DOMAIN X. TRANSILIENT* 



characters of this rock has always embarrassed 

 systematic nomenclators, they have varied in the 

 name they have bestowed on it, and in the 

 place they have assigned it. 



a I have seen in the mountains of Tyrol, 

 and especially in the large rolled pebbles in the 

 plains of Verona, which have descended from 

 them, a great quantity of those rocks which 

 might be called porphido-granites, from the 

 union of those two characters; but the most 

 curious of this kind I have ever met with, are 

 those of Corsica; of which, ten years since, I 

 deposited a hundred specimens in the beautiful 

 cabinet of Florence, under the direction of my 

 illustrious friend Fontana. 



" But it is not the granite of the earliest pre- 

 cipitation which possesses this identity of com- 

 position with porphyries ; these primary granites, 

 as I have said, are more quartzy than the others; 

 the felspar is less abundant in them, and cannot 

 represent a cement. The medium in which 

 they were formed being purer than in later 

 times, the particles differently constituted have 

 been less interrupted in the choice of places, 

 assigned them by the aggregative attraction ; 

 and if in a few of these granites some of those 

 large spots are found, which, like placards, an- 

 nounce some change in the constitution of the 



