1856.] NICOL — QUARTZITES, ETC. OF N.W. SCOTLAND. 29 



same nature. All these evidently have once been continuous, and 

 the red sandstone must have filled the valley of this most magnificent 

 of Highland lakes, as deep as the lofty summits of Sleugach and Ben 

 Eay, and have all subsequently been hollowed out and removed. The 

 western hills, towards Gairloch, are still strewed with innumerable 

 fragments of red sandstone, perched, like sentinels, in the most ex- 

 posed and perilous positions, on the very edge of some lofty cliff, or 

 on the polished summit of the domes of gneiss * . 



The red sandstone of Gairloch extends continuously into Apple- 

 cross ; and the whole of this vast formation must, therefore, be 

 older than the quartzite. I examined the relations of the two de- 

 posits on Loch Keeshorn, in 185.5, with Sir R. jVIurchison, and the 

 section (fig. 6) represents the facts as seen by us. The great 



Fig. 6. — Section across Loch Keeshorn. 



h. Mica- slate. 



mountain-district of Applecross consists entirely of red sandstone 

 rising in terrace above terrace from the shore of the loch and valley. 

 The general characters of the sandstone correspond to those already 

 noticed ; and, as a detailed section has already been given by Sedg- 

 wick and Murchison, need not be repeated here f. On the east 

 side of the valley an entire change takes place in the rocks. The 

 low green hill consists of limestone, of a light-blue colour, be- 

 coming white when weathered, and with the peculiar, fine-veined 

 brecciated structure characteristic of the limestones of Ullapool, 

 Assynt, and Durness. We examined this rock carefully for organic 

 remams, but without success. The red sandstone dips at 10°-12° 

 to W.S.W. ; the limestone, in broken irregular beds, at a higher 

 angle to the east. The narrow glen, followed by the Jeantown 

 road, exhibits a series of talcose slaty rocks, some of a light-yellow, 

 others of a dark-green colour, dipping at 45° E.S.E. (E. 20° S.) 

 in thin even beds. These beds seem to overlie the limestone, 

 though no immediate junction of the formations was seen. The 

 relation of the limestone to the red sandstone of Applecross is more 

 doubtful. The more natural interpretation would be that the sand- 

 stones had been deposited on the ends of the upturned limestone 

 beds, and subsequently partially removed by denudation ; but the 



* It is a curious fact, that on these gneiss hills by far the majority, probably 

 nine-tenths or more, of these '' perched blocks " are red sandstone, 

 t Geol. Trans, 2nd Ser. vol. iii. p. 154. 



