Mines (underwater)

“ When we have to use drainage tunnels for our mines we carry the water off from the mouth of the tunnel in a flume, placing quicksilver in the riffles, and if it is a copper mine we place scrap iron in the water and we also use the water for power to assist us in mining, so that at the present time we extract and reduce ore at a lower rate than in other parts of the world, for there is no wastefill management and no overproduction, for in all our mining operations we work those that cost the least, and we operate our coal mines in the same way. ”

“ The drowning of a coal mine not seldom occurs from the irruption of water accumulated in old wastes or ancient workings occupying a higher level in the vicinity. The growing pressure of such a body of water upon the beds or barriers below becomes enormous; and then the water, testing every weak point of the body opposed to its escape, at length unexpectedly rushes into the space which it finds open before it. All the works below are completely filled, and the mines are for a time rendered useless, or, it may be, for ever abandoned. ”

“ 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. ”

“ The smaller mines, besides being generally more superficial, are commonly situated upon acclivities, and thus an accumulation of water seldom incommodes the mining; but the larger ones are more frequently in valleys, and soon filled with water, which it is necessary to remove. This is effected by a common and cheap hydraulic Chinese machine. Sometimes a canal is made to pass close to the mine, for the purpose of facilitating the labor of removing the upper strata of sand and clay, which are thrown into it as extracted, and thus carried off by the stream. ”

“ Mines for the open sea in great numbers, moored “flying”—that is, by ships steaming at considerable speed—need anchors with automatic depth regulation. Such mechanism had undergone important changes during the war, and the new American mines needed all the improvements, to make them sure to plant at the intended level. ”

“ Indeed, when we consider the measure of the underground cavities which miners have excavated, we cannot but be surprised that grave catastrophes have not often resulted from the removal of the foundations on which the crust of our earth is laid. The 100,000,000 tons of coal yearly extracted from British mines require the withdrawal of subterranean strata equal to an area of 20,000 acres one yard deep, or 2,000 acres ten yards deep. These excavations have gone on for several years at this rate, and in smaller proportions for centuries. ”

“ Where appreciable current exists, a heavy sea may cause mines to step along, or “migrate”—there is no telling how far—and the danger from mines adrift is naturally greater near a minefield than elsewhere. Mines are designed to become safe on breaking adrift and many of them are, but far from all. Submergence in salt water may derange the mechanism for that safety purpose. There was very little current across Area A, however, and the fine tactical qualities shown by the squadron lent confidence that it could be safely conducted much nearer to our minefields than five miles. ”

“ The duration of the mines, as a whole, is therefore a difficult problem, for it involves the question whether many pieces of reef, which are now little worked or not worked at all, will in future be found worth working, owing to cheapened appliances and to a larger yield of gold per ton of rock, in which case the number of mines may be largely increased, and reefs now neglected be opened up when the present ones have been exhausted. ”

“ Another important problem that constantly confronts the mining engineer is that of drainage. Mines are, of course, great reservoirs for the accumulation of water, which must be drained or pumped out continually; and as the shafts are sunk deeper and deeper it becomes increasingly difficult to raise the water to the surface. ”

“ Mill of the Pittsburg-Silver Peak Gold Mining Co., Blair, Nevada.
Water may be too scarce for the needs of a mine or its community. There may not be sufficient to supply boilers or a mill, or for the domestic purposes of the [89] workers. On the other hand, water may be so abundant in the mine workings as to prove a deterrent factor in profitable operation. With shaft mines, having deep workings and low grades of ore, if water must be delivered mechanically, the costs for such drainage are frequently prohibitive of mining. ”

“ Submerged mines are more dangerous to the enemy because they cannot be seen and avoided. They should float far enough under the surface to remain hidden and yet not so deep that a shallow-draft ship can pass over them without hitting them. As the sea bottom may be very irregular, it is impossible279 to tell how long the anchor cable should be without sounding the depth of the water at every point at which a mine is planted. ”

“ The shafts are wide, the galleries high enough to allow one to walk upright through them. The upper stories are almost thoroughly dry, the lower ones humid; the water, however, is easily removed by hand-pumps, which raise it from story to story into a large subterranean reservoir, emptied once a week by a steam-engine of fifty-four horse-power. The veins are so extremely rich that, though they have been worked pretty constantly during so many centuries, the mines have hardly reached the depth of 1,140 feet. ”

“ When a mine is so situated that drainage galleries cannot be established, engines must be employed for pumping up the waters. Thus, in Cornwall, where most of the copper mines open almost at the sea level, an enormous influx of water can be kept in check only by an equally enormous steam-power. In the United and Consolidated Mines between Truro and Redruth, seven steam-pumps, working with the united strength 272of 2,000 horses, are kept constantly in motion, and raise above 2,500,000 gallons of water in twenty-four hours. ”

“ For the deep mines of the United States, the developed reserves have a life of perhaps only five years, but for most of these mines the life will be greatly extended by further and deeper development. The porphyry coppers, because of their occurrence near the surface and the ease with which they may be explored by drilling, disclose their reserves far in advance. The deep mines are ordinarily developed for only a few years in advance of production. ”

“ Amongst the scores of mines that were opened up, it is safe to say there has scarcely been one that, sooner or later, has not entered into a zone of serious earth-movement. In some cases, after the shoots had been dislocated by these movements, their downward continuations have been picked up again, as in the Wealth of Nations and Big River Mines—in the former it was only after about sixteen years of groping—but in most instances they were never located. ”

“ A submarine mine of to-day consists of a mine case, shaped like a ball or egg, about one yard in diameter, mounted on an anchor in the form of an iron box about 30 inches square, connected by a wire rope mooring cable, about 3⁄8 inch in diameter. The mine case contains the charge of high explosive—300 pounds of TNT in our mines—and the firing mechanism. The combination stands about 5 feet high and weighs 1400 pounds. Four small car wheels on the anchor run on steel tracks, allowing the mines to be easily moved along the decks to the launching point. ”

“ The working of the mines has been seriously impeded and made vastly more expensive by the treacherous nature of the "reef," or formation of yellowish and blue shale with which its upper part is surrounded. Wherever this rock is exposed it becomes disintegrated, and is then liable to slip down at any time, like a land-slide, upon the miners working beneath it, covering up their claims and making it extremely difficult as well as dangerous to work in them ”

“ Safety arrangements are employed to prevent the Bring apparatus working while the mine is being laid, and clockwork is sometimes added to render the mine inactive after a certain definite time or in case the mine breaks away from its mooring. Their principal advantages, as compared with the electrically controlled mines, are cheapness and rapidity of laying. “Controllable” mines are absolutely under the control of the operator on shore, their condition is always accurately known, and if any break adrift not only is the fact at once known but the mines themselves are harmless. ”

“ Thus, if such a mine were to be used at all, we should have had to plant several layers, one under the other, down to a depth of about 250 feet, so that the submarine, at [Pg 250] whatever depth it might be sailing, would be likely to strike one of these obstructions. This required such a large number of mines as to render the whole project impossible. We Americans may take pride in the fact that it was an American who invented an entirely new type of mine and therefore solved this difficulty. ”

“ The expense of working such valuable quartz mines up a hundred or more miles from the sea, will result in abandonment, where reaching them involves frequent transfers of supplies, and the working season is cut by the rigor of winter to less than half or one-third of every year. The same mines, down within the dockage of an ocean-steamer in the Sitkan district would be a steady source of wealth and industry all the year round. ”

“ An account is given of the mine barrage in the North Sea, one of the outstanding anti-submarine offensive projects of the year, thus closing the North Sea, and for which 100,000 mines were manufactured and 85,000 shipped abroad. A special mine-loading plant, with a capacity of more than 1,000 mines a day, was established by the Navy Department.
A star shell was developed which, when fired in the vicinity of an enemy fleet, would light it up, make ships visible, and render them easy targets without disclosing the position of our own ships at night. ”

“ From fire on the one hand, we pass, on the other, to the danger which awaits miners from a sudden inrush of water. During the great coal strike of 1893, certain mines became unworkable in consequence of the quantity of water which flooded the mines, and which, continually passing along the natural fractures in the earth's crust, is always ready to find a storage reservoir in the workings of a coal-mine. ”

“ Upon the bed-rock is a deposit, from three to four feet in depth, of gravel and boulders, in which the gold is hidden. This is called by the miners "pay-dirt," and to remove it to the surface and wash it is the end of mining. It is an expensive and laborious process indeed. The water has first to be controlled; and in mines of not too great depth this is done by a drain ditch along the bed-rock, commenced many claims below. In this all the claim-holders are interested, and all contribute their quota of the labor and expense of digging it. ”

“ The passages to the mines are so narrow, that persons can with difficulty pass each other; they then expand into high vaults, the roofs of which are ornamented with beautiful crystals of celestine and gypsum. On account of the excessive heat, the workmen labour in a nearly nude state, their dark brown skins sprinkled with light yellow sulphur dust, making them look savage and strange in the extreme. Towards the end of the last century, the sulphur mine of Sommatin caught fire, the conflagration causing the complete abandonment of the pit. ”

“ Since the first discovery of lead in this Territory, the number of mines has been much increased, and hardly a season passes without some new discovery. Every discovery of importance soon becomes the centre of mining attraction. As the ore is found in the diluvial soil, it is generally exhausted on reaching the solid rock; and after penetrating a considerable area of the surface with any, or but partial success, the locality is abandoned, and a new one sought. As the mines are worked without capital, and the ore is dispersed over a wide area, the number of localities is almost indefinite. ”

“ But accidents due to a flooding by surface water are not always to be obviated. Sometimes when a stream crosses the line of outcrop the water will break through into the mine and flood the lower levels in an incredibly short space of time; and this too when good judgment and prudence have been used in leaving sufficient coal for protection. The continuity and character of the strata lying between the earth’s surface and the coal face cannot always be determined. It is not often that accidents from flooding occur while mining is going on under large bodies of water. ”

“ The water was now pumped out of the mine and the machinery set to work; but the sea penetrated through the fissures of the rock, and greatly added to the labour of the workmen, while during the winter months, on account of the swell, it was impossible to convey the tin ore to the beach. Notwithstanding all these difficulties, the persevering projector was rewarded by obtaining many thousand pounds worth of tin. At length, during a gale, an American vessel broke from her moorings, and demolished the machinery by striking against the stage, when the water rushing in filled the mine. ”