234 



The specific gravity and hardness of some species of coal, have 

 procured coal in general to be distinguished, by some, by the term 

 of stone-coal. Struck by the predominance of these qualities, and 

 perceiving also the great quantity of bituminous matter contained 

 in coal, this substance has been considered, by some chemists of 

 considerable knowledge and abilities, as being an earth, or rather 

 a stone of the argillaceous genus, which has become impregnated 

 with petroleum. The impropriety of thus considering it must, 

 however, at once appear, when it is recollected, that chemical ex- 

 amination has shown, that, in common coal, the proportion of earth, 

 to that of carbonaceous and bituminous matters, is so very trifling, 

 as seldom to exceed a thirtieth part of the mass. 



In some instances, indeed, such as the slaty cannel coal, from 

 Ayrshire, in Scotland, analyzed by Mr. Kirwan, and the stony coal 

 of Macinaia, the analysis of which has been given by Signor Fa- 

 broni, the earthy parts have amounted to a fifth, and even one half 

 of the whole mass. But these are substances which deviate so 

 much from the characters of coal, as not to be admissible into the 

 same class with it, but should be rather considered as varieties of 

 slate, lime-stone, &c. 



Others have been of opinion, that coal is entirely of marine 

 origin; and formed by the fat, and various unctuous matters, which 

 have proceeded from the innumerable tribes of animals which have 

 peopled the ocean. This mass- of matter is supposed to have accu- 

 mulated, and at last to have become covered by various strata, in 

 consequence of the different changes which the surface of the earth, 

 and the receptacles of the waters of this globe, have experienced. 

 To show the improbability of this hypothesis, it is, perhaps, suffi- 

 cient to remark, that the levity of .s.uch substances could never 

 admit of their accumulation at the bottom of the sea, which, ac- 

 cording to the principles of this theory, must be supposed to have 

 taken place. 



