THE BAGSHOT BEDS OE THE LONDON BASIN. 



377 



The pebble-bed is probably seen in situ in a cutting made for a 

 footpath leading to the top of the hill, and above this there appears 

 to be a capping of sand, proved to be 16 ft. in depth on the crest of 

 the hill, and which may be the basal beds of the Upper Bagshot. 

 In the smaller and disused pit some of the Lower sands are well 

 shown, having been laid bare by the removal of the pebbly debris 

 which had accumulated at the base of the old escarpment *. The 

 few patches of pebbles which remain have been formed by the simple 

 lodgement of pebbles on a sort of ledge formed by rain-water action 

 owing to the unequal tenacity of the beds ; and they can be seen 

 to be continuous with the pebbly surface-covering of the hill-flank 

 by lines of pebbles standing on end in the sand, just as they would 

 appear to have lodged in an ancient rain-water gully. In removing 

 one of the smaller patches and a part of the principal one, to make 

 sure that they did not run into, and become incorporated with, the 

 stratified beds, I obtained out of the middle of the largest patch, 

 in the presence of H. C. Leigh Bennett, Esq., the proprietor, and 

 "W. H. Hudleston, Esq., F.H.S., an angular and discoloured flint 

 and a rolled fragment of chert, both of which are ver}^ characteristic 

 of the later plateau-gravels of the district. On the strength of the 

 above evidence, it may be confidently asserted that there is no trace 

 of pebble-beds of Lower-Bagshot age f in the sections referred to 

 or of " the existence of a pebble-bed in the Lower Bagshot of St. 

 Anne's Hill 



Now, when it is recollected that this was the only case of a pebble- 

 bed in the Lower Bagshot which could be adduced by two diligent 

 observers, we may well be sceptical as to the existence of such beds, 

 though occasional lines and layers of pebbles do occur. This being 

 so, and the Essex Bagshot pebble-beds being of doubtful horizon §, 

 we cannot allow the pebble-beds at Barkham, Easthampstead, and 

 Bracknell to be claimed for the Lower Group on account of their prox- 

 imity to the London Clay. Indeed their presence is evidence rather 

 against than for such a horizon, for the lines and layers of pebbles 

 met with here and there might have been furnished by the contem- 

 poraneous denudation of the London Clay itself ; and no greater 

 importance attaches to these, to my mind, than to occasional layers 

 of Bunter pebbles in the lower sandstones of the Keuper. Their 

 occasional presence seems to indicate inequality in the transporting 

 power of the currents, as we should expect in a fluviatile series of 

 beds, and this is perhaps all that they do indicate. 



2. False-bedding. — By " false-bedding " I understand any marked 

 departure in the stratification from a general parallelism of the 



* In three surveys of the hill, I have observed nothing which requires the 

 notion of a. fault to explain it (see Mem. Geol. Survey, vol. iv. p. 332). 



+ Quart." Journ. Geol. Soc. vol. xlii. p. 404. J Ibid. p. 417. 



§ In quoting "these in the discussion of this paper, Mr. Whitaker appears to 

 have forgotton that he had himself suggested (' Guide to the Geology of London,' 

 p. 52) that the Essex pebble-beds may belong to the Middle Group, a sugges- 

 tion with which I should entirely concur from their association with beds of 

 the lithological character of that division (Mem. Geol. Survey, vol. iv. pp. 320- 

 .328). 



