﻿Yol. 66.] SCHISTS OF THJE SCOTTISH HIGHLANDS. 605 



between the two synclines is about half a mile, measured across 

 the strike. In the second syncline, as in the first, a folded lime- 

 stone (calc-silicate hornfels) is encountered, with Leven Schists 

 above and below ; in this case, however, the limestone itself is in 

 two layers, separated by a parting of hornfelsed black slates. The 

 section of the syncline on the hillside reads as follows : — 



Thick Leven Schists in the heart of the syncline. 

 Upper layer of calc-silicate hornfels. — 100 feet. 

 Black slate hornfels.— 100 feet. 

 Lower layer of calc-silicate hornfels. — 100 feet. 



Basement of thick Leven Schists, in contact at both sides with Glen Coe 

 Quartzite. 



The black slates in the middle of this section are undoubtedly 

 part of the black Ballachulish Slates (5), since their outcrop has 

 been followed continuously from Stob Ban — save for the unimportant 

 interruptions of the Mullach nan Coirean Granite and the waters of 

 Loch Leven — to Ballachulish itself. Here, then, there can be no 

 question but that a folded core of Ballachulish Slates, separated by 

 Ballachulish Limestone from Leven Schists above and below, has 

 been bent into a sharp secondary syncline. 



It is with a feeling of rare exaltation that the geologist, after 

 satisfying himself of the reality of this syncline, into which the 

 Ballachulish Core is thrown, climbs back to the summit of the 

 ridge and, map in hand, sits down to consider the consequences. 

 This syncline, in fact, gives an insight at once into the synclinal 

 ■disposition of the Ballachulish Core through all the district lying 

 to the south. Its continuation can be recognized with certainty on 

 the map south-west of the outcrop of the Mullach nan Coirean 

 Granite (PI. XLII). Beyond this it is joined by two other similar 

 synclines on the slopes of Mam na Gualainn, and then crossing 

 Loch Leven (fig. 1, p. 594) it expands into a great basin-shaped 

 structure, measuring no less than 14 miles across. 1 The heart 

 of this basin is occupied by Leven Schists; but the map shows 

 how the Ballachulish Limestone appears from beneath this 

 covering in the Windows of Etive (PL XLIV, Sections G & H), 

 and how, too, the Leven Schists were themselves originally over- 

 lain by a great return fold of Glen Coe Quartzite, the remnants of 

 which now cap the southern hills (PL XLIV, Section H). Through- 

 out all this wide extent of country the Ballachulish Core persists : 

 its gape crops out between Ballachulish and Loch Creran, while 

 its taper end, not yet closed, is seen far away to the east in 

 AUt Coire an Easain (PL XLII). 



The Ballachulish Slide. — Once attention is given to details, 

 it is found that sliding has played an essential part in the develop- 

 ment of this wonderfully extensive and attenuated fold-core ; several 



1 These 14 miles include the downthrown portion of the basin within 

 the cauldron subsidence of Glen Coe. The latter is a great oval subsidence, 

 which has been so recently described [30] that its existence is taken for 

 granted in the following pages. 



2t2 



