^54 



ILLUSTR\TIONS OF THE 



have been originally wood * 

 the interrogatory propofed h 



The anfwer to 

 IS a redu6lio ad 



hfurdu7n, is, that moft undoubtedly it may 



e 



been wood 



th wood 



phen 



Sandftone with charred wood, that 

 coal in it, is not an uncomnjon 



coal countries. I hav 



feen 



a 



fpecimen of this kind from the Hales Quarry, 

 near Edinburgh, confiding of a piece of charred 



"wood, imbedded in fandft 



th 



d 



was 



much altered, but the remains of its fibrous 

 llrudure were diflindly vifible. This aflx)rds a 

 per fed: commentary on the fpecimen in the Flo- 

 rence cabinet. 



142. If then it be granted, as I think it muft, 

 that the two kinds of coal we have been fpeak- 

 ing of are of the fame origin, it is not very ne- 

 ceffary to enter on a refutation of Mr Kirwan's 

 theory with refped to either of them. His ac- 

 count of the formation of mineral- coal, however, 

 is fo Angular, that it cannot be paffed over with- 

 out remark. 



Mr Kirwan fuppofes, imo, That natural carbon 



was originally contained in many mouni:ains of 



the granite and porphyritic order, and alfo in 



iiliceous fchifi:us ; and might, by difintegration 



and decompofition, be feparated from the ftony 



particles. 2do, That both petrol and carbon 



are often contained in trap, fince hornblend, 



which 



* Geol. Effajs, p. 321 



