Dr. Berger on the Isle of Man, 39 



it is ferruginous on the joints, but the colour of the basis is greenish 

 grey, of a very fine grain, and full of cubic iron pyrites. It is a 

 fact worth noticing, that the parts of the rock contiguous to the 

 pyrites are whitish and earthy. 



The last sort of clay slate mentioned as occurring between 

 Slieau-y-Carnane and little Snei-feldt, has a violet reddish tinge. 

 The structure is fine slaty, the texture more clayey; talcose linings 

 impart to the spontaneous joints a glossy character. Its readier 

 decomposition makes it a better support for vegetation. The mean 

 specific gravity of the different sorts of clay slate enumerated here, 

 is 2,757. 



[h) Transition Rocks. 



We pass from the clay slate formation to transition rocks through 

 the most insensible gradations, and in this instance it is to be 

 remarked, that it is the grey-wacke and not the limestone which 

 forms the oldest member of the series. 



Grey-Wacke. 



In the Isle of Man this rock, as far as my observation has gone, 

 never contains organic remains. It is farther to be observed that 

 the tract of land occupied by the grey-wacke is less elevated ge- 

 nerally speaking, than that appertaining to the clay slate. We can 

 trace the grey-wacke all along the contour of the island, and, 

 except those places where it slopes down gradually, and is out- 

 skirted by the flcetz-limestone receding into the sea, it forms a 

 range of bold cliffs ; at Maughold-head, Banks-how, Douglas'- 

 head, Walberry-how, Spanish-head, the Calf of Man, Brada-head, 



