Vol. 6g.~] LOCH AWE SYXCLINE (ARGYLLSHIRE). 289 



outcrops of limestone ; both outcrops are pebbly and occasionally 

 conglomeratic, with large grains of quartz and felspar and fragments 

 of dark-grey pure limestone. A conglomeratic band east of the 

 stream, east of Stronesker, contains abundant fragments of 

 slaggy and compact epidiorite. 



It may be asked how the presence of epidiorite-fragments in the 

 conglomeratic beds of the district had not been recognized long ago. 

 The answer is that they had been missed at first, when there was 

 so much that was new to grapple with ; but, in 1900, just at the close 

 of his work, Mr. Hill did begin to realize their existence in certain 

 cases. By this time, however, he had come to regard the intrusive 

 nature of the epidiorites of the district as certain, and consequently 

 interpreted any conglomeratic bed in which he recognized an epi- 

 diorite-fragment as a ' crush-conglomerate.' His views are expressed 

 in a paper published in 1901 by this Society [10]. During my 

 traverse in 1906, 1 did not visit any of the localities which Mr. Hill 

 had described ; but, in 1908, I had the opportunity of carefully 

 examining the main example at Creag nam Fitheach, a mile 

 south of the head of Loch Craignish. The breccia in this case 

 consists of irregular blocks of the vesicular type of epidiorite, set in 

 a scanty matrix of gritty limestone [17, pi. vi]. On so controversial 

 a subject it must be admitted that there is room for two opinions, 

 and Mr. Hill's interpretation is supported by the fact that it was 

 adopted and applied to similar examples in the neighbourhood by 

 Dr. Peach, Mr. Grant Wilson, and Mr. Maufe. At the same time, 

 it seemed well-nigh incredible to me, when I saw the Creag-nam- 

 Pitheach exposure, that such a breccia, in which individual clastic 

 grains of quartz and felspar frequently interpose themselves between 

 adjacent blocks of epidiorite, could have originated as a crush- 

 conglomerate. Moreover, before my visit, Dr. Peach had repeatedly 

 told me in conversation that, especially since his recognition of the 

 Tayvallich volcanic group, he had grave doubts concerning the 

 'crush-conglomerates' of the northern part of the district, although 

 he had for a time admitted their existence, 



IV. The Stratigraphy. 



In his 1899 paper, published by this Society, and in his subsequent 

 writings for the Geological Survey, Mr. Hill put forward the 

 following interpretation of the Loch Awe sequence : — 

 Grits and quartzites, 

 Black slate (locally green), 

 Limestone. 

 This he regarded as a descending sequence, modified by local 

 passage of one type of sediment into another. His meaning is best 

 expressed in his own words : — 



' Although occupying a general position between the Ardrishaig slates on the 

 one hand and the black slates on the other, the limestone does not rigidly 

 adhere to that horizon, but may occur both within and above the black slate, 



