34 



ILLUSTRATIONS OF THE 



f compreffion. The weight 



ft rata of coal, wh 



intenfe h 

 been fuch 







f* th 



they 



e 



the 



Incumbent on tfie 

 ;re expofed to the 



regions, may have 

 ly and bituminous. 



fulphureous parts, though th 



hole 



w — 



was reduced almoft to full 



and th 



ing, the fulphur uniting with iron might cryftal- 

 lize, and alTume the form of pyrites. < 



30/The compreffion, however, has not in every 

 inftance preferved the bituminous, in union with 

 the carbonic part of coal ', and hence a mark 

 of the operation of fire quite peculiarr to this fof- 

 fil, and found in thofe infufible kinds of it which 

 contain no bitumen, and burn without flame. 

 Thefe refcmble, fome of them very precifely, and 

 all of them in a great degree, the produces obtain- 

 ed by the diftillation of the common bituminous 



coal ; that is, they confift of ch 



to ah earthy bails in diffe 

 is natural therefore 



proportions 



It 



to 



conclude, that this fub- 

 ftance was prepared in the mineral regions by 

 the adion of heat, which, in fome inftances, has 



7 



driven ofFthe inflammable part of the coal. That 



the heat fhould 



fome cafes, have done fo 



not 



confid 



with the genera 



ffea 



a 



ttri 



buted to compreffio 



l^he conditions necelTary 



for retaining the more volatile parts, may 



have been prefent every wh 



w 



the fame d 



gvee; 



1 



