334 THE ESSEX NATURALIST
The superficial deposits, generally a few feet only in thickness, but
which were found to thicken greatly in the region of the present river,
were generally of a sandy or silty nature and clearly contained a considerable
amount of material derived from the Reading Beds.
In Fig. 2, which gives the section proved by boreholes 1 to 9, the further
details provided by boreholes 9a, 10, 11 and 12 have been omitted. These
do not add appreciably to the general picture.
2. CHALK FLINTS FROM STANSTED MOUNTFITCHET, ESSEX
Among the materials associated with the Clactonian and Acheulean in-
dustries at Clacton, Swanscombe and elsewhere are certain zoned flints
the provenance of which is as yet unknown. They consist of a black inner
zone and a yellow-brown chalcedonic outer zone with sometimes a fine
white band separating the two. A possible source of these is suggested
by recent excavations in the Chalk at Stansted Mountfitchet.
The pit, owned by Messrs. D. Heath & Sons Ltd., has now been aban-
doned for active working, but one of the last operations was to excavate
a quantity of chalk from below the ordinary floor level of the pit. The
section now exposed shows part of a valley sloping down at an angle of
approximately 12° for some 30 or 40 feet. [Plate 12.A.] The bottom of
this valley is not reached.
In the Chalk are to be seen scattered flint nodules of which two bands
in particular were observed at about 3 feet apart. The nodules were found
to consist of irregular lumps, practically all of which had been enhanced
by a further thin skin of flint which filled in the depressions and left only
the projections of the inner zone uncovered. A characteristic feature was
that, owing presumably to earth shudder while the outer skin was in the
form of a gel, this zone was shattered by fine, roughly parallel cracks or
"faults" which only rarely affected the inner zone. It was found that,
except when a nodule was within a foot or two of the surface of the Chalk,
both inner and outer zone were of black flint. In one example, found
in situ about 2 feet down in the Chalk, the outer zone had weathered to
a white colour.
The Chalk both within the valley and elsewhere was covered by Glacial
Gravel, and lying immediately on the old land surface below this gravel
were frequent large flint nodules of a kind comparable to that already
described. They had, however, suffered some erosion so that the slight
shattering of the outer skin was largely or completely smoothed over.
Scratching on the surface of some specimens is attributed to the excavator
and not to ice action. All were stained slightly brown on the outside, and
their most characteristic feature was that the outer zone had in all examples
examined been weathered to a pale cream flint while the inner zone retained
its original black colour.
In some specimens from the scree, which were presumably from very
near the top of the Chalk, the two zones of flint were separated by a very
marked white line similar to that seen in some pebbles from Jaywick and
elsewhere which are associated with the Clactonian industry.
The writer believes that this area in north-west Essex, or an extension
of it beneath the Boulder Clay, may provide a partial answer to the question
of derivation of the Clacton flints, though comparable flakes in the
Medway valley and elsewhere may be more difficult to explain. The
channel at Stansted Mountfitchet was presumably cut by glacial meltwaters
at a time when the proto-Thames had already been diverted to a course
approximating to its present one. The erosion of the channel will have