444 THE SCHISTS OF THE SCHICHALLION DISTRICT, [vol. lxxix, 



were merely lenticles occurring sporadically in a variable band of 

 arkoses, greywacke, and dolomitic sandstone. They could not 

 therefore be till, but should be attributed to floating ice, the 

 bouldeiy patches indicating the spots where the floes unloaded. 



On the mainland, in the Tayvallich peninsula, occurred the 

 isolated Loch-na-Cille Conglomerate ; and he had inferred from 

 the Geological Survey memoir that that also was probably a 

 lenticle in a similar band covering most of the peninsula and the 

 eastern side of Loch Sween. On examining the Survey slides, he 

 found that the ' quartzite ' of this area was arkose. The Survey 

 maps did not separate these felspathic rocks from pure quartzite. 



The Schichallion conglomerate not only contained nordmarkite- 

 and quartzite-boulders similar to those of Islay, but the structure 

 and matrix appeared to be identical. The three specimens of the 

 latter now exhibited seemed to have been originally arkose, 

 greywacke, and dolomite-sandstone. He enquired whether the 

 calcareous boulders might not once have been dolomite, as in the 

 south-west. He was suspicious of the Schichallion Quartzite, in 

 which the conglomerate seemed to be wrapped, and would like to 

 know the average percentage of felspar in it. If it were really 

 the arkose-band of Islay and Tayvallich, he would expect about 

 85 per cent, of quartz, at least in the coarser parts. In that case, 

 the southern edge of the band was in contact with the Killiekrankie 

 Schists, which could be traced round its western termination (as 

 one would infer from the map) into the banded series ; and schists 

 often ran into banded series. 



The Secretary read the following communication from Mr. 

 E. B. Bailey : — 



' This paper will be recognized as one of the most important contributions 

 yet made to an understanding of the Central Highlands. The Author 

 acknowledges help from Grant Wilson's original treatment of the district, 

 and adopts from it the commonly accepted view that the Struan Flags are 

 something apart from the Perthshire Dalradian sequence. In this respect 

 the Author does not follow the lead given by Mr. Barrow ; but he seems to 

 me to have confirmed beyond doubt that writer's claim regarding the strati- 

 graphical position of the Perthshire Quartzite in relation to its Dalradian 

 associates. With a partial knowledge of Schichallion, and a considerable 

 acquaintance with the cognate districts of Islay, Loch Tummel, and Blair 

 Athol, I have no hesitation in accepting every detail of the Author's strati- 

 graphical succession. It is noteworthy that he, like myself, lias been led to 

 invert the traditional time-sequence of the Perthshire Dalradian ; although, 

 I admit, the Schichallion evidence in this direction does not seem to me 

 convincing. As regards the discordances, which the Author very properly 

 emphasizes, they are not only convincing, but arresting. They do not, in 

 Schichallion, present themselves in obvious relationship to folds ; and the 

 Author is justified in adopting a cautious attitude in their interpretation. 

 Still, it is a remarkable fact that the plane of discordance separating the 

 Schichallion Complex from the Struan Flags corresponds precisely with what 

 I have called, in the West, the basal thrust-plane of the lltay 

 Nappe.' 



The Author, in answer to Dr. Flett, stated that he thought 

 that the correlation between the Schichallion series and that 



