898 Geological Society : — 



The southerly bend of the pre-Glacial valley near Cefn to Chirk, 

 and then towards Whittington, suggests the possibility of a con- 

 fluence of the Severn and the Dee, and this is shortly discussed, 



It is shown that formerly the River Ceiriog joined the pre-Glacial 

 Dee at Chirk, and that its present course below Chirk is post- 

 Glacial. The gravels of this valley suggest that the post-Glacial 

 drainage always followed this course. It is shown, however, that 

 the Morlas Brook, which is now a tributary of the Ceiriog, was not 

 always so, its early post-Glacial course having been to the Severn. 



The slope of the pre-Glacial valley-floor and the uplift which is 

 indicated by the buried valley, now many feet below sea-level, are 

 briefly discussed. 



2. ' The Glen Orchy Anticline (Argyllshire).' By Edward 

 Battersby Bailey, B.A., F.G.S., and Murray Macgregor, M.A., B.Sc. 



The district described stretches from the head of Loch Awe to 

 Beinn Achallader, and is the south-eastern continuation of the 

 Fort William, Ballachulish, and Appin counfay dealt with by one 

 of the authors two years ago. The subject is the tectonics of the 

 schists. 



In the centre of the district a diagrammatic recumbent fold, of 

 at least 2 miles in magnitude, is exposed to view in Beinn Udlaidh, in 

 the heart of a gentle anticline, to which the name of the Glen 

 Orchy Anticline is fittingly assigned. Around the western, 

 southern, and eastern rim of this anticline, are found rocks which 

 lie upon a structurally higher level than the Beinn Ildlaidh Fold. 

 A limestone, which occurs among these rocks, is correlated with 

 the Ballachulish Limestone, and is believed to mark the core of the 

 great, recumbent, Ballachulish Fold, everywhere, in this district, 

 underlain by the Ballachulish Slide (fold-fault). Incidentally, 

 this interpretation involves a displacement of at least 24 miles 

 alons the Ballachulish Slide. Finally, an important inversion of 

 the Ballachulish Limestone and Slide is discussed in connexion 

 with a description of the Beinn Doirean and Beinn Achallader 

 range of mountains on the east side of the Glen Orchy Anticline. 



March 13th, 1912.— Dr. Aubrey Strahan, F.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. ' On the Glacial Origin of the Clay-with-Flints of Bucking- 

 hamshire, and on a Former Course of the Thames.' By Robert 

 Lionel Sherlock, D.Sc, A.R.C.S., F.G.S., and Arthur Henry Noble, 

 B.A., F.G.S. 



The paper is founded on observations made during the mapping 

 of some 260 square miles on the 6-inch scale, in Buckinghamshire, 

 Berkshire, Hertfordshire, and Middlesex. 



The superficial deposits are divided into Clay-with-Flints with the 

 associated Gravelly Drift, and the Fluvioglacial Gravels. There are, 

 in addition, certain high-level gravels, older than any of these, and 

 also the river-gravels and alluvium of the present streams, none of 

 which deposits are dealt with in the paper. 



