( 238 ) 



thin and femltranfparent lannns, whicbj 

 when touched with the point of a needle, 

 are found to be flexible and elaftic, and fe- 

 parate from each other. In the fire, as has 

 been faid, they vitrify, and the glafs pro- 

 duced from them is of a blackilh colour, 

 and femltranfparent. 



The magnetic property of thefe micas, 

 among the many I have examined, I have 

 found in none vvhich enter into the compo- 

 fition of granites not affected by the firCo 

 In my return by land from Conilantinople 

 to Italy, I coUedted fpecimens of the ftones 

 compohng the mountains over which niy 

 road led me, and, among others, of a con- 

 iiderable number of granites, which, from 

 the nature of the places where they were 

 found, were certainly not volcanic. Many 

 more I found in the Alps, and other coun- 

 tries not volcanic. On the micas they con- 

 tained I m.ade experiments with the magnet ; 

 but I did not find one, whatever was its 

 colour, which fliowed the lead fign of at- 

 tradion. In fevcral of them, indeed, I 



found 



