[Illustration: FIG. 152.—Small Tungsten Battery Lamps.]
The lamp is mounted in what is known as a miniature porcelain base receptacle. The switch may most conveniently be the type termed a "wood base" switch. In case the lamp is installed for illuminating a clock, a "pear push" and a flexible cord may be substituted for turning the light off and on in place of the switch. It can then be suitably hung alongside of the clock or bed as desired.
The wire should not be smaller than No. 18 B. & S. Gauge or else it will offer too much resistance to the electric current and full benefit of the candle-power of the lamp will not be secured. Annunciator wire is preferable. It has good insulation and at the same time is not too large to be easily run through corners, cracks, etc.
The diagram in Figure 153 shows how to connect the lamp to the battery and switch. Figure 156 shows two dry cells connected in series for use with a 2.8 volt lamp.
[Illustration: FIG. 153.—A Simple Lighting Arrangement.]
When more illumination is desired than that furnished by flashlight lamps greater candle-power will be required. The following table shows the voltages and candle-powers of those lamps which are most suitable in such an instance:
· G6….4 volts 4 candle-power
· G6….6 volts 4 candle-power
· G8 6 volts 6 candle-power
They may also be operated from dry cells. If they are intended to be in use for other than a few minutes at a time it will be well to use a battery consisting of two sets of cells connected in series multiple. The method of connecting cells in series multiple has already been illustrated in Figure 35. This will lighten the strain on the battery and it will be found that two sets of batteries used in series multiple will last *more than twice* as long as one set used alone.
[Illustration: FIG. 154.—Showing the differences between the Candelabra,
Single Ediswan and Double Ediswan Types of Lamp Bases.]
Six volt lamps of more than six candle-power are best operated on storage batteries because the current required is too great for dry cells to give efficient service in such a case.