MINING 



215 



testing the character of the foundation subsoil, or, 

 in other cases, to thousands of feet when required 

 in seeking for or estimating the value of deposits 

 of coal, salt, and ironstone. Ages ago bore-holes 

 were put down by the Chinese to a depth of 3()00 

 feet. Recently, in Europe and America, depths of 

 2000 feet have not untrequently been attained. 

 At Schladebach, near Mersehurg, the deepest bore- 

 hole in the world has been put down by the 

 Prussian government in search of coal. The sink- 

 ing occupied several years ( 1880-86), and the depth 

 attained amounted to 5834 feet. 



Bore-holes may be made by a circular l>orer 

 moved by a lever. The rods are of iron, with 

 square heads, and are turned by a cross-head 

 worked by a couple of men. In this way an auger- 

 like cutting action is effected. With harder rock 

 it is usual to advance by means of percussion.' A 

 chisel-headed tool is employed, which cuts holes of 

 3 to 4 inches in diameter. At each stroke the 

 bore-master causes the tool to turn slightly. When 

 sufficient debris has accumulated the rods are 

 withdrawn, and an instrument put down to extract 

 the powdered material and water. With a length 

 of rods amounting to 400 to 500 feet the weight is 

 enormous, and, in consequence of the concussion! 

 difficulties arise. Men are not suttifieiit to raise 

 the load. In some cases a lever is used to raise 

 the rods a few inches or feet, and to let them fall 

 suddenly. In other cases the rods are replaced 

 by a rope. This, however, from lieing wet and 

 dry alternately, is apt to snap suddenly, and the 

 rods remaining in the hole are difficult to recover. 

 The rods, too, may get twisted or the nature of 

 the iron itself be altered by the vibration. In 

 putting down a bore-hole, a tower or shears is 

 erected over the hole. By making this 60 to 70 

 feet high, the rods may lie extracted in lengths of 

 60 feet, and thus the 6 to 8 hours a day usually 

 spent in unscrewing the rods are saved. In some 

 coses it is necessary to tube or line the whole bore- 

 hole. See ISnniXO. 



Tlic> Chinese method of boring with ropes has been 

 imitated in Europe with great economy, but with 

 great liability to fracture and consequent I"-*. 

 This has been done by Messrs Mather & Platt 

 of Salford, who employ a chisel -bit with circular 

 sides so an to keep the We-hole true. This is 

 raised and allowed to fall a few inches or feet, 

 according to the nature of the ground. It is 

 attached to a weighty mass of iron with rings 

 nerving as guides. The whole mass is suspended 

 hy a Hat hempen rope. This rope passes over a 

 pulley to a drum on which a mass of ro|>e can be 

 accumulated. The pulley is attached to the piston- 

 rod of a steam-engine. 'The action of the steam 

 behind the piston lifts the pulley, and consequently 

 the tool, the rope, being clamped. The steam then 

 causes the tool to fall, and on falling it automati- 

 cally turns. A cylindrical tool can easily be inserted, 

 and a core obtained that shows the nature of the 

 rock and its inclination. At the Paris Exhibition 

 of 1802 a proposal was made to drill with a tube 

 in which diamonds were fixed. This was merely 

 intended for use on a small scale; but it was soon 

 applied to deep bore-holes. For this drill black 

 diamond is employed, a substance with the full 

 liardnss of the ordinary diamond and a certain 

 amount of toughness. " Though very expensive, 

 this method of l>oring is found advantageous when 

 great speed is required. The fall of rock in bore- 

 holes is apt to cause serious interruption on account 

 of the jamming of the rods. The sudden strain 

 iven to release them is liable to cause fracture, 

 "vj,|eg which the full work is not done by the rods. 

 Tim difficulty is obviated in several ways, notably 

 by replacing thfl iron rods by wooden ones, 30 to 32 

 feet long, with iron connections. The free-falling 



gi 

 b 



cutter proposed by Kind and the hollow rods of 

 Von Oeynhausen may be instanced as having 

 rendered good service in the execution of great 

 works. 



In order to open up a mine, tunnels or adit-levels 

 are driven on the lode or to cut it whenever the 

 contour of the country allows it. Shaft-sinking 

 involves a larger outlay of capital and greater 

 working costs. In the ordinary method of sinking 

 shafts, the workmen standing upon the bottom of 

 the pit blast out the rock, and send the excavated 

 material to the surface by means of an engine, 

 rope, and bucket. The sides of the shaft are 

 supported by timbering or walling. In water- 

 bearing strata many difficulties are encountered. 

 Brunei, the father of the great engineer, proposed 

 to obviate these by employing a circular frame 

 with a cutting ring. On this, with hydraulic 

 mortar, a wall was built and held firmly together 

 hy ties. In a second method, largely used in 

 modern collieries, beams of cast-iron are employed, 

 and 10,000 to 20,000 wooden wedges driven in, a 

 succession of cast-iron segments or rings, known as 

 tubbing, being built in. The shaft is thus sunk 

 and the water pumped out. Tubbing a shaft is a 

 very difficult operation, and the method has fre- 

 quently been known to fail after 20,000 to 30,000 

 has been spent. In order to get over the difficulties 

 and dangers, Kind, a German engineer, thought of 

 sinking a bore-hole with sufficiently large tools 

 consisting of solid masses of iron with sharp steel 

 teeth. The shaft having been bored, rings or cast 

 iron could, he thought, be fixed in and the water 

 pumped out. This was tried in 1840 in a very 

 difficult case and was found impracticable, and not 

 until 1860, when Chaudron, an eminent Belgian, 

 took the matter in hand, was the method successful. 

 A watertight l>ottom was made, half a dozen work- 

 men at the surface doing all the work. The, method 

 has been employed in the United Kingdom in a few 

 instances. One remarkable case may Tie mentioned. 

 At the mouth of the Tyne are coal-measures of 

 great value, and at South Shields attempts were 

 made to work the coal under the sea. Difficulty, 

 however, was caused by a band of magnesian lime- 

 stone highly charged with water. The enterprise 

 promised to be very costly. Tubbing was totally 

 unsuccessful, notwithstanding the fact that enor- 

 mous pumps were employed raising as much as 

 1 1,000 gallons of water per minute. The shaft was 

 14 feet in diameter, and if the pumping ceased the 

 water rose in the shaft 12 feet in two minutes. 

 Recourse was then had to the Kind-Chandron 

 method, which had previously been successfully 

 tried on the Continent. The trfpan or cutter of 

 the lioring tool was 3 or 4 feet in diameter, and the 

 hole was bored to a certain depth. A larger cutter 

 was then used. In this way the sides were formed 

 into inclined planes, so that the fragments rolled 

 into a suspended bucket in the smaller hole, the 

 bucket being raised from time to time. When a 

 [dace was reached where a watertight joint could 

 tie made, Chaudron's tubbing was applied and the 

 shaft successfully completed. In this tubbing the 

 bottom ring has a sliding case in which is placed a 

 quantity of moss, which, when the whole length of 

 tubbing comes to rest on the watertight bed cut 

 for it under water by the borer, packs together and 

 forms a tight joint. This method of sinking shafts 

 is practically self-acting. It is economical and 

 simjile, and eliminates risk to human life. In 

 ordinary shaft-sinking accidents are frequent, as a 

 screw or a hammer falling down the yawning gulf 

 is likely to produce a fatal injury. 



An ingenious device for overcoming the difficulties 

 of shaft-sinking was invented by a trench engineer, 

 Triger. This consists in damming back the water 

 by employing a constant resisting force ; that is to 



