and the other Chmmel Islands. 9 



Castle Cornet Is built is a gneiss, often approaching so near to 

 granite as to render its place in a nomenclature doubtful. It is every- 

 where crossed and intersected by veins of quartz, of trap, and of 

 felspar, curved and mixed in various ways, but tending, upon the 

 whole, to the north or north-east. More rarely there are found in 

 it veins of brick red and bright green felspar, and pebbles of the 

 same substance, or with hornblende imbedded, are found on the 

 beach, as well as coarse agates passing into quartz and hornstone. 



Proceeding from the Castle southwards, gneiss is found to consti- 

 tute the cliffs on the eastern side, often in a state of decomposition, 

 and covered with a great depth of debris. These strata, which extend 

 all along the south coast to Rocquaine Bay, seem to tend from NE to 

 SW ; and have various inclinations, but most generally 10° or 15", 

 dipping to the south. On the southern side of the island they are 

 intersected by veins of white, flesh-coloured, and red felspar, of 

 various breadths. In some places the felspar veins pass into granite. 

 Veins of quartz, and veins of a granitel consisting of quartz and 

 felspar, also traverse it. A few veins of trap are also fourd inter- 

 secting it at Rocquaine, which are occasionally superseded by trap 

 porphyry, or by the same substance containing minute grains of 

 quartz. In this tract there are wrought two or three quarries of a 

 black granitel, consisting of hornblende and quartz, and very hard. 



The constitution of this stone varies much through the extent 

 which it traverses. In some places it is a true granite, in others the 

 mica disappears, in others again this latter ingredient becomes so 

 abundant, that the stone passes into micaceous schlstus. Occa- 

 sionally also hornblende enters into its composition, as has been 

 noticed by others : when this is the case it sometimes loses the 

 foliated structure and passes into slenlte. Sometimes all the other 

 ingredients are excluded, and felspar alone remains. There may 



B 



