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

INSPECTORS OF MINES. 1^3
ter is employed inside the mines we are liable to get confnsed, because it
is affected first by the friction changing- the tension of the air, and second
by the dilference of elevation ; hence it is not reliable for either purpose
inside the mines, unless it be kept stationary, when it can be used to great
advantage.
The causes of the great friction met with in passing large (juantities of
air through mines is to be found in the contracted dov/ncasts and upcasts,
and the long and crooked small-sized main air-ways, and their tributaries,
through the interior of the mines, with the hundreds of elbows of every
angle it has to meet ; and the main air-ways being of small sectional area
the velocit}^ must be great to pass even a medium quantity, hence high
velocities and crooked ways must retard the currents extremely and cause
great friction, as the friction increases not as the simple velocity but as its
square.
Much more care is being taken in i-egard to the condition of the air-ways,
relating to size and form. In 1870 there were but few air-ways in this district
large enough to use a mine car in it, the custom being to drive small
air-wa3'S parallel with the main gangway only about large enough for the
party driving the same to work in, often having a sectional area of o feet
by 2 feet, and if it would be 3 feet by 4 or 5 feet it was considered quite
largo. The coal and dirt cut in said small air-ways (or as called in some
localities, dog holes or monkey gangways) had to be handled all by using
a wheel-barrow or other small buggy, or pitched back with a shovel, the
whole length of distance between the cross-cuts of 45 feet or 60 feet and
the thickness of the pillar besides.
Many places, however, those small air-ways were not driven, and only a
wooden brattice built along side the gangway, and generally too small to
allow any person to pass through the same, which could not be kept closer
than 60 or 70 feet from the face of the gangway for fear of blasting it from
gangway or parties opening chambers.
Others again were using brattices across shutes, with sliding doors, and
still others using doors on the entrance of each chamber to try and force
the cui'rent to the face of the mine.
At present there are but two or three parties in this district using anything
else than a large and roomy gangway in which the regular mine car
is taken through, which must have a certain sectional area to pass through,
let the price be small or the ground to cut hard it matters not.
The main air-ways are being made in most of our mines at present from
60 to 100 feet sectional area.
The air bridges or crossings are also being made about the same sectional
area.
The cross-cuts between main gangways and their air-ways, and those between
the chambers, are required to be from 35 to 40 or 50 feet sectional
area. Much trouble was experienced by the writer in breaking up the old
system of small air- ways and cross-cuts.
Under the old system of using doors on the mouth of each chamber, as
it was in some mines, any one of those being left open would necessarily
cut off most part of the whole current from all those farther in the interior
of the mine. Again even when there was what was then considered a
large air-waj^ the idea of using anything more than the slate and bone found
in the seam, and packed in with fine dirt or culm, to make up the stoppings
in the cross-cuts, was seldom thought of; and if a mine was kept iu ver3good
condition it would have the main stoppings made up of inch boards,
some places of single and others double. Now the most of our stoppings
between the main gangways and their parallel air-ways are made up of slate