San Antonio light. [volume] (San Antonio, Tex.) 1911-1993, 1924-03-30

overhead, on tlmDers or adherlng Il
the walls, dislodged and ignited, but
If there is excess dust at some place il
is carried along by pioneering" nfl
waves and feeds the flame of the ex
plosion.
The difficulty of finding employees
who will water a mine thoroughly and
cOnscientiously may nullify the best in
tentions of the management. One oil
the greatest American coal dust ex-
plosion disasters was attributed by
the state inspector to failure to water
the mine on holiday that preceded
the explosion.
Failure Not So Vital.
One of the greatest advantages of
rock busting is that failure or delay
to apply the dust for a day or n few
days is not so vital as the omission
of watering. Many roadways do not
have to be redusted more often than
one or two times per month under
adverse dust conditions. Other parts
of the mine may not need reducing
for months. The condition of the
roadways can be largely determined by
inspection, If limestone dust is used,
and checks positively by the gathering
of samples. This applies not only to
inspection from day to day by the
management, but also the more ocea.
sional state inspection. For example,
state inspector may find the condi-
ton of a watered mine admirable rs
far as coal dust is concerned on the
day of inspection, but he cannot tell
whether the mine will be safe the next
day. Usually a month or more will
elapse before he makes another in
spection of that particular mine. Mean
time the effectiveness of the watering
cannot be positively checked in the
same way that samples of dust gath
cred and tested by the management
can be if made matter of daily rec.
ord.
The cost Of rock busting in Ameri-
can mines per, ton of coal produced
is believed to be much less than that
of efficient watering. This sruah COS.
is a low price for protecting human
lives and for insurance against dis
asters that involve heavy financial
losses from the payment of death and
injury benefits and through damage
to property.
Different Dusts Used.
Most of the British collieries use
shale dust, made by grinding rough
shale from the mine or from some
mine. Limestone dust Is
used to some extent and few col
lieries buy gypsum dust. Most mines
in the north Of France use chalk dust,
others use clay.
The British regulations prohibit the
use of any character of stone dust
that would be injurious to the health
Of persons working in the mine. No
reports Of serious effects on health
from stone busting have been received
from collieries that have used it
eight or ten years. In many Ameri-
can coal mines the immediate roof ma
terial is not generally so suitable for
stone busting purposes as that in the
mines of Great Britain. When there
is a question as TO the effect Of
sDecified dust on health, samples
should be submitted to n Photographer
or to the bureau of mines. When
shale suitable for busting cannot be
found. it will usually be possible in
most American coal fields to purchase
dust from limestone, dolomite. any
drite or gypsum quarries at a rea-
sonable figure. Such materials are usu-
ally free from silica.
Results of these investigations are
in bulletin 225, copies of
which may be obtained from the De-
pertinent of the Interior. bureau of
mines. Washington. d. c.