CAGE, in mining, a contrivance in which is raised to the sur face the "tub," "tram," "hutch" or "box," as the small under ground truck or wagon which carries the coal or mineral from the working face to the shaft is called. The cage, which is constructed of steel, is usually of such a capacity as to permit of more than a single tub being drawn to the surface in each wind. The cages are in general use at coal mines; indeed their use is compulsory in Great Britain under Section 4o of the Coal Mines act of 1911, for the raising and lowering of persons at the mine except where there are ladders. At metalliferous mines, the mineral is usually teemed into a storage bin, at the bottom of the shaft or the level, from which it is loaded into a "skip," an iron or steel box running on wheels, which on reaching the surface automatically tips out the ore. But the nature of coal does not permit of such rough usage— from the view of both breakage and dust, it is undesirable.
Prior to the invention of the cage, coal was drawn to the sur face in a large wicker-work basket, or "corf." These "corves" were woven of hazel wands. After being filled they were placed on trams which were shoved and pulled by manual labour from the face to the "crane station" where they were lifted on to a horse trolley, conveyed to the shaft and there separately drawn to the surface by means of the iron bow or handle with which they were fitted. They were unwieldy and required a great deal of re pairing; they also imposed a limit on the output. The output of a large colliery as late as 1835 working a twelve hour day, was according to Mr. George Stephenson, 30o tons (1835 Report, 1842) . This means of conveying coal continued well into the nine teenth century.
The First Cage.—During the time this method of raising coal was in vogue the arrangements by which the miners—men and boys—were lowered and raised were also very primitive. Two men would sit each with a leg through a loop of the chain with boys (five or six) clinging to the rope above them. Attempts were made as early as 1816 at Washington colliery in the county of Durham to introduce a better method of raising coal to the surface than by wicker corves, but unsuccessfully. It rested with a mining engineer named T. Y. Hall, in the North of England, to introduce underground in 1833-1834 tubs running on wheels, and their conveyance up the shaft in a cage. Somewhat later he much improved the system by providing wooden guide rods in the shaft for the cage, fitted with a shoe at the top and bottom, to slide on, and keeps or kegs for the cage to rest on on arrival at the surface whilst the process of changing the tubs (substituting empty for full tubs) was being carried out.
Cages have not undergone much change since they were first introduced, except that they are usually more capacious and carry more and larger tubs, and in most modernly equipped shafts run on steel rope guides—in place of the wooden or steel rail guides, of which there were two to each cage. These ropes, usually four to each cage, are stretched from the top of the pit-head frame and tightened by weights at the bottom of the shaft. At the pit top the guide ropes pass through crossbearers and are held by clamps. By law, guides have to be provided in the case of every working shaft over fifty yards in depth, and in the case of every shaft in course of being sunk over one hundred yards in depth ; and every cage has to be provided with catches to prevent tubs falling out; and, when used for raising or lowering persons, has to be covered completely at the top and closed in at the two sides. It also has to be provided with gates or rigid fences and a rigid bar to hold on to.
The attachment of the cage to the winding rope is by means of chains, four or six, one from each corner of the cage and two "idle" chains at the sides ; but intervening between the chains and the rope capping or "capel" is a safety or detaching hook—re quired by law in the case of vertical shafts. If the winding ap paratus is used for lowering or raising persons, and in addition, if the shaft is more than ioo yards in depth, the winding engine has to have an automatic contrivance to prevent overwinding. (See WINDING ENGINE.) Every winding rope has to be recapped at intervals of not more than six months, and if used for raising or lowering persons must not be in use for more than three and a half years. All cage chains in general use have to be annealed once at least in every six months, and the detaching hook cleaned and refitted once in every three months. (R. R.)