384 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 26, 



supposition that the London clmj cropped out in these valleys, as for 

 instance in the valleys of Chobham and Blackwater. Such however 

 is apparently not the case. On the level of the first of these valleys, 

 the upper part of the lower sands and lower part of the central green 

 sands outcrop, and in the second the upper part of these green sands 

 is at or near the surface. In both cases the London clay is still covered 

 by the 100 to 130 feet of lower Bagshot sands. 



The following section shows the relation of these strata : — 



s. 



Valley of Chobham. 



Fig. 4. 



Chobham Place. 



d. Upper Bagshot Sands.^'^ ^^^ '^^ ^^^^^ ^^^^ -^f'^ ,ff0li89irp i 



Yellow siliceous sands . . . sarif !,Iria.Ya.4b.KSi%.^a&%^a8L. .adt .'i'lB. At; 100 feet. 



b. Middle Bagshot Sands .ab Jjjj .lo. aoii^«mi£. 45 



1. Clays; brown, yellow and greenish. , ,^-,. r.',, ~^,. ►-, i 



2. Clayey green sands, full of impressions of bsirea, C6fb'utd,''Turritella, Venericardia, &c. 



(See List of Fossils, p. 390.) 



3. Foliated white, brown and yellow clays, with traces of vegetable impressions. 



c. Lower Bagshot Sands. - ^ > ■ .» i < ,^ t . i 



Light yellow siliceous sands .^83ij. ^M.% i . W. J?iUfU'120 feet. 



d. London Clay (upper part of)^' ; See 'H//3ay.<|3jeMi.^ec;?fig. dO^ffoLiTlx/j 



Section where proved. .-jfXT-g g-fj- ygiij jj5jr|t ; vnolorf 5«<»A^sV-^ 



Vj r^''>5in iinjo^o '-^-''"o '-'■'•' ' ' '' ' '-9iidW ij? BiBiia U 



.giffoC) ,¥IZ .H 99a) ^^pper Bagshot Sands}io^~^A'<M haRh^U 



, Incumbent on these green sands is the upper and main mass of the? 

 Bagshot sands. Having fewer distinct argillaceous beds than occur 

 in the lower sands, the stratification of this division is not so well 

 marked and appears more confused, and the sections in it are alsq 

 rarer. , 



,, This division consists of irregular-bedded sands of a light yellow 

 colour, occasionally slightly tinged green, red, or ochreous, and as a 

 whole rather darker in its tint than the lower sands. 



Its superposition on the central green sands is in every instance, 

 where the latter are visible, very apparent. This structure is tolerably 

 apparent on the range of hills two miles north of Chobham, on the 

 side of which the green sands, in some places very fossihferous, may 

 occasionally be seen outcropping (see fig. 4) . 



Small ironstone concretions are common in this division, and 

 amongst these concretions may sometimes be detected traces of or- 

 ganic remains. The well-known blocks of light-coloured, or nearly 

 white, saccharine sandstone are met with chiefly in the upper beds 

 of these sands, generally just below the gravel. They are found by 



