coal trade bulletin - Clpdigital.org

32 THE COAL TRADE BULLETIN.
other matters may be, because a few minutes'
delay in timbering may mean a loss of life.
It must be admitted that at times even experienced
men believe the roof to be sound, when suddenly
and without warning a large block crashes
into the tunnel. This, if anything, will hie
claimed as a purely accidental occurrence; yet
even the danger from such a block ( which may
have been perfectly sound when first exposed, but
became
LOOSENED BY THE CONCUSSION
of subsequent blasting) in many cases might have
been discovered in time if there had been a systematic
and regular examination' of the entire
roof of the tunnel. For this reason you should
form the habit of examining the roof as you pass
in or out, testing all places that appear to be unsound,
and you should instruct every worker in
the tunnel to do likewise.
It should be said in this connection that "sounding"
a roof is not a proper way of determining
its safety; there are numerous cases on record
where the roof gave a satisfactory sound and appeared
solid even to very experienced men, but
in which a big block or bowlder was actually loose.
A better method of testing the roof, which is
used by many large mining companies and is recommended
by the Bureau of Mines in Miners' Circular
9, "Accidents from Falls of Roof and Coal,"
is to strike it with a pick or heavy stick, at the
same time touching the doubtful piece with the
free hand. If any vibration is felt, the rock is
unsafe and should be taken down or supported at
once. If the rock is too high to reach with the
hand, a stick should be held against the doubtful
piece while it is being struck, ancl if it is loose
the vibration can be felt through the stick.
Provide each man with a copy of the precautions
to be taken in handling explosives, which
are stated below, and see that he reads them.
Never permit even a single disregard of these
rules to go unchallenged and never fail to discharge
habitual offenders.
Don't rely in any degree whatsoever upon the
supposed "inertness" of dynamite, but at all times
use care in handling it.
Don't smoke while handling explosives, and
don't handle explosives near an open light.
Don't shoot into explosives with a rifle or pistol,
either in or out of a magazine.
Don't carry loose detonators (blasting caps) or
electric detonators in the clothing. Carry them
in special boxes.
Don't transport detonators or cartridges containing
detonators (primers) to the heading in the
same box or package with the
SUPPLY OF DYNAMITE
for the round, and do not place them side by side
after they reach there.
Don't tap or otherwise investigate a detonator
or electric detonator.
Don't attempt to take detonators from the box
by inserting a wire, a nail, or any other sharp instrument.
Don't try to withdraw the wires from an electric
detonator.
Don't leave explosives in a wet or damp place.
Keep them in a suitable dry place, under lock
and key, where children or irresponsible persons
cannot get at them.
Don't store dynamite boxes on end, as nitroglycerin
is more liable to leak from the cartridges.
Don't store or handle explosives near a residence.
Don't open packages of explosives in a magazine.
Don't open dynamite boxes with a nail puller or
powder cans with a pickax.
Don't store or transport detonators and explosives
together.
Don't store fuse in a hot place. This will
change its normal rate of burning.
Don't keep detonators, electric detonators, or
firing machines in a damp place.
Don't allow priming (the placing of a detonator
or electric detonator in dynamite) to be done
in a thawing house or magazine.
Don't use frozen or chilled explosives. Most
dynamite freezes at a temperature between 45°
and 50° F.
Don't thaw dynamite on heated stoves, rocks,
sand, bricks, or metal, or in an oven, and don't
thaw dynamite in front of. near, or over a steam
boiler or fire of any kind. Use thawers such as
are furnished by the manufacturers of explosives.
Don't take dynamite into or near a blacksmith
shop or a forge.
Don't put dynamite on shelves or other supports
which are directly over steam or hot-water pipes
or other heated metal surface.
Don't cut or break a dynamite cartridge while
it is frozen, and don't rub a cartridge of dynamite
in the hands to complete thawing.
Don't place a "hot-water thawer" over a fire, and
NEVER PUT DYNAMITE
directly into hot water or allow it to come into
contact with steam.
Don't allow thawed dynamite to remain exposed
to low temperature before using it. If it
freezes before it is used, thaw it.
Don't fasten a detonator to the fuse with the
teeth or by flattening it with a knife; use a
crimper. The ordinary detonator contains enough