Agricola, Georgius
,
De re metallica
,
1912/1950
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out of the shallower shafts; similarly at the same season it pours into the
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lowest tunnel and, meeting a shaft in its course, turns aside to a higher tunnel
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and passes out therefrom; but in autumn and winter, on the other hand, it
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enters the upper tunnel or shaft and comes out at the deeper ones. </
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<
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>This
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change in the flow of air currents occurs in temperate regions at the beginning
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of spring and the end of autumn, but in cold regions at the end of spring
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and the beginning of autumn. </
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<
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>But at each period, before the air regularly
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assumes its own accustomed course, generally for a space of fourteen days
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it undergoes frequent variations, now blowing into an upper shaft or
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tunnel, now into a lower one. </
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<
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>But enough of this, let us now proceed to
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what remains.</
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<
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>There are two kinds of shafts, one of the depth already described, of
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which kind there are usually several in one mine; especially if the mine is
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entered by a tunnel and is metal-bearing. </
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<
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>For when the first tunnel is
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connected with the first shaft, two new shafts are sunk; or if the inrush of
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water hinders sinking, sometimes three are sunk; so that one may take
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the place of a sump and the work of sinking which has been begun may be
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continued by means of the remaining two shafts; the same is done in the
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case of the second tunnel and the third, or even the fourth, if so many are
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driven into a mountain. </
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<
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>The second kind of shaft is very deep, sometimes
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as much as sixty, eighty, or one hundred fathoms. </
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<
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>These shafts continue
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vertically toward the depths of the earth, and by means of a hauling-rope
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the broken rock and metalliferous ores are drawn out of the mine; for which
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reason miners call them vertical shafts. </
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<
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>Over these shafts are erected
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machines by which water is extracted; when they are above ground the
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machines are usually worked by horses, but when they are in tunnels, other
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kinds are used which are turned by water-power. </
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<
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>Such are the shafts which
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are sunk when a vein is rich in metal.</
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<
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>Now shafts, of whatever kind they may be, are supported in various
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ways. </
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>If the vein is hard, and also the hanging and footwall rock, the shaft
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does not require much timbering, but timbers are placed at intervals, one end
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of each of which is fixed in a hitch cut into the rock of the hangingwall and
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the other fixed into a hitch cut in the footwall. </
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<
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>To these timbers are fixed
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small timbers along the footwall, to which are fastened the lagging and
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ladders. </
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<
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>The lagging is also fixed to the timbers, both to those which screen
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off the shaft on the ends from the vein, and to those which screen off the
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rest of the shaft from that part in which the ladders are placed. </
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<
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>The lagging
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on the sides of the shaft confine the vein, so as to prevent fragments of it
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which have become loosened by water from dropping into the shaft and
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terrifying, or injuring, or knocking off the miners and other workmen who
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are going up or down the ladders from one part of the mine to another. </
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<
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>For
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the same reason, the lagging between the ladders and the haulage-way on
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the other hand, confine and shut off from the ladders the fragments of rock
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which fall from the buckets or baskets while they are being drawn up;
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moreover, they make the arduous and difficult descent and ascent to appear
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less terrible, and in fact to be less dangerous.</
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