It consists of a wooden box to hold a three-cell dry battery, and is provided with a handle so that it may be easily carried. A switch by which to turn the lamp on and off is mounted on the side of the box.
The light is furnished by a three-and-one-half-volt tungsten lamp mounted on the front of an inclined wooden board arranged as shown in the illustration so as to throw the light downward. The sides and bottom of the box are grooved near the front edges so that a piece of ruby glass may be inserted. Ruby glass for this purpose may be purchased at almost any store dealing in photographers’ supplies.
The top is provided with a shield which is fastened in position by means of four small hooks after the glass is in place. The shield is used in order to prevent any white light from escaping through the crack between the glass and the top of the box. A ruby lamp of this sort must be made absolutely "light-tight" so that the only light emitted is that which passes through the ruby glass. If any white light escapes it is liable to fog and spoil any pictures in process of development.
Fig. 297.—The Electric Ruby Lamp with Glass and Shield Removed.
By removing the ruby glass and the shield, as shown in Figure 297, the light is changed into a hand-lantern. The back of the box should be made removable so that the battery can be replaced when worn out.
A Night-Light arranged to shine on the face of the clock so that the time may be easily told during the night without inconvenience is shown in Figure 298.
Fig. 298.—An Electric Night-Light for telling the Time during the Night.
It consists of a flat wooden box containing a three-cell dry battery and having a small three-and-one-half-volt tungsten lamp mounted on the top in the front with room for a clock to stand behind. The battery and the lamp are connected to a switch so that the light may be turned on and off. By attaching a long flexible wire and a push-button of the "pear-push" type it is possible to place the light on a table and run the wire with the push-button attached over to the bed so that one may see the time during the night without getting up. The bottom of the box should be made removable so that a new battery may be inserted when the old one is worn out.