to one shaft by boring a hole downward from the bottom of the second shaft, and connecting it by means of a drift with the leading shaft at different points as the sinking proceeds.

The lower strata of a deep colliery are mostly dry, and it is frequently found that after the shafts are tubbed through the water-bearing strata no further pumping is required. If tubbing is not resorted to, in consequence of seams too near the water-bearing strata having to be worked, the pumping may be more advantageously met by a third or pumping shaft sunk only through the waterbearing strata, and used solely for raising water.

Shafts must be fairly large where a daily output of 1,0co tons is to be landed, and if much more than this is aimed at, and the winding is from a great depth, possibly more than two shafts may have to be sunk on the property. If the sales are assured, a large output is more profitable than a small one: an output below a certain point results in the colliery working at a loss instead of at a profit. Very large outputs from a single shaft are only possible when there are the natural advantages of thick seams which can be easily worked, and then the shaft must be of large area, and, if deep, must be well equipped for rapid winding with cages constructed to take large trams. If a mechanical ventilator be employed both the downcast and the upcast shafts may with advantage be used for winding from a different seam of coal. Either of the shafts may be used for pumping water, but if only one shaft is used to wind, the pumps should be placed in the other, so that accidents to winding or to pumping appliances may interfere as little as possible with the operations in the other shaft.

Very large takings are pierced at different points by such shafts as are thought necessary by the engineer in charge, who allots to each pair of shafts the area that can be most economically dealt with, having regard to the exhaustion of the coal within the period of the lease, the commercial value, and possibly the divisions made by large faults or by old workings.

In South Wales, where favourable conditions prevail, a daily output of 1,000 tons is in many instances obtained, and in rare ones even 1,500 tons have been raised up a single shaft. Here the thickness of the seams allows of the use of large trams, having a carrying capacity of from 30 cwt. to 2 tons. Single-decked cages are for the most part used so as to facilitate the changing of the trams in them. In order to receive two trams ranged one behind the other the cage must be of great length. This of course necessitates large shafts, which are frequently from 18 to 20 feet in diameter in the clear. These large shafts also admit of the workings being well ventilated, which is a matter of great importance in the working of fiery seams, and requires to be kept in view as much as the question of output.

Where thin seams such as those at Radstock are worked, it is found impossible to raise large quantities of coal. In that case faults add to the difficulties of working these seams, and shafts rarely if ever exceed 10 feet in diameter. Such shafts under the prevailing circumstances meet all the demands made on them, whether for winding, pumping, or ventilation.

Deep shafts frequently take years to sink, but larger shafts, although more expensive, are not usually longer in sinking, because of the larger number of men and machinery that can be employed. It may safely be assumed that shafts varying from 10 to 20 feet in diameter will meet all the requirements of the different districts in this country.

In all new winnings two shafts are required by law, and their site is a matter requiring much thought. Other things being equal, that site which gives the largest amount of the field to be worked to the rise is preferable. The underground conveyance is thus rendered easier, and water in the workings will naturally gravitate to the shafts. If the seams of coal to be worked are lying in a horizontal or nearly horizontal position, there is an advantage in placing the main shaft in the centre of a property of moderate size so as to

command an equal area of working in each direction. The most distant point intended to be worked from one shaft must not be so far away as to render the underground conveyance difficult. Underground considerations usually give place to those of the surface, although this may entail pumping water out of dip workings, and hauling large quantities of coal up hill, and the sinking of shafts on the rise side of large faults. As a rule, the quantity of water obtained in the workings of deep collieries is very slight, and not likely to be troublesome in proceeding to the dip. The evidence obtained with respect to the dip of the seams and the direction and size of faults in the neighbourhood, and the vicinity of old workings, is often very unsatisfactory, whereas the surface conditions are of course well known. These, therefore, form a trustworthy guide to the mining engineer, who will leave the underground difficulties to be dealt with as they arise. If, however, the position which is best from a surface point of view, does not accord with that suggested by what is known of the mineral conditions, then the site must be chosen after a careful balancing of probable advantages and disadvantages. Neglect of this may afterwards cause greater working costs which no future engineering skill can rectify. A site which will suit a communication with the railway, tramway, canal, or whatever means of transport there is for the coal, is desirable. The necessity for an ample supply of pure water for the boilers and for general purposes must be borne in mind, and as rubbish must be landed during the sinking of the shafts, and possibly afterwards when the coal is worked, a convenient place must be arranged to tip it into, and the right secured to form a spoil bank. Provision must also be made for the disposal of water from the mine. If more than one royalty be leased, the winning of the different royalties, and the question of wayleave and outstroke, may affect the position chosen. It will be only after well considering and balancing these matters that a proper conclusion as to the site can be arrived at.

The tools used in sinking are hacks, or picks, for loosening the rocks and chipping back the sides. Shovels for filling the loosened rock into the kibble. Wedges for forcing out the rock by driving them into the joints. Sledges are heavy hammers with long handles for use with both hands in driving in the drill, breaking up large pieces of rock, or for striking the wedges. A hammer has a short handle, is much lighter than the sledge, and is used with one hand for hitting the head of a drill held in the other. Drills are usually made of cast steel, and are bars of different lengths having a cutting and a striking end. A jumper is a long drill used with two hands, and without a striker; the operator raising it and letting it fall with considerable force in the hole he is drilling. A scraper is a tool for removing the dirt which accumulates in a bore-hole while being drilled. A swab-stick is a deal rod bruised at one end, sometimes used for cleaning out the drill-hole. The bull is a round bar of iron, with an eye in it, for forcing clay into the interstices of the rock to keep water out of the bore-hole. Stemmers or rammers for tamping the bore-hole after the charge has been put in. Cartridges are cases containing the explosive compound to be inserted in the bore-hole. The fuse is the means by which the cartridge in the bore-hole is fired. It must allow time after being fired and before reaching the cartridge for the men to be drawn away. Kibbles, barrels, hoppits, buckets, or bowks are large iron barrel-shaped receptacles for the transference of the loosened rock from the pit bottom to the surface. The sinkers also "ride" on them.

Fig. 19 (B) shows the usual form of mining tipping kibble. It is self-righting, and the catch can be made self-acting or otherwise as desired. The strong iron bow is attached to two side trunnions placed a little below the centre of gravity on the outside of the kibble to allow of easy tipping. Special care must be taken to provide a proper means of fastening the bow of the kibble, and to keep it in perfect working order. When the spring catch gripping the bow is pulled back, the kibble is free to swing round on the bow, a light pull or push only being

necessary for the discharge of the contents which takes place whilst the kibble remains suspended. The kibble is made of wrought-iron, and the catch prevents it from tilting during the winding.

A kibble not intended to have its contents discharged in this way, but for transport to a rubbish tip after reaching the surface, is made as shown in Fig. 19 (c), but without the valve, and sometimes with chain attachment to the sides, as in Fig. 19 (A). Care must be taken in loading the kibbles only to place the broken material to within a few inches of the top. This is a matter of supreme importance to the sinkers in the pit bottom, to whom the falling of an ounce or two of stone or other substance may mean serious injury or instant death. Tipping kibbles were formerly used for winding water, and were made with a smaller bow fixed to the sides as well as with the larger one. The contents were discharged on the surface by the banksman who released the catch and pulled the kibble over by means of the smaller bow. This kind of kibble is unsuitable for winding

a large quantity of water, because it does not fill easily, the water having to flow into it over the top. It is sometimes used, however, when there is only a small amount of water in the shaft bottom. The water is then baled into the tipping kibble and wound to the surface. But baling is a tedious process, and therefore costly. Sometimes these tipping kibbles are made with an ordinary chain link placed so as to slide over one link of the bow and long enough to reach to a short vertical pin riveted to the inside of the kibble. Over this pin the link is placed to hold the kibble firmly in place. When the link is lifted the kibble turns over and empties itself. Tipping kibbles, whatever their form, need only to be disconnected from the rope at the bottom of the shaft. The other form of kibble must be taken from the rope and replaced by another at the surface as well as at the bottom of the shaft. The water-barrel is much the same as the kibble, but it has a valve in the bottom, and is used for sending the water to the surface, where the banksman pulls a handle communicating with the valve which allows the water to run out; or in another form of water-kibble the valve-spindle projects below the level of the kibble, so that when the engineman lowers it on to the runner the valve is opened by the action, and the water runs out.

Fig. 19 (c) shows a water-barrel which is made of wrought-iron with a water-tight valve in the bottom moved by a central spindle extending beneath to allow the water to run out. The barrel is lowered into the water in the shaft, and if this is of sufficient depth the barrel fills through the valve, which is lifted by the pressure of the water. When the barrel is full, the valve drops into. its place and

retains the water. The barrel is then raised to the surface, the travelling platform is pushed forward over the mouth of the shaft, and as the barrel is lowered on to it, the projection of the spindle presses lightly on the platform, whilst the kibble is kept in a vertical position by the engineman; this raises the valve and allows the water to be freely discharged, and shutes and pipes lead it away. The barrel is made to hold from 100 to 600 gallons of water. The spring hook is the means of attaching the kibble to the rope, and is shown in Fig. 20.

A pit to be finished 15 feet in diameter must be marked out 17 feet 6 inches to allow for timbering and walling. The sinking of a shaft is most frequently done by contract, and terms of agreement are drawn up between the contractor and manager, or owner, but sometimes the sinking is done on days' wages under the charge of a master-sinker. If more than thirty persons are employed in the whole of the shifts in the twenty-four hours there must be a certificated manager to comply with the Mines Act. The first few yards may be sunk by means of a windlass, after which a steam-engine of suitable size must be got. Two large balks of timber are placed across the pit, which may be afterwards timbered over, except a portion in the centre for the kibbles to pass up and down. On coming to the surface the engineman draws the kibble well up above the level of this opening, and the "banksman," or attendant, pushes the "runner" (which is a wide trolley-shaped carriage running on rails) into position, thereby covering the pit top and protecting the sinkers, whilst the engineman lowers the kibble on to it. It is then detached, an empty kibble which has been standing ready on the runner is attached to the rope, the signal given to the engineman to lift, and this being done the "runner" is pushed out with the full kibble on it, leaving the opening clear for the descent of the empty kibble. It is usual only to use one kibble in a sinking pit on account of the danger from collision which would arise if two kibbles were used. The travelling platform or runner is particularly useful for water-winding, because it receives the water discharged from the barrels and directs it to any desired channel, but it is not so convenient in use for the débris which is brought to the surface; for, although it forms an effectual cover over the shaft after the kibble reaches the surface, it is removed before the kibble descends, and the pit mouth is then left unprotected until the re-appearance of the kibble at the surface.

Two hinged counterbalanced doors are now sometimes used to close the shaft opening. These doors are hinged so that they lift upwards in two even divisions towards opposite sides, and when open they form a fence at two sides of the rectangular opening, the other two being guarded by fixed boarding. When the doors are closed they effectually seal the opening. Rails are fastened to their upper side to form a continuation of the tramway leading to the tipping ground. In the ordinary arrangement these doors have to be lifted separately, but Mr. W. Galloway has designed an improvement by means of which both doors may be opened at the same time. This is effected by an arrangement of levers and counterbalances worked by a handle and connecting links. The handle may be moved wholly or partly back, the counterbalances retaining the doors in any position into which they are moved by the handle. If only débris is to be wound up the shaft, no travelling platform is required, but if water is wound it may be still usefully employed to receive the barrel after the trap doors are closed, or it may be preferable to discharge the water as well as the material into tipping-waggons.

The tipping kibble is generally used in connection with some form of tipping waggon (see Fig. 21), which on the balanced doors being closed is pushed underneath to receive the contents of the kibble. When the kibble has been emptied, the waggon is removed, the doors are opened, and the kibble lowered into the shaft.

Tipping waggons are constructed in various forms to suit various purposes. such as the single end tip, the double side tip, and the all-round tip waggon; the general construction is the same, but they are so arranged that the contents may be discharged as described.

The body of the double side-tipping waggon shown in Fig. 21 is made of steel, and is carried upon four pairs of trunnions. A large tipping angle is thus obtained, and a free discharge of the material ensured. The sides and bottoms are formed with one plate, which is bent to further assist in the discharge. The trunnions are firmly riveted through the end plate of the body, which is strengthened by an additional inside and outside trunnion plate. Each end of the body is made with one plate, which is flanged by hydraulic machinery, and is riveted firmly to the sides. A strong half-round welded ring is riveted round the top, and holds it rigidly together. The body as thus constructed is very strong and durable. The under-frame is of channel steel, with steel bowed buffer ends, and steel angle stays across the underframe; the trunnion supports are of

angle steel; the draw-bar passes throughout the length of the under-frame, forming a central stay; the axles are of steel and the wheels of chilled iron or cast steel. Waggons with round buffer ends are far superior for light railway work to those built with corner buffers, as the liability to derailment on curves is greatly lessened. This may be of no importance in tip waggons for a sinking pit, and other buffers, if preferred, can be substituted. The trunnions are placed at such a distance apart as to ensure steady running, thus dispensing with safety chains whilst still maintaining an easy tip.

The usual capacities of these waggons are 10 and 16 cubic feet on gauges of 18 inches to 24.

After the first 6 feet of sinking has been done, which will most likely be through soil or clay, curbs or cribs must be put in. These are segments of wood (see Fig. 22) cut out to the circle of the pit, and are generally 6 inches square and made of oak or elm, the former being preferable. The joints must radiate truly from the centre of the shaft, and cleats, as shown in the sketches, secured to them at the surface in order that the joints may be brought into proper contact when the curb is fixed in the pit. Sometimes a scarfed joint is made between