244 



C. CALLAWAY ON THE LIMESTONE 



There is another difficulty in the reception of the old view. 

 According to Murchison, the limestone is conformably overlain by 

 the great mass of quartz-rock which rises into the lofty peaks of 

 Ben More. If so, then the limestone basin of Stronchrubie must 

 have been covered by an equal thickness of quartzite. It is for the 

 followers of Murchison to show how denudation could have cleared 

 off the entire mass of such an intractable rock as quartzite from the 

 limestone, and yet have made so little impression upon the mountain- 

 ridges which overhang. 



The quartzite which slopes down from the south-eastern face of 

 Queenaig passes up through a continuous quartzite ridge into Ben 

 More. It is not pretended that the limestone occurs in this line of 

 section ; but it is very singular that it should have thinned out 

 just where its presence would have been of decisive value. 



One important and suggestive fact remains. At both Durness and 

 Assynt the limestone forms a symmetrical basin, the axis of which 

 does not agree with the normal strike of the rocks which are sup- 

 posed to overlie, but which coincides with the axis of the existing 

 valley in which it lies. In Assynt the axes strike to the south-east, 

 at Durness to the south-south- west. 



I do not at present press these conclusions beyond the districts 

 observed, but submit them as an instalment towards the solution of 

 a great question. 



Discussion. 



The President said he had twice visited the area, and felt diffi- 

 culties in tracing the succession of the rocks, especially as to the 

 asserted recurrence of the quartzites. The fossils proved the lime- 

 stone to be of about Arenig age ; certainly the limestones seemed 

 to lie in a synclinal basin on the quartzites. 



Prof. Jttdd said that, after several visits to the district, he felt 

 great difficulty in offering an opinion as to the succession of beds ; 

 he thought the simple sections commonly drawn to illustrate the 

 geology of the country did not hold good. He considered that 

 Prof. Mcol had made good his position as to there being only one 

 quartzite and one limestone ; but as to the relation of these to the 

 gneiss, there was great difficulty in arriving at a satisfactory con- 

 clusion. 



Dr. Hicks agreed that the limestone series sometimes lay in 

 synclinal folds of the quartzite ; but he thought there might be two 

 quartzites, as in a case he had recently noticed in another region 

 along the same line further south. He was thoroughly satisfied that 

 the series was newer than, and did not underlie, the eastern gneiss. 



Mr. Hudleston observed that Dr. Callaway's mapping of the 

 Durness area coincided with Sir K. Murchison's section as to the 

 limestone being troughed, and also as to the reversed position of 

 the two gneisses. Further south the quartzites and limestones ap- 

 peared to be intercalated, as at Loch Emboli, where Orihoceras had 



