IN THE BRAINTREE DISTRICT.
81
Museum authorities for determination. Mr. French writes under
date of 17th April: "Another section has been made 100 paces
to the south, and at the same elevation. A dark clay is exposed
(under about a foot of soil) containing abundance of Planorbis spir-
orbis, but nothing else." On the 5th May he records the finding of
a large bone in black soil a quarter of a mile further south, and in a
like position. On the opposite side of the river, to quote from the
same letter, "there is a gravel-pit in what appears to be ordinary
Glacial gravel, of a reddish colour, and showing false bedding. At
a depth, however, of about six feet a bed of stones occur.;, black-
ened apparently by a vegetable stain." Mr. French suggests infiltra-
tion of river or brook water as producing this stain ; but one of the
specimens of stones proves to be artificially chipped, and therefore
this gravel, an isolated patch on the London Clay slope, is a Post-
glacial deposit of like age with that described above, with the eleva-
tion of which it coincides.
The brickyard at Causeway End is in very different material.
Here the Boulder Clay, exposed for many years to the action of per-
colating water, has lost, over a wide area, all trace of the chalk that
forms so large a constituent of its mass, leaving only the clay and
insoluble stones, which are separated by the usual washing process.
At one corner of the field the passage from the unaltered chalky clay
into the chalkless form is plainly seen.
North of Felstead, in the brook alongside the railway, the
Boulder Clay is seen to be overlaid by ten or twelve feet of loam,
with gravel and sand at intervals. At the base of these alluvial
deposits and resting on the floor of Boulder Clay, Mr. French has
detected the site of an ancient fire, in abundant fragments of char-
coal and calcined stones extending over several feet of the surface of
the lower clay. Further examination of this very interesting dis-
covery proved it to be of lenticular section, five feet in diameter and
ten inches in thickness. The loamy rainwash over it is five feet
thick. A small patch of very shelly sand close by contained of
aquatic species only minute Cyclas, with several terrestrial molluscs,
Cyclostoma, Zonites, Helix, Acme, &c. The Boulder Clay is an
isolated patch, the London Clay coming out in the brook bed at a
short distance above and below.
Patches of marl and peat similar to those previously noticed
occur very frequently in this part also, and yield equally rich results to
the searcher for shells. The rabbits are energetic assistants in this