220 peoceedings of the geological society. [Nov. 16, 



naglike micaceous rocks, which in parts have the same constituent 

 particles as gneiss. 



Let us first consider a few additional data, explanatory of this 

 •view, as derived from the last examination of the tracts of Assynt, 

 Durness, Eriboll, &c. 



Assynt. — New sections are now offered, to show how completely 

 the chief limestones lie between lower and upper quartz-rocks. 

 Another section is added to demonstrate how all this quartzose 

 series is followed by a second or superior limestone, which, in its 

 turn, is overlain by micaceous and gneissose schists, &c. The first 

 of these (fig. 3, p. 217) may be seen by any one who walks from 

 near the post-office of Assynt, on the west, across the ridges of lime- 

 stone, to the hills on the east-by-north. 



The lower quartz-rock, which slopes down from the edges of the 

 Cambrian rock of the Canisp, presents its uppermost band only on 

 the side of the Loch, and is followed by the passage-beds with 

 Fucoids and Annelides formerly described. To these succeed light- 

 grey limestones, of concretionary structure, which, on approaching 

 an intercalated band of syenitic greenstone, become dark-coloured 

 and fetid under the hammer. This syenitic greenstone, which is 

 best exposed at a turn of the road about a mile west of Inchnaclampff, 

 is from 40 to 50 feet thick, and as regularly bedded as the limestone 

 below and above it, though, on examination, it is seen to be a true 

 igneous rock, containing crystals of hornblende, with felspar and 

 quartz. In other parts it weathers into a softer mass, and might 

 there be taken for a volcanic ash. 



The limestone above this igneous rock is, indeed, more altered 

 than that which lies beneath it, and is in parts a crystalline marble, 

 which, many years ago, a speculator began to work for ornamental 

 purposes. These limestones and marbles, with their associated 

 igneous rocks, can be traced at intervals from 1| mile to the west of 

 Inchnadampff, along the escarpment of Stromchrubie, to near El- 

 phin, altogether a distance of about eight miles. 



Ascending from these dark limestones and marbles, dipping from 

 25° to 30° to the east and east-by-north, you pass over successive 

 ledges of partially brecciated and scaly-fractured, lighter- coloured 

 layers, and next over a succession of lighter- coloured limestone, 

 containing, however, one dark band. On rising towards the hill of 

 Cnoc-an-drein, a steep scarp presents a most systematic ascend- 

 ing section, the strata in which, rising gradually in inclination 

 to about 40°, pass up into, and are conformably surmounted by, 

 the upper quartz-rock. But, whether the inclination rises to 40° or 

 diminishes to 25°, as at the east end of the ridge above the Manse 

 of Ichnadampff, the limestone is everywhere symmetrically overlain 

 by the upper quartz-rock. This upper quartz differs from the lower 

 only in being less grey and white, and in having more of a pinkish 

 colour ; but it resembles the older rock in containing Annelide-tubes, 

 which often traverse several layers of the rock*. The accompanying 



* See woodcut, Quart. Journ. Geol. Soc. vol. xv. p. 368. 



