Dear All,
The week before last a number of members of the Institute of Materials,
Minerals and Mining (IoM3) met at the Institute's present headquarters at 1,
Carlton House Terrace.
The occasion had two purposes: one was to celebrate the centenary of the
granting of their Charters in 1915 to the Institution of Mining and
Metallurgy and the Institution of Mining Engineers, both of which have been
absorbed into the IoM3; and the other was to learn about and then visit the
building on Euston Road (with an entrance also on Warren Street) which will
be the IoM3's future head office.
During the course of the day, it was mentioned that the official opening of
the new office in November will also be associated with some form of
celebration of the bicentenary of the discovery/design in 1815 by Sir
Humphrey Davy of the flame safety lamp.
This mention of Davy's lamp stirred a memory in me, which I thought it would
be worth me placing on record (being of an age at which one's early
experiences are now history!)
So, if you have an otherwise idle ten minutes, please read on.
The Davy Lamp's Other Use
The Davy lamp, whose bicentenary of design we celebrate this year, had a
vitally important use in providing safe lighting in coal mines and showing
miners the presence of methane. Safe to use in otherwise dangerous
atmospheres, the colour of its flame could, to the trained eye, enable an
estimate to be made of how much methane was present in the air. Methane is
the gas the miners knew as "firedamp", with its threat of fire and
death-dealing explosions.
The Davy lamp, however, had another important use, as was demonstrated to
me dramatically one summer's day in 1950.
I was studying mining engineering at the Royal School of Mines, part of
Imperial College in South Kensington. In the first six weeks of the summer
vacation at the end of the first year, I went to gain practical experience
at two coal mines near Swadlincote in south Derbyshire. These were called
Cadley Hill and Bretby No 3. (My handwritten student report on these, with
maps and diagrams, is lodged with the Derbyshire County Record Office in
Matlock).
Bretby No 3 was quite close to the western edge of the coalfield. The
seams in this area were in a broad syncline (shaped like ever larger giant
saucers, the deeper, the wider), coming up to the surface (outcropping) one
after another towards the west. The workings at Bretby were in the Stockings
seam, about five feet thick, but the manager had his eye on the shallower
principal seam, known as the Main Seam, which was about seven feet thick and
contained plenty of good coal well worth trying to dig out.
There were two problems with this, however. To the west of Bretby's two
shafts, where the seam rose towards its outcrop, it was on fire. This was a
result of spontaneous combustion, supplied with air through a series of
tunnels driven illicitly to get coal during the General Strike of 1926. In
an attempt to starve the coal of oxygen, lorries came every day from Ind
Coope and Allsopp's brewery in nearby Burton-on-Trent to tip their loads of
bran mash waste onto dumps covering the entrances to those tunnels. This was
not entirely successful, however, and the dumps themselves were extremely
hot. If you plunged your hand into the surface of the mash, the tips of your
fingers were unbearably hot before your hand was fully immersed.
Indeed the ground was so hot to the west of the mine that the manager
found it necessary to employ a special gang whose job it was to go out each
morning to apply a top dressing of sand on the sleepers of the railway
siding. This was done so that the engine driver bringing the empty waggons
in which the mine's output of coal was to be despatched would not see how
charred the sleepers were. The manager was convinced that, had the driver
been aware of the state of the track, he would not have brought his engine
up it. Without the empty waggons, the mine would have had to close, which
would never have done.
In contrast, to the east of the Bretby shafts, the Main seam was flooded.
In the old days, maybe three centuries ago, many small coal pits had been
sunk on the northern outcrop of the seam. To overcome the flooding problems
encountered, the old men had driven a tunnel in the coal some four miles
across country to drain this area into the river Trent. The tunnel, whose
exact course was no longer known, served its purpose of draining the old
northern pits very well. This meant that the section of seam down dip from
Bretby's shafts contained a plentiful supply of water.
But the resourceful manager had a plan. In 1925 a company, Nadins, had had
the idea of accessing this area of the Main seam and installing powerful
pumps to take care of the incoming water supply. To do this they had driven
an inclined tunnel (a "drift") down from surface until it reached the seam.
They began near the edge of a farmer's field about half a mile east of
Bretby . This tunnel went down at an inclination of 1 in 4, steep enough to
ensure it got to a good depth rapidly. They could tell when they were
getting near to the Main seam by mapping the geological strata as they went.
The Main seam was known to have a very thin band of coal (about six inches
thick) in the layers of rock which formed its roof. This was called a marker
seam - once you got to it, one more blast and you would be through to the
top of the Main seam. In due course, after driving down 200 yards, the great
day had arrived: they had encountered the marker seam. Nadins assembled all
the pumps they possessed, connected the pipework to take away the water,
drilled the final round of holes, and blasted..
The water came in faster than their pumps could cope. It flooded the
pumps, short circuited the electrics, and that was that. Their funds
exhausted, Nadins bricked up the entrance to the tunnel, and left. And so it
had remained since the 1920s.
The Bretby manager's great idea in the summer of 1950 was to open up
Nadin's Drift, install more powerful pumps than they had had in the 1920s,
drain the Main seam and work its coal. So it was that on the Wednesday of
my last week at Bretby I was assigned to go with the group of men who were
to open up Nadin's Drift, to gain experience of a different kind to that I
had encountered underground.
It was a beautiful summer's day towards the end of July, the sun shining
brightly in a blue sky dotted here and there with small cumulus clouds. We
went in a lorry to the farmer's grassy field in which the Nadin's building
stood. Knowing we were coming, the farmer had ensured that his cattle were
grazing elsewhere, so all was peaceful.
A simple building covered the entrance to the drift. A short flat-roofed
section at the front led to a sloping part at the back, following the 1 in 4
gradient of the tunnel beneath it. The side walls were also of concrete, but
the front wall, which was obviously where the entrance had been located, was
solidly bricked up.
The first job was to demolish the brick wall. For men used to hewing
coal, armed now with sledgehammers and picks, this presented little problem.
The broken bricks were thrown into the lorry to be taken away. Within an
hour the entrance was wide open.
Standing in the opening, a fascinating view lay before one's eyes. The
floor, inset with a narrow gauge railway track, quickly bent downwards and
descended steeply. The neat concrete tunnel, seven feet square, was brightly
lit by the summer sunshine all the way down - down, down, as clear as day,
all the way to the pond of water at the bottom, perhaps fifty yards from
where we stood. The daylight streaming in from the morning sun behind our
heads meant there was no need for any artificial lighting. Even in the utter
depths, all was as clear as day. There was absolutely nothing, it seemed, to
prevent one walking all the way down without the need for any lamp.
After a brief moment absorbing this extraordinary view, the overman in
charge of the group suggested we stepped back outside. To my uninitiated
surprise he then, out in the field on this bright summer's day with glorious
sunshine, reached for his Davy lamp and lit it. Carrying the lamp by its
hook at his side, arm stretched straight downwards so the lamp flame was
close to the ground, he walked slowly into the tunnel entrance.
Once inside he was soon onto the downward slope, walking slowly. After
only a couple of paces the flame in his Davy lamp went out.
He immediately turned about and came out again into the sunshine.
"Blackdamp!" he exclaimed, the miners' name for carbon dioxide. This gas,
heavier than air, invisible and odourless, in quiet conditions dilutes then
displaces air in hollows, reducing its oxygen content. Too much of it, and
you suffocate. Nadin's Drift, the neat clear tunnel down which the sun was
shining and you could see clearly to its very depths, was full of it.
Blackdamp - a suffocating death awaiting the unwary.
The original electric power lines and switches were still in place, so a
fan and canvas ducting were rigged up, blowing in fresh air to clear out the
blackdamp. This began about mid-day on Wednesday. Every so often, a man
would go down with a Davy lamp to see how far he could go, and additional
lengths of canvas ducting would be added whenever possible. The fan was left
running all day and all night and it took until Friday afternoon before we
were able to walk down that tunnel as far as the water clearly seen on day
one.
Every advance was determined by the flame in the Davy lamp. As long as
it burned, it was safe to continue - the flame proved there was enough
oxygen for a human to breathe. A lesson to be learned, long remembered: the
Davy lamp's other use.
Tony Brewis
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