Twentieth Century Inventions: A Forecast

by George Sutherland

The limit, nevertheless, has been reached in many rich mining districts. Pumps of the most approved type, and driven by the largest and most economical steam-engines, have done their best in the struggle against the difficulty; and yet the water has beaten them. Rich as are the lodes which lie beneath the water, the mining engineer is compelled to confess that the metal value which they contain would not leave, after extraction, a sufficient margin to pay for the enormous cost of draining the shafts. In some instances, indeed, it remains exceedingly doubtful whether pumps of the largest capacity ever attained in any part of the world would cope with the task entailed in draining the abandoned shafts. The underground workings have practically tapped subterranean rivers which, to all intents and purposes, are inexhaustible. Or it may be that the mine has penetrated into some hollow basin of impermeable strata filled only with porous material which is kept constantly saturated. To drain such a piece of country would mean practically the emptying of a lake.

Subaqueous mining is therefore one of the big problems which the mining engineer of the twentieth century must tackle. To a certain extent he will receive guidance in his difficult task from the experiences of those who have virtually undertaken submarine mining when in search of treasure lost in sunken ships. The two methods of pumping and of subaqueous mining will in some places be carried out conjointly.

In such instances the work assigned to the pumping machinery will be to keep free of water those drives in which good bodies of ore were exposed when last profitable work was being carried on. All below that level will be permitted to fill with water, and the work of boring by means of compressed air, of blasting out the rock and of filling the trucks, will all be performed under the surface. For the shallower depths large tanks, open at the top, will be constructed and slung upon trucks run on rails along the lowest drives. Practically this arrangement means that an iron shaft, closed at the sides and bottom, and movable on rails laid above the surface, will be employed to keep the water out. Somewhat similar appliances have been found very useful in the operations for laying the foundations of bridges.

The details requiring to be worked out for the successful working of subaqueous systems of mining are numerous and important. Chief among these must be the needful provision for enabling the miner to see through strong glass windows near the bottom of the iron shaft, by the aid of electric lights slung in the water outside, and thus to estimate the correct positions at which to place his drills and his explosives. For this reason the work of the day must be systematically divided so that at stated intervals the clay and other materials held in suspension by the disturbed water may be allowed to settle and the water be made comparatively clear.

Specially constructed strainers for the mechanical filtration of the water near the ore face, and probably, also, chemical and other precipitates, will be largely resorted to for facilitating this important operation. Beside each window will be provided strong flexible sleeves, terminating in gloves into which the miner can place his hands for the purpose of adjusting the various pieces of machinery required. Beyond this, of course, every possible application of mechanical power operated from above will be resorted to, not only for drilling, but also for gripping and removing the shattered pieces of rock and ore resulting from the blasting operations.

From the unwatered drive or tunnel downwards, the method of working as just described may be characterised as an underground application of the "open-cut system". No elaborate honeycombing of the country below the water-level will be economically possible as it is when working in dry rock. But then, again, it is becoming plain to many experts in mining that, in working downwards from the surface itself, the future of their industry offers a wide field for the extension of the open-cut system. In proportion as power becomes cheaper, the expense attendant upon the removal of clay, sand, and rock for the purpose of laying bare the cap of a lode at a moderate depth becomes less formidable when balanced against the economy introduced by methods which admit of the miner working in the open air, although at the bottom of a kind of deep quarry. While the system of close mining will hold its own in a very large number of localities, still there are other places where the increasing cheapness of power for working an open-cut and the coincident increase in the scarcity and cost of timber for supporting the ground, will gradually shift the balance of advantage on to the side of the open method.

At the same time great improvements are now foreshadowed in regard to the modes of working mines by shafts and drives. Some shafts will in future be worked practically as the vertical portions of tramways, having endless wire ropes to convey the trucks direct from the face or the stope to the reduction works, and thus an immense saving will be effected in the costs incidental to mining. From the neighbourhood of the place at which it has been won, the ore will be drawn in trucks, attached to the endless wire rope, first along the drive on the horizontal, and then up an incline increasing in sharpness till the shaft is reached, where the direction of motion becomes vertical. Near the surface, again, there is an incline, gradually leading to the level of the ground, or rather of the elevated tramway from which the stuff is to be tipped into the mill, or, if it be mullock, on to the waste heap. The return of each truck is effected along the reverse side of the endless wire-rope cable.

Ventilation is an incidental work of much importance which it becomes more practicable to carry out in a satisfactory manner when an endless system of truck conveyance has been provided, reaching from the ore-face to the mill, and thence back again. The reason is mainly that the same routes which have been prepared for this traffic are available for the supply of air and for the return current which must carry off the accumulated bad gases from the underground workings. Fans, operated by the cable at various places along the line of communication, keep up a brisk exchange of air, and the coming and going of the trucks themselves help to maintain a good, healthy atmosphere, even in the most remote parts of the mine. In very deep mines, where the heat becomes unbearable after a few minutes unless a strong wind be kept going underground, the forward and backward courses for traffic and ventilation together are specially advantageous.

Prices during the twentieth century will depend more definitely upon the cost of gold-mining than they have ever done at any former time in the world's history. In spite of all the opposition which fanaticism and ignorance could offer to the natural trend of events in the commercial and financial life of the world, the gold standard now rests on an impregnable base; and every year witnesses some new triumph for those who accept it as the foundation of the civilised monetary system. This being the case, it is obvious that the conditions affecting the production of gold must possess a very peculiar interest even for those who have never lived within hundreds of miles of any gold mine. To all intents and purposes the habit of every man is to measure daily and even hourly the value of his efforts at producing what the economist calls "utilities," against those of the gold miner.

If, therefore, the latter successfully calls to his aid mechanical giants who render his work easier and who enable him to throw into the world's markets a larger proportion of gold for a given amount of effort, the result must be that the price of gold must fall, or, in other words, the prices of general commodities must rise. If, on the other hand, all other industries have been subjected to the like improved conditions of working, the effect must be to that extent to balance the rise and keep prices comparatively steady.