An interesting story is told in an English book by Edward Cressy, of the
great coal strike in 1912. Many factories and workshops had to close for
want of fuel. A workman from one of these, on reaching home, purchased a
sack of coal and set it up against the back door. Then he sat in the
kitchen, in which there was no fire. From time to time, when he felt
chilly he got up, flung the sack of coal across his shoulders and ran
around the yard until he became warm. That was his way of saving fuel.
He was only doing in his own fashion what all engineers and
manufacturers are trying to do in other ways all the year round.
The extent to which all manufacture and transport, all industry there,
was paralyzed during the strike, shows the complete dependence of modern
life upon fuel. In spite of the fact that in Great Britain nearly
240,000,000 tons of coal are raised annually, a temporary stoppage of
supply threw all the ordinary machinery of existence out of action and
revealed the magnitude of the debt that the world owes to those who win
precious stores of fuel from the depths of the earth.
Probably no industrial operation excites more widespread interest, when
accorded publicity, than the mining of coal, and that because of the
dangers which attend it. The annual list of victims buried beneath a
falling roof, or mangled by runaway cars, causes little comment, but
every now and then the world is startled by an appalling catastrophe in
which hundreds of men lose their lives. From the early days when growing
industry demanded more coal, inventors have been busy devising all sorts
of safety appliances for the miner.
The original safety-lamp, with which practically everyone is familiar,
is the parent of scores of others, each claiming to offer some special
advantage. All sorts of mechanical devices to prevent overwinding--an
accident which would fling the cage with its coal or human freight out
of the pit mouth--have been invented, and every section of the work has
been made as safe as human ingenuity and human skill have been able to
make it. But the number of disastrous explosions has not been materially
reduced.
Many varieties of coal give off a gas known as marsh-gas or fire-damp.
This is inflammable and, when mixed with air, violently explosive. It is
the presence of this gas that necessitates the safety-lamp. There are a
few kinds of mines which evolve no gas, and in these naked lights are
used. But all mines must be ventilated by forcing air through them with
a fan, and this air must be in sufficient quantity to keep the
percentage of gas below a dangerous standard. Most mines are examined at
regular intervals by a “fireman” who can estimate approximately the
percentage of gas present by the size of the faintly luminous “cap”
which hovers above the flame of his lamp.
Explosions have occurred, however, in cases where it is extremely
doubtful whether gas has been present in dangerous quantity, and
attention has been drawn to the possible causes. Many varieties of coal
produce a quantity of fine dust which settles in the roadways, on roof,
and sides, and floor. For many years there has been a controversy as to
the relative importance of gas and dust in producing explosions, and the
question is still one which gives rise to a lively difference of
opinion. But there is no doubt that a mixture of coal-dust and air is
explosive, and that even if an explosion is started by gas the
disturbance creates clouds of dust which gives rise to secondary
explosions and spread the disaster over a wider field than was
originally affected.
[Illustration: _Courtesy of the Link-Belt Co., Chicago._