Dr. Berger on the Isle of Man. 37 



had been employed the whole time the works were carried on be 

 correct, they came to the primitive rock in sinking a shaft forty 

 yards deep* There the granite was found to form the north side* 

 of the vein, the galena adhering to it, while the south side was a 

 stratified rock, which I shall hereafter mention. Whatever may be 

 the depth at which the primitive rock was first remarked, there can 

 be no doubt as to its existence, from the multiplicity of pieces of 

 all sizes I found among the rubbish of the mine, and which were 

 pointed out to me as such by the miner himself. 



The rock is of a coarse grained texture, somewhat loosened, 

 chiefly composed of quartz concretions, with reddish and decayed 

 felspar along with some plat-es of white mica. 



The mean specific gravity of the different sorts of granite above- 

 mentioned, is 2, 81. From the granite above described, we come 

 at once to the clay slate formation. The subsequent or intermediate 

 members to granite In the series of the primitive rocks, viz. gneiss 

 and mica slate, being either wanting absolutely, or if they exist at 

 all, having escaped my attention, or being for the present concealed 

 from our sight. 



tt Clay-Slate. 



The clay slate formation in the Isle of Man does not appear to 

 belong to the oldest kind of Werner. It is almost limited to the 

 high ground occupying Snei-feldt, Bein-y-phot, South Bor-roilva, 

 and Cronk-ne-lIry-Lhaa. It also occurs at Mount Pellier as hone 

 stone ; at Peel-hill and Balla-Gawn, as roofing slate ; and as a reddish 



* The miner from whom I received my information is a Yorkshire man, and used the 

 technical word cheek instead of that of side; an expression which I understand is 

 liliewisc employed amongst the Derbyshire miners. 



