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least three (3) inches from all conductors, and shall never be secured by uninsulated double-pointed tacks.

5. The ground-wire shall be attached to a water-pipe, if possible; otherwise may be attached to a gas-pipe. The ground-wire shall be carried to and attached to the pipe outside of the first joint or coupling inside the foundation walls, and the connection shall be made by soldering, if possible. In the absence of other good ground, the ground shall be made by means of a metallic plate or a bunch of wires buried in a permanently moist earth.]

Ground-wires for lightning-arresters and grounddetectors are not to be attached to gas-pipes within a building, because if there were heating or arcing at the point where the wires are joined to the pipe, the gaspipe might be burned through and the gas ignited.

Where wires are bunched together there is liability that they may become connected accidentally or on account of moisture. If there were bad leakage from one wire to another, the insulating covering might catch fire and carry it to the building. Rule 45 (c), consequently, requires that such wires be covered with fire-resisting material, or else that they be enclosed in an air-tight duct so that if a fire do occur it cannot have air to support combustion and cannot extend to the building.

An instrument is "shunted" when a by-path is formed round it so that the current will have a path

other than that through the instrument. A high electrical pressure on telephone, burglar-alarm, or similar circuits, which do not have to be particularly well insulated, is likely to break down the insulation and cause heating at the break. Protective devices lead these high-potential currents to the ground before they get to the wiring in the building. The rules for installing protectors are given in detail in the note under 45 (d). Since the protector is to carry off a current forced by a relatively high pressure, all the wiring from the protector to the ground is done with the same care that would be used to install a high-potential circuit, so that there will be no leakage to the building and no burning of gas-pipes.

e. The following formula for soldering-fluid is suggested:

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The following are given as a list of NON-COMBUSTIBLE, NON-ABSORPTIVE, INSULATING materials, and are listed here for the benefit of those who might consider hard-rubber, fibre, wood, and the like, as fulfilling the above requirements. Any other substance which it is claimed should be

accepted, must be forwarded for testing before being put on the market:

1. Thoroughly vitrified and glazed porcelain.

2. Glass.

3. Slate without metal veins.

4. Pure sheet-mica.

5. Marble (filled).

6. Lava (certain kinds of).

7. Alberene stone.

On the inside of the cover of The National Code of Rules, as usually printed, are the following recommendations:

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The use of wire ways for rendering concealed wiring permanently accessible, is most heartily endorsed and recommended; and this method of accessible concealed construction is advised for general use.

Architects are urged, when drawing plans and specifications, to make provision for the channeling and pocketing of buildings for electric light or power wires, and in specifications for electric gas lighting to require a two-wire circuit, whether the building is to be wired for electric lighting or not, so that no part of the gas fixtures or gas piping be allowed to be used for the gas-lighting circuit.

INDEX.

A.

Alternating current, 154.

Alternating system, rules for, 153.
Ampère, 10.

Analogies, limitations of, 8, 9.
Analogues, hydraulic, 29, 36.
Approved wire, list of, 80.

Arc, formed by two wires, 47; caused
by leakage, 48; in arc lamp, 33.
Arc lamp, automatic switch in, 96;
clamps, 97; globes, wire netting
around, 97; hand-switch, 96;
hanger-boards, 98; plated and
plain carbons for, 98; resistances,
145; rules for, 95; spark-arresters,
98; stops, 97.

Arc lights on low-potential circuits,
rules for, 144.

Attendance, rules for care and, 60.
Automatic circuit-breaker, 161.
Automatic switch, arc lamp, 96.
Automatic cut-out, incandescent
lamp, 101.

B.

B. & S. gauge, 69, 111.

Base frame, 57.

Batteries, 168.

Branches, fuses on, 129.

Burrs and fins, 143.

Car wiring, rules for, 163.
Carbons for arc lamp, plated and
plain, 98.

Care and attendance, rules for, 60.
Carrying capacity of wires, 62; table
of, 135, 136.

Casing, fixture, 144.
Catch-box, 107.
Catch, safety, 133.

Ceiling-block, fixture, 144; (rosette),
151.

Central stations, rules for, 56.
Clamps, arc lamp, 97.
Closet, fuse, 128; system, 41.
Combination fixture, 131.
Conductors, in dynamo rooms, rules
for, 60; of alternating systems,
rules for primary, 159; of alter-
nating systems, rules for second-
ary, 160; loss of force in, 13-19;
of high-potential systems, rules
for outside, 79; of high-potential
systems, rules for interior, 86; of
low-potential systems, rules for
interior, 108; of low-potential
systems, rules for outside over-
head, 104; of low-potential sys-
tems, rules for underground, 105.
Conduit, 51, 115, 124; rules for in-
terior, 122; iron-armoured, 127.
Converters, 154; rules for, 153.

Bushings for sockets, insulating, 151. Cross-connection, 81.

Bus-bars, 62.

C.

Calculation, wire, 21-27.

Car-houses, rules for, 163.

Current, 4, 5, 9, 10; alternating, 154;
choosing path of least resistance,
38; direct, 157; heating effect of,
13-18; induced, 155; unit of, 10.
Cut-out, 75; incandescent lamp auto-

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