Lead Mining Methods of Mendip and Derbyshire
For a minority of Mendip Folk, mineral mining conjures up
visions of great vaults and vast networks of passages having teams and teams of
miners hewing their existence out of the living rock. This is, of course, not an accurate picture
and the miners endured, in their efforts to eke out a living, many dangers
including those of gas, collapse and inundation.
Of the three, collapse was perhaps the easiest to deal with
as almost all of the passages were in solid limestone or toadstone, so it was
when the "old man" was driving through shale that he was troubled by
collapse problems. These were mainly
overcome by the construction of lined shafts and arched adits or levels. However, the shale also presented the problem
of Gas.
Fire Damp (CH4) only found in mineral mines when shale or
the like is exposed and the gas, when able to collect in rock crevices to mix
with four to twelve times its volume of air, is potentially lethal. The effect of its ignition could be to
produce a sheet of flame which would seal the upper part of the mine passages
and in the wake of the explosion would come the Choke Damp (carbonic ash
residue) which being heavier than air would soon overcome and suffocate any
survivors of the explosion. Another gas
hazard could arise from the imperfect combustion of the Fire Damp, Carbon
Monoxide (White Damp) was equally deadly and even if it did not kill on the
spot it had a more or less permanent effect on the inhaler as it was most
difficult to expel from the body. Explosions were not confined to being caused by gas though, the
occurrence of 'Slickensides' or 'Cracking Holes' or 'Looking Glass' (limestone
or sometimes lead ore with a ribbed and polished surface) sometimes caused
explosions of incredible violence due to stress and strain forces building up
in them. These occurrences were
particularly common in the Eyam district of Derbyshire where there are records
of many miners being killed in such explosions.
The main problem countrywide encountered by the Miner was
how to drain the workings. In Derbyshire
there was usually a simple solution by driving an adit through to the nearest
valley and so empty the water from the workings there. Sometimes, where two or more mines were
working in close proximity a joint effort was made to effect drainage.
Passages below this level were pumped out and several
methods used are worthy of note. The
Mendip miners hampered by the absence of deep valleys, hauled out the water in
nine gallon leather buckets and the miners would make use of local swallow
holes both for drainage purposes and also for spoil dumps.
One of the early pump methods in use was the Archimedes
screw which was generally produced by the use of a hollow log containing a
wooden corkscrew inside which when turned would raise a small amount of
water. However, if it was inclined at
too steep an angle the water would drain out so the more efficient Rag and
Chain type pump was used.
The Rag and Chain was used extensively in the early 17th
Century and through to the mid 19th Century. It consisted of an endless chain passed through a hollow log which was
looped and turned by a spiked wheel of 2 to 3 feet diameter. At intervals on the chain were mounted leather
bags filled with horse hair or rags and these fitted closely inside the log
pipe. When the log was immersed in the
water pumping was effected by turning the wheel and trapping water in the pipe
and transferring it to the top. This was
the first pump capable of moving large volumes of water and sludge but its
operation was exhausting to those driving it. The next generation of pumps were those of the steam age such as the
Newcomen 'atmospheric' engine and the Bolton and Watt beam engines.
But thatÂ’s another story