1856.] NICOL — QUARTZITES, ETC. OF N.W. SCOTLAND. 19 



detritus or vegetation. The outcrop of the beds is thus very clearly 

 exhibited, and the relation of the formations easily ascertained, not 

 only in the cliffs on the shore, but to the very summit of the moun- 

 tains. The village of Ullapool is situated on a flat promontory 

 formed by the detritus thrown into the loch by the Auchal river ; 

 and, as it lies not far from the junction of the various formations, 

 forms the most convenient point for investigating them. The section 

 (fig. 1) represents the general relations of the rocks on the north 

 side of the loch. It commences on the N.W. with an imperfect 

 outline of the Coygach Hills, intended merely to show some of the 

 peculiar features w^hich the red sandstone mountains assume on this 

 coast. Some of them rise into fine spiry or serrated summits, whilst 

 Ben More, the highest, forms a long narrow and precipitous ridge, 

 running to the north-east. 



The part of the section specially examined begins at Loch Kennort. 

 On its north-west shore, at the foot of Ben More, a thick mass of 

 red sandstone, divided into numerous beds, dips to the south-east at 

 a low angle (10° to 12°). This rock, with approximately the same 

 dip, appears also to form Martin Island, lying in the mouth of the 

 bay. On the south-east shore the red sandstone again crops out in 

 thick craggy masses, with a dip of 12° to 20° to the south or south- 

 west, the beds being apparently broken and curved. In the ridge 

 to the east the rock is well exposed, dipping 10° to 12° to S. 20° E.* 

 This dip continues nearly constant, both in amount and direction, 

 throughout the next range as far as the Auchal river, occasionally 

 perhaps inclining a little more to the east. In some places, even 

 where the rocks are well seen, the dip is obscured by the powerful 

 glacier action which has smoothed, striated, and rounded the rocks 

 of the entire region f. Throughout the whole of this range, the red 

 sandstone is very uniform in aspect and mineral character. Most of 

 it is a rather coarse grit, graduating into a fine conglomerate, with 

 fragments rarely an inch or more in diameter. The fragments are 

 not much water-worn, and consist especially of quartz, hornstone, 

 and felspar, — the last often decomposed. The grits are composed 

 chiefly of rounded grains of grey \itreous quartz and red felspar 

 (orthoclase), but apparently with no mica J. The general colour is 

 dark brownish red; but some portions are of a lighter red, or 

 yellowish tinge. 



The Auchal river near Ullapool has cut a deep gorge in the sand- 



* From the large variation of the compass (30° or more), I have thought it 

 better to correct the directions throughout this paper. 



t The violent pressure of the ice appears also to have occasionally altered the 

 position of large masses of rock, thus vitiating direct observations made on the 

 strata at their outcrop. 



X Dr. Macculloch has already made the observation as to the West Coast sand- 

 stone generally — " In no instance have I observed it to contain mica, nor, with 

 the exception of red jasper and that of the schist just mentioned, any substance 

 but quartz and felspar." On the other hand, Sir R. Murchison (Trans. Geol. Soc. 

 2nd ser. vol. iii. p. 164) mentions the occurrence of mica in some beds of the red 

 sandstone of Applecross, so that it is rather rare than unknown. Macculloch 

 also says, " that in no instance hitherto has it been found to contain imbedded 

 limestone." — Western Isles, vol. ii. p. 97. 



C 2 



