86 Prof. Forbes on the Topography and Geology of the 



one of the claystone veins, which here, as elsewhere, pene- 

 trated the hypersthene in abundance. 



It is important to observe, that the claystone in the neigh- 

 bourhood of the hypersthene exhibits plain marks of alter- 

 ation. It is highly crystalline — sometimes amygdaloidal, and 

 contains quartz. From this we are led to infer, most pro- 

 bably, the posteriority of the hypersthene to the inferior trap ; 

 for were it otherwise, and were the peculiarity of structure 

 of the claystone due to its having itself cooled in contact with 

 the hypersthene, a similar structure ought to be more parti- 

 cularly observed in the claystone veins which traverse the 

 hypersthene in vast numbers. But, so far as I have observed, 

 such is not the case. And even at the very place we are 

 considering the claystone is traversed by veins of its own 

 material, perfectly compact and similar to those which tra- 

 verse the hypersthene. 



This superposition is not a local phenomenon ; I carefully 

 verified it along the northern boundary of the Cuchullins. 

 The absolute height of the junction sinks again on the west- 

 ern side of the Mam-Vrechty, which is the col connecting 

 the most northerly spur of the Cuchullins (which divides Feu- 

 na-Corry from Corry-na-Criech) with the trap country to the 

 north, but may be well traced in the recesses of Corry-na- 

 Criech and the north-western outlier of the Cuchullins, called 

 Leach-a-Huilm. Corry-na-Criech. or the Corrg of the Fight, 

 is a wide and wild ravine, so called from a sanguinary combat 

 between the Macdonalds and the M'Leods, when the former 

 were surprised by the latter dividing, in this remote retreat, 

 the spoil acquired in a predatory expedition. Everywhere 

 the felspar trap dips under the hypersthene at a moderate 

 angle, which reminded me of the superposition of the granite 

 to the limestone in the Alps of Dauphine, whose picturesque 

 character, as has been said, is recalled by that of this part 

 of Skye. 



The whole phenomena of junctions and superposition now 

 described in half the circumference of the Cuchullin group, 

 and which may be almost everywhere traced from Ben Bla- 

 ven on the SE., to Leach-na-Huilm on the NW., leads us to 

 consider the hypersthene mass as a vast bed, thinning out both 



