NOME XV. P. COAIo 



NOME XV. D. COAL. 



This substance, when in contact with what 

 are called whin-dykes, those singular arrects or 

 uprights which sometimes intersect whole moun- 

 tains, is often observed to be decomposed ; having 

 lost its bitumen, and wearing the appearance of 

 being charred. The Neptunists say, that the 

 stone has absorbed the bitumen ; while the 

 Plutonists affirm that the melted stone, ejected 

 from beneath, has caused the bitumen to eva- 

 porate. 



Those immense arrects are often argillaceous, 

 but more generally of a basaltic nature. They 

 are sometimes of prodigious extent ; one of them 

 extending from Lothian through the estuary of 

 the Forth into Fifeshire, a space of twelve or 

 fifteen miles. It is observable, that where they 

 intersect the coal, the beds subside in this po- 

 sition: 



