in the breaker, where shorter lengths are needed and the strain is not so great. A rope is thus sometimes used on three or four different planes before it is thoroughly worn

out.

Partly worn ropes are frequently sold for use at slate and stone quarries.

The sockets are put on by spreading the wires in the socket, drawing them all taut and pouring the socket full of lead. It is well to surround the socket and rope with wet clay to prevent the wires outside the socket from becoming too hot, as this will impair the strength of the rope.

Flat ropes.-Although many advantages have been claimed for flat rope, it seems that the only well-founded claim is that of the counterbalancing action of the rope coiling upon itself. Flat ropes are still used at many mines in the west, but in the anthracite coal regions they are now almost unknown.

The advantage gained is more than counterbalanced by the increased wear from the rope lapping upon itself, and as the same counterpoising can be effected in several other ways, the use of flat ropes, in any but very exceptional instances, does not seem advisable.

The plan of winding a round wire rope upon itself on a narrow drum, confined between two metallic discs, has been successfully used at the Wartet colliery in France, and in England at Radcliff, Lancashire. It is questionable whether this plan is any better with round than with flat ropes.

The conical drum with a thread or groove (scroll) for the reception of the rope is undoubtedly one of the best means of equalizing the load.

Tapering ropes are not used in the Pennsylvania coal fields. When the deepest parts of our coal basins are penetrated by shafts from 1600 to 2400 feet deep, it may be advantageous to introduce ropes of unequal section, but for the comparative shallow shafts of to-day they are not necessary. They are not at all adapted to deep slopes, on which the greatest wear always occurs at the lower end of the rope, as that portion travels further and is subjected to greater friction than any other part.

CHAPTER XVI.

Safety attachments, Signalling apparatus, and Indicators.

In this chapter all of the additions to a colliery plant especially designed to reduce the probabilty of accident to a minimum, or to decrease the risk, both to life and property, from the occurrence of breakage, or from carelessness, will be taken up,-in the following order:

1. Safety catches on shaft cages, to prevent the cage from falling if the rope breaks;

2. Bridle chains to hold the cage (if the rope breaks at the rope socket) if the draw-bar breaks;

3. Bonnets to protect the cage, car, or miners from objects falling down the shaft;

4. Detaching hooks and other appliances to prevent overwinding;

5. Automatic governors and steam brakes, as a means of stopping a runaway engine;

6. Slope cage catches;

7. Drags on slope carriages, barneys, or mine cars, to stop the cars in case the rope breaks;

8. Gates and fences to protect the mouths of shafts and prevent persons from falling into them;

9. Signal wires, speaking tubes, and other means of communication between the miners below and those in charge at the surface;

10. Indicators to show the position of the cage or cars in the shaft or slope and other methods of determining this.

Safety catches.

The law requires "an improved safety catch.. on every carriage used for lowering or hoisting persons"

(269 AC.)

but the context does not make it perfectly clear that this provision is intended to apply to cages used on slopes.

"An improved safety catch" is a rather vague term, but not more vague than many other phrases occurring throughout the act and its amendments. As the meaning to be given the word "improved" is not specified, it becomes practically a dead-letter, and the requirement to be fulfilled is simply that a safety catch be placed on each cage used for raising or lowering persons.

A great many different forms of safety catches are in use, and most of them are efficient appliances.

The report of the "Committee of Safety cages," appointed by the North of England Institute of Mining Engineers (Transactions Vol. XIX, 1869 70), shows that from 1857 to 1868, inclusive, the number of deaths from broken ropes or chains was 185, and the coal mined in that period 1,043,000,000 tons, or one death to about five and one half million tons of coal mined. If the same ratio obtained in this country the number of deaths (safety catches not used) would be about five per year.

It also shows that a man might ride on a cage 400 times a year for 12,500 years before meeting his death in this way, stating that while "it cannot be denied that ascending and descending into a pit is in itself a dangerous occupation... it is found that by careful selection of ropes, chains, and other tackle, and a watchful and close inspection of the winding apparatus and shafts, the risk is so re duced that it hardly approaches that of a walk for an hour in the streets of London. It must be admitted that the safety apparatus that succeeds in reducing this risk must combine elements of no common excellence."

That the adoption of safety catches introduces an addi- . tional source of accidents, and that it increases the number of casualties by relaxing the vigilance of those in charge of the winding machinery, is doubtless true; but while the number of rope breakages is increased, the number of deaths from this cause should be decreased, if the safety catches adopted are really efficient devices.

Three kinds of springs are used to throw the catches

against the guides; 1. Rubber cushions, or spiral springs surrounding the draw-bar, often confined within a cylinder; 2. Straight or curved steel springs; 3. Spiral springs surrounding the shafts which carry the dogs.

Chisel-pointed bars thrown out against the sides of the guides have been found uncertain in action, and split and otherwise damage the guides; clamps which grasp the guides and hold the cage by friction only, have not given good results; cam-shaped dogs with a chisel edge have been found in practice to be unreliable, and often do considerable damage to the guides; the catches giving the best results and those which are used to the almost entire exclusion of other forms are cam-shaped dogs with a serrated surface that grasps the guide. Catches of this description are dependent upon the spring only to throw them against the guides with sufficient pressure to make them bite,the weight of the cage then forces them firmly upon the guides with a pressure that theoretically approaches the infinite.

Rubber cushions surrounding the draw-bar are now largely used in place of other springs. Straight or bowed springs are more likely to become deranged than other forms and are more difficult to adjust to the required tension.

The safety catches at the Pottsville shaft are operated by spiral springs surrounding the rods or shafts which carry the dogs.

Atlas Sheet No. XI shows different forms of safety catches in use in the Wyoming district. Some engineers prefer placing the dogs nearly opposite the cage platform, others place them near the top of the cage. The latter arrangement seems preferable because it simplifies the construction of the catch.

One of the chief difficulties that has been experienced in the use of safety catches is their tendency to be thrown into action by any sharp jars or shocks to which the cages or winding machinery may be subjected, by suddenly stopping the engine, or when the cage is landed at the top or bottom; but accidents from this cause are now extremely rare, and if proper care is taken in adjusting the springs

and catches, there seems to be no reason why any such difficulty should occur.

Practical tests of the catches in use, made by hanging the cage and allowing it to drop, show that they are, as a rule, very efficient devices. The dogs usually take hold at once, the cage only dropping a few inches, or at most a few feet. When the guides are very greasy or wet, the trial tests are sometimes not so satisfactory, and the cage may drop several feet before the dogs take a firm hold and stop it, and the results are still less satisfactory when the guides are covered with ice; but even in this latter case the cage sometimes drops less than one foot.

Fortunately for the utility of safety catches, ropes are usually broken while a loaded cage is being raised, and the cage has an upward momentum; if a rope breaks on the empty side and when the cage is rapidly descending (at a speed say of thirty or forty feet a second) its momentum is so great that either the catches must break, or the cage or guides and shaft lining will be torn to pieces,-the catches generally hold, and either the guides or cage suffer more or less injury under such circumstances.

In experimental tests with ice-covered guides the cage has been known to fall eight to fifteen feet before the dogs ploughed their way through the ice and took firm hold of the guides, but the momentum the cage acquired was so great that the guides were destroyed.

Bridle chains.

The law provides (Sec. 10) that "the main link attached to the swivel of the wire, or any other rope, shall be made of the best quality of iron and tested by weights, or otherwise satisfactorily to the inspector, and bridle chains shall be attached to the main link from the cross pieces of the carriage, and no single link chain shall be used for lowering or raising persons into or out of any said mines. . . ."

I have not been able to satisfy myself of the exact import of this clause; the "main link" is by some interpreted to mean the rope socket and the bridle chains are accordingly