388 Elements of Mineralogy. 



There are other mountains analogous to 

 thefe, which yet cannot properly be called 

 ftratified, as they confift only of three im- 

 jnenfe mafles ; the loweft granite, the mid- 

 dle of the argillaceous genus, and the upper- 

 moft-of lime-ftone. When they are metalli- 

 ferous, as they generally are, the metallic 

 ores are found in the argillaceous part, or 

 between it and the calcareous ; thefe ores 

 form veins or bellies, and not ftrata ; thefe 

 may be called triplicate mountains. 



Confufed mountains; that is, of a confufed 

 or promifcuous ftrudure, confift of ftones of 

 all forts heaped together without any order ; 

 their interfaces are filled with fand, clay and 

 mica ; they fcarce ever contain any ore. 



Of Volcanos. 



Volcanos, or burning mountains, are pe- 

 culiar to no climate, and have been obferved 

 in every quarter of the globe : they have no 

 neceflary or regular connection with other 

 mountains, but they feem to have fome with 

 the fea, for they are generally placed in its; 

 neighbourhood. It is true that antient ex- 

 tinguifhed volcanos have lately been difco- 

 vereci in the inland parts of moft countries 5 

 but this is one of the many proofs that the 

 fea at feme remote period covered thofe coun- 

 tries. 



