LOWER AND UPPER GREENSAND OF THE SOUTH OF ENGLAND. 
413 
limited, the upper greensand may be regarded as comprising two broad divisions, an 
upper, in which beds of chert are largely developed, and a lower, principally consisting 
of micaceous and quartzitic sands, with occasional layers of chert. The upper division 
corresponds generally with the zones C and D or Warminster beds of Barrois, and 
the lower with the Blackdown beds or zones B and part of A of the same author. 
Though these divisions are available for the upper greensand strata of the Isle of 
Wight, and the outcrops further westwards in the counties of Dorsetshire, Wiltshire, 
and Devonshire, they are not clearly recognisable in the beds of the same geological 
horizon to the north and west of the Wealden area. The upper greensand in this 
area has an altogether different facies; the beds are exposed at intervals in a narrow 
tract of country, at the base of the chalk escarpment between Godstone in Surrey 
and Selborne in Hampshire, where they occasionally form a distinct escarpment in 
advance of that of the chalk, They are known and have been described under the 
local names of malm, firestone, burrystone, and hearthstone. The peculiar character 
of these beds arises chiefly from the sponge-remains contained in them, and I propose 
to describe these before referring to the sponge-beds of the more normal deposits of 
the upper greensand in the Isle of Wight. 
Mersthcim, Surrey .—There are several exposures of the upper greensand-beds in 
the escarpment running parallel to that of the chalk, both in road-cuttings and in 
quarries, the material being extensively employed for building. In a quarry about 
Itj mile east of Merstham the following section was shown :— 
(1.) Siliceous and siliceo-calcareous rock in thin beds; those ft. 
near the surface being partially broken up ... 4 
(2.) Bed of same rock as No. 1, but in large compressed 
nodules which in places decompose to a reddish clay 
(3.) Bed of siliceo-calcareous rock. Firestone or malm 
15 8 
in. ft. in. 
0 to 5 0 
0 8 
10 0 
In an adjoining roadside cutting, where, however, the beds are not so distinctly 
shown as in the quarry, the bed marked 1 is overlaid by a layer of soft glauconitic 
I marl, which is probably the equivalent of the chloritic marl. 
The rocks of the above section are, when fresh, of a light brown tint and earthy 
aspect; they become white or grayish-white when dry, and are then considerably 
harder. The rock is minutely porous and largely absorbent of water, and when dry, 
of light specific gravity. It is soft to the touch and not adherent to the tongue. In 
some places the light brown rock gradually passes into one which is heavier, more 
compact, and of a light-bluish tint, and frequently becomes nodular. These nodules 
are locally known as flints, but they have an altogether different appearance to the 
* ‘ Reclierches sur le terrain cretace snperieur de l’Angleterre et de l’lrlande,’ p. 106. 
MDCCCLXXXV. 3 H 
