272 THE ESSEX NATURALIST
and penetrating blows it has been possible to determine the nature
of the tool point with which they were made. It had a square
section of approx. 1 cm side and its point was blunt.
It was apparent that the denehole had contained a debris cone
which had slumped to the east following the action of a mechanical
digger. The line taken by the digger is shown dotted on the plan.
A section was cut through the fallen debris down to the chalk floor.
It was composed of sandy material with a strong chalk admixture
and was quite homogeneous and barren of human artefacts. Under
the microscope the sand can be seen to be formed from fine quartz
grains with a few flint fragments. It seems likely that it is derived
from the Thanet Sand.
It is not intended to discuss the probable mode of formation
or use of features of this type but it may be useful to demonstrate
the facts which are brought to light by the discovery.
1. The existence of the denehole was quite unsuspected by the
contractors throughout their road-building operations, despite
its closeness to the surface. Therefore it must have been
closed off by its debris cone.