Accompanying this is a sketch of a serviceable ruby lamp to burn either gas or oil. The lamp should have three illuminated sides, the front one to take ruby, orange, or opal glasses. The most convenient plan is to have these glasses fixed in frames so that they can be run in grooves on one side, as shown in the illustration; thus either one or all three cau be used as required. With such an arrangement, it will not be necessary to regulate the lamp from the outside. The opal slide may be pushed in front when development starts, and may be run back when the image is fairly out. For slow plates, the orange slide is used alone; for isochromatic plates, the ruby slide; and for very rapid plates, the orange and ruby together.

Photographic Dark-room Lamp.