in the neighbourhood of Loch Ness. 213 



by a wide and dreary alpine plain, or valley, called Strath 

 Errick. This valley is almost entirely composed of granite, 

 which is of a red or grey colour, large-grained, and most com- 

 monly contains hornblende. The granite is also distinguished 

 by the frequent occurrence of small rounded, or concretion- 

 ary imbedded portions of mica-slate and clay-slate. 



On the north side of Loch Ness granite occurs, constitut- 

 ing one of the mountains (called the Red Rock) next the low- 

 est or eastern extremity, but is here remarkably small-grain- 

 ed, and, as I shall afterwards more particularly notice, differs 

 but little from the ordinary compact quartz-rock. Such is 

 the distribution of the granite. That of the quartz-rock I 

 shall describe, after explaining its characters. It appears to 

 be a rock which is daily assuming a more important place 

 than it formerly possessed in the classification of mountain 

 masses. 



3. The predominating colour of the quartz-rock of Loch 

 Ness is light red or brown, but it is to be found of a blue or 

 grey tint. The substances which compose this rock, are fel- 

 spar, quartz, and mica, but of these three ingredients the 

 quartz is the most abundant. Its texture is granular, or near- 

 ly compact, and the form of the particles crystalline. The 

 three ingredients are so intimately combined as to exhibit a 

 perfectly homogeneous structure. But it is by the hardness, 

 and the shape of the fragments produced by the hammer, that 

 this rock is chiefly distinguished from the older sandstone. 

 The hardness is indeed so great, that, in breaking off speci- 

 mens, they frequently fly into the air and ring- like clinkstone. 

 The cross fracture is uneven, very small and granular, and 

 the form of the fragments is rhomboidal, and rarely rectan- 

 gular. 



The texture of the rock, though in general small-grained 

 or compact, is, however, occasionally diversified by the occur- 

 rence of large imbedded masses of conglomerate, into which 

 those portions of the quartz-rock contiguous to it gradually 

 pass. 



The conglomerated variety occurs in the neighbourhood of 

 Foyers, and on the margin of Loch Ness, between Inverness 

 and the General's Hut. But it is most abundantly found in 



