ISLE OF MAN. - GEOLOGY. GRANITE. 535 



interior extent seems never to exceed half a mile, but 

 the boundary must remain conjectural, since it scarcely 

 appears at the surface and has not been there quarried. 

 This judgment respecting its boundary is only founded 

 on the external form of the land. It contains one or two 

 small patches, or portions of beds, of white sandstone, but 

 of no value : the red, being compact, easily quarried, and 

 raised in large blocks, has been used for building. 



Such is a brief and popular view of the rocks which 

 are found in the Isle of Man. 



In proceeding to those scientific details more pecu- 

 liarly interesting to geologists, I shall, as on other occa- 

 sions, describe the rocks according to their superposition ; 

 that order which, whenever it can be followed, is by far 

 the most instructive and intelligible.* 



The granite already mentioned is situated two or three 

 hundred feet above the sea, on a steep declivity, and 

 has been laid bare in one place by a small farm road, in 

 another by the mountain stream which has worn a deep 

 channel in it. Unfortunately, the place where it appears 

 is surrounded by various small streams, and lies under a 

 rapid slope of the mountains ; from which causes perhaps, 

 among others, it is every where so overwhelmed by allu- 

 vial matter as to be completely insulated among a mass 

 of rubbish. This accumulation is so extensive and at 

 the same time so deep, since it in many places exceeds 

 twenty or thirty feet, that the schist is no where visible in 

 the vicinity of the granite. The streams, which have 

 caused such deep channels, have not yet succeeded in 

 reaching the solid rock, except at the point just described ; 

 the masses of granite, which occur at the small bridge 

 over the Doon river, being transported blocks ; not the 

 fixed rock, as they appear to be on a superficial view. 

 No information can therefore be obtained respecting the 



* The Sections, Plate XXXII. fig. 6, 7, will serve to explain the 

 general relations of all the rocks of the island. 



