626 MESSES. CXOTTGH, MATTEE, AND BAILET. ON [-^ ov - i 9°9j 



In Coire Mhorair, farther east again, the lavas are steeply 

 overturned, for their junction with the Schists, marked by basal 

 sediments, sweeps out distinctly farther northwards in the valley- 

 floor than on the two flanking ridges. The fault lies a little to the 

 north of the base-line of the volcanic group in this corrie, and its 

 position is well defined, as the subsequent detailed descriptions 

 will show (fig. 9, p. 654). 



In Coire Odhar-mh6r, dips measured in the basal beds of the 

 volcanic series, and in shaly intercalations at higher levels, range 

 from 40° to 80° away from the fault, the position of which is again 

 well marked (fig. 9). 



Prom Sron a' Choire Odhar-bhig to Sron na Creise the volcanic 

 rocks are steeply upturned, at angles averaging 50°. Along this 

 part of its course the base of the group is generally about three- 

 quarters of a mile distant from the fault, although roughly parallel 

 to it. 



In the Cam Ghleann the lavas and breccias of the volcanic 

 group are undisturbed ; but on the slopes of Meall a' Bhuiridh they 

 are suddenly upturned in the immediate vicinity of certain quartz- 

 veins which here mark the position of the fault. 



Yet, while it is true that the great mass of the Old Eed volcanic 

 and sedimentary rocks of Glen Coe occupy a compact area, 

 included within the great boundary-fault, there are a few small 

 outlying patches which cannot be ignored : — 



(1) An isolated outcrop of quartzite breccia north-west of Stob Mhic 



Mhartuin (fig. 7, p. 649). 



(2) A small outcrop of rubbly breccia, consisting mostly of fragments of 



quartzite, with a few bits of igneous rocks, on the western flank of Sron 



a' Choire Odhar-bhig, exposed near the foot of the ridge and between 



two branches of the boundary-fault (fig. 9, p. 654). 

 (3 & 4) Breccias on the slope of Sgor nam Fiannaidh and at the head of 



Gleann Charnan, already described, p. 621. 

 (5) Several isolated patches of breccia and rhyolite between the two branches 



of the fault on Beinn Ceitlein. 



In the first two instances cited above it is exceedingly difficult to 

 understand the relation of the breccias to the topography buried 

 beneath the volcanic rocks, unless it be admitted that the deposits 

 represent material which has fallen down an earthquake-fissure or 

 into some other hollow of equally special character (cf. p. 622). 



There is no difficulty, however, in regarding the other patches 

 as outliers occupying inequalities in the pre-volcanic surface of 

 erosion. It is probable enough that, originally, the volcanic rocks 

 of Glen Coe spread out for a considerable distance beyond their 

 present limit, and they may even have been continuous with the 

 lava fields of Lome. 



(2) Distribution of the Highland Schists in relation 

 to the faulting. — It is beyond the scope of this paper to discuss 

 the tectonics of the Highland Schists of the district, but a glance at 



