and indicates the amount of current given out by the generator, and shows instantly if there is any undue load, such as would be produced if too many lamps were put in circuit, or if there was a serious loss of current from poor insulation of wires. A reliable ammeter clearly marked to show the full load of the machine should be placed in the armature circuit of each constant potential generator, so that the liability of the destruction of the generator by overloading, short circuit, grounds, etc., may be seen in time and obviated. There is no special hazard with this meter.

Switches. These are for throwing in and out all the circuits, and must be double pole, have non-combustible bases, and be mounted on the face of the board.

LIGHTNING ARRESTERS.-Overhead wires entering a generating station require special provisions to arrest any lightning discharge which may seek to use them as a line of conductivity, as, if not thoroughly provided for, the atmospheric electricity would pass through switches, over fuses, through the dynamo, and then ground, producing a burning out of instruments and dynamo, and very probably a fire in any nearby combustible material; it is, therefore, necessary to provide a lightning arrester for each side of every such circuit, placing it, if possible, on the outside of the building, or, where not so placed, placing it as near as possible to the entrance of the wire into the building; the arrester must be mounted on a non-combustible base in a readily-accessible place, isolated from all combustible materials, and connected with at least two earths by straight wires without any kinks or coils, not smaller than No. 6 B. & S. (0.162 inches), and not in contact with any pipes or other metal within the building; the arrester must be so constructed as not to maintain an arc after the discharge has passed.

In all cases, kinks, coils and sharp bends in the wires between the arresters and the outdoor lines must be avoided as far as possible.

MOTORS. The construction of a motor is similar in its parts to that of a dynamo, the only difference between them being in the manner of winding the wire. The difference in their action is that, whereas mechanical energy is used to produce an electrical current in a dynamo, the reverse is brought forward in a motor, for here an electrical current is used to produce mechanical

energy. In consequence of the similarity of motors and dynamos, the dangers are identical, consequently all rulings pertaining to dynamos hold with equal value as regards motors.

Rheostat. The motor should be in full view from the rheostat, so that in starting the motor it will always be in sight in case of any derangement occurring.

Switch. Where the motor is over one-quarter horse-power, a double-pole switch must be so placed as to protect both the rheostat and motor.

Cut-out.—A double pole, or two single, cut-out must be located in similar manner to the switch, so as to afford protection against excessive current. The ordinary lightning fuse blocks are not desirable for this work, as the distances are too short, and an arc started will maintain, as the hot block in connection with the metal tips will furnish an excellent conducting path; these fuses ought to have about an inch in length for each hundred volts used.

CIRCUITS.-Series. Arranged in succession. When lamps are arranged in succession in a circuit, so that the current goes through one after the other, they are said to be in series. A constant current with a variable pressure is generally used.

SERIES CONNECTION.

Multiple.—Ordinary incandescent lamp circuits are usually connected in multiple; that is, the lamps are arranged parallel with each other.

MULTIPLE CONNECTION.

Multiple Series.—The arrangement of electric apparatus in a circuit in a number of series, which minor series are then arranged in parallel. There is a special hazard here in overloading the dynamo by throwing in more series than the capacity of the generator will stand, and thus either burn out the armature or all of the generating apparatus by a short circuit. A variable current and constant pressure is used.

MULTIPLE SERIES CONNECTION.

Series-Multiple.-The lamps are arranged in series, in parallei, and the series connected. This is the most hazardous way of lighting, as by an accident to one lamp in a series an increased current must be taken care of by the remaining lamps of that series and a burning out of lamps, connections and circuit is apt to follow, and the thrown hot metal, etc., is liable to cause fire. The current is a constant one.

SERIES-MULTIPLE CONNECTION.

No system of multiple-series or series-multiple for light or power will be approved on high-potential system.

WIRING.-In generator rooms, the wires to and from generators, switch board, rheostats or other instruments and thence to outside lines are especially a source of danger, as in case of any arc, short circuit, ground or contact with wire of a higher potential anywhere in the circuit the whole capacity of the system would be concentrated in them and an excess of heat energy developed, hence they must be in full sight, readily accessible, wholly on glass or porcelain insulators and kept rigidly apart. As the vibration of a building or conductor is apt to abrade the insulation of the wire where it passes through walls, floors or partitions, it becomes necessary to prevent contact between the conductors and walls, floors and partitions by the use of glass or porcelain tubes; wash water on a floor is liable to collect around a conductor passing through the floor and cause a deterioration of the insulation of the conductor, hence the further need of insulator tubes.

Outside Work, All Systems and Voltages.-These wires are liable by coming in cantact with other conductors, by a break in a wire, by sagging, by moisture or some other accidental cause, to produce a ground or short circuit with the consequent damage to dynamos and appliances; it is therefore necessary that they be firmly secured to properly insulated and substantially built supports (the tie wires to have an insulation equal to that of the conductors they confine), be so placed that moisture cannot form a cross connection between them, not be less than a foot apart, and not in contact with any substance other than their insulating support. Service wires must have an approved rubber insulating covering, and line wires, other than service, must have an approved weatherproof, or rubber insulating covering. Service blocks must be covered over their entire surface with at least two coats of waterproof paint. To prevent contact with roofs by sagging the wires must be run at least 7 feet above the highest point of any flat roof and at least one foot above the ridge of any pitched roof over which they may run or to which they may be attached. Dead insulated guard irons or wires must be so placed as to prevent the wire falling in case of an accident to insulator, and to prevent contact with other conducting wires or substances to which currents may leak; special precautions of this kind must be taken where sharp angles occur, or where any wires might possibly come in contact with electric light or power wires. As the petticoat, glass or porecelain, insulator offers less chance of a leakage of current due to moisture, it is the only one approved. Where entering a building from outside, terminal insulators must be provided with drip loops (i. e., loops made in the wires between the insulators and the entrance holes in the building; these are for the purpose of providing points for collecting and dropping any water that may collect on the wire before it can enter the building); the holes through which the conductors pass must be bushed with non-combustible, non-absorptive insulating tubes slanting upward toward the inside.

Telegraph, telephone and similar wires must not be placed on the same cross-arm with electric light or power wires, and when placed on the same pole with such wires the distance between the two inside pins of each cross-arm must not be less than 26 inches.

Inside Work, All Systems and Voitages-General Rules.— The hazards are principally from poor insulation, small-sized wires, moisture degenerating the quality of the insulation, from conductors being too close to each other, poor joints, contact with wood or any other substance than insulating materials, all of which are apt to produce short circuits, grounds or arcs and speedily produce fire.

TABLE OF CARRYING CAPACITY OF WIRES.

B. & S. G.

Rubber-Covered Wires. Weatherproof Wires. Circular Mills.