Reports of the Inspectors of Mines of the anthracite coal regions of ...

174 ANNUAL REPORT OF THE
or bone and lime mortar. In some instances brick are used, and a few have
nsed cement, and it gave good satisfaction.
Much opposition was manifested to the introduction or recommendation
by the writer of stone walls and mortar to be used in the construction of
all the main stopping and on tlie sides and tops of main doors. Some parties
tried to satisfy the requirements by building their stoppings of scantling
3 inches by 4 inches for props or uprights, and then place inch boards
on either side, filling the intermediate spaces with screened ashes, sand or
clay ; but this packing would eventually settle down and the structure
would let the air screen through. Next thing the wooden work would decay
and require renewing, so that by the time that the mine would be two
or three years old, and need to stand a heavier pressure, the whole thing
was rotten. Other parties tried clay to pack up their stoppmgs, and as
mortar, building stone or bone on either side, and the middle with clay. I
tried to show that it would not answer, but its use was not abandoned until
1 finally succeeded in getting them to calculate the actual cost per perch
when it received its death warrant, its cost being about four times that of
masonry on the surface.
The parties who have used the stone and mortar stoppings now agree
v.'ith me, and will say unhesitatingly that they are much the cheapest kind
of stoppings to use. Time does not aflect their capability to withstand the
extra drag or pressure brought upon them as the mine becomes extended,
whereas the wooden ones would be affected by the rot, and consequently
their efiSciency must be inversely to the time of their service required from
the time of their construction. Add to the above deficiency the fact that
the drag increases in proportion to the extension other things being equal.
The next department in which we have advanced in materially is in the
arrangement of doors, to assist in keeping the main currents steady around
to the faces of the working places.
Under the old regime very few check-doors were used in this as well as
other districts, unless it be in mines where fire-damp was generated, when
they could not be dispensed with, and even there the matter of doubling
doors was never attempted. At present there are check-doors sufficient in
each current or split in every mine to force the main body of the said split
or current around to the faces of ^ach and every working place in its territory,
whether there be explosive gas generated in the mine or not. The
enormous quantity of gunpowder used in blasting the rock and coal in a
mine, especially so in our anthracite mines, adds much to the requirements
of ventilation. Many of our mines use three-quarters to one pound of gunpowder
for eacn ton of coal mined ; hence if a mine produces 1,000 tons of
coal daily, and taking three-quarters of a pound of powder as being used
per ton, = 750 pounds of powder. This is only one of many other items
affecting our ventilation, but I mention this because this item is heavier in
our mines than in the bituminous mines.
To come back to the matter of doors, I would state that our main doors
are being erected in a very substantial manner. They are hung on pieces
of s(}uare timber, eight or ten inches square, which are niched into the roof,
and tlie whole built around with good stone and lime mortar, faced or pointed
over. Those main doors are put up in pairs, called in tlie mining law
they are placed apart, with sufficient distance between them
double-doors ;
to allow a team and a trip of mine cars to pass through the first and afterward
be closed while the trip is yet in motion before there be any occasion
to open the second door. In this way the one is a check-up the other; in
other words, one of the two doors is to be at all times closed to protect the
current from breaking. The distance between those- doors is regulated by