mUTTONIAN THEORY. 



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we know of the pure bitumens, except the cir~ 

 cumilance juft mentioned, is of a more ambigu- 

 ous nature, and may be reconciled with different 

 theories. The drops of petroleum contained 

 within the cavities of the limeftone, mentioned, 

 at § 31., are however ftrong facls in confirmation 

 of Dr Hutton's opinions, and they are furniflied 

 by the fubilances purely bituminous.. A careful 

 examination would probably make us acquainted 

 with others of the fame kind, for limeftone is very 

 often the matrix in which petroleum and afphal- 

 tes are contained. The greateft mine of afphal- 

 tes in Europe, that in the Val de Travers, in 

 the territory of Neufchatel, is in limeftone, from 

 which, though it in fome places exudes, it is in 

 general extraded by the application of heat. 

 The ftrata for feveral leagues are impregnated 

 with bitumen ; and, if examined with atten- 

 tiop, would probably afford fpecimens fimilar 

 to thofe which have juft been mentioned. 



173. It is a general remark, that, where pe- 

 troleum is found, on digging deeper, they come 

 to afphaltes ; and, at a depth ftill greater, they 

 difcover coal. This probably does not hold in- 

 variably ; but it is certain, that moft of the 

 fountains of petroleum are in the neighbourhood 

 of coal ftrata. Petroleum and afphaltes are 



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found in great abundance in x\lface, in a bed of 

 land, between two beds of clay or argillaceous 



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