Horse Haulage. — This is usually a secondary form of haulage, and is adapted to meet the circumstances that exist at the place where it has to be applied. In certain cases roads may be laid out with the intention of using them as horse haulage roads. When this is done the inclination should be such that the horse is able to do the maximum of work with the minimum of effort. This condition is obtained by arranging the gradient of the road so that the pull required to drag the empty tubs inbye is equal to that required to move the loaded ones out. This gradient can be calculated and the road driven accordingly. With a normal size of tub and using bridge rails the gradient would be in the neighbourhood of 1 in 130. Ponies of 11 or 12 hands are often employed, but where the roadways are of sufficient height more efficient work is obtained by employing heavy horses.

Self-Acting Inclines. — Where coal is being brought from rise workings it is usual to take advantage of the effect of gravity, as when the gradient is sufficiently steep, gravity can be utilised to provide the necessary motive power. This is done by providing a double track and fixing a wheel with a brake attachment at the top of the incline. A rope is passed round this wheel and carried to the foot of the incline, where it is hooked to a set or rake of empty tubs. An equal number of loaded tubs are placed on the other road at the top of the incline and attached to the upper end of the rope. When the loaded tubs are released they descend the incline and drag up the empties by the rope which connects the two sets. Speed is controlled by means of the brake attached to the wheel round which the rope passes. In steep inclines the rope is passed two or three times round this wheel to prevent it from slipping.

The available power in a self-acting incline is gravity acting on the loaded tubs, and the gravitational pull upon them must be sufficient to overcome all the other resistances involved, including the effect of gravity upon the empty tubs. The flattest gradient at which an incline will be self-acting can be calculated when the weights of the load and the empty tubs are known, also their frictional resistance and the weight and friction of the connecting rope to be used. For ordinary conditions the flattest gradient at which the incline will be self-acting is in the vicinity of 1 in 26.

Jig planes. — A jig plane is a modification of the selfacting incline where the descending loaded tub hauls up a counterweight running on a separate and often an extremely narrow gauge track. The counter-weight or back balance is so arranged that its weight in descending is just sufficient to haul up the empty tub. These jigs or cuddies, as they are sometimes called, are used where the inclination is too steep to lower the loaded hutch or raise the empty without their aid. They are generally used to run single tubs from the face to the main levels in highly inclined seams.

Direct Acting or Dook Haulage. — In this form of haulage the rake is drawn up the incline by power, the empties being run back by gravity. In this system a single track is all that is necessary unless a large output has to be dealt with, in which case the track may be double. If a double track be laid, then two drums are provided and the rope so coiled on them that the empty rake is being lowered while the load one is being raised. When a single track is used only one drum is necessary, and it is usually fitted with a clutch and brake so that it may be detached from the gear while the empty rake is being run back. The power may be steam, compressed air, or electricity. In most modern collieries it is usually electricity. A direct acting dook haulage gear of this class is shown in Fig. 81. The maximum speed of a haulage of this kind is frequently about 10 miles an hour, the average being somewhat less, depending on the rate at which the load is accelerated and brought to rest.

Endless Rope Haulage. — In this form of haulage a wire rope passes from the haulage gear to a return wheel at the extreme end and back to the haulage gear. The ends of the rope are spliced together to form a continuous length. The tubs are attached singly or in pairs by some form of clip, or they may be run in rakes coupled to a grip bogie. The system requires a double track, the empty tubs going in on one side and the load ones returning on the other. Where the roof is good these two tracks are laid side by side in one road, or if this is likely to prove disadvantageous owing to the roof being bad, the tracks may be laid in two separate parallel roadways, each of such width as will accommodate a single track. This latter arrangement is in certain eases a decided advantage, as it may readily permit of all the loaded tubs being brought to the one side of the pit bottom or landing bench, and the empties all taken away from the other.

The rope may run at the floor level supported on rollers, or it may be carried above the level of the tubs and supported at intervals by mushroom pulleys. In the former case various forms of clips or catches are used to attach the tubs, while in the latter they are attached by means of lashing chains. In British practice the speed of the rope may be from 1½ to 4 miles an hour, 2 miles per hour being a common speed. In some American mines high speed, endless rope haulage is adopted, but on the whole it does not seem to offer any material advantage over the slow speed system. Endless rope haulage is best suited for uniform gradients where the inclination is not too great, but if the tubs are attached to the rope by means of lashing chains the system may be used to advantage on any inclination however steep. When the gradients vary, the tendency of the rope is to lift up to or towards the roof in the hollows, and to bear hard on the rollers at the high parts. These conditions are unfavourable for under-rope haulage, but the difficulties can be overcome by carrying the rope above the tubs (over-rope haulage), attaching them by chains and using mushroom pulleys as bearing up or bearing down pulleys as the circumstances demand. This method may be used to cope with cases where the grades vary to such an extent as to be against the load at some parts of the roadway, and in its favour at others. In such cases the tub is attached by two chains, one in front and one behind. On the up-grade the tub is pulled by the chain in front, while on the down-grade it is held back by the one behind.

In all cases of endless rope haulage some arrangement to take up the slack rope and provide the necessary tension on the slack side is required. The arrangement usually consists of an adjustable wheel fitted close to the driving pulley, the wheel being mounted on a carriage which runs on a short inclined plane. The necessary tension is obtained by loading this carriage or by a suspended weight acting on the carriage through the medium of a short length of rope or chain.

The endless rope system admits of a regular delivery of tubs at definite intervals, and because of its slow speed is very free from accident. The power required is small in comparison to the output, and altogether there is no form of underground haulage more suitable for main roads. A haulage gear of the endless rope type is shown in Fig. 82.

Main and Tail Rope Haulage. — This system is adopted where the grade is irregular or where the roof is of such a nature that a single road is wide enough to keep open without causing considerable trouble and expense. Two drums, both of which are worked by clutches, and carried on the same shaft, are used. One drum carries the main rope, the other the tail rope. The tail rope passes from the drum alongside the road and round a wheel at the inside end, then back to the marshalling station where the empty tubs are collected. When a rake of empties has been made up, the tail rope is fastened to the inside end of them, the main rope being attached to the other. The haulage gear is then set in motion and the rake of empties dragged inbye by means of the tail rope carrying the main rope behind it. On arrival at the terminus, the main rope is transferred to the front of a loaded rake and the tail rope attached behind. The loaded rake is now drawn from the inside by means of the main rope. The two drums are thus both in operation at the same time, one being driven by the power supplied to the gear, the other running loose on the shaft but in the opposite direction, and controlled by a brake. Where the grade is in favour of the load, the tubs composing the rake are prevented from over-running the main rope by the person in charge holding on to the end of the rake by means of the tail rope with its drum and brake. The speed of running is often as high as twelve miles an hour, but depends upon the nature of the road and the quality of the track. This high speed has one serious drawback: should the rake leave the rails considerable damage is sure to result. The large number of tubs that must be run on each rake requires considerable room at each end of the haulage road, and the intermittent nature of the delivery of the coal causes more confusion and consequent loss of time than takes place with the endless rope system. The main rope must be the length of the road and the tail rope twice this length, thus 50 per cent. more rope is required for a given length of roadway, and there is more tear and wear than takes place with an endless rope. The power required is such as will give the maximum speed on the steepest gradient, and altogether the system is not so efficient as an endless rope one. A haulage gear of this class is shown in Fig. 83.

Signalling. — On long haulage planes it is necessary to transmit signals from the terminus or certain other stations on the roadway to the person in charge of the haulage gear. For such long distance work there is no rival to electrical signalling, but, owing to the rough nature of the work and the presence of dust and moisture, special appliances have to be used. Where employed in the mine, signalling apparatus must be of a character that will not cause such sparking as might ignite inflammable gas, should it be present. In order to reduce danger from this source electrical signalling apparatus must conform to certain specifications which are laid down in the Special Rules of the Coal Mines Act.

Accidents on Haulage Roads. — The best method of preventing accidents on haulage roads is to provide separate travelling roadways for the men to travel to or from their work. This, while it completely protects the man whose work is elsewhere, does not protect those who may be employed in repairing or attending to the haulage road. In eases where men have to be exposed to the risks of runaway tubs, trailers and safety chains should be used where their use is at all possible. The trailer is a forked piece of metal attached to the last tub of a set which is being hauled uphill. In the event of the rope or a coupling giving way, the tubs run back and the prongs of the trailer catch the sleepers, and either hold the tubs or throw them off the rails. Safety chains are chains which are attached to the rope hose and the last tub passing from front to back of the set. Should a coupling become undone or give way, the chain comes into operation and prevents a breakaway. These are merely supplementary precautions to prevent accident, arid the ordinary refuge holes must be provided along the roadway to conform to the Mines Act. A common class of accident to boys who drive ponies, especially in the North of England, is to be caught and crushed by the tubs which the pony is hauling. This is due to the lads riding on the limbers in front of the tubs. These limbers are a pair of shafts to which the pony is harnessed, and they form a tempting seat for the driver. In Scotland a tail chain is used instead of limbers and few accidents occur, as the drivers have less chance of sitting in front of the tubs. The only real remedy for this class of accident seems to be insistence on more rigid discipline to prevent this riding on the limbers.