FAULTS INCIDENT TO THE PROTECTION OF LIGHTING AND POWER CIRCUITS.1

BY LUCIUS T. STANLEY AND WALTER E. HARRINGTON.

IN the present state of the art there are two common methods of protecting electric circuits, viz.: By means of metallic fuses and by means of magnetic cut-outs.

Metallic Fuses.-To adopt the language of a noted company, which is a large manufacturer of metallic fuses in various forms, "fuse wire is a safety device designed to break the electric circuit when an excessive current passes, and it breaks the circuit because it is heated to a temperature at which it melts." Such a device as is thus defined would be a perfect protector to electric circuits if it were possible to predetermine absolutely-first, the current it will safely carry indefinitely, and, second, the actual current in excess of this safe normal load that will "blow" the fuse instantly, under any and all conditions of lapsed time, character of service, etc.

The authors then give a list of the principal causes which render it impossible to devise a metallic fuse that is absolutely and under any and all circumstances a protector to an electrical system, and express their belief that in the present advanced state of the art fuses are not only totally inadequate and inefficent but actually dangerous.

The Magnetic Cut-Out is commonly defined as a device which opens the circuit at a set strength of current. In the light of certain phenomena brought forth by experiments made by the writers, they believe that this is not a full and complete definition. In fact they think it is misleading. They then give the general principles governing all the various forms produced by the several manufacturers, including the long-throw knife blade switch, operated by a trip actuated by the armature of an electro-magnet, and a device for blowing out the arc. The arc can be broken by an auxiliary break or by the electro magnetic blowout. The authors then discuss the difficulties encountered with this type of apparatus, and conclude as follows:

A magnetic cut-out which would exhibit a long stride toward ultimate perfection would be a switch operated to open by the direct action of a magnet upon the switch bar in such a manner as to cause the current itself to drive the bridge away from the switch plates, thus insuring the quickest possible response to an abnormal current. The break at the switch terminals should be protected by a by-path or shunt across the switch terminals, composed of a fuse wire of a carrying capacity sufficient to carry the current for a period of time ample to allow the switch bridge to reach a point of safety, and of a fusing capacity that will cause it to "blow" instantly when the switch bridge has thus reached a point of safety. The magnetic circuit should be so arranged that the point of saturation would be beyond the capabilities of the flux incident to the opening of the switch upon the passage of a current at which it might be set and expected to open. Consequently, when abnormal currents, in excess of that at which the switch was set to open, occurred, the result would be an acceleration of movement of the plunger up to the point of saturation, and the time element would thus be reduced to a minimum.

THE IMPORTANCE OF COMPLETE METALLIC CIRCUIT FOR ELECTRIC RAILWAYS.1

BY J. H. VAIL.

THE author stated that many devices for making the track and earth combined a more complete and low resistance circuit had been resorted to, such as burying copper or iron plates, old rails or old car wheels, and connecting them to the track; or, at frequent intervals, driving iron rods down in the earth and connecting by wires to track; or by making actual connection with wire from tracks to gas and water pipe systems. For supposed reinforcement of the track, a bare wire of iron or copper has been used buried in the earth, laid parallel to the track, and connected at frequent intervals; also the supposed electrical connection of rails at joints, by bond wires of iron or copper, having only a small fractional part of the capacity of the rail as a conductor.

Frequent tests prove that the earth itself cannot afford the free path for the current that was anticipated. Earth conductivity has been overestimated. Iron and lead pipes, being better conductors than earth, must of necessity carry the current, if no superior path is offered by the method of construction. The natural moisture of the earth hastens the destructive electrolytic action of the current on these pipes. In some soils electrolysis is more rapid than in others. The rapidity of action depends upon the chemical constituents of the soil.

It has been stated that in an electric railway system where a connection has been made to water pipes, the pipes have carried as much as twenty-eight per cent. of the total current. Instances

1. Abstract of a paper read before the National Electric Light Association, Washington, D. C., Feb. 27, 28 and March 1, 1894.

are known where as much as forty per cent. is carried on the pipe systems. It has been proved by test that the electrolytic action of even five amperes of current on an iron pipe is considerable, and that much damage will result in one year. The rapidity of action depends upon the character of soil, amount of moisture and quantity of current; the destructive action is constant and sure. Any system using ground plates, ground rods or substitutes therefor, or bare return track wire buried in the earth, is constructed primarily to utilize the earth as return circuit; when the earth does not afford good return the current is sure to follow the water pipes, gas pipes or other buried conductors offering the path of least resistance. We now see that these prove to have been only make-shift methods to reduce the cost of construction.

With the electric railway, the track forms one side of the consumption circuit, and must be so treated in regard to distribution of current as to utilize its carrying capacity equally with the other side, and thus equalize the delivery of current. The electric conductors composing a system of distribution for electric railways should be so thoroughly well proportioned as to show the minimum variation of pressure throughout the system, even when all the cars are in operation. This equality of pressure is an important requisite for the economical working of the motors. The author has tested electric railway systems operating with a station pressure of from 500 to 550 volts, and showing only 300 to 325 volts on various divisions of the system. Here is a direct loss between dynamos and motor car of over forty per cent. Is it, therefore, any wonder that some roads report extraordinary coal consumption? Such loss in pressure indicates radical faults in the original planning of the system and the distribution of copper. The rail sections are in many systems of ample conductivity to carry more than the requisite current, provided they are perfectly bonded and properly connected by feeders with the dynamos. We must, therefore, bond the rail joint in such a mechanical manner as to maintain perfect electrical contact, and with sufficient metal to restore at the joint nearly the full conductivity as that of the rail itself; and at the same time to give the existing joint plates their present freedom of motion.

For the purpose of comparison, we will assume that iron has six times the resistance of copper. (The actual proportion being 1 to 5.63).

These figures serve to show how utterly absurd it is to bond a track of seventy-pound Trails with iron rail bonds No. 4 or No. 0 in size, and to pretend to reinforce their conductivity with a No. 0 iron or even a No. 0 copper wire. It is like laying a twelve inch water main and then putting a one-half-inch pipe alongside to help it out. The author believes that ninety-nine per cent. of the money expended for so-called supplementary wire is absolutely thrown away. The same money expended in other directions will give 2. Table prepared by G. F. Sandt, E. E.

3. Data furnished by A. E. Kennelly.

more adequate return. The track system of all electric railways should really be the positive side or outgoing circuit. It will be readily understood that as the current travels from positive to negative, therefore any arc which occurs between the trolley wheel and the trolley wire will carry metal from the trolley wheel and deposit it on the trolley wire. If the reverse method of connection is made, the trolley wire will lose the metal which will be deposited on the trolley wheel, and in time the strength and conductivity of the wire must be seriously impaired, eventually resulting in breakages.

The author here stated that a trial was made four years ago under favorable conditions-not to avoid electrolysis, but to save copper. Physical difficulties of operation were developed which warned the experimenters to avoid the three-wire system in future electric railway work. Having carefully analyzed the whole matter, be now felt justified in recommending the complete metallic circuit as the standard for the best electric railway practice. This can best be obtained by the following method: First. By so bonding the track as to render the rail joints of as low resistance and nearly equal conductivity to the rails, and to execute this work so as to maintain this improved condition; and, Second. The track system must be supplied with insulated feeders leading directly from the bus bars in the station to predetermined points of the track system, and thus offer a perfect low resistance path for this side of the electric circuit, the same as is obtained with the All of these features and trolley line and the overhead system. improved methods have been put in practice by the author.

The item of cost cannot properly be urged as an objection, because where the whole construction requires a large investment, every detail of the work should be so executed as to be permanent and enduring. The track feeder system will be far less costly than the double trolley system. Whether track feeders should be laid underground or erected overhead is a question largely controlled by local conditions and capital available. The author ex

A PIPE ATTACKED BY ELECTROLYZING CURRENTS IN THE STREET.

pressed a preference for underground work as being more permanent and subject to the least cost for repairs, and has provided for all contingencies in the following manner: First. By a careful study of the conditions under which a system will be operated; these important points being ascertained with reasonable accuracy, the requisite supply and distribution of current for the service is determined, and the system of conductors arranged to meet the requirements. For the proper supply of electric current, the important underlying principles of the feeder system must be thoroughly understood. Second. The conductivity and current-carrying capacity of the track system is calculated, and a system of insulated track feeders is provided, leading from the switchboard in station and connecting at predetermined points, and with a calculated fall of potential. This will be found to result in reduced fuel consumption, better working of the motors, a most satisfactory reduction in repair accounts, and an improved general economy of the entire system. In the system of distribution secured by the above method, the use of ground plates, rods or other insufficient methods it needless; the current travels only over the paths provided for it, and electrolysis of gas and water mains is entirely obviated.

REPORT OF THE COMMITTEE ON DATA.'

BY H. M. SWETLAND, T. CARPENTER SMITH, E. F. PECK, G. G. H. BLAXTER, C. E. SCOTT, Committee.

We are requested to furnish this convention with the facts regarding the amount of coal used in actual practice to produce a given quantity of electricity. The information was obtained by correspondence, and furnished the committee in amperes, volts, and hours on each circuit, and the amount of coal used covering this period, including that used for banking fires, etc. The aggregate electrical output for twenty-four hours was then calculated and compared with the total amount of fuel used, giving the watt-hours per pound of coal. All improbable and apparently erroneous reports were discarded, and the tabulated statement herewith comprises intelligent replies from a large number of the 1. Abstract of a Report made at the National Electric Light Association meeting, Washington, D. C., February 29, 1894.

Jinc.

15

60

8,960 ant. bkwt.

6,100 bituminous

15

1,600

8.190 Pittsburgh

3,500 bituminous

Jinc.

612

156

120

121,680

1,844,000

4,800 bituminous

7,380 slack

52

186

67

65

90

83

96

92

104

Average Watt-hours per pound coal, 91.7.

Where there are blanks in the table, details were not given.

per pound of hard screenings where about 8,000,000 watts were generated, running full twenty-four hours, as against the report which claims only 30 watt-hours per pound of soft coal, the total output being less than 60,000 watts and the service being furnished only seven hours. The best reports do not compare favorably with the results secured in generating power for manufacturing purposes.

In order to facilitate this comparison, we have prepared a table based on 90 per cent. mechanical efficiency in the engine and the same efficiency in the dynamo:

From this estimate of engine and dynamo loss, 11⁄2 pounds of coal should produce 402.21 watt-hours. We have a report from the Chelsea Jute Mills, of Brooklyn, N. Y., covering a period of six days, where an average of 653.3 indicated horse-power was developed from a coal consumption of 1.482 pounds per indicated horse power per hour, the load varying from 495.21 to 764.96 horse-power. This equipment consists of Corliss compound condensing engines and vertical tubular boilers. The plant was in operation 10 hours each day. The figures given cover the whole amount of fuel used, including banking, etc. The fuel used was George's Creek bituminous coal.

If our percentage of efficency is correct, and if we could have a fairly uniform electrical output, this plant ought to produce over 400 watt-hours, or double that of the most favorable report given us, more than double that of the next best report, thirteen times the efficiency of the plant making the lowest report, and between four and five times the average efficiency of the whole report.

No attempt has been made in this report to classify equipments, as was originally intended, but with the information here furnished as a basis, the work can be readily classified, additional information secured, and the original scheme of establishing an average basis of efficiency for the several lines of equipment can be carried out. We believe the tendency of the work is to encourage more careful records, which in turn assist in locating and eliminating losses, and we hope future reports by this Committee will show a much better average than 88.4 watt-hours for one pound of coal.

A DRAWBAUGH TRANSMITTER patent ISSUED.

Among the patents issued Feb. 20 was one for a carbon telephone transmitter to Daniel Drawbaugh on his application filed July 26, 1880. When the application was made Drawbaugh also applied for another patent on carbon transmitters which would have controlled all use of carbon, but this it will be remembered, was rejected two years ago when the Berliner patent, with which it interfered, was issued. The Drawbaugh Company appealed to the courts from the decision of the Patent Commissioner, and the case comes up for trial on March 12.

The first claim of the present patent is as follows:

In a telephone transmitter, a diaphragm carrying two resistance varying electrodes electrically insulated from each other, in combination with opposing electrodes mounted upon vibratory supports and provided with means for adjusting the initial pressure between said electrodes."

THE WASHINGTON CONVENTION would have been noteworthy, if for no other reason, from the active participation of Mr. Samuel Insull as an out-and-out central station man from Chicago, although not long ago he shaped the destinies of one of the biggest manufacturing companies. It is believed that Mr. Insull has, as usual, a shrewd idea of the right end of the business.

PRESIDENT CLEVELAND has but one predecessor in office living, but President Armstrong had the pleasure of seeing around him ex-presidents Weeks, Perry, Huntley, Morrison and Ayer, all dignified mandarins of the gold button. The presence of these gentlemen was greatly appreciated as testifying to their interest in the Association's welfare.

N. E. L. A. STANDARD RULES FOR ELECTRICAL CONSTRUCTION AND OPERATION.1

CENTRAL STATIONS.

CLASS A.-FOR LIGHT, HEAT OR POWER.

These rules also apply to Dynamo Rooms in Isolated Plants, connected with or detached from buildings used for other purposes. Also to all varieties of apparatus of both high and low potential.

The floors of Central Stations should be cleaned thoroughly at least once a week, and especial care taken that oil is not thrown from the machinery, as floors and machinery saturated with oil increase greatly the fire risk.

Oil, waste and such supplies should not be kept in the loft or cellar, and where it is impossible to remove them to a separate building,automatic sprinklers must be installed. Generators or Motors.

1. Must be located in a dry place.

2. Must be insulated on floors or base frames, which must be kept filled to prevent absorption of moisture, and also kept clean and dry.

3. Must not be exposed to flying or combustible materials.

4 Must each be covered with a waterproof cover when not operating.

In no case must a generator be placed in a room where any hazardous process is carried on, such as the working room of a cotton, jute, flax, woolen or flour mill. Care and Attendance.

A competent man must be kept on duty in the room where generators are operating.

Oily waste must be kept in metal cans, and removed daily.

Conductors.

From generators, switchboards, rheostats or other instruments, and thence to outside lines, conductors:

1. Must be in plain sight.

2. Must be wholly on non-combustible insulators, such as glass or porcelain. 3. Must be separated from contact with floors, partitions or walls through which they may pass, by non-combustible insulating tubes.

4 Must be kept rigidly so far apart that they cannot come in contact.

5. Must be covered with non-inflammable insulating material sufficient to prevent accidental contact.

6. Must be ample in carrying capacity to prevent heating. (See Capacity of Wires Table.)

7. Must be connected by splices or joints equal in carrying capacity to the conductors themselves, soldered, if necessary, to make them efficient and per

All outside overhead conductors (including services):

1. Must be covered with some insulating material, not easily abraded. 2. Must be firmly secured to properly insulated and substantially built supports, all tie wires having an insulation equal to that of the conductors they confine.

8. Must be so placed that moisture cannot form a cross-connection between them, not less than a foot apart and not in contact with any substance other than proper insulating supports.

4. Must be at least seven feet above the highest point of flat roofs and at least one foot above the ridge of pitched roofs over which they pass or to which they are attached.

5. Must be protected, whenever necessary, in view of possible accidents to conductors or supports, from possibility of contact with other conducting wires or substances to which current may leak, by dead insulated guard irons or wires. 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.

6. Must be provided with petticoat insulators of glass or porcelain. Porcelain knobs, cleats and rubber hooks are prohibited.

7. Must be so spliced or joined as to be both mechanically and electrically secure without solder. They must then be soldered to insure preservation and covered with an insulation equal to that on the conductors.

1. Adopted at the Washington Convention, March 1, 1894. NOTE. These Rules are subject to amendments or alterations, and will be modified from time to time as experience and the exigencies of electrical development demand. All such changes will receive the official sanction of the National Electric Light Association, and be given immediate publicity, upon their adoption.

1. Must be where they enter buildings from outside terminal insulators to and through the walls, covered with extra waterproof insulation and must have drip loops outside, preferably slanting upward toward the inside, and bushed with waterproof and non-combustible insulating tube.

2. Must be arranged to enter and leave the building through a double contact service switch, which will effectually close the main circuit and disconnect the interior wires when it is turned "off." The switch must be so constructed that it shall be automatic in its action, not stopping between points when started, and prevent an arc between the points under all circumstances; it must indicate on inspection whether the current be "on" or "off," and be mounted on a noncombustible base in a position where it can be kept free from moisture and easy of access to police or firemen.

8 Must be always in plan sight, never covered, except in special cases, where an armored tube may be necessary.

4. Must be covered in all cases with a waterproof and, as far as possible, non-combustible material that will adhere to the wire, not fray by friction, and bear a temperature of 150° F. without softening.

5. Must be in dry places kept rigidly apart at least ten inches, except when covered (in addition to insulation) by waterproof, non-conducting and non-inflammable tubing, which must be strong enough to protect the insulating covering from injury. Conductors thus placed may be run not less than three inches apart, and be fastened with staples, under which are placed mechanically rigid insulating strips or saddles of greater width than the metal of the staple, by which possibility of injury to the tube may be prevented.

6. Must be in damp places attached to glass or porcelain insulators, and separated ten inches or more.

7. Must be, when passing through walls, floors, timbers or partitions, treated as in central stations under like conditions.

LAMPS AND OTHER DEVICES.

Arc Lamps.

1. Must be carefully isolated from inflammable material.

2. Must be provided at all times with a glass globe surrounding the arc, securely fastened upon a closed base. No broken or cracked globes may be used. 3. Must be provided with a hand switch, also an automatic switch, that will shunt the current around the carbons should they fail to feed properly.

4. Must be provided with reliable stops to prevent carbons from falling out in case the clamps become loose.

5. Must be carefully insulated from the circuit in all their exposed parts. 6. Must be, where inflammable material is near or under the lamps, provided with a wire netting around the globe and a spark-arrester above, to prevent escape of sparks, melted copper or carbon.

Incandescent lamps in series circuits, having a maximum potential of 850 volts or over, must be governed by the same rules as for the arc lights, and each series lamp provided with a hand switch and automatic cut-out switch; when lights are in multiple series, such switches and cut-outs must not control less than a single group of lights. Electro-magnetic devices for switches are not approved.

Under no circumstances will incandescent lamps on series circuits be allowed to be attached to gas fixtures.

CLASS C.-OVERHEAD CONDUCTORS. INCANDESCENT (LOW PRESSURE) SYSTEMS.-800 VOLTS OR LESS.

1. Must be provided with suitable protecting devices at the ends of tube or conduit service inside the walls of buildings, as a guard against moisture and injury.

2. Must be terminated at a properly placed double pole house cut-out. 3. Must be of specially insulated conductors after leaving the tube or conduit, and separated by at least ten inches, until the double pole cut-out is reached. Inside Wiring.

Wires should be so placed where practicable that in the event of the failure or deterioration of their insulating covering the conductors will still remain insulated.

At the entrance of every building there shall be a double pole switch placed in the service conductors, whereby the current may be entirely cut off.

Conductors.

1. Must not be of sizes smaller than No. 16 B. & S., No. 18 B. W. G., or No. 3 E. S. G.

2. Must not be paraffine covered.

3. Must not be covered with soft rubber tube.

4. Must not be laid in mouldings of any kind in damp places.

5. Must not be laid in mouldings with open grooves against the wall or ceiling.

6. Must not be laid in mouldings where less than half an inch of solid insulation is between parallel wires, and between wires and walls or ceilings.

7. Must not be laid in plaster, cement or similar finish, without an exterior metallic protection.

Wherever conductors cross gas, water, or other metallic pipes, or any other conductors or conducting material (except arc light wires), they should be separated therefrom by some continuous non-conductor at least one inch. In crossing arc light wires the low tension conductors must be placed at a distance of at least six inches. In wet places an air space must be left between conductors and pipes in crossing, and the former must be run in such a way that they cannot come in contact with the pipe accidentally. Wires should be run over all pipes upon which condensed moisture is likely to gather, or which by leakage might cause trouble on a circuit.

In rooms where inflammable gases may exist, or where the atmosphere is damp, the incandescent lamp and socket should be enclosed in a vapor-tight globe. This is not to be understood to include rooms where illuminating gases are used in the ordinary manner.

In breweries, stables, dye-houses, paper and pulp mills or other buildings specially liable to moisture, all conductors, except where used for pendants : 1. Must be separated at least six inches.

2. Must be provided with a durable, moisture-proof covering.

8. Must be carefully put up.

4. Must be supported by porcelain or glass insulators.

Moisture-proof and non-inflammable tubing may be accepted in lieu of such

construction.

2. Must not be of such material or construction that will be injured by plas. ter, cement, or other surrounding material, or that the insulation of the conductor will ultimately be injured or destroyed by the elements of its composition. 3. Must not be so constructed or placed that difficulty will be experienced in removing or replacing the conductors.

Must be continuous from one junction box to another or to fixtures, and of non-inflammable material, and of as substantial character as the existing gas and water pipes, in order to afford mechanical protection from injury by saws, chisels or nails.

Architects and builders should provide suitable wireways or openings in all buildings at the time of their construction, in which could be placed electric wires and conduits according to the requirements of the building.

Prior to the installation of the wires, powdered soapstone should be blown through the conduit tubes to facilitate the drawing in of the same.

4. Must not be depended upon for insulation. The conductors should be covered with moisture-proof material.

The object of a tube or conduit is to facilitate the insertion or extraction of the conductors, to protect them from mechanical injury and, as far as possible, from moisture.

Conductors passing through walls or ceilings must be encased in a suitable tubing, which must extend at least one inch beyond the finished surface until the mortar or other similar material, be entirely dry, when the projection may be reduced to half an inch.

Double Pole Safety Cut-Outs.

1. Must be placed where the overhead or underground conductors enter a building and join the inside wires.

2. Must be placed at every point where a change is made in the size of the wire (unless the cut-out in the larger wire will protect the smaller). This includes all flexible conductors. All such junctions must be in plain sight.

3. Must be constructed with bases of non-combustible and moisture-proof material.

4. Must be so constructed and placed that an arc cannot be maintained between the terminals by the fusing of the metal.

5. Must be so placed that on any combination fixture no group of lamps requiring a current of six amperes or more shall be ultimately dependent upon one cut-out.

6. Must be, wherever used for more than six amperes, or (where the plug or equivalent device is not used) equipped with fusible strips or wires, provided with contact surfaces or tips of harder material, soldered or otherwise, having perfect electrical connection with the fusible part of the strip.

Safety Fuses.

Safety fuses must be so proportioned to the conductors they are intended to protect that they will melt before the maximum safe carrying capacity of the wire is exceeded.

All fuses, where possible, must be stamped, or otherwise marked, with the number of amperes equal to the safe carrying capacity of the wire they protect. All cut-out blocks when installed must be similarly marked.

The safe carrying capacity of a wire changes under different circumstances, being about forty per cent. less when the wire is closed in a tube or piece of moulding than when bare and exposed to the air, when the heat is rapidly radiated. It must be clearly understood that the size of the fuse depends upon the size of the smallest conductor it protects, and not upon the amount of current to be used on the circuit. Below is a table showing the safe carrying capacity of conductors of different sizes in Birmingham, Brown & Sharpe and Edison gauges, which must be followed in the placing of interior conductors.

8. Mouldings, where admissible, must have at least two coatings of waterproof paint, to be impregnated with a moisture repellant.

Cleatwork.

1. Cleatwork is not desirable, and cleats must not be used unless in a very dry place.

20

15

5

2. Must not be used unless in a place perfectly open for inspection at any time.

8. Must not be used unless they are of porcelain, or well-seasoned wood, filled, to prevent absorption of moisture.

4. Must not be used unless they are so arranged that wires of opposite polarity, with a difference of potential of 150 volts or less, will be kept at least

Switches.

1. Must be mounted on moisture-proof and incombustible bases, such as slate or porcelain.

2. Must be double pole when the circuits which they control are connected to the fixtures attached to gas pipes, and when six amperes or more are to pass through them.

3. Must have a firm and secure contact, must make and break readily, and not stick when motion has once been imparted by the handle.

4. Must have carrying capacity sufficient to prevent heating above the surrounding atmosphere.

5. Must be placed in dry accessible places and be grouped, as far as possible, being mounted, when practicable, upon slate or equally indestructible backboards.

Motors.

1. In wiring for motive power, the same precautions must be taken as with the current of the same volume and potential for lighting. The motor and resistance box must be protected by a double pole cut-out, and controlled by a double pole switch.

Arc Lights on Low Potential Circuits.

1. Must be supplied by branch conductors, not smaller than No. 12 B. & S. gauge.

2. Must be connected with main conductors only through double pole cut-outs. 3. Must be furnished only with such resistances or regulators as are enclosed in non-combustible material, such resistances being treated as sources of heat. 4. Must be supplied with globes protected as in the cases of arc lights on high potential circuits.

Fixture Work.

1. In all cases where conductors are concealed within, or attached to, fixtures, the latter must be insulated from the gas pipe system of the building by an insulating joint, the material of which shall not be affected by gas or changes of temperature.

2. When wired outside, the conductors must be so secured as not to be cut or abraded by the pressure of the fastenings or motion of the fixtures

3. All conductors for fixture work must have a waterproof insulation that is durable and not easily abraded, and must not in any case be smaller than No. 16 B. & S., No. 18 B. W. G., or No. 3 E. S. G.

4. All burrs or fins must be removed before the conductors are drawn into a fixture.

5. The tendency to condensation within the pipes must be guarded against by sealing the upper end of the fixture.

6. No combination fixture in which the conductors are concealed in a space less than one-fourth inch between the inside pipe and the outside casing will be approved.

7. Each fixture must be tested for possible "contacts" between conductors and fixture, and for "short-circuits" before the fixture is connected to its supply conductors.

8. The ceiling blocks of fixtures should be made of insulating material. Electric Gas Lighting.

Where electric gas lighting is to be used on the same fixture with the electric light.

1. No part of the gas piping or fixture shall be in electrical connection with the gas lighting circuit.

2. The wires used with the fixture must have a non-inflammable insulation, or, where concealed between the pipe and shell of the fixture, the insulation must be such as is required for fixture wiring for the electric light.

8. The whole installation must test free from "grounds."

4. The two installations must test perfectly free of connection with each other. Pendants and Sockets.

No portion of the lamp socket exposed to contact with outside objects must be allowed to come into electrical contact with either of the conductors.

Cord Pendants.

1. Must be made of conductors, each of which is composed of several strands insulated from the other conductor by a mechanical separator of carbonizable material, and both surrounded in damp places with a moisture-proof and a noninflammable layer.

2. Must be protected by insulating bushings where the cord enters the socket. 3. Must be so suspended that the entire weight of the socket and lamp will be borne by knots above the point where the cord comes through the ceiling block or rosette, in order that the strain may be taken from the joints and binding screws. All sockets used for wire or cord pendants should have openings at least equal to one-quarter inch gas-pipe size.

4. Must be allowed to sustain nothing heavier than a four-light cluster, and in such a case special provision should be made by an extra heavy cord or wire, as a mechanical reinforcement.

5. Must be equipped with keyless sockets, as far as practicable, controlled by wall switches. In no case may a lamp giving more than fifty candle-power be placed in a key socket on a flexible pendant.

Electrical Heating and Cooking.

In general the same precautions should be taken in the installation and operation of electric heating and cooking appliances as are applicable to circuits for electric light and power.

The practice of attaching heating and cooking appliances to lamp sockets is to be deprecated. Proper circuits must be provided, fully protected by double pole safety fuses and switches, and the appliances themselves should be kept from contact with inflammable materials.

Flexible cords should be used with strands separately covered with noninflammable insulation, and both wires or strands covered with a waterproofing, and that by a braiding, and especial care should be taken to make proper connections on all appliances, and each should be plainly marked with the maximum volts and amperes they will safely carry.

CLASS D.-ALTERNATING SYSTEMS. CONVERTERS OR TRANSFORMERS.

Converters.

1. Must not be placed inside of any building, except the Central Station, unless as hereinafter provided.

2. Must not be placed in any but metallic or non-combustible cases, which cases should be connected to earth.

3. Must not be attached to the outside walls of buildings unless separated therefrom by substantial insulating supports.

4. Must not be placed in any other than a dry and convenient location (which can be secured from opening into the interior of the building, such as a vault), when an underground service is used.

5. Must not be placed without safety fuses at the junction between main and service conductors, and safety fuses in the secondary circuits where they will not be affected by the heat of the converter.

Primary Conductors.

In those cases where it may not be possible to exclude the transformers and primary wires entirely from the building, the following precautions must be strictly observed:

1. The transformer must be located at a point as near as possible to that at which the primary wires enter the building.

The primary lead of a transformer should be heavily insulated with the highest class insulation, such as vulcanized pure india-rubber of the best quality, preferably covered with a high class outer covering, and such leads should have a minimum length of eighteen inches.

2. Between these points the conductors must be heavily insulated with a coating of moisture-proof material, and in addition must be so covered and protected that mechanical injury to them or contact with them shall be practically impossible.

3. The primary conductors, if within a building, must be furnished with a double pole switch, and also with a double pole cut-out where the wires enter the building, or where they leave the main line on the pole or in the conduit. These switches should, if possible, be enclosed in secure and fire-proof boxes outside the building.

4. The primary conductors, when inside a building, must be kept apart at least ten inches, and at the same distance from all other conducting bodies.

Secondary Conductors.

The conductors from the secondary coil of the transformer to the lamps, or other translating devices, must be installed according to the rules for "Inside Wiring" for "Low Potential Systems."

CLASS E.-ELECTRIC RAILWAYS.

Power Stations.

All rules pertaining to arc light wires and stations shall apply (so far as practicable) to street railway power stations and their conductors.

Railway Systems with Ground Return.

Electric Railway systems in which the motor cars are driven by a current from a single wire, with ground or floor return circuit, are prohibited, except as hereinafter provided:

1. When there is no liability of other conductors coming in contact with the trolley wire. 2. When the location of the generator is such that the ground circuit will not create a fire hazard to the property.

3. When an approved automatic circuit breaker, or other device that will immediately cut off the current in case the trolley wires become grounded, is introduced in each circuit as it leaves the power station. This device must be mounted on a fire-proof base, and be in full view of the attendant.

Trolley Wires.

1. Must be no smaller than No. 0 B. & S. copper, or No. 4 B. & S. silicon bronze, and must readily stand the strain put upon them when in use.

2. Must be well insulated from their supports, and in case of the side or double pole construction, the supports shall also be insulated from the poles immediately outside the trolley wire.

3. Must be capable of being disconnected at the power house, or of being divided into sections, so that, in case of fire on the railway route, the current may be shut off from the particular section and not interfere with the work of the firemen in extinguishing the flames. This rule also applies to feeders. 4. Must be safely protected against contact with all other conductors. Car Wiring.

All wires in cars must be run out of reach of the passengers, and shall be insulated with a waterproof insulation.

Lighting and Railway Power Wires.

Lighting and power wires must not be permitted in the same circuit with trolley wires with a ground return, except in street railway cars, car houses and power stations. The same dynamo may be used for both purposes, provided the connection from the dynamo for each circuit shall be a double pole switch so arranged that only one of the circuits can be in use at the same time.

Any electric railroad employing a ground return shall under no circumstances take its circuits into any build ng for light, power or other purposes, save in the case of the power and car-houses of the company.

Where light or power is supplied from the railway circuits employing a ground return for use in the power house or car house of the company, only the highest class of approved insulated wire must be used, the same to be supported on insulators and readily accessible at all times. Infiammable mouldings or casing concealing the wires must not be used.

1. The wiring in any building must test free from "grounds" before the current is turned on. This test may be made with a magneto-bell that will ring through a resistance of 20,000 ohms where currents of less than 250 volts are used. 2. No ground wires for any purpose may be attached to gas pipes within the building.

3. All conductors connecting with telephone, district messenger, burglar alarm, watch clock, electric time and other similar instruments, must, if in any portion of their length they are liable to become crossed with circuits carrying current for light or power, be provided near the point of entrance to the building with some protective device which will operate to shunt the instruments in case of a dangerous rise of potential, and will open the circuit and arrest an abnormal current flow. Any conductor normally forming an innocuous circuit may become a source of fire hazard if crossed with another conductor through which it may become charged with a relatively high pressure.

Wm. J. Hammer, Chairman; Wm. Brophy, James I. Ayer, A. M. Young, H. J. Smith, Committee reporting to 17th Convention.

M. D. Law, Chairman; Jas. I. Ayer, Wm. Brophy, Wm. J. Hammer, A. M. Young, Committee reporting to 16th Convention.

M. D. Law, Chairman; Wm. Brophy, Jas. I. Ayer, Wm. J. Hammer, A. M. Young, Committee reporting to 15th Convention.

A. J. De Camp, Chairman; M. D. Law, S. E. Barton, Wm. Brophy, T. Carpenter Smith, Committee reporting to 14th Convention.

UNIVERSITY OF MINNESOTA.

MR. MORGAN BROOKS, president and general manager of the Electrical Engineering Co. of Minneapolis, Minn., delivered a lecture recently before the professors and students of the Engineering Department of the University of Minnesota, on the Telephone, showing its development from smallest beginnings to its present perfection. The lecture was an able and interesting one.