\ 



WALTON COMMON EXPOSING LONDON CLAY ETC. 163 



or imperfect pipe-clay, intermediate in quality between the true 

 Bagshot pipe-clays and the more sandy beds of ordinary London 

 Clay." The same author mentions * that at a place called Hartley 

 Row only one foot of sand intervenes between the Ramsdell Clay of 

 the Lower Bagshots and the blue London Clay. This 1 foot of sand 

 possibly is the attenuated representative of No. 1 of the Walton - 

 Common section. The thickness of the Ramsdell Clay at Hartley 

 Row is stated to be 8 feet, so that the total thickness of the two 

 basal members of the Lower Bagshots is nearly the same at both 

 jjlaces, only the distribution is difterent. When this No. 2 group 

 has been exposed for some time, it is highly probable that browns 

 and buffs will be the prevailing tints. 



We next come to the consideration of No. 3, which represents the 

 basal portion of the main mass of the Lower Bagshots as developed 

 in this area. The lowest portions, just over the Blue Bagshots, are 

 generally of a darker buff than those higher up, and, on the whole, 

 rather larger in the grain, though smaller than Bagshots No. 1. 

 Colour, when wet, like common brown sugar, feebly coherent, except 

 where very small ochreous lumps exist. The elements of this sand 

 are mainly those of No. 1 already described. The constituent gra- 

 nules, besides being smaller, are more equal and less clean. They 

 average about -O'lG millim. in diameter. Little flakes of white mica 

 are rather more obvious, and there is more argillaceous matter, 

 generally spread in very thin sheets throughout the bedding. The 

 green grains, both pale and dark, are also fairly abundant. 



At the bridge, and for about 25 yards to the westward of it, this 

 division of the Lower Bagshots has been cut out entirely. Presently 

 we perceive little outliers of it cemented to the ferruginous base of 

 the gravels by more or less of an iron-pan (see fig. 5). Traced 

 towards the west, it is found increasing in thickness for a while, 

 until cut out entirely by the first gap which forms the boundary of 

 block C. 



Plateau-gravel, Sfc. in Block: C. — The superficial beds of this 

 division are usually from 14 to 15 feet thick, showing a consider- 

 able increase over what obtains in the London-Clay area : they are 

 also more sandy. For some part of the distance the Plateau-gravel 

 reposes on the " Blue Bagshots ;" and there is an appearance, as 

 indicated in fig. 5, of a portion of this bed having been incorporated. 

 Towards the end of the block, as we approach the first gap, large 

 masses of reconstructed sand, with only a few layers of pebbles, 

 constitute the lower portions of what we must still call the Plateau- 

 gravel. These sands are mainly derived from the Bagshots, such as 

 we see in this district; but they contain other elements in addition. 

 It is not always easy to draw the line between the superficial beds 

 and the unshifted Bagshots. 



Block D. (Pig. 1.) 



In this block the Bagshot Beds are represented by No. 3 alone, 

 with the exception of a faint trace of the " blue beds " just at the 

 * Op.cit.p.SU. 

 Q. J. G. S. No. 166. K 



