244 



the hard and close-grained hornblepd and felspar into clay. By so 

 minute a disintegration, the bituminous particles must have been 

 set free ; and must have risen to the surface, with as great a degree 

 of rapidity, as the earthy and metallic particles would have sought 

 the bottom. But, on the supposition of Mr. Kirwan, the bitumi- 

 nous and carbonaceous, the earthy and the metallic particles, be- 

 ing all suspended in the same fluid, a deposition of the carbon and 

 bitumen must have first taken place, and this have been succeeded 

 by the descent of the earthy, and of the still more ponderous 

 metallic particles. 



It appears equally difficult to conceive the formation of beds of 

 shale, by the subsidence of bitumen. If; says Mr. Kirwan, the 

 petrol were in the greatest proportion, it frequently sunk first, in the 

 form of a soft bitumen, carrying with it the clay,, and forming beds 

 of shale, or bituminous shale, according to its proportion. Consi- 

 dering this position, with all that care and deference, which a dis- 

 sent from the opinions of so justly celebrated a chemist ought to 

 excite, I still arn unable to discover, how the effects, here described, 

 could possibly result from such a combination of circumstances, 

 as those to which they are thus ascribed. 



Mr. Hatchett, whose most valuable observations on the bitumens 

 have very much facilitated our inquiries, into the nature and origin 

 of these substances, is very decidedly of opinion that coal, as well 

 as the other bitumens, are of vegetable origin ; although he does 

 not deny the possible intermixture of animal matters. But we shall 

 soon have occasion to advert more fully to these observations, to 

 which the science of chemistry is so much indebted. 



Mons. Patrin states, that volcanoes throw up large quantities of 

 bituminous and argillaceous matters; and he derives the origin of 

 coal from this source : supposing that coal, and its interposed beds 

 of stone, have been deposited by the alternate ejection of bitumen, 



