Reports & Proceedings — Geological Society of London. 91 



Views of the Nile cliffs show the general nature of the country 

 and conditions. Successive changes of level are indicated by 

 (1) the collapse of immense drainage caverns far below present 

 level; (2) the filling of valleys with debris up to 650 feet above 

 the present sea-level; (3) the gouging-out of fresh drainage-lines 

 through the filling ; and (4) rolled gravels on the top of cliffs 800 feet 

 above sea-level, since when there has been no perceptible denudation 

 by rain. The great extent of these elevations and depressions is 

 likely to be connected .with similar movements at Gibraltar, which 

 are believed to synchronize with the movements of glacial periods in 

 Northern Europe. The evidence of the flint ages agrees with this 

 connexion. 



Lantern-slides were exhibited by Professor W. M. Flinders Petrie 

 in illustration of his lecture. The photographs will be published in 

 Ancient Egypt for April, 1915. 



2. January 6, 1915.— Dr. A. Smith Woodward, F.R.S., President, in 



the Chair. 



The following communications were read : — 



1. "The Silurian Inlier of Usk (Monmouthshire)." By Charles 

 Irving Gardiner, M.A., F.G.S. 



The Usk inlier lies a few miles north of Newport (Mon.). Between 

 the coal-fields of South Wales and the Forest of Dean the Old Red 

 Sandstone is bent into an anticline, the axis of which runs very 

 nearly north and south. This has been denuded away to the west of 

 Usk, and Silurian beds have been exposed, the rocks seen being 

 of Ludlow and Wenlock age. 



In the southern part of the inlier the Silurian rocks are arranged 

 in two anticlinal folds, the axes of which run nearly north and south 

 and dip southwards. These folds are separated by a fault. The 

 western one is named the Coed-y-paen Anticline, the eastern one the 

 Llangibby Anticline. The Old Bed Sandstone is believed to rest 

 unconformably on the Ludlow Beds along much of the margin of the 

 Coed-y-paen Anticline ; and beneath the Ludlow Beds, which are 

 about 1,300 feet thick, come 35 to 40 feet of a Wenlock Limestone, 

 which covers Wenlock Shales ; of these latter some 850 feet are seen. 

 It is impossible to separate the Ludlow Beds into an upper and 

 a lower series, owing to the absence of the Aymestry Limestone. 

 They are composed mainly of sandy shales and sandstones above, and 

 of sandy shales with layers of calcareous nodules or of calcareous 

 bands below. 



Bayia navicula is a common fossil up to 240 feet from the top of the 

 Ludlow Shales, and Holopella gregaria and H. obsoleta occur only in 

 the uppermost beds. 



At their base the Ludlow Beds seem to pass conformably down into 

 the Wenlock Beds, and the Wenlock Limestone is probably not at the 

 summit of the Wenlock Shales. The Wenlock Limestone occurs 

 either in irregular layers separated by sandy shales, or in massive beds 

 largely made up of crinoid fragments. Corals are rare in it. 



