[ 264 ] [Book VI. 



CHAP. XLL 



PIT COAL. 



Different Species of CoaLNenvcaftle CoalCulm. Slate Coal. 

 Cannel Coal. Kilkenny CoaLBovey Coal. Peat. Coke. 

 Coal Tar. Natural Hiftory of Coal.Obfer<vaiions relative to the 

 Deluge. 



PIT COAL is a fubftance of which there are 

 many varieties, the caufes of which have not been 

 afcertained, as all the kinds afford very nearly the fame 

 refuks by chemical analyfis. But before the different 

 fpecies of this mineral are mentioned, it is necefiary to- 

 notice a fubftance which agrees in all its chemical 

 properties with charcoal, pofleffing at the fame time- 

 moft of the external characters of pit coal, and which 

 Mr. Kirwan confiders as the natural carbonic prin- 

 ciple. Its colour is black or greyifh black, with a 

 luftre approaching to the metallic. It is without tranf- 

 parency, and its fracture is foliated or flaty. It ilains 

 the fingers. This defcription is taken from the pureft 

 ipecimens which have yet been procured j namely, thofe 

 found near Strido in the territory of Florence. This 

 'fubftance is infoluble in acids. In a ftrong heat it 

 reddens, but does not flame. Expofed to a porcelain 

 heat for feveral hours in covered crucibles, it entirely, 

 or almoft entirely, evaporates like the diamond *. 

 Diftilled it yields a fmall quantity of water, but no 

 air, oil, acid, or alkali. Kilkenny coal is nearly allied 



* The reader will find that the diamond itfelf is probably 

 a fubftance of this nature, by confulting Chap. 44, where the dia- 

 mond is treated of as an inflammable fubftance. 



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