PLEISTOCENE GEOLOGY OF THE THAMES VALLEY. 361 



in length. Some are smaller than this, but none are larger. One 

 may be seen between Palmer's Avenue and Sockett's Heath 

 trending in a general east and west direction. Another has its 

 head situate about one furlong to the west of the Small-pox 

 Hospital and trends, roughly speaking, north and south. The 

 other valleys which occur in this district all follow either the one 

 or the other of the directions indicated above. They are wholly 

 confined to that portion of the district in which the High Terrace 

 Gravel rests directly upon the Chalk or in which only the Thanet 

 Sand intervenes between the former and the latter. In the 

 northern portion of the eastern tract, where the more argillaceous 

 Woolwich Beds and the London Clay come on under the gravel, 

 the valleys are absent. 



That they do not owe their origin to fluviatile erosion 

 operating since the deposition of the High Terrace Drift is 

 evident from the fact that they do not cut through the gravel, 

 which on the contrary invests the valley bottoms as completely 

 as it does the high ground round about. This objection also 

 operates against any agent of subaerial denudation which 

 involves the mechanical removal of detritus from off" the surface. 

 It seems inconceivable that the valleys could have been fashioned 

 in the Thanet Sands before the deposition of the drift, for in that 

 case they Avould either have been filled up and so would have 

 given but slight evidence of their existence at the surface, or else 

 they would have been efifaced by the ordinary erosive action of 

 the river. 



The first section that threw any light upon the development 

 of these valleys was one exposed in a gravel pit at Sockett's 

 Heath. Here the regularly stratified gravels described in 

 Section III. of this paper were seen, on the western face of the 

 pit, to have been bent down inwards from the north and from the 

 south so as to form a syncline of some fourteen or sixteen feet in 

 depth and about fift\' feet in width. This trough was filled up 

 with confused and unstratified gravel resting upon equally 

 confused and irregular sand and loam, the whole of this infillin"- 

 material possessing the appearance of having been tumbled in 

 from above (Fig. 2). All the stones as they approached the 

 centre or base of the syncline were seen to become perfectly 

 vertical, which plainly showed that it was a downward move- 

 ment that had placed them in their present position. The axis 



