160 ASSOCIATIONS OF [Ch. VIII. 



At the junction of the mass of granite with the strata, in- 

 numerable processes, or veins, may be seen spreading out 

 from the granite in every possible direction : these veins are 

 occasionally of large size, but in general they are small, and 

 even do not exceed a thread. Although they can be traced 

 into the large mass of granite, they sometimes appear both 

 to originate and end in the limestone, presenting rather the 

 aspect of detached lumps and irregular processes, than of 

 veins. So confused is this interference, that a portion of 

 granite is often found entangled in the limestone, and in- 

 sulated parts of the latter rock are sometimes contained in 

 the former ; and the smaller veins may be seen reticulating 

 the schist and limestone in the most intricate and amusing 

 manner. " As long as these veins continue of a few inches in 

 breadth, their mineral character is the same as the adjoining 

 granite : as they diminish, however, the hornblende gradually 

 disappears ; although, in the cases in which the vein traverses 

 hornblende-schist, this mineral is increased in quantity. But 

 the vein of mixed quartz and felspar is the most common ; 

 and this, as it continues to diminish in size, ultimately 

 becomes mere felspar, or else a compound of felspar and 

 quartz, so intimate, that the magnifying glass discriminates 

 the particles no longer, and the whole is only distinguishable 

 from common felspar by its peculiar fracture and superior 

 hardness." * 



In short, wherever granite-veins have been observed at 

 the junction of the granitic and schistose rocks, they exhibit 

 similar phenomena to those of Cornwall. With very little 

 alteration, therefore, we may, with Mr. Carnef, sum up the 

 evidence on this subject in the following manner : 



1. The composition of the granite- veins is generally dif- 

 ferent from that of the main body of granite, and it is very 

 frequently of a much smaller grain. It will, however, be 



* Geol. Trans., vol. iv. p. 265. et seq. 



t Geol. Trans, of Cornwall, vol. ii. p. 69. 



