Reports and Proceedings — Geological Bociety of London. 327 



the north and sharply to the south. There is thus formed a true 

 synclinal depression striking westwards, with a low pitch, into the 

 English Channel. The complete disappearance of the fold on crossing 

 the Cuckmere cannot be satisfactorily explained by the normal process 

 of dying out, the distance being too short for so rapid a recovery. It 

 is suggested, therefore, that a transverse fault may exist beneath the 

 alluvium of that river, thus, perhaps, accounting for the narrow gorge 

 at Cuckmere Haven. The top of the zone of Marmcpites testudinarius, 

 which lies in an approximatel)'' horizontal position at about the level 

 of the 300 foot contour on one side of the river, sinks below sea-level 

 in the trough of the fold on the other side. The fault, if it exists, 

 seems to die away rapidly northwards, since no trace of it lias been 

 detected higher up the valley towards Alfriston. This feature would 

 be expected from the nature of the movement. The relation of the 

 Seaford fold to the main flexures of the South Coast is considered, and 

 it is suggested that this fold represents the eastern termination of the 

 structural area known as the Hampshire Basin, being, in fact, 

 a continuation, en ichehn, of the Purbeck-Isle of Wight system. 



Certain existing physiographical features are ascribed to the 

 influence of this flexure, which facilitated the retention of the Eocene 

 cover in the synclinal hollow thus formed. A result of mapping the 

 outcrops, also, has been to prove that the numerous dry valleys in 

 this area are not of the nature of ' sinks' or ' dolinas', but are true 

 valleys of surface-erosion. Attention is drawn to certain features of 

 these valleys. 



A brief comparison is made between the fossils of the inland 

 exposures and those of the cliff-section, the most notable difference 

 being the evidence in the former of a C'oww^ws-band at the top of the 

 zone of Jlicraster cor-anguinum. 



11.— May 26, 1909.— Professor W. J. Sollas, LL.D., Sc.D., E.R.S., 

 President, in the Chair. 



The following communications were read : — 



1. "The Cauldron Subsidence of Glen Coe and the Associated 

 Igneous Phenomena." By Charles Thomas Clough, M.A., F.G.S., 

 Herbert Brantwood Muff, B.A., F.G.S., and Edward Battersby Bailey, 

 B.A., F.G.S.' 



The succession of volcanic rocks in Glen Coe is mainly a series of 

 lava-flows, of which there are three types — augite-andesite, hornblende- 

 andesite, and rhyolite. Agglomerates, tuffs, and sediments form but 

 a small portion of the sequence. The Lower Old Bed Sandstone age 

 of the rocks is proved by the occurrence of plant-remains in shales at 

 the base. The sequence is divisible into groups, which are not, how- 

 ever, persistent over the whole area. Each group may contain 

 different types of lava, which interdigitate one with the other. It is 

 probable that the district was supplied from more than one centre, the 

 foci being independent as regards type of material erupted, although 

 their periods of activity overlapped. 



> Communicated by permission of the Director of ILM. Geological Survey. 



