﻿Vol. 66.~] FOLDS IN THE SCHISTS OP THE SCOTTISH HIGHLANDS. 595 



Perhaps the most picturesque feature in connexion with this 

 wonderful Ballachulish Core is the glimpse that we get of it through 

 what, to borrow the illuminating Swiss expression, we may call 

 the Windows of Etive (fig. 1 & PL XLII). Here, and in fact 

 everywhere between Ballachulish and Allt Coire an Easain, the core* 

 is underlain by the Ballachulish Slide, which cuts out a great thick- 

 ness of Leven Schists. This observation gives a minimum displace- 

 ment of 14 miles for the Ballachulish Slide. How much greater the 

 total displacement may be must remain a matter of conjecture for 

 the present, and perhaps for all time : the proved displacement of 

 the Moine thrust of the JSTorth-West Highlands is, it will be 

 remembered, only 10 miles, but this is probably not more than a 

 small fraction of the whole. 



A third core, the Aonach Beag Core, crops out on the east of 

 Ben Nevis (fig. 1). It occupies a structural position intermediate 

 between that of the Appin and Ballachulish Cores, and is of quite 

 minor importance, including in its gape the Ballachulish Limestone, 

 alone of all the groups from 1-6. 



II. Stratigraphy. 



(1) The Cuil Bay Slates are preserved only in the heart of 

 the Appin Core. Their outcrop is surrounded by an intermediate 

 zone, characterized by intercalations of black and grey pelitic sedi- 

 ment, through which they merge into the Appin Phyllites. This 

 is the only character as yet known which distinguishes the Cuil Bay 

 Slates from the Ballachulish Slates (5) to be described presently. 



Although the Cuil Bay Slates are not themselves met with in 

 the Ballachulish Core, the marginal zone just described has been 

 recognized in this position to the south-east of Fraochaidh, near 

 Glen Creran. 



(2 & 3) The Appin Phyllites and Appin Limestones 

 are best considered together, as, in places at any rate, there appear 

 to be two beds of Appin Limestone, one occurring at the margin of 

 the pebbly Appin Quartzite (4), and the other at some little distance 

 from this margin intercalated in the phyllitic series. 



The name Appin Phyllites is used, for want of a better, to 

 connote a group consisting of grey pelitic sediments, among which 

 are intercalated, in many outcrops, numerous bands of flaggy fine- 

 grained quartzite. 



In the Appin Core the group is well exposed on the Onich shore,, 

 where the quartzite intercalations appear to be restricted to that 

 portion which intervenes between the two beds of Appin Limestone 

 already mentioned. The rest of the group at Onich consists of 

 massive grey mica-slates. In the Cuil Bay district on the south 

 the grey pelitic rocks are rather more sandy than on the Onich 

 shore. Abundant quartzite intercalations are again met with as the 

 Appin Limestone is approached, but the existence of two separate 

 beds of the latter has not as yet been proved anywhere between 

 Cuil Bay and Appin. Xear the south-eastern margin of the core,. 



