130 TECHNOLOGY. 
Whenever the workings are driven below the natural means of drainage. 
or below the level of the plain, recourse must be had to mechanical power. 
The water is sometimes raised in buckets or tubs, but most frequently by 
pumps of various construction. The common suction-pumps are used for 
inconsiderable depths; for great depths forcing-pumps with hollow pistons 
or solid plungers are employed, all of which have been fully described in a 
former article. We add the description of an excellent lifting-pump in the 
mines of Huelgoet, which is set in motion by a hydraulic ram (pl. 26, 
jig. 29). cis the working barrel, closed at the top, but open at the lower 
end; Pp is the piston, tx’ the valve-box; when the piston descends, the 
water ascends through the suction-valve, s, into the valve-box and the 
barrel, and by the upward stroke of the piston it is raised through the lift- 
valve. Both valves are conical, without any packing. The leather packing 
of the piston-rod, x, is seen in fig. 33; that of the piston, which is a spring- 
packing, in jigs. 31 and 34. A small lateral tube, wu’ ww’, provided with 
stop-cocks, connects the suction and lifting-pipes and the barrel, and serves 
to fill the suction-pipe with water when the pump has not been in action 
for a length of time. A small valve, w, which is loaded with the pressure 
of one atmosphere, shows at all times whether the suction-valve is in good 
condition, as, when it does not close perfectly tight, the pressure of the 
upward stroke will cause the valve, w, to open. /%g. 32 shows the joining 
of the several pieces of the lifting-pipe. 
Water containing copperas in solution is injurious to leather packing by 
rendering it hard. In such cases plungers of solid metal without any pack- 
ing are to be preferred (fig. 30), and in the copper and zinc mines in Corn- 
wall they are generally in use. 
Before: closing this article we must say a few words about some mines 
which claim our attention, either by the peculiarity of the mode of working 
or by their picturesque appearance. Among these are the Swedish mines 
at Falun and Persberg; of the former we have given an exterior view 
(pl. 28, fig. 1), and a view of the great cauldron with the head of the work- 
ing-shaft (pl. 25, jig. 2); and of the second the exterior view (pl. 23, jig. 2) 
and the interior view of the rock chambers (pl. 25, jig. 1). The copper 
mines at Falun and Persberg have long been celebrated, but are now nearly 
exhausted. In the time of Gustavus Adolphus they yielded yearly over 
5,000,000 pounds. The principal entrance, which we have represented, is 
240 ft. deep and 60 ft. wide, and was formed by a terrible caving in which 
occurred in 1687. It was then resolved to suspend the working, but upon 
a revolt of the miners the labors were resumed. 
A singular impression is made upon the beholder by the interior of the 
mill-stone quarry at Niedermendig on the Rhine (pl. 26, jig. 2), with its 
colossal arches and pillars. The quarrying of the stones is quite simple. 
The hardness of the stone is such that neither masonry nor timbering is 
required, but immense pillars are occasionally left to support the roof. 
The stone is blasted in large blocks, which are first worked cylindrical, and 
split with wedges into disks of the required thickness; the stones are then 
dressed, the hole is cut, and they are sent up to the surface completed. 
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