§ 27. BITUMEN. PETROLEUM, NAPHTHA. 703 



matter, resulting from vegetable decomposition, are adequate 

 to produce copper pyrites, and even metallic copper from 

 water holding salts of copper in solution. The pyrites or 

 copperas, as it is termed, so abundant in the Wealden strata 

 of the Isle of Wight, has originated from this cause 



27. Bitumen, Petroleum, Naphtha. — The changes 

 effected in vegetable matter during its conversion into coal, 

 also give rise to various bituminous productions. Mineral 

 oil is an inflammable fluid which often occurs in carboni- 

 ferous deposits, sometimes forming powerful springs. 

 Naphtha is another liquid of this nature, which is nearly 

 colourless, and transparent, burns with a blue flame, emits 

 a strong odour, and leaves no residuum. In driving a 

 level through coal shale in Derbyshire, springs of naphtha 

 burst forth, and covered the surface of the water in the 

 level ; and having been accidentally set on fire by the 

 approach of a candle, formed a burning spring, which con- 

 tinued some weeks. 



Petroleum is of a dark colour, and thicker than common 

 tar ; in the carboniferous strata of Coalbrook Dale, and in 

 some parts of Asia, this substance rises from coal-beds in 

 immense quantities. From a careful analysis of petroleum, 

 and certain turpentine oils, it is clear that their principal 

 component parts are identical ; and it therefore appears 

 evident that petroleum has originated from the coniferous 

 trees, whose remains have contributed so largely to the 

 formation of coal ; and that the mineral oil is nothing more 

 than the turpentine oil of the pines of former ages — not 

 only the wood, but also large accumulations of the needle- 

 like leaves of the pines may have contributed to this 

 process. We thus have the satisfaction of obtaining, after 

 the lapse of thousands of years, information as to the more 

 intimate composition of those ancient forests of the period 

 of the great coal formation, whose comparison with the 

 present vegetation of our globe is a subject of so much 

 interest. The mineral oil may be ranked with amber, 



