and the other Channel Islands, 1 1 



ted and green felspar, which are found at Castle Cornet. The same 

 highly coloured felspars are also occasionally intermixed so as to 

 form a constituent part of the granite, which thus becomes exceed-, 

 ingly beautiful. 



Among the various pebbles which I picked up on the beach, I 

 observed a black siliceous schistus and hornblende slate, but from 

 whence they had been detached I could not discover: the latter 

 however is known to be common in gneiss as well as in granite 

 rocks. 



At Grande Rocque are large masses of slenite, which are quarried 

 to form building stones. It is the only rock of this nature on the 

 Island, and its produce is fully equal in beauty to that of the cele- 

 brated quarries of Mont Mado in Jersey, although it cannot be raised 

 in such large masses. The felspar is the predominant ingredient, and 

 it is either white or flesh-coloured. It is traversed by veins of a 

 similarly constituted stone, but more minutely compacted and of a 

 brick red colour. In some places indeed the veins seem to consist 

 of a felspar basis, with grains of quartz and hornblende imbedded, 

 approaching in its nature to a petunse porphyry. It is here an uni- 

 versal rule that where the granites are traversed by veins of a similar 

 nature, the vein is the most compact of the two. As the hornblende 

 is sometimes wanting in these stones, and as mica is sometimes pre- 

 sent, we meet with many other granitic varieties. I observed in one 

 place lumps of argillaceous porphyry stuck in granite, as has been 

 noticed by Baron Born. 



The predominant rock towards the bay of St. Sampson's, is a grey 

 or black granitel, consisting of quartz and hornblende mixed in 

 Various proportions. Detached masses of this rock are also found in 

 the higher grounds, as well as among the gneiss of the southern coast. 



b2 



