1859.] MURCHISON NOETH HIGHLANDS. 219 



Inn, or between Rhiconich and Durness. There, these bottom-beds, 

 in the form of pebbly red conglomerate, quite identical with that on 

 the summit of Cape Wrath*, are well exposed in nearly horizontal 

 beds on the banks of the rivulet which descends from the high 

 plateau two miles south of the Gwalin, and again to the north of 

 that inn on the sides of the high road. Here, as at Cape Wrath and 

 elsewhere, all the pebbles consist of the fundamental gneiss or of 

 the associated red granite. 



In their simple uniform composition, these very ancient sandstones 

 and red conglomerates differ essentially from the much younger 

 Old Red Sandstone which is exposed on the East Coast, where the 

 pebbles and ingredients change, as before shown, with those older 

 rocks respectively on which they repose, and out of the materials of 

 which they are composed. 



These Cambrian rocks, which are so nobly exposed in mountain- 

 masses along the West Coast, are confined (the reader will recollect) 

 to that Western meridian, and nowhere advance more than a few 

 miles eastward into the interior of the mainland ; but, as they occur 

 as coarse conglomerates on the eastern shore of the Island of Lewis 

 (where they also rest on a vast breadth of the fundamental gneiss), 

 they must certainly at one period have been much more extensively 

 distributed. The district, on the mainland, where these Cambrian 

 strata can be most easily studied is in the mountain of Queenaig in 

 Assynt, particularly along the fine escarpment between its summit 

 and the Kyle of Strom, where they repose in striking unconforma- 

 bility upon the old gneiss, and are covered, also unconfonnably, by 

 the quartz-rocks of Lower Silurian age. 



The phenomenon relating to these Cambrian sandstones which 

 may well strike the geologist as he passes over the summits of 

 Suilven and Queenaig, is that these very ancient rocks, on which 

 unquestionably the Lower Silurian rocks repose, should be simply 

 sandstones and grits which have undergone much less change than 

 the sandstone which lies upon them, — the latter having been metamor- 

 phosed into quartz-rock. However difficult it may be to account for 

 this fact, it is at all events most instructive as regards tin origin and 

 Succession of lift in lh, crust of the earth, and sustains my view of a 

 beginning. For here (and 1 have applied the same argument before 

 to the Cambrian sandstones of the Longmynd, which certainly un- 

 derlie the qnartz-rock of the Stiper Stones t) the older of the two rocks 



in Scotland lias offered no trace of fossils, whilst the more crystallized 

 structure above exhibits unmistakeable signs of former living things. 

 Silurian Quartz-rocks and Limestones. — The excursion of last 

 summer reassured me that I had not erred in stating that the greai 

 band of limestone of Assynt. I tunics-. &C, was fairly intercalated in 



qnartz-rock, both inferior and superior ; that, besides the chief hand. 



there was another and superior limestone overlying the Upper quartz- 

 rock ; and further, that all these were conformably superposed hy 



* See former description of these pebble-beds, Quart. Joum. ffcol. s««r 

 roL xv i' 362 

 t s,,- ■ Silurian System,' p 284, and Siloria, 2nd edit p. 39 



