220 



Geological Society :■ 



B. Injection schists, formed by the intrusion of veins, which had 

 acquired parallelism by pressure. Veins of diorite in diorite pro- 

 duced duplex diorite-gneiss, and veins of granite in diorite origi- 

 nated granite diorite-gneiss. 



It was further noted that 



(1) Generally the particular varieties of schist occurred in the 

 vicinity of the igneous masses to which they were most nearly 

 related in mineral composition. 



(2) The mineral banding of the rocks in the field was more like 

 vein-structure than stratification. 



The Author accepted the received view of the age of the schists. 

 The parallel structure was clearly antecedent to the Cambrian 

 epoch, and the occurrence of similar rocks as fragments in the 

 Uriconian conglomerate of Shropshire seemed to indicate that the 

 Malvernian schists were older Archsean. 



April 27.— Prof. J. W. Judd, F.R.S., President, in the Chair. 



The following communications were read : — 



1. " On the London Clay and Bagshot Beds of Aldershot." By 

 H. G. Lyons, Esq., R.E., F.G.S. 



The Author first described the section from Thorn Hi]l on the 

 N. to Redan Hill on the S., plotted from the 6-in. Ordnance Survey 

 on a scale of 6 in. to 1 mile horizontal, and 12 in. to 1 mile vertical. 

 This section comprises beds from the Woolwich and Reading series 

 to the Upper Bagshot inclusive. It showed a dip of 2|° to the N., 

 which is regular or nearly so throughout. A few feet of Upper- 

 Bagshots occur on Thorn Hill (365 feet) ; at the base of these the 

 Pebble-Bed crops out, forming also much of the surface of the South 

 Camp. The Middle Bagshots on the south slope of the hill are 

 estimated from the South Camp boring at 53 feet, with a marked 

 clay-bed at the base ; and below these a few feet of the Lower Bag- 

 shots are exposed in the intervening valley. The greater part of 

 Redan Hill (364 feet) is made up of Lower Bagshots ; but towards 

 the top a few feet of the basal clays of the Middle Bagshots have 

 been exposed by a recent trench. Although the elevation is prac- 

 tically the same as that of Thorn Hill, the rest of the Bagshot series 

 is cut out owing to the northerly dip. These results differ from 

 those of previous observers, e. g. the Geological Survey carry the 

 Lower Bagshots to the top of the Redan Hill, as do Messrs. Monck- 

 ton and Herries ; whilst of the anticlinal, alleged by Mr. Irving to 

 exist in this traverse, there appears to be no trace. The Author 

 also observed that the arguments for overlap of the upper beds and 

 for the erosion of the London Clay are not borne out by the facts. 



The second section described runs from Gravel-Pit Hill on the N. 

 to Ash Green on the S. It was drawn to the same scale, and showed 

 the beds from the Chalk to the Middle Bagshots inclusive. Dip 

 northerly 2^° to 2 b 50' at south end. A spur of the Fox Hills 

 (Gravel-Pit Hill) is seen to consist of Upper Bagshots of the normal 

 type down to the lower shoulder of the spur, which is capped by the 

 Pebble-beds marking the junction of the Upper and Middle Bag- 



