88 Prof. Forbes on the Topography and Veology of the 



hypersthene in small concretions, and form only a variety of 

 the Cuchullin rock ; but a careful examination by Mr Necker, 

 whose authority is conclusive, of a specimen which I took, 

 decided in the negative. Other specimens of rock from the 

 same quarter appeared, however, to contain hypersthene in 

 imperfect crystals ; so that the separation of the Cuchullin 

 rock from the common traps which constitute the promon- 

 tory of Ru-Dunan, and which overlie the sandstone of the 

 Isle of Soa,* is not yet made out. I believe, however, that 

 a more careful examination than I was able to make of the 

 promontory opposite Soa, would lead to the discovery of 

 some kind of junction of the rocks. Near the latter point, I 

 observed dykes of a blackish colour, strong lustre, ringing 

 sound, excessive hardness, and so splintery a fracture, that 

 it is difficult to detach a portion without wounding the hand. 

 These may probably consist of hypersthene and felspar in a 

 highly compact form. Their external appearance is almost 

 undistinguishable, even at hand, from that of an ancient 

 ruin. On the slope of the western CuchuUins, I found blocks 

 of basalt containing olivine. Its origin is illustrated by a 

 remark of Dr MacCulloch,f who found basalt passing into 

 pitchstone upon Garsven, which he supposes to have come 

 from a dyke. 



The descent below Garsven to the head of Scavig Bay, is 

 very steep. The character of the hypersthene becomes more 

 and more perfectly developed ; and it may be observed, that 

 the perfection of that rock in its mineral character, and in 

 the distinctness of its concretions, or even crystals, is greatest 

 near the centre of the group, that is, in the neighbourhood 

 of Loch Coruisk. Rude hexagonal crystals of the hyper- 

 sthene are exposed by the weather, in the surfaces of 

 the rocks, but it is rarely possible to detach them. The 

 hypersthene occurs also in veins mixed with magnetic iron 

 ore. The finest mineralogical specimens, in situ, of hyper- 

 sthene are to be seen here. But the flat country near Sli- 



* MacCulloch, p. 369. He says, that the hypersthene rock overlies 

 the red sandstone. This seems to me to require confirmation, though I 

 am not in a position to refute it. 



t Descr. i., 482. 



