38 Scientific Proceedings, Royal Dublin Society. 



us by Professor Geikie, and was readily acknowledged by his 

 fellow travellers. 



On the second day our route from Ullapool to Inchnadamff, 

 a distance of twenty-six miles, lay along a tract of country border- 

 ing the Silurian and Cambrian formations. We passed under 

 several grand escarpments of Cambrian sandstone ; the most 

 remarkable being thatof BenmoreCoygeagh (Plate IX., fig. 2), which 

 faces the south, and terminates abruptly on the side next the 

 ocean. The cMs of horizontal sandstone rise to a height of about 

 3,000 feet;, and are worn into deep gullies by the action of torrents. 

 Nevertheless, the face of the escarpment rises like a great wall of 

 red sandstone from the crest down for a thousand feet, where the 

 slopes commence. A short distance further north we came in 

 view of " The Stack," an isolated mass of Cambrian sandstone, 

 (Plate IX., fig. 1) also in horizontal beds; and, beyond, the heights of 

 Coulmore* and Coulbeg, the former capped by the lower quartzite 

 of the Lower Silurian series. 



Throughout this tract the "Durness Limestone" became more 

 and more conspicuous as we proceeded northwards ; its thick- . 

 ness increased till, on approaching the head of Loch Assynt, it 

 expanded to about 1,000 feet, and rose in a conspicuous escarp- 

 ment above the foot of the quartzite slope at the eastern base of 

 Canisp. The presence of the limestone amongst the hills and 

 valleys is marked by a band of verdure in the midst of the sterile 

 tracts of heather formed by the quartzites both above and below. 

 The limestone is generally weathered as white as chalk, but in 

 some places contains beds of dolomite weathering rusty brown. 

 It is but very slightly altered, and frequently contains cavities 

 exceedingly like those left by fossil shells ; but with the excep- 

 tion of an Orthis ( ? ) found by Mr. Symes, we did not succeed in 

 obtaining a single specimen of organic origin. 



On approaching Inchnadamff we skirted the eastern base of 

 Canisp. This is an escarpment of Cambrian sandstone capped 

 by quartzite, rising in a grand mural cliff facing the Atlantic. It 

 terminates abruptly along the shore of Loch Assynt, and from the 

 north shore of the loch the whole structure of the mountain is 

 clearly revealed. The lower quartzite is seen to descend with a 



» Coulmore, together with Canisp and Suilyen, are represented in one of the illus trations 

 in Murchison's " Siluria," 4 Edit., p. 170 ; and are graphically described by Hugh Miller. 



