Vol. 68.] THE GLEX ORCHT ANTICLIIfE. 171 



known in the Leven Schists of the type district, but are not often 

 really conspicuous, except in the outcrop which passes immec) lately 

 west of the Kinloehleven Eeservoir. Apart from this difference, 

 depending upon metamorphism, the mica-schists of Beinn Udlaidh 

 resemble the Leven Schists of Loch Leven and Glen Nevis very 

 closely ; and, as the rest of the sequence is so clearly comparable, 

 we have no hesitation in regard to their correlation with this 

 group. 



The tectonics of Beinn Udlaidh are extremely simple and 

 •diagrammatic. The Leven Schists and Glen Coe Quartzite have 

 been folded into the heart of the Eilde Plags in the form of a 

 recumbent anticline^ closing towards the north-west. The minimum 

 magnitude of this Beinn Udlaidh fold is 2 miles. Owing to a 

 variety of favourable circumstances — including the nature of the 

 topography, the abundance of exposures, the marked lithological 

 contrasts, the absence of slides, and also of any serious complication 

 due to later movements, — the Beinn Udlaidh fold is clearer and more 

 readily understood than any yet described in the Scottish High- 

 lands; in fact, it can take its place alongside of the best examples 

 of small-scale recumbent folds afforded by the Alps. 



Localities showing the close of the fold are, of course, of critical 

 importance. They are two in number : one of them is the steep 

 western slope of Beinn Bhreac Liath ^ lying between Sections A 

 & B (figs. 2 & 3, pp. 168 & 169). Exposures are not continuous in 

 the most important part, but they are fully sufficient, for at short 

 intervals the hill is washed bare by lateral streams ; at the south- 

 eastern end of the slope the escarpments of the various bands give 

 rise to conspicuous crags. Half-way up the hill-face a thick mass of 

 gently-inclined mica-schist forms a very definite belt, with quartzite 

 and flags both above and below ; in a north-westerly direction this 

 belt of mica-schist thins out, allowing the upper and lower bands 

 of quartzite to come together : finally, the quartzite disappears, and 

 the flags are left continuous. 



The other locality for showing the close of the fold is situated at 

 the bottom of Glen Orchy (Sections F, G, & H, p. 169). Nothing 

 could be much clearer, once the mapping has been completed, than 

 the manner in which the band of Glen Coe Quartzite, underlying 

 the Leven Schists, sweeps across the River Orchy to meet the 

 band which overlies the same. A little west of the crucial point 

 the overlying band is displaced by a small normal fault; but, fortu- 

 na^ly, this accident does not in the least afl"ect the matter at issue. 

 Exposures, although not continuous, are quite adequate, and can be 

 reached at once from the road and from a bridge which crosses the 

 River Orchy in the most convenient position imaginable. 



As appears from the map and sections (figs. 2 & 3, pp. 168 & 169), 



^ Anticline is here used in the sense of anticline of observation 

 [l,.p. 600]; there is no implication that the Leven Schists and Glen Ooe 

 Quartzite are older than the Eilde Flags. 



- Pronounced approximately BenVrecLeea. 



a. J. G. S. No. 270. 



