Journal of Proceedings. xxi
in his "Miscellaneous Notes on Deneholes, 1883," printed in the present
volume of the 'Transactions.' The mode of work was the same as on
previous visits, and many of the observations given in the papers
referred to were repeated and confirmed.
While waiting on Friday for the "rigging up" of the tackle, attempts
were made to measure the height of the water in the well close to Gravel-
pit Barn, on the right hand side of the path leading up into the wood
from Grays. The water-level was found to be 71 ft. below the surface.
As the level of the ground at this spot is not more than from 12 ft. to
15 ft. below that of Hangman's Wood, it would appear that the floors of
the Deneholes there are very slightly above the permanent water level of
the chalk in this district.
No. 4 pit having been entered and examined, Dr. Cory made some
observations with a dry and wet bulb thermometer which he had brought
with him specially for that purpose. The readings were as follows :—
On Saturday morning the explorers were early on the ground, and
Mr. Arnold Spiller, assisted by Mr. Brougham Young, kindly undertook
the task of "photographing a Denehole," a feat of subterranean camera
work presenting very special difficulties on account of the great heaps of
sand which cut the line of sight from one chamber to another. No. 3
pit was chosen for the experiments, and the necessary apparatus care-
fully lowered down the shaft. For the light, magnesium burning in
oxygen was employed ; two quart bottles of the gas, and two feet of the
metal in the form of ribbon, being used for an exposure, and in con-
sequence of the gas being only partially consumed during one exposure
the same volume could be employed twice. To focus the picture, candles
were placed in different parts of the chambers, so that, although all that
was visible on the ground-glass were a few bright specks, by a little skill
and calculation it was possible to adjust the camera to take in the
required field of view, and at the same time be approximately in focus.
Then, to take the photograph the camera was placed on a stand about
two feet above the sand mound, on which one of the magnesium lights
stood immediately beneath the lens, a sheet of white cardboard being
employed as a reflector ; the other bottle of oxygen was placed on one
side of the chamber, but concealed from view. Some of the photographs
thus obtained were shown at the Autumnal Exhibition of the Photo-
graphic Society. From the cause above stated the views were confined
to one chamber each, and consequently they give no idea of the peculiar