Drift (mining)

“ Rock and earth on the one hand, and metal and ore on the other, are filled into buckets separately and drawn up to the open air or to the nearest tunnel. If the shaft is not deep, the buckets are drawn up by a machine turned by men; if it is deep, they are drawn by machines turned by horses.
It often happens that a rush of water or sometimes stagnant air hinders the mining; for this reason miners pay the greatest attention to these matters, just as much as to digging, or they should do so. ”

“ It will also now be seen why the drift is the simplest and most economical mode of making an entrance to a mine. In this method there is no expense for removing earth or for cutting through rock, nor any cost at any time of pumping water or of hoisting coal. When the fact is remembered that it sometimes costs from $50,000 to $100,000 to sink a deep shaft through hard rock, and that to this amount must be added the cost of buildings, machinery, and repairs, and the perpetual cost of pumping water and of hoisting coal, the economy of the drift method will be appreciated. ”

“ It will be seen at once how that, in sinking a new shaft into a coal-seam, the possibility of an unknown fault has to be brought into consideration, since the position of the seam may prove to have been depressed to such an extent as to cause it to be beyond workable depth. Many seams, on the other hand, which would have remained altogether out of reach of mining operations, have been brought within workable depth by a series of step-faults, this being a term applied to a series of parallel faults, in none of which the amount of down-throw is great. ”

“ When mines are fully worked, the main shaft is frequently continued down to other seams of coal, which are excavated in the same way as the first seam. In such cases the workings communicate with each other by shafts called ‘staples,’ which are sunk at intervals between the seams of coal.
GENERAL VIEW OF MINING OPERATIONS.
The principle of long-wall working (Shropshire and Derbyshire method) is the extraction of all the available coal by the single process of first working, maintaining the roads by means of stone-walls or wooden props. ”

“ It is therefore only near the outcrop, or where the mine is not deep, that a fall in it disturbs the earth at the surface. But in the mining of the upper veins such disturbances were frequent. In passing through the coal regions one will occasionally see a depression, or a series of depressions, in the earth’s surface to which his attention will be attracted on account of their peculiar shape. They are not often more than ten or fifteen feet in depth, and though of irregular outline their approximate diameter seldom exceeds sixty feet. ”

“ Here the tunnel suddenly ended, and from the blank back 'face' a rough, broken pile of coal streamed down on both sides of the car and reared up before it against the roof.
'Just shovel 'er full, then wait till the motor takes her out and sends in an empty, and fill that one. I’ll look in on you once in a while and see how you’re getting along.'
Then he turned and walked down the track and left me in the dim light of my single pit-lamp.
II
In the first days of coal-mining—as in many mines to-day where modern methods have not superseded those of old-time miners—a man did all the work. ”

“ Twenty yards from this was a cone of black earth twice the height of a man. This was their pile of pay dirt. For five days now, they had been working on the second 35 mine of the seven. The pay dirt they had struck was not as rich as they hoped to find, but it would repay the labor of sluicing. It was growing richer each hour. They hoped in time to uncover the mother-lode. This would pay for panning and yield a rich reward.
It was placer mining. Beside the mine entrance stood a steam thawer, a coal-heated boiler such as is used for driving a sawmill or grist-mill engine. ”

“ The most remarkable advance, which in recent, or perhaps in any, times has been made in the practice of mining consists in the substitution of machine for hand labour in rock boring. The importance of this change is obvious, and very great. Not only is the miner relieved thereby of the labour of boring, but the speed with which the shot-holes may be bored is increased a hundredfold. This gain of speed offers many practical advantages. The ability to sink a shaft or to drive a heading rapidly may ensure the success of an undertaking, and save indirectly the expenditure of large sums of money ”

“ The artificial ditch supplies the want. The ditches are made by large companies, which sell the water by the "inch." An inch of water is as much as will run out of an orifice an inch square, with the water standing six or seven inches deep in the flume over the orifice. The depth of water over the orifice is called the "head." The orifice is usually two inches high, and as long as necessary to give the amount of water desired. Nobody wants less than ten or twelve inches for mining: a "sluice-head" is about eighteen inches; a "hydraulic-head" is from forty to two hundred inches. ”

“ The placer miner throws the dirt into the water, which then does the work; whereas the pulverizing of rock is a nice operation, requiring constant attention. Quartz requires a mill and water-power; placer dirt is washed in a simple sluice. Dirt containing ten cents in the cubic yard may pay the hydraulic miner, but the quartz miner must have a hundred times as much in a cubic yard of vein stone, or he cannot work. The placer gold, when freed from the baser material surrounding it, is much of it in coarse particles, which are easily caught by their specific gravity ”

“ If the air of a mine contains a sufficient quantity of the gas, and a flame accidentally fires the mixture, there results one of those disastrous explosions with which the history of coal mining has unfortunately only made us too familiar. ”

“ On our knees we pushed the buggy into the room, took up the hammer, broke up the coal into lumps we could handle, filled up the small box, dragged it out into the entry and emptied it into a heap. This is called "buggying" coal. It is the most laborious part of mining. Whenever a new man would be placed with the convicts for instructions in mining he would have to buggy coal just as long as it was possible to get him to do so. ”

“ When the coal seam thins out so rapidly that the floor and roof come nearly together, this state of things is called a pinch, or squeeze, though the latter term is more properly applied to the settling of the roof rock after the coal has been mined out. The inequalities of a coal seam that have now been mentioned, although perhaps but a small portion of those that are daily met with in the process of mining, are neverthless characteristic of the whole. ”

“ The seam is worked on successive levels, but, even then, it is impossible to prevent constant accidents from the fall of coal or the sudden collapse of a roof. Take it the world over, and ten miners are killed every day in collieries alone. I told you coal mining was dangerous. ”

“ This ore is frequently almost as hard as iron itself, many of the pieces thus dislodged being too large for convenient handling, either by the steam shovel or in the chutes at the wharves, and must be still further broken up. This is sometimes done by the men with picks; but in mining on a large scale, where the deposit is all of a very hard nature, crushing machines are used. ”

“ In rich fields, there are from three to ten of these rich layers or beds of coal, one above another. It often happens that the thickest and best layer is the lowest, and when this is the case, it is usually mined first, regardless of the fact that some, and possibly all, of the higher beds are dislocated and broken or filled with deadly gases. Nearly all this loss could be avoided by simply mining the upper stratum first. ”

“ The round walled shafts have a longer life than timbered shafts. All these advantages pertain much more to mining coal or iron than metals, for unsound, wet ground is often the accompaniment of coal-measures, and seldom troubles metal-mines. Ventilation requirements are also much greater in coal-mines. From a metal-miner's standpoint, round shafts are comparatively much more expensive than the rectangular timbered type. ”

“ Before leaving the question of shale mining, it should be explained that the shale miner is subject to dangers much as his colleague in the coal-pit, but the volume of gases found in the shale seams is not so great as in the coal measures. These, however, are 140 of an explosive nature, the most common being fire-damp.
Once above ground, the shale is conveyed to breaking machines by endless wire-rope haulage. Passing through the machines, it is broken into suitable sizes for distillation, and drops into hopper-shaped hutches. ”

“ Those who are acquainted with the present practice of mining are aware that when an estate is taken, and about to be worked for coal, the first question to be decided is the dip of the measures, in order that the sinking may be made203 “on the deep” of the whole range. The pits are not sunk at that part of the same range where, at first sight, the coal appears the most accessible, but, on the contrary, at the deepest part. It is then carried on to some depth below the coal seam which is to be worked, in order to form a “sumpf” or receptacle from which the water may be wound or pumped. ”

“ The inequalities of roof and floor, the pitching seams, the folds and faults and fissures, all the [31] accidents and irregularities of formation and of location, make up but a few of the problems which face the mining engineer. But the intellect and ingenuity of men have overcome most of the obstacles which Nature placed in the way of successful mining when she hardened the rocks above her coal beds, crowded the earth’s crust into folds, and lifted the mountain ranges into the air. ”

“ By the separation of seams one from another, and by varied intervals of waste sandstones and shales, such a measured rate of mining is necessitated as precludes us from entirely robbing posterity of the most valuable mineral fuel, while the fuel itself is preserved from those extended fractures and crumblings and falls which would certainly be the consequence of largely mining the best bituminous coal, were it aggregated into one vast mass. ”

“ You see, there are three ways of opening a coal-mine, Miss Bessie, of which this is the very simplest. The river, there, has cut down through the seams of coal and left them exposed, so all we have to do is to hunt up those most favorably located and work right back into them. That sort of entrance is called a drift, and is the cheapest as well as simplest, because every blow of the pick brings down so much coal. ”

“ He's got to know his business thoroughly or he's useless to the mine boss and a danger to all his fellow-workmen.
"And that isn't all, Anton, not by a good deal!
"Coal mining might be bad enough, even if the coal seams always ran level. But it's very seldom that they do. They run up-hill and down-hill in all sorts of fashions and play hide-and-go-seek in a way that's fairly bewildering.
"Nearly all coal seams are broken up by faults. The coal suddenly seems to stop, and, when you go to hewing it the pick suddenly hits [Pg 51] against a rock wall, right on the level of the seam. ”

“ In view, then, of these reasons, it is proper to decide that mining is a term broad enough to cover the operations of extracting coal and metallic ores from the ground and of preparing them for shipment or metallurgical treatment.
Coal is always coal, no matter in what thickness of deposit it is found. It may not be minable coal because in thin seams or because so intercalated with layers of slate or "bone," that the mine's mixture, or so-called "run of mine," is not salable. ”

“ However, as the lowest layers are nearly four miles deep, they will probably never be worked."
"Why not?"
"To start with, the cost of haulage to the top would be enormous. But, aside from that, a good [Pg 48] many mining engineers figure that the temperature at that depth would be above boiling point. You know, in general, the farther you go down in a mine, the hotter it gets."
"What do you mean by a seam being 'workable'?" the boy queried. "Can't all coal be dug out?" ”

“ The miners work is as follows; first they sink a shaft so many feet down, and then when they get down deep enough they start sapping forward, putting up timbers as they go. They have to work very quietly as Fritz also does some sapping and if too much noise is made the miners themselves are liable to go up in the air and come down in pieces, and I do not think that anybody would relish that idea. Mining is done now on a very large scale. ”

“ The miner then holding the pan with the open end from him, blows out the sand, leaving the particles of gold. He must blow gently, just strong enough to blow out the sand, and no stronger. From time to time he must shake the blower so as to change the position of the particles, and bring all the sand in the range of his breath. ”

“ In mining regions where water transportation is interrupted during certain months of the year the mineral must be stored underground, or in great stock-piles on the surface. In coal mining the market demand varies in different seasons, and surface storage is sometimes necessary to permit regular work at the mines. For coal, iron ore and other cheap minerals, mechanical handling by many different methods is used in loading and unloading railway wagons and vessels, and in forming the stock-piles and reloading the mineral therefrom. ”