152 



ILLUSTRATIONS OF THE 



lar appearances is fo great, as hardly to have ef- 

 caped the obfervation of any mineralogift. Mr 

 Kirwan admits, that wood-coal is often found un. 

 der bafaltes=^: 



but what is elTential to be remark 



d is, that, in th 



ftance 



both the 



wood-coal, and the common mineral-coal, lying 

 under that rock, and the one paffing gradually 

 into the other. It appears, indeed, that many of 

 the fads w^hich Mr Kirwan produces, in treating 

 of what he calls carboniferous foils, are quite in- 

 conliilent with the diftindion he would make 

 between wood-coal and mineral-coal f . 



140. It is, however, 

 fiances in which the w 



■ue,, that there are in 

 d-coal, or foffil-wood 



as it is ufually called, forms ( 

 iTnconneded with the ordinary 



beds, quite 

 and ftrati- 



fied in fome refpeds differently. Such is the 

 Bovey coal in Devonfliire, the wood- coal in the 

 north of Ireland, and perhaps the Surturbrandt of 

 Iceland. With refped to the Bovey coal, it does 

 by no means anfwer to one of Mr Kirwan's re- 

 marks, viz. that late obfervations haveafcertained, 

 that no fiich parallelifm of the beds, as in mine- 

 ral-coal, nor even any diltind: number of ftrata, 

 is found. In the Bovey coal, the number of 

 llrata is very well defined, by beds of clay re- 

 gularly interpofed ; but as to the extent of thefe 



beds, 



* 



Geol. Effays, p. 310. 



t ibid, p-311. 



