MINING 



317 



1476 



pumped up ; by A B and E p the whole extraction are carried on. The ores are raised 

 in these shafts to the level of the waggon-gallery (galerie de roulage) i, by the 

 whims 1, q, provided with ropes and buckets. 1, 2, 

 3, 4, fig. 1475, represent the positions of four water- 

 wheels for working the whims ; the first two being 

 employed in extracting the ores, the last two in 

 draining. The driving-stream is led to the wheel 1, 

 along the drift I ; whence it falls in succession upon 

 the wheels 2, 3, 4. The general system of working 

 consists of the following operations : 



1. The bed of ore is got at by the transverse 

 galleries m, n, o, q, r, s, which branch off from the 

 extraction-shaft, and terminate at the wall of the 

 main bed ; 



2. Great faults are scooped out at the level of the 

 workings, by moans of fire ; 



3. The roofs of these vaults are progressively 

 propped with mounds of rubbish ; 



4. The ores thus detached, or by blasting with gun- 

 powder, are then collected ; 



5. Lastly, they are brought out to the day, and 

 washed near z. 



Of the Instruments and Operations of Subter- 

 ranean Mining. It is by the aid of geometry, in the 

 first place, that the miner studies the situation of the 

 mineral deposits on the surface and in the interior 

 of the ground; determines the several relations of 

 the veins and the rocks ; and becomes capable of 

 directing the perforations towards a suitable end. 



The instruments are : 



1. The magnetic compass, which is employed to 

 indicate the direction of a metallic lode. 



2. The graduated semicircle, which serves to 

 measure the inclination or dip; this instrument is 

 also called the clinometer. 



3. The chain or cord for measuring the distance of one point from another. 



4. When the neighbourhood of iron makes the use of the magnet uncertain, a plate 

 or plane table is employed. 



In order to penetrate into the interior of the earth, and to extract from it the ob- 

 jects of his toils, the miner has at his disposal several means, which may be divided 

 into three classes : 1, manual tools ; 2, gunpowder ; 3, fire. 



The tools used by the miners of Cornwall and Devonshire are the following : 



Fig. 1477. The Pick. It is a light tool, and somewhat varied in shape according 

 to circumstances. One side used as a hammer is called the poll, and is employed to 

 drive in the gads, or to loosen and detach prominences. The point is of steel, care- 

 fully tempered, and drawn under the hammer to the proper form. The French call it 

 pointerolle. 



Fig. 1478. The Gad. It is a wedge of steel, driven into crevices of rocks, or into 

 small openings made with the point of the pick. 



Fig. 1479. The Miner's Shovel. It has a pointed form, to enable it to pene- 

 trate among the coarse and hard fragments of the mine-rubbish. Its handle being 

 somewhat bent, a man's power may be conveniently applied without bending his body. 



The blasting- or shooting -tools are : a sledge or mallet, Jiff. 1480 ; borer, fig. 1481 ; 

 claying-bar, fig. 1482; needle or nail, fig. 1483; scraper, fig. 1484; tamping-bar, 

 fig. 1485. 



Besides these tools, the miner requires a powder-horn ; he is supplied with safety- 

 fuse (see SAFETY-FUSE) ; tin cartridges for occasional use in wet ground ; now more 

 frequently is he supplied with cartridges made with well pitched paper. 



The borer, fig. 1481, is an iron bar tipped with steel, formed like a thick chisel, 

 and is used by one man holding it straight in the hole, with constant rotation on 

 its axis, while another strikes the head of it with the iron sledge or mallet, fig. 1480. 

 The hole is cleared out from time to time by the scraper, fig. 1484, which is a 

 flat iron rod turned up at one end. If the ground be very wet, and the hole gets 

 full of mud, it is cleaned out by a stick bont at the end into a fibrous brush, called 

 a swab-stick. 



Fig. 1486 represents the plan of blasting the rock, and a section of a hole ready for 

 firing. The hole must be rendered as dry as possible, which is effected very simply 



