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



which we did not explore, Mr. Cunningham describes the gneiss as 

 resting conformably on the quartzite and limestone. The same 

 observer also figures and describes a very singular instance of this re- 

 markable relation on Loch More. His section shows a lower highly 

 inclined gneiss, covered unconformably by an ascending series of 

 quartz-rock, limestone, and gneiss, all conformable to each other. 



The next locality which I shall notice is the vicinity of Durness, 

 where the limestone is distinguished by containing organic remains 

 in considerable abundance. The general relations of the rocks are 

 shown in fig. 4. The western shore of the Kyle of Durness consists 

 partly of gneiss, partly of the quartzite in thin even beds, some of 

 them full of the cylindrical bodies, but often more branched and 

 coral-like in their forms than either at Assynt or Ullapool. This 

 rock dips at 20° to S. 60° E., and, on the road to Cape Wrath 

 Lighthouse, overlies red sandstone and conglomerate, dipping uncon- 

 formably at a lower angle (10° N., 25° E.). The red sandstone 

 exhibits no peculiarities, the lower bed being a not very coarse con- 

 glomerate of slightly rounded fragments of quartz and red or white 

 felspar, in a reddish-yellow basis of sand. Mr. Cunningham noticed 

 the quartzite in this place alternating with " strata of slate-clay of a 

 character little diifering from that which is associated with the red 

 sandstone of the coal-series*." On the east side of the Kyle the 

 low country is chiefly limestone. On the shore near Balnakiel 

 House, where it contains the fossils, it dips at 10° E., but in one 

 place folds over in a low arch. The principal mass is of a dark-blue 

 colour, very hard and siliceous, striking fire readily with the hammer. 

 It contains large lumps of reddish-brown chert, with innumerable 

 flinty concretions of singular forms ; and, when weathered, the 

 surface has a peculiar rough aspect, as if covered with broken corals 

 or shells. Other beds are of a light-grey colour, and more arenaceous 

 texture ; and others again more argillaceous, and divided by a kind of 

 cleavage into laminae from a quarter to half an inch thick. In general 

 aspect it closely resembles some of the carboniferous limestones where 

 altered by trap. 



Beyond Durine, the limestone still dips east, but at a higher angle 

 (20° to 25°), and alternates with beds of a more arenaceous character. 

 Beyond the Smoo Cave it is cut ofi" by gneiss in nearly vertical 

 beds, with a W.N.W. direction. This rock forms the ridge running 

 south-west from near Rispond to the Gualin. The eastern declivity 

 of these hills is, however, covered by the quartzite, sloping down in 

 vast beds to Loch Eriboll, and in some cases extending to the tops of 

 the mountains. Many parts of this quartzite are soft, almost friable 

 sandstone, not harder than the common grits of the coal-formation. 

 The low ground on the eastern shore of Loch Eriboll, and the under 

 declivities of the hills, are of limestone, in some places overlaid by a 

 similar arenaceous quartzite. In the hills above Eriboll House this 

 limestone series is overlaid by gneiss, which also dips south-east to- 

 wards Loch Hope. The infra-position of the limestone to the gneiss 

 in this locality has been recognized by many observers, from the time 



* Essay, p. 92. 



