ft 



66 



ILLUSTRATIONS OF THE 



rocks, are fo nearly alike, that in a general 



f geology, they do not req 



to be diftin 



guiflied. It is material to remark, that, though 

 metallic veins are found indifcriminately in all 

 the different kinds of rock, whether ftratified or 

 otherwife, they are moft abundant in the clafs 

 of primary fchifti. All the countries moft re- 

 markable for their mines, and the mountains 

 didinguifhed by the name of metalliferous, are 

 primary, and the inftance of Derbyfliire is per- 

 haps the moft conliderable exception to this rule, 

 that is known. This preference, which the 

 metals appear to give to the primary ftrata, is 

 very confiftent with Dr Button's theory, which 

 reprefents the rocks of that order as being moft 

 changed from their original polition, and thofe 

 on which the difturbing forces of the fiibterra- 

 neous regions have aded moft frequently, and 

 with great eft energy. The primary ft rata are 

 the loweft, alfo, and have the moft dired com- 

 mication with thofe regions from which the 

 mineral veins derive all their riches. 



m 



-> i 



1. Of Whinjlone. 



I 



6 1. Beiide the veins filled with fpar, and con- 

 taining the metallic ores, the ftrataare interfe^l- 



ed by veins of whinftone, porphyry and granite, 



the 



» 



