NICOL SOUTHERN GEAMPIANS. 



205 



side of the glen consists of gneiss dipping 50° or 70° to S. 40°-50° E. 

 Further up, the red granite, still full of veins of porphyry, crosses 

 the stream, and is well exposed at a small fall in the river. Still 

 higher the valley contracts, and gneiss forms the lower portion on 

 both sides ; the beds much contorted, but dipping on the whole about 

 70° to S. 42° E. 



Fig. 10. — Porphyry Vein in Granite, Ben Nevis. 

 (Length about 30 feet.) 



The lower portion of Glen Nevis thus consists essentially of gneiss, 

 dipping, more regularly than might have been expected in the 

 vicinity of such a mass of granite, to the S.E. The mountains on 

 that (the south-east) side of the glen appear generally to be capped 

 by quartzite, which ought thus to overlie the gneiss. A great part 

 of this region, however, is now a mere desolate deer-forest, without 

 house or path, so that even in the finest seasons — and these too 

 rarely occur for the geologist — it is difficult of examination. In one 

 of the ravines on the south side of the Glen the following section 

 was observed (fig. 11). 



Fig. 11.- 



-Section of the South side of Glen Nevis. 



N. 



a. Quartzite. 



b. Gneiss. 



c. Red Granite 



d. Mica-slate and Gneiss. 



e. Red Granite. 



The bottom of the valley is red granite — a branch of that in Ben 

 Nevis. It is covered by a fine-grained gneiss or hornstone, probably 

 altered by the igneous rock, which dips at 60° to S. 27° E., and above 

 passes into chloritous mica-slates, some dark, others light grey, and 

 also dipping at 65° to S. 27° E. These slates are in turn covered 

 by a bed of red granite, perhaps from 100 to 150 yards wide, which 

 runs along the face of the southern hills, and in another ravine is 

 traversed by a vein of the dark Ben Nevis porphyry. The granite 



