( 197 ) 



And did other metals exlft In the entrails 

 of volcanos, and the neceflary clrcumftances 

 concur to their cryftalUzation, it Is Indubi- 

 table that this may be effedled by fire as 

 well as by water. Thus we fee that, by 

 taking certain precautions, metalHc fub- 

 ftances afliime a regular and fymmetrical 

 difpofition within the crucible. The fame 

 Is true of bafaltes, the prifmatic configu- 

 ration of which, though not ftridly a cry- 

 ftallization, has the moft exad: refemblance 

 to it. Obfervation, llkewife, teaches us 

 that the fame combination of earths, ac- 

 cording to different circumflances, forms 

 prifmatic bafaltes, fometimes in the humid, 

 and fometimes in the dry way. The flone 

 called trapp, found In the mountains of 

 Sweden, is configurated in prifms, though 

 thofe mountains are of aqueous origin ; and 

 the horn-ftone, which is fo analogous to 

 the trapp, has the fame configuration at Fe- 

 licuda, notwithflanding it is a true lava. 

 In the fame Ifland, likewife, other bafalti- 

 form lavas have for their bafe fhoeri ia 

 mafs, and thofe of the crater of Vulcano, 

 O 3 the 



