Cuchullin Hills in Skye, 85 



ate space scarcely admits of the necessary examination ;"* 

 and in the geological map of Skye, the one rock is made to 

 pass into the other by a faint shading all round, the bound- 

 ary following Glen Sligachan ; whence I conclude that even 

 this most accessible part of the district was unvisited by him. 

 The extreme barrenness of soil which pervades the Cuchullins 

 renders the detection of junctions, and all other geological 

 phenomena, more than usually easy. It has been said that the 

 hypersthene overlies the felspar J'ormation, whilst this last 

 probably passes, by insensible degrees, into claystone and 

 greenstone. These last form dykes, which, between Glen 

 Sligachan and the Cuchullins, are often vertical, and directed 

 towards that group. The absolute elevation of the boundary 

 of the hypersthene increases as we proceed westwards ; so 

 that, in point of fact, the greater part of the elevation of the 

 Cuchullins in that direction is not due to the thickness of the 

 hypersthene, but to the underlying common trap-rocks (a 

 fact hitherto unsuspected), which here attain a height of 

 2050 feet above Sligachan, in the ravine marked Feu-na- 

 Corry in the map, immediately to the west of the highest part 

 of the ridge. In this Corry the immediate superposition of 

 the hypersthene is observed ; and that is a much more abso- 

 lute superposition than in Hart-o-Corry, where the rocks are 

 in some degree side by side. Here the claystone (which the 

 rock most resembles) runs under the hypersthene at a low 

 angle, dipping to the SE., the tendency to cleavage of the 

 hypersthene being in the same direction. So sudden is the 

 transition, that we ma/ stand on the claystone and touch the 

 hypersthene ; probably, too, hand- specimens may be pro- 

 cured, including both rocks. Indeed, I broke such in the 

 immediate neighbourhood ; but they may have belonged to 



* Description, i., 368 ; and again, p. 386, — " For the sake of topo* 

 graphy, it would have been desirable to define the region occupied by 

 this rock, although it is of little consequence in a geological view, &c. 

 * * * The difficulty of ascertaining its extent arises from the 



thoroughly inaccessible nature of the eastern declivity of this ridge, and 

 from the almost insuperable obstacles which impede its examination in 

 other parts." 



