No wires smaller than No. 14 B. & S. are allowed except for flexible cords and in fixture work; tie wires must have an insulation equal to the conductors they confine, joints must be properly made, stranded wires must be soldered before being fastened under screws or clamps, and when they have a greater conductivity than No. 10 B. & S. copper wire they must be soldered into lugs; there must be no contact with walls, floors, timbers or partitions through which they may pass, but the wires must be separated from all such places by non-combustible, nonabsorptive insulating tubes, such as glass or porcelain, and in no case must they be in contact with gas, water or metallic piping or any other conductor or conducting material which they may cross, but must be kept free from such by some continuous and firmly-fixed non-conductor, creating a separation of at least one inch, and where run in wet places an air space must be left between all conductors and pipes in crossing; the wires should be run over rather than under pipes, and must be so placed and run that they cannot come in contact with pipes accidentally. Where underground wires are brought into a building they must be protected against moisture and mechanical injury, and all combustible materials must be kept away from them and from their immediate vicinity, and they must be so arranged as to shunt the current through the building around any catch-box.

The lower limit is specified for rubber-covered wires to prevent gradual deterioration of the high insulations by the heat of the wires, but not from fear of igniting the insulation. The question of drop is not taken into consideration in the above tables.

The carrying capacity of sixteen and eighteen-wire is given, but no smaller than fourteen is to be used, except in fixture work and in flexible cords.

For insulated aluminum wire the safe carrying capacity is 84 per cent of that given in the foregoing tables for copper wire with the same kind of insulation.

Constant-Current Systems; Principally Series Arc Lighting.— Wires must have an approved rubber insulating covering, must leave and enter the building through an approved double-contact service switch, mounted in a non-combustible case, kept free from moisture and easy of access. They must always be in plain

sight, be supported on glass or porcelain insulators, which separate them at least one inch from the surface over which they are run, must be kept rigidly at least 8 inches from each other, except within the structure of lamps, on hanger boards, in cutout boxes, or like places where a less distance is necessary; must, on side walls, be protected from mechanical injury by a substantial boxing, retaining an air space of one inch around the conductors, closed at the top (the wires passing through bushed holes), and extending not less than 7 feet from the floor; when crossing floor timbers in cellars or in rooms, where they might be exposed to injury, wires must be attached by their insulating supports to the under side of a wooden strip not less than onehalf an inch in thickness.

Low-potential systems, that is, any circuit attached to any machine, or combination of machines, which develops a difference of potential between any two wires of over ten volts and less than 550 volts, shall be considered as a low-potential circuit, and as coming under this class, unless an approved transforming device is used, which cuts the difference of potential down to ten volts or less. The primary circuit not to exceed a potential of 3,500 volts.

Wires must not be laid in plaster, cement or similar finish, nor be fastened with staples, nor be fished for any great distance, and must be protected on side walls from mechanical injury, and where crossing floor timbers in cellars or in rooms where they might be exposed to injury they must be attached by their insulating supports to the under side of a strip of wood not less than one-half inch in thickness and not less than 3 inches in width; twin wires must never be used except in conduits or where flexible conductors are necessary.

For open work in dry places the wires must have an approved rubber or "slow-burning" weatherproof insulation, must be rigidly supported on non-combustible, non-absorptive insulators, which will separate the wires from each other and from the surface wired over in accordance with the following table:

Rigid supporting requires under ordinary conditions, where wiring along flat surfaces, supports at least every 41⁄2 feet. If the wires are liable to be disturbed, the distance between supports should be shortened. In building of mill construction, mains of No. 8 B. & S. wire or over, where not liable to be disturbed, may be separated about 4 inches, and run from timber to timber, not breaking around, and may be supported at each timber only.

This rule will not be interpreted to forbid the placing of the neutral of a three-wire system in the center of a three-wire cleat where the difference of potential is not over 300 volts, provided the outside wires are separated 21⁄2 inches.

For open work in damp places, such as breweries, sugar houses, packing houses, stables, dye houses, paper or pulp mills, or buildings specially liable to moisture or acid or other fumes liable to injure the wires or their insulation (except where used for pendants) wires must have an approved rubber insulating covering; must have no joints or splices and must be rigidly supported on non-combustible, non-absorptive insulators which separate the wire at least 1 inch from the surface wired over, and they must be kept apart at least 21⁄2 inches for voltages up to 300, and 4 inches for higher voltages. Rigid supporting requires, under ordinary conditions, where wiring over flat surfaces, supports at least every 42 feet. If the wires are liable to be disturbed, the distance between supports should be shortened. In buildings of mill construction, mains of No. 8 B. & S. wire or over, where not liable to be disturbed, may be separated about 4 inches, and run from timber to timber, not breaking around, and may be supported at each timber only.

Wires must never be placed in moulding, in concealed or damp places, or where the difference of potential between any two wires in the same moulding is over 300 volts, and in conduit work must not be drawn into the conduits until all mechanical work on the building has been completed as far as possible, and where the alternating system is used the two or more wires of a circuit must be drawn in the same conduit.

For concealed "knob and tube" work the wires must be rigidly supported on non-combustible, non-absorptive insulators which separate the wire at least I inch from the surface wired over.

Rigid supporting requires, under ordinary conditions, where wiring along flat surfaces, supports at least every 41⁄2 feet. If the wires are liable to be disturbed the distance between supports should be shortened. Must be kept at least 10 inches apart, and, when possible, should be run singly on separate timbers or studdings; must be separated from contact with the walls, floor timbers and partitions through which they may pass by non-combustible, non-absorptive insulating tubes, such as glass or porcelain. When from the nature of the case it is impossible to place concealed wiring on non-combustible supports of glass or porcelain, an approved armored cable with single or twin conductors may be used where the difference of potential between conductors is not over 300 volts, provided it is installed without joints between outlets, and the cable armor properly enters all fittings and is rigidly secured in place; or, if the difference of potential between wires is not over 300 volts, and if the wires are not exposed to moisture, they may be fished on the loop system if separately incased throughout in flexible or approved conduits. Conduit used for mixed concealed knob and tube and conduit work must be continuous from outlet to outlet, comply with rules covering interior conduits, and must at outlets for combination fixtures be bushed with approved flexible insulating tubes, extending in continuous lengths from the last porcelain support to 1 inch beyond the outlet, except that an approved outlet insulator may be used. At outlets where there are no gas pipes, either this class of construction or porcelain bushing tubes may be used.

For Fixture Work.-Wires must not be less in size than No. 18 B. & S., and when on the outside of the fixture must be so secured as not to be cut or abraded by the pressure of the fastening or the motion of the fixture.

Interior Conduits.-These are tubes for the purpose of carrying wires, and are used on account of the facilities they afford for the insertion and extraction of the conductors, and to prevent any mechanical injury or injury by moisture to the insulation of the wiring; they are lined with insulating material or are made of insulating material, but all wires run through them must be insulated the same as conductors in other places; the conduits must first be run, continuously, from one junction box to another or to fixtures, and thoroughly installed as a system free from danger

of injury by any nails, saws, chisels, etc., before conductors are placed in them; at each outlet they must be provided with an approved outlet box or plate, and where metal conduits enter junction boxes, and at all other outlets, etc., they must be supplied with a capping of approved material fitted so as to protect the wire from abrasion; the metal of the conduit must be permanently and effectually grounded.

High-Potential Systems, that is, any circuit attached to any machine or combination of machines, which develops a difference of potential, between any two wires, of over 550 volts and less than 3,500 volts, shall be considered as a high potential circuit, and as coming under that class, unless an approved transforming device is used, which cuts the difference of potential down to 550 volts or less. The wires must have an approved rubber insulating covering, must be in plain sight, never encased, and must be rigidly supported on glass or porcelain insulators, which raise the wire at least one inch from the surface wired over, and must be kept about 8 inches apart. Under ordinary conditions for rigid supporting, the supports where the wiring is over flat surfaces should be every 41⁄2 feet, but if the wires are apt to be disturbed the supports should be closer together. In buildings of mill construction, mains of No. 8 B. & S. wire or over, where not liable to be disturbed, may be separated about ten inches and run from timber to timber, not breaking around, and may be supported at each timber only. The wires must be protected on side walls from mechanical injury by a substantial boxing, retaining an air space of one inch around the conductors, closed at the top (the wires passing through bushed holes) and extending not less than 7 feet from the floor; when crossing floor timbers, in cellars or in rooms, where they might be exposed to injury, wires must be attached by their insulating supports to the under side of a wooden strip not less than one-half an inch in thickness.

Extra High-Potential Systems, that is, any circuit attached to any machine or combination of machines, which develops a difference of potential, between any two wires, of over 3,500 volts, shall be considered as an extra high-potential circuit, and as coming under that class, unless an approved transforming device is used, which cuts the difference of potential down to 3,500 volts or less.