quently necessary where the earth has a tendency to run and fill the pit; and when there is a troublesome amount of water, no better and cheaper plan has yet been devised than the clay filling used in this instance. When the water is troublesome, and the soil or drift of any considerable depth, the filling should certainly be thicker than that used (12") at this shaft.

Compartments.

All hoisting shafts are divided into compartments. At large collieries two compartments are usually used for raising coal, a third for the pumps or pump-rods and columnpipe, which is also often used as an upcast airway, and a fourth held in reserve for lowering timber and raising and lowering the miners, etc.

Two compartments are occasionally used in common as an airway and for the pumps, and sometimes two compartments are held in reserve for lowering timber, etc., and for raising and lowering miners.

When the whole of the shaft is used as a down-cast, a very small compartment answers for the pump-rods and column pipe, and the practice is to divide the shaft into two large compartments for winding coal, men, and mine supplies, and one small compartment for the pumps, column pipe, etc.

A reserve hoisting plant is sometimes placed at the second opening and used exclusively for raising and lowering the miners and mine timber, etc., (as at the Exeter colliery,) this opening being at the same time used as an up-cast, the hoisting shaft being used as a down-cast, or as both up-cast and down-cast.

The size of the compartments depends upon the size of the cage, which is necessarily governed by the size of the mine car.

At the Hollenback shaft the compartments are 11' 6" X 7'; at the Exeter shaft (see Atlas Map II) the compartments are seven feet wide between the buntons.

The arrangement of buntons to carry the guides, brattice, pump rods and column pipe in an untimbered shaft is clearly

shown by this Exeter shaft drawing. In this particular case they are placed at intervals of six feet from center to center and are simply let into the rock on each side a sufficient distance to give a good bearing.

The guides are in some cases simply bolted (by bolts with countersunk heads) to the buntons, but a better plan is to let them into gains cut on the bunton, as by this plan heavier guides may be used, and the bolts are subjected to less strain.

Atlas plate No. II also shows the arrangement of the buntons in the cribbing at the Exeter shaft, and the substantial masonry curbing, one side of which is used as a foundation for the head-frame.

A much lighter form of timbers is shown by Page plates 6 and 7 at a shaft at Mahanoy City, in which the main frame is made of 6"x12" timber, the buntons the same size, the vertical braces or struts 6"X8"; the guides are 6"X8" and are sunk into shallow gains cut in the buntons. This form of timbering is very common for shallow shafts. This shaft is 18 feet long by 12 feet wide and is divided into three compartments.

Practical Details-Sequence of Operations.

When the location and size of the projected opening have been determined, and staked out on the ground, an open pit is commenced in the loose earth and sunk as such to the bed rock. This pit is usually made from 4 to 8 feet, or more, larger than the size of the shaft, thus allowing from 2 to 4 feet on each side for masonry or timber cribbing. When the loose earth or soil is deep or when it is of a sandy character, or too soft to sustain itself, a light temporary crib is necessary (which is sheathed if the material is loose sand or quicksand) to sustain the walls until bed-rock is reached and the permanent stone-curbing or timber-cribbing built.

While the pit is being excavated preparations are made for erecting the hoisting engine and boilers. The winding (sinking) engine is best located opposite one end of the shaft and not opposite the side, for if the latter location is chosen it will interfere with the erection of the permanent plant and it will be impossible to shift the head-frame with

out throwing the rope out of line; again, with the engine opposite one end of the shaft two head-frames may be erected and both buckets may be operated from the drum without the use of deflection pulleys.

As the load to be lifted during the sinking operations is comparatively light, from one to three thousand pounds,the engine foundations are not massive. In some cases a timber crib ballasted with stone answers every purpose, but under ordinary circumstances a rough stone foundation of moderate depth or a combined stone and timber seat will cost but little more and give better results.

The engine foundations having been staked out, a suitable pit is dug, the foundations are laid, and the sinking engine and drum set up while the shaft-pit is being dug and cribbed.

When the pit is cribbed with timber, no stone curbing being used, the timbers are usually set "skin to skin"; the frames are securely mortised together and held in place by keys inserted in gains cut in each frame immediately opposite each other. For crib work curbing, square timber 10"x12", 12"X12", or 12"x14", is commonly used, but larger timber has been used at a few shafts. Enough of the decomposed rock at the bottom of the pit is removed to expose a hard firm floor on which to set the cribbing.

The sides are braced by heavy buntons of square timber, which divide the shaft into compartments. These are sometimes not inserted when the cribbing is built, but the shaft is left clear of all such obstructions until finished.

In large shafts the buntons in the cribbing are placed only one or two feet apart, and in yielding ground are sometimes placed in juxtaposition, ("skin to skin").

When the pit is deep the loose earth is sometimes raised by a windlass; but the method usually adopted is either to cart it out through a cut, or to shovel it upon stagings, from which it may either be shovelled or wheeled away in barrows.

When a stone curbing is erected instead of a timber crib. bing, the process is precisely the same; but it is necessary to place inside of this a timber framing (or buntons) to carry

the keeps or wings, the cage guides, steam and column pipe, pump-rod guides, etc., etc., but these timber frames are then set some distance (usually from three to eight feet) apart. They are sometimes built into the masonry, but are frequently inserted afterwards.

When the pit has been completed, and the cribbing or curbing finished, the work of sinking through the rock may be commenced as soon as the sinking head-frame is built and the engine and boiler setting completed.

The head-frame is best built on heavy sills laid across the shaft and resting on the cribbing or curbing. These sills may be bolted to the cribbing to secure greater rigidity, and the frame itself is securely bolted down to the sills.

The head-frame being completed, the rope wound on the drum, the engine and boiler connections made, the work of sinking through rock begins.

When the rock is naturally soft and has a tendency to slip, or when a considerable thickness of partially decomposed rock is passed through before striking solid strata, the work of timbering must be carried downward pari passu with the sinking, but when the strata passed through are hard and self-sustaining, the opening is usually left untimbered until the sinking is completed; and under such conditions the timbers are set at a considerable distance apart, their office being not to support the sides so much as to carry the guides, column-pipe, pump-rods, etc.

When the timbering must be carried down with the sinking, it is usually necessary to set the frames at short distances apart. Two methods of holding the frames in place are in use: 1. By wedging them fast by wooden wedges driven in between the frame and the rock. 2. By making the end or side pieces longer than the width or length of the shaft, and setting them in notches and wedging them in place.

When the timbers are to be wedged fast, they are held in place either by props or are suspended by chains or bolts from the set above, until firmly fastened.

In driving the wedges two objects are accomplished: 1. The timbers are securely fastened. 2. They are brought