r 





^ry f 



\ 



i ve If; 



tlier 



It 



silii 



t 



lis!: 





d 





lit 



1& 



J- 



B 



«: 



i 



i 



' H 



OPf 



/ 



HUTTONIAN THEORY. 



151 



.* 



and formation entirely different. He therefore 



•endeavours to afcertain the diftinguifliing cha- 

 racters of each, confidered geologically. 



139. But here the leading diftindion, implied 

 in all the reft, that the two kinds of coal are ne- 

 ver found in the fame bed, but always in differ- 

 ent fituations, and with different laws of flrati- 

 fication, is exprefsly contradi6led by matter of 

 fad. Coal, as is faid above, with its ligneous 

 texture quite apparent, and coal with no fuch 

 llrudure vifible, are often found in the fame 

 feam, are brought up from the fame mine, and 

 united in the fame fpecimen. I have a fpeci- 

 men from a bed of coal, in the Ifle of Sky, found 

 imder a bafaitic rock, confifling of a ligneous 

 part, which graduates into one in which there is 

 no vellige of a fibrous texture, and in which the 



L 



furface is fmooth and gloffy, with a fradure al- 

 moft vitreous. 



The upper part of the fpecimen 

 is therefore perfed wood-coal, and the under 

 part perfed mineral-coal, in the language of 

 Mr Kirwan; at the fame time that the tranfition 

 from the one to the other is made by infeniible 

 degrees. This fpecimen, were it perfedly fo- 

 iitary, is fufiicient to prove the identity of the 

 two fpecies of coal we are now fpeaking of, and 

 to fhew, that the difference between them is ac- 

 cidental, not effential. The fpecimen, however, 

 is far from being folitary ; the number of fimi- 



K4 



iar 



