234 REPORT ON THE DENEHOLE EXPLORATION
much filled-up denehole, offering no field for exploration. The
exact positions of the shafts of Nos. 6 and 15 would necessarily
remain doubtful were we dependent solely on underground observa-
tions, but there is no difficulty in identifying them on the surface.
Having reached in No. 15 the remotest pit in this direction, we
must now retrace our steps into No. 10, and thence into Nos. 11
and 14.
The short tunnel between Nos, 10 and 11 gave us admission into
a somewhat exceptional pit, while another connecting the lateral
chambers of No. 11 placed the whole denehole before us. Evidently
intended to have been a six-chambered pit of the ordinary type, the
existence of a large "pipe" in the Chalk had checked the formation
of the more northerly of the two primary chambers. This pipe must
descend 8 or 9 ft. into the chalk, or from 4 to 5 ft. lower than the
pipes in Nos. 2 and 4. In consequence of its existence, the primary
chamber in which it appears only attains a length of about 6 ft. 6 in.
On tunnelling from No. 11 to No. 14, the workmen met with
another pipe. This long tunnel was decidedly the most unfruitful
in results of any we have made. When we reached No. 14, we found
the entrance barred by a mass of incoherent sand and gravel unsafe
to tunnel through, and the end of which could not be ascertained
by means of the auger. Turning to the left, we managed by means
of a branch tunnel to penetrate into an almost filled up chamber,
but further progress was again stopped by rubbish. We had, there-
fore, only to retire to No. 11, feeling much disappointed at the state
of No. 14. For surface observations had shown us that the depres-
sion around its shaft was extremely slight and much below the average,
the size of this hollow being usually a fair index to the amount of
debris below. But in this case it would seem that, though the fall of
material down the shaft had been slight, the collapse of part of the
roof had taken place, a collapse that, as in No. 1, had been accom-
panied only by the formation of a subterranean dome in the Thanet
Sand.
The chamber of No. 11, nearest to No. 10, being traversed by a
single plank, the depth below which was from 5 to 6 ft., the work-
men were directed, on October 7th (1887), to fill it up to some extent
with sand from the mound around the shaft of No. 11, close by, so
as to avoid the risk to our visitors at the Field Meeting of the follow-
ing day of sprained ancles or broken legs. Excavating somewhat
rashly, they caused a fall of sand, which enabled us to look up the shaft