Basalt between the Fields of Coal. 193 



new modifications, and all the phenomena, to 

 which the advocates of either theory refer, in 

 support of each hypothesis ; or which the in- 

 genious though puny chemistry of art endea- 

 vours to exhibit in proof, or in imitation, of the 

 sublime laboratory of nature. 



' 



An accidental discovery by Sir James Hall 

 in some measure accounts for the different ap- 

 pearances of basalt, which, when cooled rapidly, 

 has the appearance of glass. 



In the collieries near Ayr, basalt dikes in 

 some instances separate the coal fields. The 

 coal adjoining these dikes, to the extent of 

 fifteen feet or more, is as completely charred as 

 if done in an oven. 



Below the beds of solid basalt here, are strata 

 of a substance resembling the ore of iron ; on 

 which the operation of combustion seems very 

 apparent. 



Having pledged myself on no occasion to 

 disguise any feeling or sentiment that should 

 arise in my mind, though I hazard the loss of 

 reputation as an admiring geologist, I must 

 acknowledge I was disappointed in my first 

 views of the renowned Causeway. Dr. John- 



VOL. i. o 



