Cuchullin Hills in Skye. 89 



gachan is strewed with blocks, among which may be found 

 metalloid hypersthene of the greatest beauty. But I am un- 

 able to say whence these are derived ; for in the whole height 

 of the Scuir-na-Gillean I have not found any specimens of 

 comparable beauty. 



Having now noticed the chief phenomena attending the 

 junction of the hypersthene with other rocks, we shall refer 

 to the veins or dykes which traverse it, and which may be 

 expected to throw some light upon its origin and epoch. 

 These veins are, for the most part, of claystone, of a dull grey 

 colour, which traverse the hypersthene in surprising numbers, 

 and through and through the very heart of the formation, and 

 from the level of the sea up to the very highest summits. 

 Yet their mass is never great, so far as I have observed. It 

 must have been injected into the fissures of this most solid 

 of all rock formations in a state of intense liquidity ; at times 

 enveloping masses of the hypersthene, at others, giving the ap- 

 pearance of numerous alternating strata. Fig. 1, (Plate V.), 

 represents a branching vein, beautifully exposed on the ascent 

 fromCoruisk towards the Strona Stree,the shaded part repre- 

 senting hypersthene, the light part claystone. Fig. 2 is close 

 to it, and exhibits the appearance (perhaps delusive) of a vein 

 of hypersthene within the claystone vein. Fig. 3 exhibits an 

 extraordinary display of claystone veins on a grand scale, 

 very near the summit of the Cuchullins, on the southern face 

 of a black crag which separates Bruch-na-Fray from Loat-o- 

 Corry (above Hart-o-Corry), and which I drew when close 

 to it on my walk (or rather scramble) from Bruch-na-Fray 

 to Scuir-narGillean. The tendency of the fundamental rock 

 to split into parallelopipedons, which have then been perma- 

 nently separated by the injection of the claystone, is beauti- 

 fully seen ; and even this sketch contains but a portion of 

 the extensive ramification there displayed. 



There is, throughout the system of claystone veins, a ge- 

 neral tendency to parallelism, which corresponds, no doubt, 

 to one of the natural cleavages of the rock. In the higher 

 Cuchullins, from whence Fig. 3 is taken, the prevalent dip is 

 to the S.E., corresponding to the cleavage of the rocks paral- 

 lel to the bed which they form, and which has been already 



