6
THE ESSEX NATURALIST
all part of the same denehole. The chamber of No. 15, which is
connected to No. 6, is obviously a primary one, the other two
being a pair of lateral chambers. The direction of those of No. 14
is only 10° different from that of the newly opened chamber of
No. 15, and it may well be one of the other pair of laterals of
No. 15. If this is true, then the question arises as to the position
of No. 14 and No. 15, as both holes are marked on the 1887 plan
of the surface. A possible explanation is that the map of the
surface is inaccurate and that No. 15 is actually further to the
east of No. 6. Another possible explanation is that one of the
depressions, which were shown as 14 and 15, was due to reasons
other than the subsidence of a blocked denehole shaft. It may
be possible to resolve this anomalous situation by taking samples
of the soil from various positions in the wood and at various
depths.
A preliminary report of some of these explorations was given in
a short paper, which was read before the Essex Field Club on
March 21, 1959. In the discussion which followed, a question was
raised as to whether the floor of the deneholes was of chalk or of
flint. It was suggested that if it was of flint, then this might be
the reason why the holes were dug. This question assumes, of
course, that the holes were man-made; a fact which has yet to
be proved. However, to try and answer this question, excavations
were performed in one of the lateral chambers of No. 10. This,
which was the one investigated in 1887, was chosen as it appeared
to be the most likely place in which to be able to reach the
floor, without too much work. The rubbish was cleared from the
floor at a point more or less in the mouth of the cavity. A hole
about six inches deep was cut in the floor, which proved to be of
chalk. Part of the mound of soil blocking the shaft was excavated
also, in order to find out what lay on the floor directly under the
shaft. The first 12 inches of the mound consisted of blocks of
chalk together with much smaller lumps of chalk. The chalk
blocks appeared to have been roughly squared, but it is quite
probable that it occurs in this shape when the roof of a hole
collapses. In fact, a portion of the roof which collapsed between
Nos. 5 and 6 produced lumps of chalk, which appeared to have
been "squared up". On top of the chalk the soil was quite
gravelly and it appeared to lie in layers which sloped at an angle
of about 10-20° from the horizontal, from the shaft down to the
ends of the chambers. The gravel gradually gave way to the
typical sand, from which most of the mound appeared to have
been made. It is probably too early to draw definite conclusions
until an entire mound of debris has been examined. However, the
evidence does appear to support the idea put forward in 1887,
Holmes & Cole (1887), that the shafts were blocked by the gradual
denudation of the top of the shaft.
A fact, which does not seem to have been reported before, is
the presence of small holes in the chalk walls of No. 3. These
holes appear to have been made by water, because they show the