to which the suspending chains are attached, and which, when the weight is carried, keep the eccentrics EE from coming in contact with the guides; D is a spring for giving motion to the levers CC, and eccentrics EE, if the rope breaks; F a wrought-iron plate at side of cage to carry the apparatus ; GG frame-work of cage. From this description it will be readily understood that if the suspending rope breaks, the springs will force the eccentrics EE against the guides, and the cage will remain suspended.

It will also be observed that every time the cage is on the keeps, both at the top and bottom of the pit, the rope will slacken and the apparatus will

come into action and press upon the guides. By altering the edges of the eccentrics they can be made to suit iron wire guides.

Calow's Safety Cage.-This differs from Broadbent's inasmuch as it is not dependent on its action on any direct attachment to the rope. Fig. 62 shows a perspective view of the apparatus.

A is a guide, the other being removed for the sake of exhibiting the mechanism of the cage; B the suspending rods or chains; E an eccentric carried by a shaft H, on which is also keyed a lever, C; D is a spring which is made to suspend the weight I, and keep the eccentrics E clear of the guides so long as the speed of the descending cage does not approach that of a falling body. But by the cage falling, or through any sudden jerk, the pressure of the weight I on the spring D ceases to be so intense, and therefore, the spring lifts it and sets in motion the eccentric E, which grips the falling cage. The apparatus, therefore, does not come into action each time the cage is stopped or rested on the keeps.

There are many other safety cages, but the principle of their operation is somewhat similar to those described.

DETACHING HOOKS.-Closely associated with safety cages are contrivances of a similar character for preventing the cage from falling when severed from the rope through overwinding. The object sought to be accomplished in these overwinding safety appliances is to cause the link by which the cage is suspended from the rope to release its hold of the rope and take hold of a portion of the framework of the headgear.

The Mines Act, 1887, does not make the use of any overwinding appliance compulsory, but a limit of speed is fixed, when men are being raised, if the mine is not provided with an automatic contrivance to prevent overwinding.

Fig. 64.-ARRAngement of CaTCH-PLATE IN HEADGEAR FOR ORMEROD'S SAFEty Link.

Ormerod's is one of the best of these safety links, and is the invention of Mr. Edward Ormerod, of Atherton, near Manchester. In Fig. 63 (A) is a cross view of the link; (B) a side view of the same; (c) represents the position it assumes when wound up into the cylinder, the rope shackle being disconnected, and the link firmly locked in its position; (n) shows the rope shackle re-connected for lowering the link through the cylinder. Fig. 64 shows a section of the cylinder as fixed in the headgear or pit frame, also the platform for convenience in re-connecting the rope shackle.

It will be seen from the illustrations that the apparatus when in ordinary use, as in Fig. 63 (B), is wider at the bottom than the top; but in the event of overwinding, the link is drawn into the bell-mouthed cylinder F F in Fig. 63 (c), the wide part of the link at HH coming in contact with the cylinder at FF, thereby closing the bottom part of the link, also causing the top part to expand and the projections to catch over the top of the cylinder, while at the same time the rope shackle A is forced out of its seat, thus being allowed to go free; the bottom shackle B drops into the slot D and locks the link firmly in its position. The cage being suspended from the chain cannot fall back. To prevent the possibility of the link becoming disarranged in ordinary work, a small pin, P, is inserted through the plates, which pin is sheared off as the apparatus passes into the cylinder.

C.M.H.

I

For lowering the cage the shackle is attached to the ear on the middle plate as shown in Fig. 63 (D). On removing the pin C, and slightly winding the rope, the middle plate (having a slotted hole in it) is elevated into the position shown, and allows the apparatus to pass down through the cylinder, and safely lower the cage. Humble's improved hook (Mr. Stephen Humble's patent) is shown in Figs. 64A and 64B, the former being in working order, and the latter detached and suspended upon the catch plate. This hook is said to be more largely used than any

other, there being upwards of 7,000 in use throughout the mining world, and it being so well known little explanation is required here. It has full bearing on shackle pins, for high speed winding and heavy loads. A simple catch plate is used, in place of a cumbersome cylinder, and the hook is fitted with a very simple and efficient automatic lowering gear, by which the hook and cage can be instantly lowered after an overwind.

Forster & Brindle's is another of these detaching hooks, and is shown in Fig. 65. Two similar plates, A and B, are suspended upon a pin, C, and are made so that

in passing through the detaching plate they are pressed in. On emerging from the upper end of the detaching plate they open out again so as to prevent the hook from returning. In case

of a partial overwind the hook enters the detaching plate, but perhaps not sufficiently to cause shearing of the rivet which must precede detachment; the plates then clutch the point of sustainment and prevent the cage from falling back. Where the overwind is complete, the plates A and B are pressed in as they pass through the sustaining plate, and immediately after being through, are pressed out by plates D and E, which also cause detachment. The rope is expeditiously re-attached, to effect which the connection with the rope is made, and the weight tightened on it, the two plates, A and B, are pressed in by hand, and kept in whilst being lowered through the detaching plate, after which work may be resumed. There are many other patent detaching hooks, but the difference between them and those described is not sufficient to justify a description of each.

Fig. 65.-FORSTER AND BRINDLE'S DETACHING HOOK.

To some extent the same remarks apply to the use of disconnecting or

detaching hooks as those on safety cages. They have been known to fail at the moment of their need--probably owing to the high speed at which the cage was overwound. A lamentable example of this occurred in Yorkshire in 1886, where the cage with ten men in it was overwound, broke the bolts and fastening of the catch-plate and carried it away. The hook detached at the same time and the cage and catch-plate fell down the shaft and the ten men were killed.

It is necessary sometimes to have pipes placed in the shaft to convey steam or compressed air to an underground engine, and to place pumps or a rope communicating with an underground engine plane from the engine at the surface, but the method of securing the pumps will be described later on.

The HEADGEAR, Fig. 66, consists of a pulley-frame which may be of pitch pine timber, or wrought iron, that in the Fig. being of timber. The uprights,

two or four in number, forming the frame, and the two backstays or inclined pieces are the main features of a pulley-frame, and are so arranged as to best resist the strain on the pulleys, which is of a twofold character, viz., the vertical strain from the load in the shaft and a side strain towards the engine. The uprights vary in height from 30 to 70 feet, and are generally made of pitch pine from 12 to 16 inches square. The backstays are of the same sectional size, and should be placed at an angle to the uprights, and as nearly parallel as possible to the ropes from the drum to the pulleys. A good rule is to let the rope make not less than an angle of 45 degrees in going over the pulley. Diagonals and strengthening pieces are also placed across the uprights near the pulleys for strengthening their support. Pulley-frames made of iron admit of a greater length than wood. It is unwise to have the pulleys placed too near the level of the pit top, for with engines on the first motion, and having large drums, half a stroke of the engine may take the cage to the pulleys.

One of the inclined pieces should have steps and a hand-rail formed on it, or

a separate ladder provided, so as to admit of an attendant going up to examine the head-gear and oil the pulleys.

Each upright should rest in an iron footing placed upon a specially prepared pillar to take the vertical pressure. The backstays should each rest on ashlar

or concrete foundation, and not against the engine house wall. Where space is limited and the engine house is necessarily erected rather near the shaft, there is no objection to the backstays being taken through the engine house wall so as to rest against the engine pillars. They should always be taken up to the centre of the pulleys, and not as sometimes seen to a point below this which gives the backstays less resisting power to the strain on them. The whole framework should be frequently painted for the preservation of the material composing it.