Flash Lights.
—These are portable electric lamps composed of a miniature incandescent bulb, which with one or more dry cells are enclosed in a frame to suit the purpose of their use. They are made in pocket sizes or in form to be conveniently carried in the hand and are convenient and efficient lamps wherever a small amount of light is required for a short time. The electricity for operating the lamp is supplied by a battery of dry cells (to be described later), or by a single dry cell. In each case the incandescent bulb is suited to the voltage of the battery.
In replacing the bulbs care must be taken to see that the voltage is that suited to the battery. The voltage is usually stamped on the lamp base or marked on the bulb. In case a lamp intended for a single cell is used with a battery of three or four cells, the lamp filament will soon be destroyed. The reverse will be true should a lamp intended for a battery be used with a single cell. The single cell giving not much more than a volt of electromotive force will not send sufficient current through the lamp filament to render it incandescent.