THE ESSEX FIELD CLUB. 145
the centre of the pit, and from it, in most cases, three chambers branch out on
one side and three on the other, in a kind of double-trefoil pattern. The largest
chambers are those which are opposite the openings at the bottom of the shaft,
and the greatest length of each cavern is that obtained by measuring the length
of a straight line passing through the centre of the shaft to the ends of the oppo-
site chambers. Originally separate, these deneholes are so close together that
the thin chalk partition between two chambers in adjacent pits has sometimes
been accidentally fractured. Though there are, as already stated, more titan fifty
separate deneholes in Hangman's Wood, only five shafts are now open, the rest
having fallen in at various periods.
Fig. 3.—Ground-plan of Denehole No. 3, showing damage caused subsequent to explorations
in 1887.
The shafts are narrow, and were originally less than three feet in diameter.
The geological section of each varies only in the slightest degree. The chalk
appears to be lying nearly flat, but the thickness of the old river gravel at the
surface varies slightly, so does that of the chalk roof of the chambers ; and the
height of the caverns, as already mentioned, is somewhat variable. The shaft of
the pit ("No. 3" on the plan published in the Report alluded to above) by
which the descent was made at the present meeting presents the following section
of strata traversed :—
The origin and raison d'etre of these interesting pre-historic pits, which hear a
general resemblance to those which occur at Crayford, Bexley, and other places on
the Kentish side of the river Thames, is still to some extent a matter of conjecture,
in spite of the extended work carried on at a great expense by the Club in 1884
and 1887, when the accumulations of Thanet sand, chalk, and general cebris were
carefully sifted to the level of some of the original floors; but they are undoubt-
edly of great age, and the general opinion is that they formed refuge-, or