EOCKS OF THE NORTHERN HIGHLANDS. 389 



The section just described appears at first sight to be the normal 

 Assynt succession, with the limestone metamorphosed. It is the 

 most serious difficulty I have encountered ; but I have represented 

 the facts without extenuation. I may observe that the occurrence 

 of the flags in their regular position is strongly confirmatory of my 

 views on the " Upper " Quartzite ; but that is a minor point. If the 

 succession here is unbroken, I must admit that the Eastern Gneiss is 

 newer than the Assynt Series. But there is the strongest reason for 

 placing a fault between the flags and the limestone. For, as we have 

 seen, if we follow the limestone to the S.W., we find it in one place 

 immediately underlain by Hebridean, and in another underlain by 

 and intercalated with the Caledonian. Unless, then, we admit that 

 the quartzite and flags pass into Hebridean, and then into the thin- 

 bedded gneiss, we must concede the existence of a fault. 



To summarize the facts described, we have the following reasons 

 for separating the Loch Ailsh limestone from the dolomite of the 

 Assynt series : — 



(1) The former is metamorphosed; the latter is not. 



(2) The former is largely composed of calcium carbonate; the latter 



is everywhere a dolomite. 



(3) There are nowhere any signs of a passage between the two. 



(4) The former is intercalated with quartzite, and sometimes with 



gneiss ; the latter is dolomite from top to bottom. 



(5) There is strong evidence of a fault between the former and 



the lower members of the Assynt series. 



E. The Caledonian brought over the Assynt Series by a Reversed 



Fault. 



Our previous discussions having cleared up some preliminary 

 difficulties, we are now prepared to investigate the main question, 

 Does the Eastern Gneiss conformably succeed the Assynt Series ? 



The Knochan Section. — By Sir E. I. Murchison and Dr. Geikie the 

 newer gneiss of this locality is said to conformably overlie the 

 Dolomite ; but Nicol places a fault between the two. The rocks 

 are clearly exposed in the escarpment overhanging the high road ; 

 and some of the phenomena appear to support the Murchisonian 

 view. Doubt, however, is thrown upon this interpretation by the 

 fact that, a short distance east of the section of Murchison and 

 Geikie, the strike of the Dolomite suddenly twists round through 

 a right angle, while the strike of the gneiss remains unaltered. 

 This seems to be inexplicable, except on the hypothesis that 

 the Dolomite had undergone considerable dislocation before the 

 gneiss was brought over it. 



But a more serious difiiculty remains. Within about a mile of 

 where the newer gneiss rests upon the Dolomite, lies the Camaloch 

 mass of Hebridean. This massive gneiss occupies a considerable 

 breadth of country, and can hardly be less than several hundred 

 feet thick. As its place is, ex hypothesis between the Dolomite 

 and the Caledonian, it follows that this great mass of rock, together 



Q.J.G.S. No. 155. 2f 



