Yol. 68.] THE GLEN OECHT ANTICLINE. 167 



suspected, but not proved. It was found, too (as was, in fact,^ 

 already known at the time), that a band of rock mapped as 

 epidiorite by Grant Wilson around the flanks of the Beinn Doirean 

 range (Sheet 46) was in reality a tremolite-schist representing an 

 impure limestone, frequently accompanied, it is true, by definite sills 

 of epidiorite. The Allt Coire an Easain section was mapped, and a 

 metamorphic limestone was found in it. This and the Beinn Doirean 

 limestone were both taken to be on the same horizon as another 

 better -known limestone already mapped by Messrs. Kynaston, 

 Maufe, and Clough in the region of the Windows of Etive. During 

 the same traverse the Loch Dochard limestone was visited and its 

 true nature recognized by Mr. Clough, who, in Mr. Kynastou's 

 absence, modified the account given of it in the Memoir descriptive 

 of Sheet 45, then passing through the press. Another conclusion 

 arrived at as a result of this traverse was the correlation of 

 the mica-schist mapped by Grant Wilson in Beinn Doirean with 

 that occurring in the Beinn Udlaidh, Loch Dochard, Allt CoirQ an 

 Easain, and Etive sections. This correlation has subsequently 

 been maintained, although in 1910 it was pointed out that the 

 Loch Dochard mica-schist is probably on a much lower structural 

 level than that of Allt Coire an Easain and of the region around 

 the Windows of Etive [1, p. 616]. 



The results outlined above were all obtained by members of the 

 Geological Survey Staff employed in their official capacity. Our 

 field-work last year was carried on in holiday-time. As will be 

 seen presently, it has confirmed the suggestion just mentioned 

 in regard to the relative structural positions of the mica-schists 

 of Loch Dochard and Allt Coire an Easain, and has shown, what 

 was totally unexpected even in 1910, that the mica-schist of 

 Beinn LTdlaidh is similarly situated on a much lower structural 

 level than that of Beinn Doirean. Another unforeseen discovery is 

 the finding of outliers on the summits of the Beinn Doirean range 

 in which the Beinn Doirean limestone and its associated strata 

 occur in inverted sequence, as compared, that is, with the succession 

 prevalent throughout the rest of the district now considered. 



This last result was obtained by Mr. Macgregor, who has re- 

 mapped the Beinn Doirean range. Beinn Udlaidh and the country 

 to the south has been revised by Mr. Bailey. The Loch Dochard 

 Eold, and the sections of Allt Coire an Easain and of the Windows 

 of Etive, have not been re-examined since the publication of the 

 earlier paper already referred to [1]. 



III. Tectonics. 



In describing the geology of the Glen Orchy district there can be 

 no question as to where we should begin. Beinn Udlaidh affords a 

 firm foundation whereon to build. 



(A) The Beinn Udlaidh Fold. 



Three rock-groups enter into the composition of the Beinn 

 Udlaidh Eolcl — a flag group, a quartzite group, and a mica-schist 

 group. 



