29 
and more argillaceous, and this again into the underlying chalk marl. As 
the proportion of clay increases the rock becomes less pervious to water, 
so that while none at all can be obtained from the upper strata, both the 
lower are exceedingly retentive. In many of the high-lying farms the 
whole supply of water for every purpose is obtained from rain stored in 
tanks at the surface, and, as may be imagined, a hot summer is an exceed- 
ingly trying time to the stock and sheep owners of this largely pastoral 
district, who often lose many out of their flocks in such seasons from want 
of water. The few wells that have been sunk to the water-bearing strata 
are sometimes as much as 250 or 300 feet in depth. At a lower level we 
find the more argillaceous strata turned up by the plough and in some 
spots retentive enough to afford springs. In the locality now to be 
described they form a wide terrace, on which lies a bed of gravel of 
considerable thickness. It is the great store-house of road-metal for the 
neighbouring parishes and as a consequence the quarry now covers many 
acres of ground. It consists solely of sharp, broken flints, and well 
rounded flint pebbles, with a red siliceous sand in large proportion. It is 
not worked to a greater depth than 12 feet and the labour consists solely 
in screening out the stone from the sand which is then thrown back and 
often sown with corn. 
It is evident from the sharpness of these flints that they have not been 
moved far from the place where they were broken and there is no room to 
doubt that they are the remains of thick beds of upper chalk once continuous 
over the valley. The mass of carbonate of lime removed must have many 
times surpassed that of the remaining flints, yet the former has entirely 
disappeared while the sharp edges of the latter have not been rounded. 
The gravel seems to have no organic remains of its own but some belong- 
ing to the chalk are to be met with. The commonest are Ananchytes 
ovatus, and a Spatangus, of course silicified. I have several times searched 
the quarry for flint implements but in vain. Hundreds of chips and flakes 
may be met with which might easily pass as artificial but I have never 
found one that I could say was not perfectly natural. 
At a rough estimate this, which may be called the upper gravel, lies 
not less than 200 feet above the river. 
At a lower level and on the other side of the Thames, much nearer to 
the present stream, is exposed in several places another, which may be 
termed the middle gravel, so different in its composition that the two 
cannot be confounded. Its composition is various, not uniform, as was 
that of the preceding. Flint is still the chief, but not the sole constituent, 
