168 Proceedings of the Royal Physical Society, 



fine-grained granite. It is indeed a sort of link between 

 granite and porphyry. Some of the coarser grained arenaceo- 

 argillaceous strata seen at this place also show a transition 

 to a kind of syenitic granite, — a fine-grained mixture of 

 quartz, felspar, and horneblende, with or without mica. The 

 appearances at the junctions of the granite and greywacke 

 of Cockburnlaw, in Berwickshire, are exactly similar to those 

 so beautifully exhibited at this part of Glencoe. Further up 

 the glen, highly metamorphic rocks occur, blending the 

 characters of the porphyry and schistose rocks in endless 

 variety. The strata and laminse are distinctly marked, ver- 

 tical, with a N.N.E. strike. These consist of quartz, com- 

 pact felspar, and micaceous hornblende, being technically 

 gneiss. Many rocks in Glencoe which have been termed 

 porphyries are evidently nothing more than highly meta- 

 morphic schists, generally dark coloured, frequently retain- 

 ing most unequivocally their original planes of stratification, 

 and containing less or more felspar absorbed from the 

 igneous masses which caused their metamorphism. The 

 whole glen, as well as the wild and rugged district between 

 it and Ben Nevis, are of the highest geological interest, 

 especially as bearing upon the subject of this paper and 

 igneous metamorphism in general. Of the wondrous scenery 

 of this part of Scotland it is unnecessary to speak. 



2. Ben Nevis. — At Nevis bridge, and across the level mouth 

 of the glen to where the ascent begins, metamorphic schists, 

 similar to those seen in Glencoe, dip S.S.E. 50° and upwards. 

 Immediately on commencing the ascent on the west side, 

 granite appears, the faces of the rock having a direction 

 nearly N.N.E. to S.S.W. At the top of the first ascent 

 (about 2500 feet or more), the granite is extensively ex- \ 

 posed, massive and divided by fissures running E.N.E. to 

 W.S.W., which look suspiciously like traces of planes of 

 stratification. These are crossed by a few others ranging 

 N. by E. to S. by W. This granite appears to be a com- 

 pound formed by the fusion, or partial fusion, of the strati- 

 fied rocks by the porphyry. The coincidence in the direc- 

 tion of its principal divisional planes with the strike of the 

 schists at the mouth of the glen, seems much in favour of 



