OF THE THAMES VALLEY. 73
This expression of opinion led us to carefully scrutinise all
the sections touching on the question which were still open, to
see whether any evidence of the gravels having been deranged
by the dissolution of the chalk beneath could be found. Our
notes of this examination are subjoined in full, the result being
that we are reluctantly compelled to join issue with Mr.
Whitaker. In Part I. of this paper we have paid considerable
attention to the processes of this underground dissolution of the
chalk, and while we have there recognized how important such
processes are and to what a vast extent they have operated in
this district, we in this case could recognise but trifling manifes-
tations of their working.
In the large pit of the Grays Chalk Quarries Company on its eastern side,
going up the slope of the upper working towards the north, we meet with the
following succession. At first there is from four to seven feet of loam and marl,
with many stones from the Drift. Some of the pebbles are vertical, others more
nearly horizontal; the former are imbedded in the marly matrix, and are nearest
the surface of the chalk, upon which the series rests; the latter are imbedded
chiefly in the clay or loam, which is nearest the surface. The junction between
the marl and the loam is very irregular, and the entire series is very clearly a
mixture of rain-wash with the residual products left by the dissolution of the
chalk. The superficial loamy portion becomes more sandy northwards. A little
further on the stony marl thins out to below the level of the working, while the
thickness of the loamy portion exposed increases to eight feet. About ten yards
further to the north we find the stony loam ending off with a sharp junction
against bedded sand and loam, resting in turn on rubbly chalk. There is an
appearance here of "piping," but the stratified series is affected by it as well as
the subaerial. A little higher up the following section was noted :—
Black earth .. .. .. .. 1ft. 6in.
Stony sand, the pebbles principally small black Ter-
tiary flints, but with a little drift material; the
stones lying in all positions, about .. .. 1ft. 0in.
Fine sandy loam with pockets of gravel .. ., 3ft. to 5ft.
Sand and gravel, well bedded .. .. .. 3ft. to 4ft. exposed.
Higher up the rain-wash clay comes on again, and is about 4 feet thick, and
beneath this gravel and sand is exposed to another 4 feet. The dissolution product
—marl—rises up again here and there, and seems to show that most of the sand
and gravel noted so far owes its position to "piping" and "slipping." Still
further north we meet with finely bedded sand and gravel, the beds being
contorted or bent to a slight extent, about 4 feet in thickness and overlaid by a
little of the rain-wash. The gravel rests upon 3 or 4 feet of brown loam, which
in turn rests upon rubbly chalk. A little higher up the Thanet Sand comes into
the section, and just near its fringe the overlying gravel and loam together with
it appears to be let down in pipes. For another 20 yards the gravel rests directly
upon Thanet Sand, and there is slight evidence of "piping." This brings us to
one of the side workings at the upper end of the continuous slope ; the section in
this is somewhat obscure, but there seems to be more clay.