﻿I860.] 



NICOL N.W. HIGHLANDS. 



95 



is well seen on the south side of Loeh Glen Coul, where the quartzite, 

 which, only one or two miles south, expands into the great mountain- 

 group of Assynt, has been denuded almost to a single bed. 



The section (fig. 7) of the northern side of Glasven shows the 

 true structure very clearly. The low hills on the west, near Kyle 



Fig. 7.- — Section of Glasven. 



Ferry-na- Loch-na- Corry 

 cairn. Ganvich. Derg. Glasven. 



e\ Quartzite. b. Red sandstone. a. Granitic gneiss. 



aa. Gneiss with hornblende. s. Syenite. 



Sku Ferry and Unapool, consist of gneiss and hornblende-rocks, the 

 strata often at very low angles (dip 12° N. 15° E). They are 

 covered by red sandstone, stretching south, in a broad terraced 

 valley, up into the corries of Qneenaig. This valley is bordered on 

 the south-east by a precipitous cliff of quartzite, formed by a 

 great sheet of rock, which, sloping down from the summit of 

 Queenaig, folds over on the south to Loch Assynt, on the north to 

 Loch Glen Coul. The quartzite is well seen on the west side of 

 Loch-na-Ganvich, where the burn from the lake has almost cut 

 through the cliff in a deep ravine, and forms a picturesque waterfall 

 within a few yards of its exit*. The quartzite dips at 10°, to S. 

 53° E.. apparently below the ridge of Glasven, hitherto represented 

 as entirely consisting of quartzite. The east side of the lake, how- 

 ever, I found was syenite, intermixed with nearly vertical masses 

 of granitic gneiss running jNT. 10°-15° W. This rock forms the 

 whole north side of Glasven as far back as the tarn of the Corry 

 Derg. The high bare cliffs on the south-east of this small lake 

 exhibit a beautiful section. The northern extremity consists of the 

 syenite, overlain on the south by undulating beds of . quartzite f. 

 This rock forms the summit and southern slopes of Glasven ; but 

 the syenite passes below and reappears on the other side of the 

 mountain. I have again found it in the inner corries of Ben 

 Uarran and Ben More ; so that it probably forms the axis of the 

 whole range of mountains. From the Corry Derg it extends north 

 to Cnoc-na-Craig-Ganvich and the head of Loch Glen Coul, where 



* We have here, therefore, a miniature of the phenomena of Niagara and the 

 American lakes. The erosive action has only to proceed a few yards further in 

 order to drain the lake ; but from the extreme hardness of the quartzite this may 

 require a very long period. — See Sir C. Lyell's Travels in North America, vol. i. 

 pp. 29-46. 



t The little tarn is shut in on the north-west by moraines or glacier-mounds. 

 These on the north, opposite the syenite cliff, are entirely composed of syenite 

 boulders ; on the south, where the cliff is quartzite, of quartzite boulders, with a 

 mixed group between. 



