460 Bntinh Association — J. Home, F.R.S., etc. — 



Thrust, where the outcrop of that thrust lies to the east of a broad belt of 

 displaced materials. There, Lewisian gneiss, Torridon Sandstone, and 

 Cambrian quartzite are sheared and rolled out, presenting new divisional 

 planes parallel with that of the Moiue Thrust. The Lewisian gneiss 

 shades into flaser gneiss and schist, and ultimately passes into a banded 

 rock like a platy schist. The pegmatites show fluxion structure with 

 felspar ' eyes ' like that of the rhyolites. At intervals in these zones of 

 highly sheared rocks, phacoidal masses of Lewisian gneiss appear, in 

 which the Pre-Torridonian structures are not wholly effaced. The sills of 

 camptonite and felsite intrusive in the Cambrian rocks become schistose, 

 and together with the sediments in which they occur appear in a lenticular 

 form. All these mylonized rocks show a characteristic striping on the 

 divisional planes, due to orientation of the constituents in the direction of 

 movement. 



Still more important evidence in relation to the question of regional 

 metamorphism is furnished by the Torridon Sandstone. In the case of 

 the basal conglomerate the pebbles have been flattened and elongated, and 

 a fine wavy structure has been developed in the matrix. In the district of 

 Ben More, Assynt, planes of schistosity, more or less parallel with the 

 planes of the Ben More Thrust, pass downwards from the Torridon con- 

 glomerate into the underlying gneiss. Both have a common foliation 

 irrespective of the unconformability between them. Again, along the 

 great inversion south of Stromeferry, foliation has been developed in the 

 Torridon conglomerate and overlying Lewisian gneiss, parallel to the plane 

 of the Moine Thrust. The Torridon grits and sandstones south of Kin- 

 lochewe and between Kishorn and Loch Alsh are similarly affected by the 

 Post-Cambrian movements. Mr. Teall has shown that the quartz grains 

 have been drawn out into lenticles and into thin folia that wind round 

 ' eyes ' of felspar. A secondary crypto - crystalline material has been 

 produced, sericitic mica appears in the divisional planes, and in some 

 instances biotite is developed. In short, he concludes that in these 

 deformed Torridonian sediments there is an approximation to the 

 crystalline schists of the Moine type. The stratigraphical horizon of these 

 rocks can be clearly proved. The subdivisions of the Torridon Sandstone 

 have been recognized in those displaced masses which lie to the east of the 

 Kishorn Thrust and to the west of the Moine Thrust. It is worthy of 

 note also that in the belt of highly sheared gneiss south of Stromeferry 

 that comes between the Torridonian inversion in the west and the Moine 

 Thrust on the east Mr. Peach has found folded and faulted inliers of the 

 basal division of the Torridon Sandstone that have a striking resemblance 

 to typical Moiue schists. 



Regarding the age of these Post-Cambrian movements, it is obvious that 

 they must be later than the Cambrian Limestone and older than the Old 

 Red Sandstone, for the basal conglomerates of the latter rest unconformably 

 on the Eastern Schists, and contain pebbles of basal quartzite, pipe-rock, 

 limestone, and dolomite derived from the Cambrian rocks of the North- 

 West Highlands. 



East of the Moine Thrust or great line of displacement extending from 

 EriboU to Skye, we enter the wide domain of the metamorphic rocks of 

 the Highlands, a region now under investigation, and which presents 

 difficult problems for solution. Two prominent types of crystalline schists 

 (Caledonian series, Callaway, and Moine schists of the Geological Survey) 

 have been traced over wide areas in the counties of Sutherland, Ross, and 

 Inverness, and across the Great Glen to the northern slopes of the 

 Grampians. Consisting of granulitic quartzose schists and muscovite- 

 biotite schist or gneiss, they appear to be of sedimentary origin, though 

 crystalline. They are associated with recognizable masses of Lewisian 



