Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/474

Rh 456 MINING [WINDING. Each boat long by 4 feet 6 inches wide, and 2 feet 11 inches deep, carries 5 or 6 tons. Where roads have a strong gradient, inclined planes are employed, either self-acting if the mineral has to be lowered, or worked by stationary engines if the mineral has to be raised (see COAL, vol. vi. p. 69). 9. Winding, or Raising in the Shafts, with the Machinery and Apparatus required. In speaking of the transport by underground roads, we mentioned that the mineral is occa sionally brought to the surface on the backs of men or boys. In other cases daylight is reached by adit-levels provided with railroads ; but in by far the greater number of mines it is necessary to hoist the mineral, and often much rubbish, up vertical or inclined pits generally known as shafts, In beginning to sink a shaft from the surface, or in sinking a winze, hand-power applied by a windlass is sufficient. The broken rock at the bottdm of the shaft is shovelled into a wooden or iron bucket (kibble), which is drawn up by a rope passing round the barrel of the wind lass. When a depth of 20 or 30 yards has been reached it is more advantageous to introduce horse-power, and the usual machine by which this power is applied, called a gin or horse-whim, is a common sight in many metalliferous districts. It consists of a vertical axis carrying a barrel or drum 8 to 12 feet in diameter, round which is coiled the rope, which after passing over a pulley hangs down the shaft. The axis carries an iron pin at each end, the lower one working in a stone and the upper one in a socket in the span-beam or cross-bar of the supporting frame. Under the barrel is a long driving beam to which a horse is harnessed, and, as will be readily understood, the kibble is drawn up or lowered down as the horse walks round. It is most economical to have two kibbles, for then they balance each other. Where steam and water-power are not available, a large number of horses or mules are sometimes harnessed to whims, and ore raised from depths of 200 fathoms. These, however, are exceptional cases; and, especially since the introduction of portable engines, the use of steam-power even for comparatively small depths, such as 100 yards, is daily increasing. In hilly districts water-power is generally at hand, and huge reservoirs are frequently constructed for .storing the rainfall, and so affording an adequate and con stant supply. It may be utilized by water-wheels, turbines, and water-pressure engines. There are three systems of winding by steam or water- power which are in regular use : (1) by buckets (kibbles), baskets, or bags swinging loose in the shafts ; (2) by boxes working between guides (skips, Cornwall) ; (3) by cages carrying one or more waggons. The buckets are made of wood, sheet-iron, or sheet-steel. Their shape varies ; it may be round or elliptical, straight in the side or bulging in the middle. Fig. 84 represents a kibble made of sheet-iron. When the shaft is inclined, the side upon which the kibble slides is carefully lined with boards (bed-planks) resting upon cross sleepers. Planks of hard wood like beech last longer and require fewer repairs than deal boards. In the Harz, poles fixed lengthwise take the place of boards, which are customary in Great Britain. Even where shafts are perpen dicular a lining of planks is often put in round the winding compartment, unless the space is considerable, and the kibble then glides up smoothly, and there is less risk of accidents. A more modern system is to use wire-rope guides for the kibble, which is thus kept from swinging about. Another advantage of this plan is that a light cage can easily be substituted for the kibble and used for the ascent and descent of the men. Mr Galloway has patented a method of sinking shafts with wire-rope guides, the upper ends of which are coiled upon drums at the surface. By adopting this expedient the guides can be lengthened as the shaft is deepened. A word must be said about the actual loading and emptying of the kibble. Sometimes, as already mentioned, the kibble is filled at the working place or from a shoot (pass, Cornwall) carried down into the level, and then conveyed on a trolley to the shaft, where it is hooked on to the rope and drawn up. More frequently the filler standing in the plat loads the kibble with a shovel ; and in order to save time two kibbles are often provided, one being filled while the other is making the journey to and from the surface. In this case it is necessary to have some kind of clevis, which will enable the kibble to be readily detached from the winding-rope, and quickly and securely fastened on again. On its arriving at the surface the lander seizes an eye or ring at the bottom of the kibble by a pair of tongs suspended by a chain, and the rope is now lowered. The kibble is thus turned over and the contents fall into a tram-waggon. The inconveniences of this method of winding are considerable, especially in inclined shafts where the direction and amount of the inclination are not constant. There is great wear and tear of the bed-plank and casing-boards ; and, unless constant attention is paid to repairs, places are worn out where the kibble catches, causing the rope to break. The fall of a kibble and its contents not only does much damage to the shaft, but also is a source of danger to the men. The introduction of boxes (skips) working Skips, between guides or conductors was therefore a decided step in advance, for the system allows the winding to be carried on with less friction and with greater rapidity and safety. The guides are often made of pieces of timber (like r, fig. 53) bolted to the end- pieces and dividings. It is only in perpendicular shafts that guides made of wire-rope or iron rods can be applied. The skip is a box of rectangular section made of sheet-iron or sheet-steel, with a sloping bottom, and provided with a hinged door closed by a bolt for discharging its contents. Fig. 85 J shows how the skip runs upon Fig. 85. the guides by means of four cast-iron or (better) cast-steel wheels. In an inclined shaft the guides sometimes have iron rails laid on them so as to diminish the wear. Some of the skips in Cornwall are made to hold as much as a ton and a half of tin-bearing rock. The skip is filled with a shovel by a man standing in the plat, but a better plan is to arrange shoots leading from large hoppers, so that the ore can be made to run in without any shovelling. The skip is sometimes tilted completely over instead of being emptied by a hinged door ; this arrangement is in use in some of the German mines, where the skip is made of wood, and is guided on each side by two pins or rollers running between two conductors. When the skip has reached the surface two catches are made to support the lower rollers, whilst the upper ones pass through openings in the front guides, and the skip, turning upon the lower ones, is tipped over and so emptied. The most satisfactory system of winding is by cages ; there is Cage, less handling of the mineral, and the hoisting proceeds at far greater speed. This system, which is almost universal* in collieries, is employed also for working deposits of othr minerals, and, though 1 Moissenet, Annales des Mines, ser. 6, vol. ii., 1862, plate vii.