6 MISCELLANEOUS DENEHOLE NOTES, 1906.
Deneholes in the Grays Chalk Pits.
The northward extension of these large chalk-pits in recent
years has caused the discovery and destruction of many dene-
holes. The two quarries I am about to mention lie from one to
two miles south-west of Hangman's Wood, and towards their
northern ends the Chalk is covered by Thanet Sand and old
Thames gravel, or by Thanet sand alone, the total thickness
attained by the two formations seldom exceeding some twenty
or thirty feet. On March 23rd, 1903, I received a letter from
Mr. W. Whitaker, stating that during an excursion of the
Geologists' Association to Grays on March 21st he and others
had seen a denehole shaft, square in shape, at the most northerly
prolongation of the Lion Works pit, east of Millwood Lane, and
a little south-east of Mill Wood. He added that two others had
been found in a field close by, their shafts also being square. I
visited Grays a few days after and saw the square shaft, but on
succeeding visits was not fortunate enough to see anything
more. But as these, and possibly others, must have been seen
by gentlemen connected with the Lion Works during the
enlargement of the great chalk-pit, they have, in all probability,
not passed away unnoted.
As regards the square shaft, Mr. F. C. J. Spurrell remarks in
his paper on deneholes in the Archaeological Journal for
1881, that the "Matamores," or subterranean granaries of
Northern Africa, especially in Algiers and Tunis, have
(according to M. de Lasteyrie) shafts generally of a square
form and from 30ft. to 40ft. deep, the shaft just admitting a
man.
Probably the nature of the material is the chief influence in
regulating the shape of shafts of this kind. Where, for instance,
Thanet Sand is the only bed traversed, the shaft might be
circular on account of the uniform quality and singular stability
of that formation. But where beds of various degrees of
stability were penetrated a square form might be preferable.
For then, on the foot-holes at one angle becoming too large and
indefinite in shape, at some part of the shaft, for stability, the
three other corners might, each in turn, be tried. A round
shaft on the other hand, on the foot-holes failing somewhere at
some distance from both the top and the bottom, would become
useless so far as ascent by means of foot-holes was concerned.