Motion Picture Operation, Stage Electrics and Illusions / A Practical Hand-book and Guide for Theater Electricians, Motion Picture Operators and Managers of Theaters and Productions

Bunch Lights.

Bunch Lights.—Bunch lights are made up according to the plans shown in Figure 188. They are used only on the stage. No very brilliant illumination can be obtained from them. In one well-known production a bunch light containing one hundred 32 c.-p. lamps was used without obtaining the result desired. The light cannot be concentrated as can that from arc lamps. Bunch lights, however, have the advantage of not requiring so much attention as arc lamps and can often be used on a shallow stage where arc lamps would be out of place. Bunch lights are sometimes made double, two on one stand; two colors can thus be used at the same time and certain color changes facilitated. Color effects or changes in colors are brought about by inserting colored gelatine slides in front of the lights.

National Electrical Code Rules for Bunch Lights.

Must be substantially constructed of metal and must not contain any exposed wiring.

The cable, feeding same, must be bushed in an approved manner where passing through the metal, and must be properly secured to prevent any mechanical strain on the connection.

Chandeliers.

Chandeliers.—The rule which requires all wiring about brackets to be enclosed, naturally would apply here also. In connection with chain fixtures, which are at present very popular, this requirement is generally overlooked if good reinforced cord is used. Ordinary fixture wire or flexible cord should not be used. The weakest part of a chain fixture is indicated in Figure 189 by the arrow. The opening at this place is, as a rule, too small and not well reamed out. Fixtures used on the road are constantly giving way at this point. The opening should be large enough to pass reinforced cord and should be well reamed out. If the opening cannot be made large enough to give the wire a little free movement, it is advisable to wrap tape around the wire and the metal in such a way as to prevent all motion of the wire at this point. The same observations also apply to the other end where the cord enters the socket.

Another frequent source of trouble with chandeliers is found at the end of the stem where connection is made to the cable which feeds the fixture. See Figure 190. Very often fixture wire is brought out here, but this will soon break. The stage cable, or reinforced cord, should be run down to the bottom of the fixture and connections there made to the wires leading to the various arms. There are many fixture hooks made up after the manner shown in Figure 191 which have a small opening for the wire at the point indicated by the arrow. This opening is always too small and in such a case it is best to arrange a tee as shown. A chandelier must always be hung in such a manner as to avoid strain coming on the electrical conductors.

Colors.

Colors.—Where a certain color is wanted, during the whole show, from a certain light source, the incandescent lamps themselves may be colored. Prepared colors for this purpose are on the market and it is best to use them. Where the colors in a scene change rapidly there must be some colored material available which can be quickly interposed between the light and the scene. The manner in which this is done for bunch lights is indicated in Figure 188. The same method is also used in connection with open-arc lamps, but for spot lights there is another method, shown in Figure 192. This is a so-called color wheel and the colors can be changed by simply revolving the wheel until the proper color is in front of the lens. An automatic color wheel is on the market which allows the operator to control colors at a distance by means of an electric circuit and magnet. This device cannot be used with flood lamps and has the further disadvantage of casting unavoidable shadows during the change of colors. Where detachable color holders are used, it is possible to change from one color to another by almost imperceptible degrees by holding the frame in the hand and bringing it gradually from a distance to the front of the lamp. In this manner the shadows cast by the frame can be avoided and the color brought very gradually into the scene.

Dimmer Box.

Dimmer Box.—The dimmer box, as the name implies is a box which contains the resistances required for dimming lights used on the stage. It comes into service only with the more pretentious shows which carry foot-lights or border-lights. A typical wiring diagram is shown in Figure 193. This diagram supposes that not more than three colors are used. A small candle power incandescent lamp should always be installed in the box so that the operator may see what is necessary in dark scenes. This lamp should have its own fuse protection. This is a point very often overlooked by operators. The box is usually made of wood and lined with metal. It should be deep and nearly square, so as to occupy a minimum of space. If a shallow box is used, it will be necessary to place the switches in a separate compartment from the fuses, so that the latter may be always enclosed, even while the dimmers and fuses are being operated.

Provisions should be made for the cables to lead out through suitable bushings at the side instead of over the top of the box as is so often done. In some dimmer boxes the slip connectors are fitted into the side of a box so that the male end may be inserted from outside. This makes it unnecessary to bush the cables through the box.

Electric Sign Imitations.

Electric Sign Imitations.—These are used mostly in representations of city night scenes. A flasher sign can be imitated by cutting small round holes in the curtain to outline the reading matter on the sign. Behind these holes a moon box is placed, the lamps in it being on a flasher or controlled by “skeedoodle” sockets, thus giving the effect of an electric sign on a flasher. In case the effect of a steady burning sign is wanted the flasher is omitted.

Electric signs imitating falling water have in turn been imitated according to the plan outlined in Figure 194. On the side nearest the audience is the curtain A, upon which the sign is painted and in which there are a number of holes representing the electric lamps in the original sign; behind this curtain is a grating B, also full of holes; and behind this revolves a spiral C, so arranged as to obstruct intermittently the light which is behind it. The object is to imitate, as nearly as possible, the action of the lights in the original sign.

Electric Stage Effects.

Electric Stage Effects.—A large number of stage effects can be produced by properly painted mica discs which are caused to move in front of the lens of a spot light arranged for the purpose. A view of such a contrivance is given in Figure 182 and is known as the “Sciopticon”. The effects are changed by clockwork which is adjustable as to speed. The device is arranged to slip in front of the lenses and can be attached in a moment.

A list of some of the effects obtainable is given below:

• Avalanche
• Climbing monkeys
• Cyclone with flying objects
• Falling leaves
• Fireworks
• Flame
• Flowing water
• Flying birds
• Lightning
• Moving clouds
• Niagara Falls
• Ocean waves
• Rainbow
• Rain
• Rising fire and smoke
• Rolling lava
• Sand storm
• Snow storm
• Swimming fish
• Twinkling stars
• Volcano
• Water falls

The above list is given to illustrate the possibilities of this method of producing effects. They are, however, rather expensive and some of them require several machines to be in operation at the same time.

Explosions.

Explosions.—Nearly all explosions are set off by the melting of a fuse through an electrical short circuit. The explosive powder is placed above, encloses the fuse, and is ignited when the fuse blows.

Such explosions are often forbidden by inspectors but there is no danger from them if the powder, etc., is enclosed in a suitable wire mesh open on all sides. This will not interfere with the explosion and will prevent the flame, which lasts but an instant, from coming in contact with scenery or people. Where such explosions are used they are generally the most important part of the act, and every possible precaution must be taken to avoid the chance of failure. They are, therefore, often arranged on two circuits with a throw-over switch so that in case one fuse fails the circuit can be immediately closed on the other. See Figure 195. It requires some time to throw-over a switch, and in order to make doubly sure that the fuse will blow at the right time, two fuses and two separate wires may be used and connected at the same time by a simple double-pole switch. The latter arrangement has the disadvantage that one of the wires might be broken, or the contacts bad, without the defect ever being noticed until the other wire also fails and the explosion misses entirely.

It is best to use the throw-over switch and to use the wires for the first connection in alternation so that a defect may be noticed at once. If the same wire were used each time the throw-over switch would be open to the same objection as the double-pole switch. In selecting fuses for this work it must be borne in mind that the powder which is placed over the fuse has a certain cooling and conducting effect, and that often, therefore, a fuse which would readily blow if in the open would not blow if covered with metallic powder.

Face-O-Graph.

Face-O-Graph.—This is an arrangement of two powerful arc lamps with the necessary lenses and objective by which the face of an actor can be projected upon a screen. This effect is very trying to the face and eyes of the actor. The face must be brought very close to the arc lamps and must be held upside down during the performance. From forty to fifty amperes are used in each arc lamp. The optical principle is explained in another chapter.

Festoons.

Festoons.—Festoons should be made up as shown in Figure 196. Weatherproof sockets are generally used because the common brass shell sockets have too many parts that are liable to work loose on account of the constant handling the festoons are subjected to with traveling productions. The use of porcelain sockets, however, should be avoided; mica sockets seem to be generally preferred. The soldering also should be carefully done and only at the end, as indicated by the arrow in the cut. The branch wires are often taped to the main cable as indicated, but often also, circular loom is slipped over the cable in such a manner that the branch wires are supported by it. Short lengths of loom must be slipped on the cable before the tapes are made. A really well made festoon will last a long time and give very little trouble; while a poorly made one will cause much annoyance and much unfavorable comment from inspectors. Most of the festoon troubles are due to poor support of the branch wires. A single festoon does not often carry more than ten or twelve lights and usually not more than six or eight.

A certain style of shade is very much in vogue in connection with festoon lamps and this shade makes the use of lamp guards impossible. If the shade is made of gelatine there will be but little need for the guard, but celluloid shades should not be allowed. All combustible material that is to come near the lamp or the socket should be fireproofed.

The National Electrical Code Rule for String or Festooned Lights.

Wiring of same must be of approved type; joints to be properly made, soldered, and taped, and staggered where practicable. Where lamps are used in lanterns or similar devices, approved guards must be employed.

Fire Dance.

Fire Dance.—This effect is generally illuminated from below the stage, the light being thrown upward through glass. Special arc lamps, equipped with powerful reflectors, are often used and generally several of them are required to produce the proper effect. If spot lamps are to be used they should not be turned upward but instead reflectors placed at an angle of forty-five degrees, should be provided to throw the light upward. See Figure 197. If a spot lamp is turned upward, the heat of the arc rising will be great enough to make condenser breakage a very serious problem. It is also difficult to keep a horizontal arc working properly.

Fireflies.

Fireflies.—The “fireflies” are miniature incandescent lamps strung about among the scenery and on the clothing or in the hair of performers. No attempt should be made to operate these from any other source than a low-voltage, low-amperage battery. It is best to subdivide them as much as possible to avoid short circuits. A short circuit on one lamp would put out a group of one hundred as quickly as it would ten. Such lamps are often arranged on a keyboard by which single lamps or small groups may be lighted intermittently, thus giving the effect of fireflies flitting about.

Fireplaces.

Fireplaces.—The commonest and best fireplace is made up of a few lights arranged in regular strip fashion, the strip being placed in a practical fireplace filled with coal or large pieces of glass, such as broken pieces of lenses. For a very simple effect, red colored globes are used. The effect can be enhanced by using lamps of amber, red, and white and connecting each lamp to a dimmer which can be worked off the stage. This is capable of producing a flaming effect. A further enhancement of the effect is sometimes produced by placing colored asbestos about the lights. This or other suitable material can be made to represent glowing ashes very nicely. Very often the illumination of the fireplace is by means of colored globes strung about among the logs. For this purpose they must be equipped with strong guards and wired with stage cable. Actual gas flames are also often mixed in with the electric illumination. In a mechanical way the effect of flame is often imitated by colored cloth so arranged that a small fan motor placed beneath it can blow it upward.

In a certain well-known production, an imitation of the crater of a volcano is made by arranging a number of fan motors under a large piece of silk which rests upon a frame and revolves over the motors. Parts of this silk are provided with pockets and are loose so that they may be blown upward to represent flame while the major portion only undulates, representing a sea of molten lava. Strips with red lights are used to intensify the effect.

A small motor operating a suitable ratchet has been used to imitate the sounds of wood crackling in the fire. “Chemical smoke” is also often used to enhance the effect. This can be purchased of supply houses.

Flat Irons.

Flat Irons.—See “Heaters”.

Flowers.

Flowers.—On the vaudeville stage, electrically lighted flowers are sometimes used. These are often wired by simply running fixture wire or flexible cord along a wire stem and fastening a small socket to it. Flowers lighted in this manner, however, will not be allowed in theaters where there is inspection. A better method is shown in Figure 198. Armored cord is used for the stem and a miniature socket is placed at the end. All splices are within the junction box which supports the stems. Instead of the armored cord ordinary fixture tubing may be used. Baskets of flowers and small bouquets are generally lighted from batteries.

Fountains.

Fountains.—The illumination for electrically lighted fountains is sometimes obtained from incandescent lamps, but no very showy effects can be produced with them. Where they are used in a manner which subjects them to moisture they must be wired in waterproof conduit and fittings and the lamps must be covered by a watertight globe. For brilliant effects arc-lamp illumination is necessary and the arc must of course be below the water. As arc lamps when tilted upward break condensers very rapidly, the light is usually reflected upward by means of mirrors set as indicated in Figure 197.

Fuses.

Fuses.—There is no part of the electrical equipment of a traveling production so much abused as the fuse. It is provided primarily for the protection of apparatus and should never be of greater capacity than is needed to carry the load put upon it. There is nothing whatever gained by the use of larger fuses. If the load is not in excess of six amperes, a six ampere fuse will carry it as readily as a twenty ampere fuse. If a short circuit occurs the twenty ampere fuse will blow as readily as the six ampere fuse and, in addition, will cause destruction of a socket or whatever may be the cause of the trouble as well as an increased fire hazard. Notwithstanding the above, it is a rare exception when one finds the circuits of a traveling outfit properly fused. For this there are two reasons. One is that, owing to frequent handling and moving, fuses work loose; and thus, to the natural heat produced by the load, there is added a certain amount of heat produced in the poor contacts. Trouble of such a nature can be lessened by the use of larger fuses, but only to a very small extent. It is far better to go over one’s fuses two or three times a week and tighten the screws and contacts to avoid this trouble than to use over-large fuses.

Another reason for the overfusing, of plugging boxes especially, is found in the fact that arc and incandescent plugs are interchangeable. If, therefore, each circuit is fused at thirty amperes one need not worry about which pocket an arc lamp is connected to. This practice is, however, very bad, a table lamp, for instance, with a thirty-ampere fuse behind it would be likely to cause flash and smoke enough to alarm an audience. Some provisions should be made so that one can easily distinguish between arc and incandescent pockets or divisions in plugging boxes. The main requisite which determines the style of fuse to be installed for stage effects is that of quick renewal in case of blow-out.

Gas Globes.

Gas Globes.—Electric light is so convenient on the stage that even gas light is imitated by it. In one production in which it was desirable to show the front of a theater illuminated by gas, the gas globes were made up of cloth cut as shown in Figure 199. Behind each imitation globe a small incandescent lamp was arranged.

Glass Shades.

Glass Shades.—An imitation of these for small desk or table lamps is often made by placing a strip of colored gelatine between two layers of wire mesh. The wire screen keeps the gelatine straight and the whole is more serviceable than glass and less liable to break.

Heaters.

Heaters.—Under this head come flatirons and water heaters. Flatirons are carried by many actors who cause much trouble by connecting them to lighting circuits. In many places the house electrician prevents their use by fusing his lighting circuits so low that the addition of a flatiron immediately blows the fuse. If used at all, the flatirons should be of the smaller kind. Small heaters are also extensively used upon the stage.

National Electrical Code Rule for Electric Heaters.

It is often desirable to connect in multiple with the heaters and between the heater and the switch controlling the same, an incandescent lamp of low-candle power, as this shows at a glance whether or not the switch is open, and tends to prevent its being left closed through oversight.

Must be protected by a cut-out and controlled by indicating switches. Switches must be double-pole except when the device controlled does not require more than 660 watts of energy.

Must never be concealed; but must at all times be in plain sight. Special permission may be given in writing, by the Inspection Department having jurisdiction, for departure from this rule.

Flexible conductors for smoothing irons and sadirons and for all devices requiring over 250 watts must have an approved insulation and covering.

For portable heating devices the flexible conductors must be connected to an approved plug device, so arranged that the plug will pull out and open the circuit in case any abnormal strain is put upon the flexible conductor. This device may be stationary, or it may be placed in the cord itself. The cable or cord must be attached to the heating apparatus in such a manner that it will be protected from kinking, chafing, or like injury at or near the point of connection.

Smoothing irons, sadirons, and other heating appliances that are intended to be applied to inflammable articles, such as clothing, must conform to the above rules so far as they apply. They must also be provided with an approved stand, on which they should be placed when not in use.

Stationary electric heating apparatus, such as radiators, ranges, plate warmers, etc., must be placed in a safe location, isolated from inflammable materials, and be treated as sources of heat. Devices of this description will often require a suitable heat-resisting material placed between the device and its surroundings. Such protection may best be secured by installing two or more plates of tin or sheet steel with a one-inch air space between or by alternate layers of sheet steel and asbestos with a similar air space.

Must each be provided with name-plate, giving the maker’s name and the normal capacity in volts and amperes.

Lighthouse Effect.

Lighthouse Effect.—To increase the effect of a lighthouse painted upon the scenery, a strip of suitable length with one light at each end is provided. The strip circuit contains a flasher so that both lights are turned on and off at regular intervals. One lamp must be behind the head of the lighthouse, the other where the reflection of the upper light would appear in the water.

Lightning.

Lightning.—The standard method of producing lightning effects upon the stage is by means of the device shown in Figure 200. A magnet and the arc-striking carbons are arranged in series and take current through a resistance. Normally the carbons are in contact and when the switch is closed the current passes through the magnet and carbons. The current energizes the magnet and causes the upper carbon to separate from the lower, thus striking the arc. The arrangement must be such that the arc is immediately broken, thus de-energizing the magnet; this allows the movable carbon to close the circuit again, thus repeating the operation. This device if uninterrupted will give a rapid succession of lightning effects and it may be suspended in the wings as it is entirely automatic. At the right of Figure 200 is shown another lightning striker which is operated by hand.

Where it is not prohibited, a very good lightning effect can be obtained by arranging a file and a piece of carbon as opposite poles of the circuit and scraping them together. It is a bad practice, however, to strike an open arc on any stage. There should always be wire mesh around it to prevent the escape of sparks.

Automatic strikers can be purchased which will make an open arc lamp produce good lightning effects. Another method of producing lightning is that of flashing some of the border lights. This will do in an emergency but does not compare with the other methods. Sometimes the effect of a bolt of lightning striking a certain place is imitated by an arc sliding swiftly down a wire. In order to strike the arc at the proper moment, the apparatus being somewhere up in the flies, a small fuse is connected from one carbon to the other. The current when turned on passes through the fuse, melts it, and establishes the arc. The carbons are incased in a very small wire-mesh enclosure and the whole device is made to slide swiftly down a tight wire leading to the proper place. The more pretentious shows often use several lightning machines to avoid the monotonous effect of all lightning strokes coming from the same direction. One resistance may be made to serve for any number of lightning machines provided only one machine is used at a time.

Lugs.

Lugs.—Lugs must be provided for all leads where more than 30 amperes are used. It is even more necessary to follow this rule in connection with portable theater equipment than with other wires because they are more apt to work loose.

For the connections to the arc lamp and rheostats it is not practicable to use soldered lugs because no solder will stand the heat. Two styles of lugs that may be used are shown in Figure 201. The cuts will also explain the manner of connecting the lugs. At the left, the bare lugs are shown; in the center the copper of the conductors is shown inserted into the lugs, and at the right the whole conductor is shown bent back, the metal of the lug catching over the insulation to keep it from fraying out. The wires feeding arc lamps are always asbestos covered and this covering fits loosely to the wire and must be held in some such manner. A stock of such lugs should always be carried, as the leading-in wires to arc lamps, using heavy currents, frequently burn off.

Moon Boxes.

Moon Boxes.—These boxes are generally made up as shown at the left in Figure 202. The opening is from twelve to fourteen inches in diameter. Four lamps give very good illumination. The frame must be provided with hooks so that it may be suspended at any desired part of the scenery. It is always hung close behind a curtain and must be so arranged that the lamps cannot touch the curtain. The wires should be entirely enclosed in metal of No. 20 sheet metal gauge after the manner of strips. Very cheap productions often carry moon boxes made up of an incandescent lamp fastened in a tin dish, similar to the one shown at the right in Figure 202.

Moonlight on Water.

Moonlight on Water.—This and all similar effects can be produced through the “Sciopticon” but this requires the use of an arc lamp and is expensive. A cheap way of producing the effect is illustrated in Figure 203, which represents a metal cylinder, perforated as shown, inside of which there are a number of incandescent lamps colored to suit. The cylinder is slowly revolved and the moving shadows and streams of light thrown upon the scene produce the effect.

A somewhat similar method of producing this effect, as also that of a waterfall, is illustrated in Figure 204. In this case a spiral capable of being moved by clock work is revolved about an electric lamp and gives the effect of falling water. Both of these devices work behind curtains.

Musical Acts.

Musical Acts.—There are numerous musical acts upon the road in which the beat of the music is emphasized by lighting colored lamps in time with the tunes. It is advisable to arrange all such acts to operate by batteries. In many places inspectors will not allow high-voltage contacts to be used open, and it is often difficult to enclose them in a practical manner. By using dry batteries the apparatus is taken out of the jurisdiction of inspectors and all danger of fire is also eliminated.

Musical Bells.

Musical Bells.—Sets of musical bells properly tuned and connected to a keyboard from which they can be operated electrically are carried in stock by dealers in theatrical supplies. Sets are usually made up of eighteen bells and they may be played from a distance.

Oil Lamps.

Oil Lamps.—These have been imitated by arranging a small battery inside of the base of the lamp. This battery would supply current only during the short time that the lamp was being carried about. The base of the lamp is also fitted with electrical contacts which rest upon similar contacts fitted into the table, and through which the lamp is kept burning by a storage battery while it is resting upon the table. A small dry battery, such as is placed in the base of an oil lamp, would not keep the light burning for a long enough time.

Pin-Plug Connectors.

Pin-Plug Connectors.—These are provided to connect cables to effects used on the stage. The essential points of a good connector are: It should grip the whole cable, thus making it unnecessary to strip the outer braid from any exposed part of the cable; and it should offer no live screws or contacts on the outside. These conditions are fulfilled by the connector shown in Figure 205. In some of these connectors, however, the part that grips the cable (indicated by the arrow) is made of metal, and this, if forced down too tight, may cut into the cable and cause a short circuit. Several instances of this kind have been known to occur. Pin-plug connectors must always be connected so that the projecting pins are dead when the plug is disconnected.

A special warning against the use of such connectors as are illustrated at the right of Figure 205 is necessary. Their cheapness brings them into use very often, especially with acts that do not carry competent electricians. The wires are always working loose; projecting ends are bare, and if the connector is twisted, a short circuit results. Where they must be used in an emergency, they should be heavily taped, the tape being placed between the conductors and all around the plug, as shown in the figure.

Branch-off connectors such are shown in Figure 206 are often used to tap off lights from the main cable. Where plug connectors are used for arc lamps they must be made up as shown in Figure 207. The asbestos-covered wires necessary to be used with arc lamps cannot be used in cable but must be separately connected.

The National Electrical Code Rules for Pin-Plug Connectors.

Must be of an approved type, so installed that the female part of the plug will be on the live end of the cable, and must be so constructed that tension on the cable will not cause serious mechanical strain on the connections.

Plugging Boxes.

Plugging Boxes.—Plugging boxes are used to obviate the necessity of running a large number of wires over the stage to the different stage pockets. They are also a necessity because many theaters are not equipped with a sufficient number of stage pockets to accommodate all of the devices large productions carry. The plugging box should be fireproof; should have self-closing doors so that there may be no liability of open fuses being left among the scenery where they are used. Most of the plugging boxes in use at the present time are arranged for link fuses. A link fuse, however, requires more time to install than a cartridge fuse and the latter would therefore seem much more desirable. A cut of a much-used plugging box is shown in Figure 208.

The National Electrical Code Rules for Portable Plugging Boxes.

Must be constructed so that no current-carrying part will be exposed, and each receptacle must be protected by approved fuses mounted on slate or marble bases and enclosed in a fireproof cabinet equipped with self-closing doors. Each receptacle must be constructed to carry thirty amperes without undue heating, and the bus-bars must have a carrying capacity equivalent to the current required for the total number of receptacles, and approved lugs must be provided for the connection of the master cable.

Rheostats.

Rheostats.—Portable stage equipment being intended for use in all parts of the country must be adjustable to all kinds of lighting systems. For this reason it is not practicable to use auto-transformers as is commonly the case where arc lamps are fed from alternating-current circuits. Simple rheostats or resistances are therefore always used. With these it is immaterial whether the current be alternating or direct except in so far as the quantity is concerned.

Alternating current being less efficient in the production of useful light than direct current, the amperage must be greater and this produces a greater loss in voltage, the loss being always proportional to the product of current times resistance. The drop in voltage over a certain resistance is therefore always greater, when an alternating-current arc is used, than it is with direct; but as the alternating-current arc operates at a lower voltage than the direct this is not objectionable and simple resistances give satisfactory results whether used with one kind of current or the other. The traveling show must also be prepared for different voltages and a suitably arranged group of resistances is very convenient in this respect.

Figure 209 shows a box made by the Chicago Stage Lighting Company containing a number of resistances which may be connected in various ways to obtain different results. In Figure 210 at A is given a diagram representing the wire in a single section. One such section placed in series with an arc lamp will give a certain current. If we connect two of them in parallel, as in B, we shall obtain not quite double the current, since this arrangement does not affect the resistance of the arc which also influences the current strength. If the connections are made as in C, we shall have but half the current obtainable by the use of one section, or the same current in case we are dealing with double the voltage. If A is suitable for 110 volts, then C is suitable for 220 volts and D for 550. In E we have the connection which would give us, for 220 volts, the same current B would give with 110. It can thus be seen that a group of such resistances can be made to fit an arc lamp to almost any voltage that is likely to be met with.

Nothing but metal and porcelain must be used in the construction of these resistances and they must be on stands which raise them well above the floor. The connections to the resistances should ordinarily be made with asbestos cable. It is necessary to keep close watch of the wire used to make up the resistance especially if it becomes very hot during a run. A resistance in which the wire becomes red hot should not be used. There are productions in which it is necessary to place the arc lamps and their rheostats directly in the way of flying paper used to make “snow”. In such cases the resistances must be tightly enclosed. This destroys the ventilation and they will readily become overheated. For use with such productions resistances may be specially wound and arranged, or they may be made separate from the arc and placed in a safe location.

Stage Cables.

Stage Cables.—Stage cables are subject to very rough usage, but there are some very good makes on the market, and by purchasing the best, one can expect long service. Cuts of various kinds of cable likely to be used upon the stage are given in Figure 211. A is the ordinary stage cable; B is used for heaters; C is reinforced cord; and D is the parallel cord. The last two must not be used on the floor. The size of the wire to be used depends upon the apparatus which the cable must supply and can be determined from Table VII which gives the carrying capacities. Only approved cables should be used.