Auxiliary operations.—Having now considered mining in the most simple point of view which the subject admits—as the arrangement of a system of subterranean works adapted to effect the great objects of discovery, extraction, ventilation, and drainage, it remains to notice the various auxiliary operations which the progress of these works will have required,'"and the complicated machinery which will thus have been called into action, both on the surface and underground. The auxiliary works in question will have been directed towards two distinct objects, one portion of them being subsidiary to the actual working of the mine itself, and the other directed to the mechanical preparation of the ores extracted, so as to render them fit for the smelting works, to which they are finally consigned for reduction, this last process being sometimes carried on upon the spot and by the same parties, and in other cases being performed at a distance by a distinct agency. We now proceed to consider the former of these two classes.
The underground works of a mine will not have proceeded far before it becomes necessary to provide for several very important contingencies ; water filters rapidly in, and, excepting where mines are worked by day levels or adits (or even then on sinking below them), requires some power to be provided for drawing it out; excavations are formed which require support; ventilation in places requires to be aided by mechanical means ; and lastly, the continually increasing extraction of ore and rubbish renders powerful and efficient means indispensable for its discharge.
y. Drainage ; Horse-Whim—The drainage of a mine is one of the earliest things which it becomes necessary to provide for, as mineral veins are generally more open and porous than the surrounding rock, and thus form natural reservoirs into which the surface water collects. When penetrated by the workings of a mine, this natural drainage is rendered still more complete, and water pours abundantly into the excavations. The most obvious mode of relief, where local circum stances are favourable, is of course the formation of an edit, but ex cepting in very abrupt and mountainous countries, where this work can be readily executed, mechanical power soon becomes necessary. This may be in the first place afforded merely by a " horse-whim," which will serve to raise both the water and the stuff broken in sinking; and in Mexico, before English skill and capital were applied to the working of the mines, this simple apparatus was the only power used in their drainage and extraction. Its application on the large scale is however so enormously expensive, so complicated, and so inconvenient, that in the mines of Europe it is only used upon a limited plan, and mechanical power is substituted as soon as possible for animal labour.
The machine alluded to consists of an upright shaft carrying a large cylindrical cage ur drum, and turned round by a long lever, to which the horses are attached. A rope is coiled round the cage of the whim, with both ends at liberty, so that while one end is winding up, tho other is unwinding, and both pea over a pulley placed above the shaft, having Large iron buckets or kibbles attached to them, which by this arrangement are kept alternately rescinding and descending, one kibble being loaded at the bottom while the other is emptied at the surface. This apparatus is termed a " whim" in Cornwall, but in the north of England • " whimsey" or "gin." Where mines are not very deep it is a convenient auxiliary in the extraction, but is only useful for drainage when the quantity of water is very trifling, as in sinking a mere trial shaft. (See Fig. 5.) the influx of water in a mine becomes at all considerable, recourse must be had to the power either of water or of steam to discharge it to the edit, or the surface, as the Can may be. Should local circumstances be favourable to the application of water power, it will of course have the preference, being recommended both by its economy and steadiness of action. The nearest stream of water available for this purpose will be turned into an artificial watercourse, or " leat," and conducted to the mine so as to obtain a sufficient fall to turn an overshot water-wheel, whose diameter and width will be regu lated to receive it.. Where a constant and abundant supply of water can be ohtaiued,this power becomes extremely valuable, and the miner avails himself of it with great ingenuity, constracting large reservoirs in the valleys through which the stream pauses, to render the supply more equable in time of drought, and erecting as many water-wheels on the mine, each receiving its supply from the tail of the other, as the declivity of the ground will admit. The water-wheels used in mines are invariably overshot ; they vary from 10 or 12 feet in diameter to more than 50 feet, and from 2 or 3 to 6 or 7 feet in breast: some of the largest exceed 100 horse-power. The German miners have long been celebrated for their skilful application of water-power which, from the mountainous nature of their mining districts, early presented itself to their notice. In this country, from the general application of the steam-engine to the drainage of mines, water-power has been lees cultivated; but many fine instances of its use may be seen in some of our mines, where eir cumetance• have been favourable to its adoption. Among these may be named the Fowey Console Mines in Cornwall, the mines of Wheal Friendship and Wheal Betsy in Devonabire, and of Gramington in Yorkshire. The application of a water-wheel to the drainage of a mine Is shown in Fig. 6.