earthy pitch, or asphaltum, so abundant 

 in the island.' 



The Pitch Lake is one and a half miles in circumference ; the bitumen is solid and 

 cold near the shores, but gradually increases in temperature and softness towards the 

 centre, where it is boiling. The solidified bitumen appears as if it had cooled, as the. 



