Mine shaft

“ After the shaft demonstrates that the dirt is rich, and precisely the altitude at which it lies, a tunnel is cut to strike it. The shaft may be the cheaper for prospecting, but the tunnel is usually the cheaper if any large amount of dirt is to be taken out.
The shaft is dug by one man in the hole, and one or two are employed at a windlass in hauling up the dirt. Mining-shafts in placer diggings are rarely over one hundred feet deep; but one was dug in Trinity county to the depth of six hundred feet, for the purpose of prospecting, but it found neither pay-dirt nor the bed-rock. ”

“ Shaft-mining did not come in before 1450, when the stream tin was exhausted. The use of the adit cannot be traced back beyond the beginning of the seventeenth century. The only way of draining the mines was by rag and chain pumps, each consisting of an endless chain, broadened at intervals by leathern bindings, to fit snugly into a pipe from 12 to 22 ft. long, worked by a windlass at the surface. ”

“ I descended into several of the mines, among others into the Descubridora, which is one of the deepest, and I always felt that I had good reason to congratulate myself on returning to the surface of the earth in safety. Rotten blocks of wood and loose stones serve for steps, and, where these cannot be placed, the shaft, which in most instances runs nearly perpendicular, is descended by the help of rusty chains and ropes, whilst loose fragments of rubbish are continually falling from the damp walls. ”

“ In deep mines, as has already been said, it is customary to build stables not far from the foot of the shaft, and to keep the mules there except when for any reason there is a long suspension of work. ”

“ The shaft may be either vertical or inclined, according to local conditions, especially according to the position of the ore body. The inclined shaft is sometimes known as an incline. A shaft is usually rectangular in section. In very small mines it may be no more than four feet square, but in large mines the shafts are much larger, large enough to permit the working of at least two hoists, called cages or skips. There must also be room for pipes, both for carrying down compressed air and for the carrying out of water. Large mines frequently have shafts as much as 12x18 feet in diameter. ”

“ For the purpose of better ventilating the mine, an enormous fan, forty feet in diameter, formed like the paddle-wheels of a steam-ship, and kept constantly revolving by steam-power, was placed over a shaft sunk for that sole object. The suction caused by the enormous paddles drew up all the foul air and noxious vapours from the whole of the mine, and at the same time drew in from another shaft, more than a mile distant, a current of fresh air, amounting from 70,000 to 80,000 feet per minute, thus doing the work of a furnace far more effectually, and at much less cost. ”

“ The pillars, owing to the great height of the roof, are very massive. For twenty feet of rock they are about fifteen feet thick. The descent to the mines is by a shaft—a perpendicular opening of six, eight, or ten feet square; this opening is used for the general purposes of ventilation, drainage, lifting the mineral, as well as the miners. It varies in dimensions according to the extent of the excavations. In some of the English mines the part of the bed of rock-salt excavated amounts to several acres; but in some parts of Europe the workings are even more extensive. ”

“ Next to the shaft-house another house is built, where the mine foreman and the other workmen dwell, and in which are stored the ore and other things which are dug out. Although some persons build only one house, yet because sometimes boys and other living things fall into the shafts, most miners deliberately place one house apart from the other, or at least separate them by a wall. Now a shaft is dug, usually two fathoms long, two-thirds of a fathom wide, and thirteen fathoms deep ”

“ At the bottom of this shaft was millions of dollars worth of copper and level after level of expensive workings; and some great stirring of the earth was cutting it off, crushing the bottle off at the neck. Every night, every shift, the swelling ground moved in, breaking stulls and square-sets like tooth-picks; and now with solid steel and quick-setting concrete they were fighting for the life of the mine. ”

“ In metal mines under Cases II and III (outcrop properties) the ore output requirements are seldom beyond the capacity of one shaft. Ventilation and escape-ways are usually easily managed through the old stopes. Under such circumstances, the Page 73 conditions warranting a second shaft are the length of underground haul and isolation of ore-bodies or veins. Lateral haulage underground is necessarily disintegrated by the various levels, and usually has to be done by hand. ”

“ At length these pillars are removed, and props of wood placed instead, and thus the whole mine is worked out. There are miles and miles of passages in which tramways are laid down, leading to the shaft, up which the coal is raised. As the air in the mine has a tendency to get foul and close, it is necessary to send currents of wind into the passages to blow it away. The chief object is to make the wind come down one shaft, and then to bring it along through the passages, and so up by another shaft. If the wind which came down were allowed to wander about, it would produce no good effect. ”

“ At many mines, however, the greater convenience of having the stables on the surface induces the operators to have the mules hoisted from the shaft every night and taken down every morning. They step on the carriage very demurely, and ascend or descend without making trouble. They are especially glad to go up to their stables at night. Where mules are fed in the mine, and especially in those mines that have stables in them, rats are usually found. How they get down a shaft is a mystery. ”

“ There is only a hole in the ground, where mining is carried on in much the same manner as in other kinds of mines. The shaft is sunk and lined with timbers to keep the dirt from falling in, just as in other mines. In working salt mines, however, water is almost as bad as earth, and therefore a layer of clay is put between the timbers and the earth. There are the usual galleries and pillars, with roof and floor of salt. The workmen try to get the salt out in lumps or blocks as far as possible, and so they bore in drill holes and then blast with dynamite or powder. ”

“ A gold mine now consists of a shaft or pit dug several hundred feet down into the rock, with levels or galleries running off from it and with big openings like rooms made where the rock was dug out. The roofs of the rooms are supported by great timbers. To break away the rock, the miner makes a hole with a rock drill worked by electricity or compressed air, puts powder or dynamite into the hole and explodes it. The broken rock is then raised to the surface and crushed in a "stamping mill." Here the ore is fed into a great steel box called a "mortar." ”

“ The ascertained area of the mine is several acres; the depth of the deposit is unknown. The first shaft was sunk a hundred feet; below this a shaft of seventy feet fails to find any limit to the salt. The excavation is already large. Descending, the visitor enters vast cathedral-like chambers; the sides are solid salt, sparkling with crystals; the floor is solid salt; the roof is solid salt, supported on pillars of salt left by the excavators, forty or perhaps sixty feet square. When the interior is lighted by dynamite the effect is superbly weird and grotesque. ”

“ Most of the veins are in such places that shafts are more easily dug than tunnels. After the excavation has extended twenty or thirty feet below the surface, it is usual to dig a perpendicular shaft, so as to strike the vein sixty or seventy feet below the surface, and from this point the miner or "drifter" works upward, and as he loosens the rock it falls to the bottom of the shaft, where it is put in the bucket to be hoisted to the surface. Our quartz mines are generally in dry hills, so that they are not troubled much by water ”

“ Where mining is done by shaft there is seldom any other way provided for the passage of workmen in and out than the way by the carriage. A small shaft for the admission of air is sometimes driven down to the highest part of the seam, and ladders are placed in the opening on which men may climb up and down, but these ladders are seldom used save in an emergency. It is made obligatory upon operators, by the act of 1885, to provide two openings to every seam of coal that is being worked ”

“ Although such shafts would have a longer life, the duration of timbered shafts is sufficient for most metal mines. It follows that, as timber is the cheapest and all things considered the most advantageous means of shaft support for the comparatively temporary character of metal mines, to get the strains applied to the timbers in the Page 75 best manner, and to use the minimum amount of it consistent with security, and to lose the least working space, the shaft must be constructed on rectangular lines. ”

“ Let us suppose that a mine has been already opened; that a “lode”—that is, a vein of quartz with metal in it—has been discovered cropping out of the earth, and that it has been dug down upon from above, and dug in upon from the sea-cliffs. A shaft has been sunk—in other words, a hole excavated—let us say, two or three hundred yards inland, to a depth of some forty or fifty fathoms,—near the sea-level. This shaft is perhaps nine feet by six wide. The lode, being a layer of quartz, sometimes slopes one way, sometimes another, and is occasionally perpendicular. ”

“ It is as a consequence necessary to take some special steps to provide an efficient system of ventilation throughout the mine. This is effectually done by two shafts, called respectively the downcast and the upcast shaft. A shaft is in reality a very deep well, and may be circular, rectangular or oval in form. In order to keep out water which may be struck in passing through the various strata, it is protected by plank or wood tubbing, or the shaft is bricked over, or sometimes even cast-iron segments are sunk. ”

“ MINERS DESCENDING SHAFT IN OWEN’S SAFETY CAGE.
In many mines the workmen climb up and down the shafts on fixed ladders, with landing-stages for resting; and it may easily be imagined how severely their strength must be taxed when, after their hard day’s labour, they have still to ascend step by step a thousand or even two thousand feet, before they can return to their families. ”

“ If the material to be mined lies in a horizontal bed, the shaft is sunk down to the level of the material to be mined or a little below. Tunnels are then made, leading sidewise from the shaft into the substance to be mined. The material to be mined is worked out along these tunnels, carried to the shaft and hoisted to the surface. When the material which is being mined is worked out, it often is necessary to put in timbers to keep the mine open. If, for example, a horizontal bed of coal is being mined, the taking out of the coal leaves the rock above unsupported. ”

“ 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. ”

“ Unlike bad companions, however, they increase its value at the point of meeting by thickening it. Whatever course the lode takes, the miner conscientiously follows suit. His shaft slopes much, little, or not at all, according to the “lie of the lode.”
It is an ancient truism that water must find its level. Owing to this law, much water accumulates in the shaft, obliging the miner to erect an engine-house and provide a powerful pumping-engine with all its gear, at immense cost, to keep the works dry as he proceeds. ”

“ Added to these various dangers which exist in the coal-mine, we must not omit to notice those accidents that are continually being caused by the falling-in of roofs or of walls, from the falling of insecure timber, or of what are known as "coal-pipes" or "bell-moulds." Then, again, every man that enters the mine trusts his life to the cage by which he descends to his labour, and shaft accidents are not infrequent. ”

“ With it came overhead stoping, in which, after the shaft has been sunk, the level driven and timbered, and a raise made, the miner begins breaking down the ore from over his head, allowing it to run down into chutes. From these it is drawn out into cars pushed along the tracks in the level. The waste is allowed to accumulate on top of the stulls, or timbers, forming the top of the level above referred to, and serves as a platform upon which the miner stands in breaking down more ore. ”

“ Sometimes, when the mining is done by shaft or slope, there is a separate entrance for men and mules, a narrow tunnel or slope, not too steep, and in this case, though his duties lie entirely in the mine, the driver boy must take the mule in from the outside stable in the morning and bring him back at night. ”