264
THE ESSEX FIELD CLUB.
circular shaft passes through some 60 feet of Tertiary sands and loams and
penetrates the chalk to a further depth of 30 feet. The descent is simple ; a
windlass, a swinging seat attached to the wire cable, a couple of stout labourers
at the cranks and in a few minutes we are down. A faint light streams down the
shaft, but it is powerless to illumine the galleries which run away on either hand
into perfect darkness. Lanterns and candles soon reveal our surroundings. A
lofty gallery, some 20 feet high, 9 feet wide at the floor level and narrowing to a
flat roof, about 4 feet in width, runs through the dead white chalk, to a working
face, three or four hundred yards away, where the miners are busy with pick and
shovel. The mine consists of a set of these galleries with cross tunnels which
form approximately a square with the shaft in its centre. Down the centre of
the main galleries are two rows of flat metals, on which run the small trolleys
used to convey the chalk from the working faces to the shaft, through which all
the chalk is raised. The dimensions of the tunnels are regulated principally by
the nature of the chalk—where this is firm and free from "joints," the width may
exceed nine feet and the height may be 25 or even 30 feet. Where the chalk is
even in texture the side walls are dressed fairly smooth by the pick, but where
joints are abundant, or the chalk is less firm, the dressing is necessarily rougher.
More than one gallery in this matter-of-fact chalk mine has walls as evenly
dressed as the celebrated alcoves containing "altar tables" at Chislehurst.
Very great attention is paid to the "joints" or planes of fracture of the
chalk ; the direction of a passage may need to be altered or it may be abandoned
altogether if the direction of the "joints" makes either the roof or the corners
of the passages unsafe. While the condition of the walls and roof throughout
the mine requires frequent inspection, all corners need constant care, for here
falls frequently occur, and any error of judgment in shaping a corner may have
dangerous consequences.
The work of cutting the chalk in these passages requires much experience.
The mine manager himself superintends the driving of all new headings, shapes
the roof and trims the corners ; the workmen do the rough cutting after the roof
has been made secure. Throughout the mine the same bed of hard chalk forms
a remarkably flat roof. A similar bed of hard chalk is often to be seen in the
roof of the numerous dene-holes which occur within a few miles of this mine.
One point in which these galleries compare favourably and instructively with
the Chislehurst mine is their stability. Here huge pillars, never less than 15 to
20 feet square, are left to support the roof, but the Chislehurst miners, either
through ignorance or wilful disregard of correct principles, cut their galleries
much too close together, hence the numerous "falls" which have blocked many
tunnels and given rise, on the surface of the ground, to meal depressions which
have been incorrectly described as deneholes.
After tramping more than two miles along these lofty passages we again
stood at the foot of the shaft and ascended to the upper air, leaving behind us
this modern "maze," whence during the last 50 years more than 100,000 tons
of chalk have been raised to contribute to the bricks and mortar of the
Metropolis.
It is worth noting that an outcrop of Chalk from under Thanet Sand (exactly
as at Chislehurst) occurs on the east side of the valley, within a 1/4 mile of the
shaft of the mine, and chalk has been worked here in an open pit and by means
of a gallery driven horizontally into the hill for a short distance, but this gallery
is of no great age—probably not more than 40 or 50 years.