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

INSPECTORS OF MINES.^ U
Dejuxd for Mi.vixg DeVELOI'MKNTS.
The characteristic necessity for developing deep mines, like all other industries,
necessitated the substitution of steam machinery for manual labor,
and during the last few years has brought into market a large number of
drilling machines, amongst which, however, is the Diamond drill. The
damage done to a mine by using steam power for this purpose was very
great upon the timber and structure of the locality, therefore a demand for
air-compressors had sprung up, and wholly answers the purpose so admirably
that all other systems have givep way to its march. It is found that
air can be conducted any distance, and through any temperature, Avithout
condensation, and with much less leakage than steam ; and instead of it
having to be brought out of the mine in pipes, like steam, it is used as a
ventilator, and practically cools the locality.
Some trouble is experienced in winter from freezing vapor, and even the
machine when working. This vapor has also made it impossible, so far, as
to use compressed air expansively to any large extent, as steam is worked
with such excellent results for economy, because the temperature of the air
decreases so much in expanding that the water vapor contained in it condenses
and freezes up the machinery.
It is, therefore, of the greatest importance that the air should be perfectly
dry, but this is difficult to obtain, as the great heat generated in the compressor
during the act of compression necessitates a constant artificial cooling
of the compressing cylinder, which has been done by injecting a stream
of water into the cylinder at each stroke, or keeping a large quantity of
Avater working to and fro in it. In order to obviate those difficulties. Captain
John Ericsson constructed a compressor, with open upright top brass
pump cylinders, immersed in a bath of water, which washes the inside walls
of the cylinder at every stroke, with water lying on the pump buckets,
without ever allowing the water to come in contact with the compressed
and heated air.
The power required to compress air is considerable, making it a rather
expensive motor, and should be made as economical as possible ; and this
is accomplished by attaching to the large engines found at the collieries for
pumping and hoisting than by a small separate cylinder, working without
expansion. AVherever possible water is utilized. To avoid loss from the
continuous running of the compressor when the drills, &c., may be stopped,
a relief valve is made, which is set to any determined pressure, and opens
a relief post from the pumps into the atmosphere as soon as that pressure
is exceeded in reservoir and pipe, and this allows the pumps to run without
accumulating pressure or consuming power.
Compressed air in a dry C3dinder does not obviate* the trouble with condensed
water completely, as the vapor suspended in the atmospheric air,
when taken in, is much more than can be held suspended in the diminished
volume after compression, and after the air is cooled down again to common
temperature.
To remove this vapor in the atmosphere a condenser is provided for cooling
the compressed air completely, and depositing and running off the condensed
water before the air enters the pipes. The great shafts of the Pliili.delphia
and Reading coal and iron company at Pottsville, in Schuylkill
county, the sinking of which was successfally Accomplished with the use
of compressed air and the Diamond drill. The result obtained from this
source is highly satisfactory. The company succeeded in reaching the E
or Mammoth vein in these shafts at a depth of 1,980 feet, besides all the
overlying veins. The Primrose vein was found at a depth of 1,G00 feet in