OF EAST BERKS AND WEST SURREY. 561 



^N'eocomian. On comparing their altitudes some allowance has to be 

 made for slight Post-Pliocene movements producing some changes 

 of the relative levels. They remain as indexes of the ancient 

 Pliocene lines of drainage northwards, having preserved the present 

 hills from degradation ; while the originally higher ground has been 

 scored with the present valley-system. 



Evidence of Glaciation. 



With one apparent exception * I know of no distinct evidence of 

 glaciation in the part of England referred to in this paper, nor in 

 the Thames Yalley above 240 ft. (o.d.), though many examples of it 

 have been described at lower altitudes. If we assume, therefore, 

 that these mark the ]3eriod of the maximum glaciation of the old 

 Thames Straits, we have to allow for a very considerable amount 

 of excavation of the present valley-system of this part of England 

 prior to the Glacial Period. 



§ 1. In a new pit t at the Brickyards of Messrs. T. Lawrence and 

 Sons, close to the Xine-mile Ride, between the Wokingham and 

 Binfield roads, a fine section has been recently opened, exposing the 

 laminated basal clays of the Middle Bagshot, with the underlying 

 Lower Sands. The claj^s here are splendidly contorted, and overfolded 

 by great masses of gravel, in some cases weighing several tons apiece, 

 having been driven, probably in a solid (frozen) condition, into them. 

 The lamination of the clays is distinctly traceable in the contortions, 

 and leaves no doubt as to the nature of the agencv which has here 

 been at work. Altitude, 230 to 240 ft. (o.d.). 



The gravel is one of the secondary or terrace-gravels of the 

 country, derived from the older Plateau-gravels, with an increased 

 proportion of flint pebbles, furnished by the destruction (prior to 

 the glacial action) of the pebble-beds of the Bagshot terrain to the 

 south. 



§ 2. In the Tangley cutting of the South- Western Railway near 

 Wokingham, on the other side of the valley, very distinct glaciation 

 of the same laminated clays is seen at the top of the cutting above 

 the Lower Sands at about 220 ft. (o.d.). 



§ 3. At Sunninghill the same succession is seen in the railway- 

 cutting, with similar folding, puckering, and included pockets of 

 gravel, at about 220 ft. (o.d,). 



* The case here referred to is that of a, completely unstratified gravel, with 

 scarcely any pebbles in it, which occurs on Lodge Hill, Broadmoor, at 400 ft. 

 (o.d.). The angular fragments stand in all positions in it. May it not, from 

 its exceptional character and altitude, be a glacial deposit of the cold Plio- 

 cene age (Etheridge, ' Manual of Greology,' p. 6-52 ; and Lyell's ' Student's 

 Elements,' p. 181). The pit has been recently i-e-opened. It reminds me of 

 nothing so exactly as of the moist masses of loose, incoherent, subangular stuff, 

 which every observer of higher Alpine phenomena is familiar with in the trail of 

 the minor suowfields as they retreat up the smaller valleys during the summer. A 

 repetition of such deposits of trail for a number of seasons would give just 

 what we see in the pit on Lodge Hill. 



t This pit has been considerably extended since the note referring to it at the 

 foot of p. 164 of vol. xliv. of the Society's ' Journal ' was written. 



