352 MINERALOGY OF ARRAN. 



Remarks on the Our men of fire make their favourite element operate as 

 theory. Can many contradictions, as the hocus-pocus tricks imputed to 

 phlogiston by the older chemists. At one time, phlogiston 

 could not penetrate the most porous bodies ; at another, 

 the most dense were insufficient to confine it. At one time, 

 it was the cause of gravity and attraction ; at another, of 

 levity and repulsion. 



These gentlemen assert, that blind coal has had its bitu- 

 men evaporated, by the great heat which elevated the strata, 

 from Avant of sufficient pressure to confine it; and that 

 bituminated coal retained its bitumen, while subjected to 

 this heat, in consequence of the enormous pressure which 

 prevented its escape. 

 How came the But I would ask these gen f lemen — How came the clay 



bitumen here s f ra t a m the same alternation with the coal, to retain their 



on this hypo- ' ■ ' 



thesis? bitumen, while the coal was deprived of it: But especially, 



how came a stratum of clay, included between two stratum 



of coal, to retain its bitumen, while both the stratum of 



coal lost theirs? I do not see how these gentlemen can 



answer these questions, in a way consistent with their 



theory. 



None in the They refer us to the sandstone which covers the blind 



thelitinTcoaf coa, 3 an( * alle g e we sha11 Dnc * some traces* of the bitumen 

 there. But though I examined the sandstone strata which 

 formed the immediate roofs of the strata of coal, and many 

 others, with the utmost care, I could not find the smallest 

 visible trace of bitumen in them: nor could I trace the 

 slightest mark of vegetable impression, either in the sand- 

 stone, or in the bituminated shiver connected with the 

 blind coal. 

 Bituminous Bitumen, particles of coal, and remains of vegetables, 



coal formed j have alwayg f onn a j n the sandstone strata that covered 

 from vegetables, J ,«,.,* , , , 



bituminated coal ; and often, in the coal itself, vegetable 



remains occur. Hence I inferred, that such coal had been 

 formed from vegetables; and the marks I formerly as- 

 signed of sandstone, including coal, applied only to bitu- 

 bJind coal not. minated coal. Blind coal appears to be mi generis, and 

 to have been formed without the aid of vegetables. 



But without pretending to assign the mode of its for- 

 mation, I think I am warranted to assert, it was not 



formed 



