Evening star. [volume] (Washington, D.C.) 1854-1972, 1911-02-12

| believe in coal dust explosions until the great
| disaster a few years ago, which killed one
thousand people. This was proved beyond
question to have been attributable to coal
dust. At the present time, IN some coal
mines of France, the curious precautionary
expedient is adopted of placing heaps of
stone dust on light platforms suspended
| from the roof. If an explosion of coal dust
occurs, the lar caused by it will precede the
advancing flame, and the stone dust, thrown
down by the conclusion, will prevent the
| ignition of coal dust in the immediate neigh
borhood of the workers.
| Explosions of coal dust in mines are most
likely to occur in autumn and winter, when
the air below is very dry. The air pumped
in by the ventilating machine at a low tenn
perature is warmed when it gets into the
depths and absorbs mo sture. Then it passes
out, carrying the moisture with it. 1t was
estimated by experts recently that one mine
in Pennsylvania lost in this way fifty tons
of water out of it's atmosphere in twenty
four hours. With a view to obviating the
difficulty various expedients are being tried,
one of which consists n passing steam into
the mine with the fresh r. By this means
the underground workings are supplied with
humid air. 1t goes without saying that coal
dust floating in moist air is much less
ignitible.
The big danger in coal mine is from the
"blown out shot" When the miner has
drilled hole, put in charge of explosive,
and set the latter off, he expects It to break
up the mass of COAL Sometimes, however,
instead of doing this, it shoots back out of
the hole into the mine. If the air is full of
coal dust an explosion is likely to follow
But this danger is greatly increased if the
explosive used has long flame. One may
pass his finger quickly through candle
| flame without being burned. The same idea
applies to the flame of the miners explosive.
| Hence it is that Government experts are
| trying to develop, for coal mining purposes,
explosives with short flames which do not
last long. They have set up at the expert
ment station in Pittsburgh special appara-
tus for this purpose, consisting OF tall iron
chimney standing on a concrete base. When
an explosive is touched off in the bottom of
the chimney, its flame darts upward through
the latter, and is photographed by an in
genious device.
How Gunpowder Acts
THE most Familiarity known explosive is
ordinary gunpowder, which consists of
saltpeter nitrate of potash), charcoal, and
sulphur. The sulphur is merely for igni-
ton, it's purpose being the same as that for
which it is put on the end of a sulphur match.
The charcoal, which is pure carbon, is the
ingredient that burns. Why, then, the salt
peter? Simply because saltpeter contains
the oxygen required for combustion. All
three of these ingredients are reduced to fine
dust and thoroughly mixed together. When
the sulphur is ignited, the heat thus gener-
ated causes the saltpeter to give up its oxy-
gen to the particles of charcoal with which
it is SO intimately mingled. The charcoal is
burned in a tremendous hurry; in other
words, converted instantly into hot gas,
which, as it expands, is powerful enough to
rend to pieces a receptacle in which it may
be confined, or to drive bullet out of a
gun.
The process, it will be observed, is sub
stantialy the same as that concerned in an
explosion of -four dust, or sugar dust, or
sawdust or coal dust; the only difference
being that, in the case of gunpowder, the
oxygen required for combustion is supplied
to the charcoal dust by the saltpeter mixed
with it, whereas in the other instances the
dust, of whatever inhammable kind, derives
the oxygen from the air in which it floats.
ABRAHAM LINCOLN