488 



THE GEOLOGIST. 



the quartz-rocks and limestones of Durness and Assynt. The author mentioned 

 also that Professor Harkness, having subsequently traversed the ground, had 

 supplied him with sections and notes confirming the accuracy of his views, and 

 especially illustrative of that phenomenon to which Sii' Roderick had attributed 

 the greatest importance, namely, the broad distinction between the fundamental 

 gneiss and the^ micaceous schists and flagstones superposed on the Silurian 

 quartz-rocks and limestones. 



Referring to the gneiss of Cape Wrath as the fundamental rock of the dis- 

 trict, and as the equivalent of the " Laurentian rocks" of Canada, Sir Roderick 

 pomted out its massiveness, its granite-veins, its liigh degree of metamorphism, 

 and the westerly dip of its laminae, as characters distinguishing it from the 

 micaceous flagstone and chloritic schists which have been termed the " younger 

 gneiss," which has a general easterly dip, and which, when near intrusive rocks, 

 take on a gneissose structure, especially to the east. A few more details were 

 given of the red sandstones and conglomerates of Cambrian age lying uncon- 

 formably on gneiss. The Silurian quartz-rocks and limestone were then de- 

 scribed as seen in their successive and conformable strata in three clear and 

 important sections, showing how completely the chief limestones lie between a 

 lower and an upper quartz-rock ; and how all this series is followed by another 

 limestone, which in its turn is conformably overlaid by micaceous flagstones. 

 The first of these sections is to be traversed along a line from the post-ofiice of 

 Assynt, on the west, across the ridges of limestone of Inchnadamff to the 

 quartzose hills of Cnocaudrien, Ben Uran, and Ben More, to Kinloch and Loch 

 Ailsh. Some greenstones are interbedded at Inchnadamff and at Loch Ailsh, 

 and some porphyry intrudes at Cnocaudrien, but the conformable sequence of 

 the strata is not thereby at all interfered with. 



The next section is on the south bank of Loch More. Here the lower 

 quartz-rock lies unconformably on the bottom gneiss, the Cambrian rocks being 

 absent, and a gradual passage from the upper quartz-rock into the micaceous 

 flags of Ben Neath and Kinloch was clearly seen. A third, and, if anything, a 

 still better section was foUowed from Benspiomiach, on the west, across Loch 

 EriboU to Meolbadvartie and Ben Hope. Above Eriboll a specimen of Ortho- 

 ceras Bronrpiiartii has been found in the quartz-rock overlying the lower lime- 

 stone. The upper limestone is here overlaid by a clear succession of quartzose 

 beds and micaceous flagstones, which pass upwards into mica-schists of Meol- 

 badvartie, in which is interbedded a thin band of felstone, without any disturbance. 

 This condition of the strata extends along the strike for twenty or thirty miles 

 at least. At Whiten Head, the northern prolongation of the quartz-rock of 

 Eriboll, the limestone has died out, and the two quartzose bands have united 

 into one great series. The author observed no reversal in the dip of the over- 

 lying micaceous beds at any point along the northern coast ; and he was 

 strengthened in his conviction that these flaggy strata, altered here and there 

 by plutomc influences, are really an overlying series, younger in age than the 

 lower Silurian quartz-rocks and limestones of Durness and Assynt. Sir 

 Roderick further repeated his belief that probably the crystalline rocks of the 

 Highlands will be mainly found to fall into the same category, and will in time 

 be paralleled with Siluiian rocks of the south of Scotland. Lastly, he ob- 

 served that, with local exceptions, he believed that these flagstones and mica- 

 schists were unaffected by mechanical cleavage. 



Geologists' Association.— The meetings of this Society were resumed on 

 October 3rd, when the first part of a Memoir on the EchinidEe of the Chalk, 

 by E. Cresy, Esq., was read. At the second meeting, on the 7th ult., the 

 reading of this paper was concluded. 



