( m ) 



fome feltfpars only being perceivable in it 

 in the form of v/hite fpots, 



I have faid, a little above, that black mi- 

 ca is one of the component parts of this 

 granite. 1 fliall here add, that when it is 

 detached from the volcanic rock and ap- 

 proached to the magnet, it will adhere to it 

 like a particle of iron ; which property it 

 fhares with other black micas, before de- 

 fcribed, and with almoft all I fnall hereafter 

 have occafion to mention. This curious 

 phenomenon was pointed out to me at Ve- 

 nice, before I made my excurfion to the 

 Euganean mountains, by that excellent na- 

 turalift Sig. Giovanni Arduino. The greater 

 part of the ftreets of that capital are paved 

 with thefe Paduan ftones, and it was in 

 fome of them I was fliown this quality by 

 Sig. Arduino. He, indeed, was of opinion 

 that thefe fhining black particles were rather 

 particles of iron than of mica ; but ocular 

 examination convinced me that they apper- 

 tain to this ftone ; fmce with the lens v/e 

 may perceive that they con fill of delicately 



thin 



