CHAPTER IX.

GAS LIGHTING.

When it is desired to light clusters of gas jets situated in inaccessible places, or a number of them simultaneously, this method finds ready application. It operates in the division of a long spark among a number of burners, the gas being turned on at the main and the primary circuit of a Ruhmkorff coil closed and opened until the succession of sparks ignites the gas, Fig. 55. There are various commercial forms of these burners, prominent among which is the "Smith jump spark" burner.

A lava tip is provided with a mica or isinglass flange midway between the tip and the lower end of the burner. This flange isolates the electrodes from any possibility of the spark straying away to the metallic pillar in which the burner is inserted. The multiple lava tip burner is intended for use where a very short burner is needed, also for flash rings multiple lights. Here the tips are placed close enough together to ignite by contagion. In this case one of the common tips is removed from the ring and a multiple lava tip substituted. It is customary to allow sixteen burners to one inch of spark. Any number of series can be operated alternately by means of a suitable switch.

The wire used to connect the burners is generally bare copper, and as small in diameter as will sustain its own weight without injury, the amount of the current being infinitesimal. It is supported on porcelain or glass knobs screwed to the wall or ceiling, being carefully planned to avoid any metallic substances to which the spark might be tempted to escape. In wiring chandeliers, the wire is run through glass tubes wherever there is any liability of its coming near the metal pipes. There is a very great danger of this jumping of the spark where it is not wanted, and the utmost care must be taken in planning the course the wires shall take. Even a damp wall will cause trouble or a gilt cornice, although the latter may be entirely insulated from the ground. The switch bases for the groups of circuits must be of hard rubber, and the switch points and levers be placed so far apart that there is no liability of the spark jumping, which it certainly will do if it gets a chance. Ordinary insulated wires are ineffectually protected by the rubber compounds used. Glass, mica, and better still, a large air gap are the only insulations that will serve, for the tremendous potential or voltage of the current must be carefully considered whenever insulation is necessary. The coil is better provided with a spring key in the primary circuit than a vibrator, it gives better control of the circuit and probably a larger and better spark.

GAS LIGHTING IN MULTIPLE.

The spark which occurs at the contact breaker of a Ruhmkorff coil is held in check by the condenser; were no condenser used, it would possess considerable powers of combustion. Using a large primary coil and a few cells of open circuit battery, this spark is made to pass across the path of a gas jet, which it instantly ignites. The contact breaker consists of a platinum point, fixed on the gas tip, and a German silver spring, carried on a lever, which latter is pulled across the tip so as to make and break the circuit at the burner orifice. Some burners are provided with a ratchet arrangement, by which pulling the lever once turns on and lights the gas, pulling again turns it off; others require the gas to be turned on first.

Reference to Fig. 56 will show the connections to two burners _P P_ and an automatic burner _A_, to be described later. The coil _C_ is a core of soft iron, about ¾ inch diameter and eight to ten inches long, wound with from two to four pounds of magnet wire, Nos. 12 or 14 B & S. One side of the battery goes to ground or to the gas pipe, thus forming the return circuit. The wiring on the fixtures is done with No. 20 to 24 B & S gas fixture wire, insulated with four windings of silk or cotton. This is fastened to the lacquered brass work by means of thick shellac varnish, it being tied on first with thread, which can readily be removed when shellac is dry and hard. The wire is held on the insulated collar of the burner by a small nut and screw, and great care must be taken to ensure no grounding. The setting up of a gas-lighting outfit is extremely simple, but it often fails for want of care. There must be the best possible insulation between wire and metal work.

AUTOMATIC BURNERS.

There are several forms of these burners, but the principle of all is the same. A gas burner protrudes from the top of a brass case which encloses the actuating mechanism. This mechanism consists of two electromagnets, the armature of one opening a valve and allowing the gas to flow, at the same time vibrating a platinum-tipped rod, which produces a series of sparks at the burner tip. These sparks ignite the gas, and a second magnet is provided to shut off the flow of gas, thus extinguishing the light. Some devices use one electromagnet for both lighting or extinguishing, but the majority are with double magnets. The circuit is worked from a push button situated at any desired location, and having a white and black button, one for lighting and the other for extinguishing. The principal automatic burners are the Holtzer, the Boston, and the Bartholdi, between which there lies little choice, so admirably are they constructed.

BARTHOLDI AUTOMATIC BURNER.

Instead of a rotating stop-cock, as in other automatics, a gravity valve is employed in the Bartholdi, which is held to its seat by the weight of the armature and connecting stem, as shown in Fig. 57. When the gas is turned off the valve rests upon its seat, as indicated in the cut. By a closure of the electric circuit at the turn-on button, two of the helices _M P_ are energized, causing the armature _J_ to be lifted, thus, by means of the stem _H_, raising the valve _G_ from its seat into the dotted position, and opening the gas way so that the gas may issue to the tip, as shown by the arrows. At the same time, the top of the valve strikes against the end of the lever _W_, causing the circuit to be broken at the spark points _T U_, resulting in a continuous sparking as long as the finger presses the button. The magnet when raising the armature has also twisted or partially revolved it, so as to bring the notch _d_ in the armature over the end of the hook _e_, as shown in dotted lines. When the circuit is broken by lifting the finger from the button the notch falls into the hook and the valve is locked open.

To extinguish the flame the turn-off button is pressed, when a second magnet (not shown in cut) lifts the armature and twists it in the opposite direction, so that when the circuit is broken the armature falls free to its normal position, closing the valve.

In wiring up an automatic burner it is necessary to run two wires to it, one from the white button and another from black button on push plate _S_. Reference to Fig. 58 will make this clear. Most burners are provided with two binding posts inside the brass case, and the wires are run through a rubber-bushed hole in the base. If the push has already been set in position and wired up, as per Fig. 58, have the buttons pressed alternately, when on touching the binding posts on automatic with the wires, the lighting or extinguishing connection is easily selected. The lighting armature in most automatic burners buzzes violently, while the extinguishing one only strikes once on contact being made. Fig. 58 shows how to connect up two pushes to one automatic, one push, perhaps, being located downstairs and the other upstairs in the case of a hall lamp. In setting up these burners care must be taken not to bend contacts or alter adjustment, and absolute precaution is necessary that no crosses or weakly insulated places are in circuit. After burning for some time it often happens that the burner refuses to light, only buzzing feebly or not at all. If feebly, the trouble is in battery, which should consist of, at least, four or six cells of open circuit battery with low internal resistance, such as Samson-Law carbon cylinder, or for occasional use large, dry cells.

If no click is heard on pressing white button, examine all connections; if still no trouble is found, examine the platinum break. The platinum tip may be bent by the continual hammering against the platinum tip on vibrating rod, preventing contact on collar, or that soot has formed there. These are the commonest maladies of automatic burners, and can be easily remedied by readjusting platinum tip and cleaning. Contacts here must be clean. In general wiring use waterproof office wire or, better still, rubber-covered wire; for fixtures use the fixture wire before described. When shellacking the wire to the fixture don't attempt to connect up batteries until the shellac is dry and hard, say for half a day. Electric gas-lighting is fruitful of trouble if the work is not well done. Another cause of trouble may arise from a dirty burner not allowing the gas to strike near the contact (clean the burner), or the collar carrying contact may have shifted, perhaps short-circuited; it should be insulated with a thin strip of asbestos. Although white lead at the joints makes a fairly good contact, some persons prefer to use tin-foil, a piece of foil being worked around screw thread and the burner screwed on; it prevents leaks as well as lead if well done, and makes better contact. As a short circuit on the wires will cause all the burners to fail, many devices have been invented to open the circuit upon such an occurrence. These will be found described in the catalogues of electrical stores; they do not come within the province of this book for description.