The inspection of wiring for incandescent lights in buildings, on behalf of the insurance companies, is now so rigid that the householder whose wires have been accepted by the insurance inspector can feel himself tolerably safe in regard to them. They should, however, be occasionally examined, where visible, to make sure that the insulation is not wearing off, and that they are not exposed to water. Any wet surface, or damp rag, or piece of metal in contact with the wires, which can act as a medium, even of very slight electrical communication, between two wires of opposite polarity, will increase the amount of current used, as shown by the meter, without producing any useful result; and, if the leakage is serious, it involves great danger of setting the house on fire. Safety-fuses, also, in dwelling-house work, are frequently fixed on wooden boards, and enclosed in a wooden cabinet, although the burning out of a fuse, through an accidental short-circuit or otherwise, often sets fire to dry woodwork near it.

Incandescent lamps themselves are often carelessly handled, particularly where they are attached to flexible wires, as is frequently the ease in dwelling-houses. It should never be forgotten that the common belief, that an incandescent lamp never gets very hot, is correct only when there is a free circulation of air around it; and, when this circulation is impeded, the bulb soon becomes hot enough to set fire to inflammable materials. Destructive conflagrations have been caused by leaving incandescent lamps, attached to a flexible wire, in contact with bundles of cloth, or similar articles, and it is hardly possible to exercise too much care in keeping such lamps out of harm's way.

Incandescent lights.

Where current for incandescent electric lights is not available, an electric spark is often used for lighting gas, either in a "pendant" or "pull" burner, or an "automatic" burner. In the "pendant" burner the pulling of a chain serves to turn on the gas, and at the same time to send a spark through it between two platinum wires, which are made to pass by each other, with momentary contact in the escaping stream, a second pull turning the gas off again. In the automatic burner the gas is turned on or off by means of electromagnets, concealed in the casing of the burner, the current which operates them being controlled by one or more pairs of buttons, placed in any convenient part of the house, and serving at the same time to produce the necessary spark for lighting the stream of gas. If well put in, and well cared for, a system of this kind is extremely Electric gas-lighting convenient, and gives very little trouble. The pendant, or pull, burners are kept free from any leakage of gas, the supply being controlled by a tapered plug, just as in the case of an ordinary key. In the automatic burners, as the tapered plug must be put in so loosely as to be readily thrown in either direction by the attraction of the little electromagnets, there is much more danger of leakage; but, if obtained from a good manufacturer, they are generally reliable. The electrical part of the system, however, is easily thrown out of order by carelessness, and its operation should be understood, so that any derangement may be quickly and intelligently remedied.

The current for electric gas-lighting is obtained from a battery, usually of six or less cells, of the ordinary open-circuit type, with carbon prisms for conducting electrodes, the soluble electrode in each cell being a rod or plate of zinc, and the cells being filled with a saturated solution of ammonium chloride. As the battery current is too low in tension to give a spark capable of lighting a stream of gas, a "spark-coil," consisting of a large wooden spool, wound with insulated wire, and having a "core" of iron wires, is introduced in the circuit, by which the tension of the current is sufficiently raised to give the spark desired.

In order to do their work well, the cells of the battery should be filled about two-thirds full of the ammonium chloride solution; the carbon prisms, which are generally secured by rubber bands to a "pole piece" passing through the glass cover of the cell, should be in place; the zinc rod forming the soluble electrode should be in good condition, and the wires, which should connect the zinc of one cell to the carbon pole piece of the next, must be firmly secured by their appropriate binding-screws; the extra wires, one from the carbon at one end of the battery, and the other from the zinc at the other end, being properly connected with the spark coil, and through it with the wires of the lighting system. To produce the spark required it should then only be necessary to make momentary contact, by means of the appropriate button, for the automatic burner, or to draw the platinum wires of a pull burner against and past each other by means of the chain; and, if the spark fails to appear, a systematic investigation should be made to determine the cause of the trouble.

Battery.

The burners should first be examined, removing for the purpose the cap of automatic burners, as it often happens that the difficulty is not electrical but mechanical, resulting simply from the gumming up of the moving parts of the burner with oil and dust, or the displacement of the ratchet wheel which actuates the gas-key in the pull burners, or of a spring, or of the platinum wires, so that they do not come in contact when drawn past each other by the chain, or by the electromagnets of an automatic burner.

If, after any defects in these particulars have been remedied, by washing off old oil with kerosene if necessary, or by replacing any disarranged parts, the spark still fails to appear, the electrical portion of the apparatus may be examined. If the battery has been long in use, the sal-ammoniac solution may have evaporated to dryness, or may have been reduced to so low a level as no longer to act vigorously on the zinc; or its chemical energy may be exhausted, as will be the case after a year or two of use. In any case the liquid in the cells should be filled up to the two-thirds level, by adding to what is left in them either water alone, or a fresh saturated solution, made by dissolving sal-ammoniac in hot water. The cells should not be filled more than two-thirds full, or the solution will creep over the edge by crystallization. Pure ammonium chloride only should be used, such as is sold by dealers in photographic goods and general chemicals, put up in pasteboard boxes, or by dealers in electrical goods in small paper bags, each containing a sufficient charge for an ordinary battery cell.