370 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [DeC. 1, 



the E.S.E. from the marine bay called the Kyles of Strome, over the 

 moimtains ranging into the interior*. 



In Durness, beds of pure and very impure, highly cherty, and 

 cavernous limestone alternate with altered schists and finely granu- 

 lated and laminated hard siliceous sandstone of divers colours, both 

 red and grey, as exposed in ledges upon the shore near Balnakiel. 

 These hard and tough rocks are interlaced with geodes marking the 

 lines of stratification, as well as by thin courses of flinty chert. The 

 concretionary structure is well exhibited at Craig Sarsgrun, about 

 three miles south of the Durin Innf, where the concretions vary in 

 size from an inch to several feet in length. The concretions are 

 often white, sometimes pink, and therefore present a striking contrast 

 to the dark-grey escarpment. Many of these beds are almost quartz- 

 rock ; but as they contain some calcareous matter, the natives usually 

 call them all " limestones." 



The geologist can easily detect the calcareous portions by the 

 weathering of the escarpment, which presents partially eroded lines 

 along the course of the small concretions. These rocks are all more 

 or less affected by a slaty cleavage, which, being highly inclined, 

 disposes the rock to jut out in sharp protruding bosses through the 

 green sward by which the calcareous band is characterized. 



Although the ascending order of the quartz-rocks and limestones 

 is everywhere the same as in Assynt, i.e. a strong band of limestone 

 interposed between masses of regularly stratified quartz-rock, the 

 subjacent Cambrian conglomerate disappears in Durness, and the 

 lower quartz-rock rests at once upon the old and fundamental gneiss. 

 This is seen on the west shore of the Kyle of Durness, and also near 

 Bispond upon the coast, in the escarpments of Ben Spionno in 

 Durness, and at other places in the interior to the S.S.W., i. e. Ben 

 Stack, &c. The western face of Ben Spionno is indeed entirely 

 composed of the lower quartz, which, sloping down to the east by 

 south to Loch Eribol, is there seen to dip under the limestone of the 

 Chorrie Island and to form fine calcareous terraces along the eastern 

 side of the loch. These limestone-bands are in their turn overlaid 

 by other quartz-rocks. (See fig. 3, p. 364.) 



During my last visit to the North-west in company with Mr. 

 Peach, I confirmed what is stated in the previous sentences. Thus, 

 proceeding from the district of the Parph, or from Cape Wrath on 

 the W.N.W. to Durness on the E.S.E. , the succession exposed in the 

 accompanying section is admirably seen. The older gneiss and Cam- 

 brian sandstone (a and h) have been already spoken of; and OL the 



* Previous to my last visit, Colonel James had re-assured me that the lime- 

 stone extending from Assynt to the N.N.W., by Glendhu, Mealhom, Loch Dionart, 

 and Camvel, to the eastern shore of Loch Eribol, occupies everywhere the same 

 position I had assigned to it as subordinate to the white quartzose beds. The 

 best section which he examined, in reference to this part of the succession, was 

 along the course of the Lone River, which falls into Loch Stack ; and there an 

 overlying as well as an underlying quartz-rock is clearly exposed. 



t The Inn of Durin, kept by Mrs. Ross, is strongly recommended to explorers, 

 as also the Inns at Loch Inver, Inchnadampf, and Scourie. 



