582 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



the sea at Ben Keannaben near Rispond in a perpendicular cliff 

 200 or 300 feet high, runs south-west for about seven miles, 

 attaining an elevation of 2500 feet in Ben Spinnue, and it is against 

 this immense wall of rock of vertical gneiss that the whole eastern 

 side of the Durness limestone rests. 



The greater part of the western front of the limestone extending 

 along the shore of the Kyle exhibits as beautiful an example of the 

 elevation of the land at different and very distinct periods as I have 

 ever seen ; several raised terraces or old sea-beaches with rocky 

 fronts can be distinctly traced along the whole western line. But 

 it is at the point opposite the old Ferry-house that the finest succes- 

 sion of terraces is seen ; here six different terraces can be counted, 

 each terrace extending half a mile in length, and presenting a rocky 

 front of about 15 feet in height, the highest and farthest removed 

 from the sea being a quarter of a mile from the present coast-line 

 and about 100 feet above the level of the sea. These terraces, like 

 the rock itself, all dip to the south-east. 



It is not my present intention to allude to the fossils of this deposit 

 further than to say that Mr. Peach has discovered them in various 

 parts of the Duirness limestone, both on the sea-shore and in the 

 interior, that Mr. Salter has pronounced them to be Lower Silurian, 

 and that his decision has been approved of by other palaeontologists. 

 There is one feature, however, of the Duirness limestone to which I 

 would advert, and which made it to be generally known and an 

 object of interest even before the discovery of the fossils, and that 

 is the celebrated Cave of Smoo. 



The cave itself has been so often described and is so well known 

 to tourists that any further description is unnecessary. It is the 

 creek or cove at the upper end of which is the cave proper which 

 is interesting to the geologist, because it exhibits the finest sections 

 of the limestone which are to be found in the whole deposit. This 

 creek runs into the land nearly due south for about 400 yards, the 

 width varying from 30 to 40 yards, and the sides ranging in per- 

 pendicular cliffs from 30 to 80 feet in height. The black and gloomy 

 aspect of the cliffs is relieved by regular horizontal layers of white 

 quartz 6 inches in thickness, intercalated or stratified along with the 

 limestone at distances of from 6 to 8 feet apart, giving the cliffs the 

 appearance of the side walls of a noble cathedral of Nature's own 

 building. Throughout the whole deposit, wherever you get a good 

 section of a cliff, these layers of quartz appear always conformable 

 to the limestone and dipping with it at the same angle. The layei's 

 are sometimes only 2 feet apart, giving the appearance of regular tiers 

 of masonry to a large portion of the deposit. The thickest of these 

 interstratified layers of quartz is within a few yards of the road. at 

 the ground- officer's house, Sandgoe Bay ; it is from 3 to 5 feet in 

 thickness, very compact, and of a milky whiteness, and may some 

 day prove valuable for economic purposes. StiU proceeding eastward 

 the limestone reappears in Island Hoan, at the mouth of Loch Erri- 

 boll, and in Island Chonie, near the south or upper end of the loch. 

 On the mainland it is visible at the head of the loch in the face of 

 the magnificent cliff called Craig na fielin, some 600 feet high, in the 



