122 BOOK V. 



out 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. 



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 maj;- 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. 



