18 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 19, 



almost horizontally in thin even beds, and moulded into these strange 

 forms by the slow agency of natural causes. Many authors have 

 consequently been induced to notice them, from the time when 

 Pennant, deceived by their external aspect, described them as formed 

 of white marble ; and Williams, with a more accurate knowledge of 

 mineralogy, as granular quartz*. Of these it is sufficient to mention 

 the memoirs * On Quartz Rocks,* and the volumes on the Western 

 Isles by Dr. Maccullochf, the very valuable memoir on the Con- 

 glomerates and other Secondary Deposits on the North Coasts of 

 Scotland by Professor Sedgwick and Sir Roderick I. Murchison|, 

 and the * Geognostical Account of Sutherland ' by the late Mr. R. H. 

 Cunningham §. These well-known works might be supposed to have 

 exhausted the whole subject ; but the discovery, in the winter of 1854 

 -55, of better-preserved and more distinct fossils by Mr. Chas. Peach 

 in the limestones of Durness invested these rocks with a new interest. 

 Sir R. I. Murchison, wishing to verify his former observations, re- 

 visited this region in the autumn of 1855, and, having kindly 

 requested me to accompany him, we examined several of the most 

 important sections together |1 . Last summer I returned to the west 

 coast, and visited several points which we had passed over in the 

 previous year. As my observations now extend over almost the 

 whole tract, from Cape Wrath and Durness on the north to Loch 

 Alsh and Skye on the south, I am induced to lay the results before 

 the Society, in the hope that they may throw some light on these 

 interesting formations^. 



Sections in the Northern part of the District. — In describing 

 the rocks I shall commence with the sections seen near Ullapool, 

 on Loch Broom, as these are apparently typical of the relations 

 in other localities, which they thus tend to explain. Measured 

 from the outer headlands, this bay, or sea-loch, runs for more than 

 twenty miles into the interior, intersecting successively all the various 

 formations. Both shores are formed by ranges of hills, descending 

 abruptly to the water, and generally very thinly covered either with 



* Pennant's * Tour in Scotland' ; Williams's ' Natural History of the Mineral 

 Kingdom.' 



t Memoirs ' On the Geology of Various Parts of Scotland,' and *■ On Quartz 

 Rock,' in Geological Trans. 1st series, vol. ii. pp. 388 and 450 ; Western Isles of 

 Scotland, vol. ii. pp. 89, 508, 675. 



X * On the Structure and Relations of the Deposits contained between the 

 Primary Rocks and the OoUtic Series in the North of Scotland.' Geol. Trans. 

 2nd series, vol. iii. p. 125. 



§ In the Transactions of the Highland Society, vol. xiii. p. 73-114. 



II See Report of British Association (Glasgovp) for 1855 ; Trans. Sect. p. 85. 



^ In justice to my predecessors I may mention, that at the time they examined 

 the West Highlands there were even less facilities for visiting these remote parts 

 of the country than at the present day, when steamboats have done so much to 

 render them accessible. The uncertain climate, too, places a great bar to geolo- 

 gical investigations ; and Sedgwick and Murchison specially state, that the stormy 

 and wet weather which they encountered in these districts prevented their full 

 exploration of the mountains. Sir R. Murchison and myself, in 1855, were again 

 impeded in our researches by the rains and mist that so frequently obscure the 

 best and most instructive sections on this humid coast. 



