File:The Quarterly journal of the Geological Society of London (13206282554).jpg

382
PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .May 26,
rence, in the upper part especially. This structure is best exhibited
around Woking, Horsley, and White Hill near Egham. A peculiar
local instance in these lower Bagshot sands of their sudden transition
into, or rather of the sudden substitution of clays, occurred at the
railway-cutting at Goldsworthy Hill near Woking. Immediately
under the central green sands, the upper part (for a depth of five or
six feet, which was as far as it was exposed) of the underlying fine
white siliceous sands were there seen passing horizontally and abruptly
into a dark grey laminated clay (see Fig. 3. at point marked "2/")'
This variation of structure is of very local character, as this bed of
clay does not even appear at the outcrop of the same sands on the
south side of the hill at less than a quarter of a mile distant. To the
north however it is apparently more persistent, and it is probable that
part of the neighbourhood of Chobham, which stands on the upper
beds of the lower sands, is in some measure indebted to the occasional
presence of this bed for its good supply of water and general fertility.
In the western districts of the Bagshot sands this lower division
again becomes very argillaceous, passing into light brown loams.
Their lowest beds remain however usually the most sandy.
Amongst the subordinate lithological characters is the frequent pre-
sence in the sands of small plates of mica (especially where slightly
laminated with clays), of large grains of yellow and transparent quartz, ,
pebbles of black rolled flints, thin layers and nodules of iron sand-
stone, and a few concretionary masses of saccharine sandstone, which
are more compact and harder than those in the upper sands, and by
no means so abundant.
The following section exhibits the details of the divisions and the
general structure of the Bagshot sands : —
Fig. 3.
tt- Upper Bagshot Sands. ieet-
Yellow and light ochreous siliceous sands. A few casts of Turritella, Cardium, Natica
Ostrea and Nummulites are of very rare and local occurrence. Sandstone concretions
at "o " 150
b. Middle Bagshot Sands.
1 . Coarse greenish sand with a few flint pebbles 2