1out of the shallower shafts; similarly at
the same season it pours into the
lowest tunnel and, meeting a shaft in its course, turns aside to a higher tunnel
and passes out therefrom; but in autumn and winter, on the other hand, it
enters the upper tunnel or shaft and comes out at the deeper ones. This
change in the flow of air currents occurs in temperate regions at the beginning
of spring and the end of autumn, but in cold regions at the end of spring
and the beginning of autumn. But at each period, before the air regularly
assumes its own accustomed course, generally for a space of fourteen days
it undergoes frequent variations, now blowing into an upper shaft or
tunnel, now into a lower one. But enough of this, let us now proceed to
what remains.
lowest tunnel and, meeting a shaft in its course, turns aside to a higher tunnel
and passes out therefrom; but in autumn and winter, on the other hand, it
enters the upper tunnel or shaft and comes out at the deeper ones. This
change in the flow of air currents occurs in temperate regions at the beginning
of spring and the end of autumn, but in cold regions at the end of spring
and the beginning of autumn. But at each period, before the air regularly
assumes its own accustomed course, generally for a space of fourteen days
it undergoes frequent variations, now blowing into an upper shaft or
tunnel, now into a lower one. But enough of this, let us now proceed to
what remains.
There are two kinds of shafts, one of the depth already described, of
which kind there are usually several in one mine; especially if the mine is
entered by a tunnel and is metal-bearing. For when the first tunnel is
connected with the first shaft, two new shafts are sunk; or if the inrush of
water hinders sinking, sometimes three are sunk; so that one may take
the place of a sump and the work of sinking which has been begun may be
continued by means of the remaining two shafts; the same is done in the
case of the second tunnel and the third, or even the fourth, if so many are
driven into a mountain. The second kind of shaft is very deep, sometimes
as much as sixty, eighty, or one hundred fathoms. These shafts continue
vertically toward the depths of the earth, and by means of a hauling-rope
the broken rock and metalliferous ores are drawn out of the mine; for which
reason miners call them vertical shafts. Over these shafts are erected
machines by which water is extracted; when they are above ground the
machines are usually worked by horses, but when they are in tunnels, other
kinds are used which are turned by water-power. Such are the shafts which
are sunk when a vein is rich in metal.
which kind there are usually several in one mine; especially if the mine is
entered by a tunnel and is metal-bearing. For when the first tunnel is
connected with the first shaft, two new shafts are sunk; or if the inrush of
water hinders sinking, sometimes three are sunk; so that one may take
the place of a sump and the work of sinking which has been begun may be
continued by means of the remaining two shafts; the same is done in the
case of the second tunnel and the third, or even the fourth, if so many are
driven into a mountain. The second kind of shaft is very deep, sometimes
as much as sixty, eighty, or one hundred fathoms. These shafts continue
vertically toward the depths of the earth, and by means of a hauling-rope
the broken rock and metalliferous ores are drawn out of the mine; for which
reason miners call them vertical shafts. Over these shafts are erected
machines by which water is extracted; when they are above ground the
machines are usually worked by horses, but when they are in tunnels, other
kinds are used which are turned by water-power. Such are the shafts which
are sunk when a vein is rich in metal.
Now shafts, of whatever kind they may be, are supported in various
ways. If the vein is hard, and also the hanging and footwall rock, the shaft
does not require much timbering, but timbers are placed at intervals, one end
of each of which is fixed in a hitch cut into the rock of the hangingwall and
the other fixed into a hitch cut in the footwall. To these timbers are fixed
small timbers along the footwall, to which are fastened the lagging and
ladders. The lagging is also fixed to the timbers, both to those which screen
off the shaft on the ends from the vein, and to those which screen off the
rest of the shaft from that part in which the ladders are placed. The lagging
on the sides of the shaft confine the vein, so as to prevent fragments of it
which have become loosened by water from dropping into the shaft and
terrifying, or injuring, or knocking off the miners and other workmen who
are going up or down the ladders from one part of the mine to another. For
the same reason, the lagging between the ladders and the haulage-way on
the other hand, confine and shut off from the ladders the fragments of rock
which fall from the buckets or baskets while they are being drawn up;
moreover, they make the arduous and difficult descent and ascent to appear
less terrible, and in fact to be less dangerous.
ways. If the vein is hard, and also the hanging and footwall rock, the shaft
does not require much timbering, but timbers are placed at intervals, one end
of each of which is fixed in a hitch cut into the rock of the hangingwall and
the other fixed into a hitch cut in the footwall. To these timbers are fixed
small timbers along the footwall, to which are fastened the lagging and
ladders. The lagging is also fixed to the timbers, both to those which screen
off the shaft on the ends from the vein, and to those which screen off the
rest of the shaft from that part in which the ladders are placed. The lagging
on the sides of the shaft confine the vein, so as to prevent fragments of it
which have become loosened by water from dropping into the shaft and
terrifying, or injuring, or knocking off the miners and other workmen who
are going up or down the ladders from one part of the mine to another. For
the same reason, the lagging between the ladders and the haulage-way on
the other hand, confine and shut off from the ladders the fragments of rock
which fall from the buckets or baskets while they are being drawn up;
moreover, they make the arduous and difficult descent and ascent to appear
less terrible, and in fact to be less dangerous.