A drag of this form has been in use at the Mount Pleasant slope at Hyde Park for twenty-three years and has given entire satisfaction.

A single drag is sometimes attached to the hind car of each loaded trip. On slopes of moderate pitch a single drag may be all that is necessary to hold three or four cars, but on steep dips it is evident that greater safety is assured by the use of a drag on each car. The advantage of using a detachable drag of this kind is evident; it is attached to the coupling of the hind car of the loaded trip by the bottom-men, when the trip arrives at the top it is detached and sent down in an empty car,-the risk of accident to the empty trip is thus avoided.

Gates and fences.

The law provides that "the top of each shaft shall be securely fenced by vertical or flat gates, covering the area of said shaft, and the entrance of every abandoned slope, and air or other shaft, shall be securely fenced off." While the wording of this clause is rather ambiguous its import is clear. It is evidently intended to prevent persons falling down shafts and slopes.

The number of such accidents is not small, but it has doubtless been decreased by the provisions of this act of the Legislature.

The plan generally adopted is to fence in all portions of the shaft mouth except that part opposite the winding compartments and to close these with gates. On the side the cars run off the carriage, the gates are frequently made double and hung so that they will close without assistance. On the other side a heavy beam forms the gate to prevent empty cages running into the shaft. This beam is lifted and held out of the way by the cage, so that the car can pass beneath it.

Another plan is to place vertical sliding gates at all the openings; these are lifted by the cage and settle into place when the cage descends.

All of these are satisfactory methods. Flat (horizontal) 'doors are not used except to close air-shafts which may be

used in emergency for raising the miners, or occasionally for lowering mine supplies, etc.

The law does not require gates at landings below the surface, but in shafts and in steep pitching slopes they are frequently used, not so much as a safe-guard against accidents to miners, as to prevent cars and other objects from falling down the shaft or slope.

It is doubtful whether the adoption of gates decreases the number of accidents from miners and laborers falling down shafts and slopes, but it certainly does reduce the risk of accident from cars and other objects falling down.

Signal wires and Speaking tubes.

The law of 1870 requires (Sec. 10) every colliery operator to "provide and maintain a metal tube from the top to the bottom of such slope or shaft, suitably calculated and adapted to the free passage of sound therein, through which conversation may be held by and between persons at the bottom and top of the shaft or slope, and also the ordinary means of signalling from and to the top of the shaft from the bottom, .

The "ordinary means of signalling" is by a wire running from the bottom to a gong, or hammer and plate, in the engine room, and is for the purpose of signalling to the engineer when everything is in readiness for him to hoist the cage, of informing him whether he is raising coal, rock, or men, and where he is to stop the cage.

Two signalling wires are generally used, one running as above described and the other running from the mouth of the shaft or slope to the engine room. The engineer does not start the engine until he has received two signals, one from the top and one from the bottom, indicating that everything is ready for another winding.

The signals vary at different collieries; they generally run from one to four or five strokes ; two strokes from the bottom is commonly used to indicate that everything is ready, three strokes that men are on the cage or car to be raised, etc., but there is no uniform system.

When coal is raised from several different levels, addi

tional wires with gongs of varying pitch, (or hammer and plate signals) are added, but two landings are often worked with only one signal wire.

A rough sketch of a "hammer and plate" (a piece of boiler plate iron) signal is shown by Fig. 49. This method of signalling is preferred by many to the use of gongs.

Speaking tubes are generally made of two-inch iron tubing. In some cases the tube is run into the engine room, but often extends no further than the mouth of the shaft or slope. It is seldom provided with a whistle, as in a tube of this size and with a length of three to twelve hundred feet it is difficult if not impossible to blow a whistle. When the top-man wishes to communicate with the bottom (and vice versa) he simply raps on the tube with an iron bar, a stone, or any hard substance, and the noise thus made is perfectly audible at the other end of the tube.

An ingenious device has lately been added to many speaking tubes, especially at shaft collieries in the Wyoming district, whereby the speaking tube is converted into a signalling apparatus. Small brass cylinders about six or eight inches in diameter by about six inch stroke are attached to the tube. These cylinders form small air pumps; when the piston is thrust in by a quick push on a knob affixed to the end of the piston rod, the compressed air operates the clapper of a gong situated at the other end of the tube.

While this device requires the occasional inspection of a skilled mechanic to keep it in perfect working order, it is probably less likely to cause as many and as frequent stoppages as those occasioned by the breakage of signal wires.

Two or more speaking tubes are frequently used for communication with different levels, but branch tubes are sometimes used.

The wire used for signalling is rarely smaller than ordinary telegraph wire (No. 8.) and often much thicker,-from No. 6 to No. 2. Rapid oxidation from mine water, moisture in the air, and the sudden jerks to which it is subjected make large sizes necessary. Small wire rope has been used, but unless kept thoroughly greased it rusts very quickly, and is objectionable on account of stretching, and of its tendency to kink unless kept stretched tight.

Indicators.

The indicator attached to the Pottsville winding plant has already been described. Indicators of a much more simple type are commonly used.

A very common method is to insert an iron pin, about an inch in diameter, into the center of the drum shaft, and wind a small chain or cord around the pin. This cord is carried over a small sheave or pulley, and a weight carrying a pointer, a block of wood, a ball, or a slide carrying a gong, is attached to the other end. The weight or pointer rises or falls in front of a board, or between guides, on which lines are marked to indicate different points in the shaft or slope. When a gong is used, adjustible striking points are fastened to the guides by set screws, as shown by Fig.

48.

Some indicators are made so that the chain or cord entirely unwinds and is again wound up during each winding.

The same object may be accomplished by using two indicators-one for each cage-but this plan is open to many objections.

The addition of the gong to indicators of this class is undoubtedly advantageous. It constitutes an additional safeguard against overwinding, and is open to no well-founded objection.

a

CORD OR CHAIN

Song

Indicators operated by a cord or chain wound around a pin on the drum shaft, or around some revolving portion of the winding gear, are more common than any other form. It is, however, evident that they are not entirely reliable, but if the cord or chain overlaps in winding, the error of the indicator is always on the safe side, for it indicates the arrival of the cage at the top before it reaches the landing; but if during the unwinding of the cord or chain the latter becomes caught or entangled with coils still on the shaft, or if it binds in the sheave or pulley through which it runs, the cage may reach the landing before the position of the pointer indicates its arrival.

ак

AC.

Fig. 48.

Atlas Sheet No. VII shows the indicator used at the Laurel Hill colliery. The pointer travels back and forth in front of a black-board, on which the different landings are indicated by white paint or chalk marks. The pointer is moved by the rotation of the screw shaft, which is driven by motion taken from a drag crank and transmitted by two pairs of bevel gears.

When the drum in not geared direct to the engine, the indicator is frequently driven by a bevel gear from the drum shaft or a bevel gear bolted to the drum spiders.

The Laurel Hill indicator is also made to do duty in scoring the number of cars raised. At each winding the pointer catches in a ratchet wheel behind the two dial faces shown in the drawing, and the number of cars is shown at any time by reference to these dials. This device is intended to replace, or act as a check upon, the car-board. on