An automatic feed arc lamp for photographic portraiture is expensive.

A clockwork arrangement or an electro-magnet causes the carbons to be drawn together or separated until the correct position is obtained automatically. A hand-feed lamp, however, although demanding more attention than an automatic apparatus, would serve the purpose, and could be fitted up for about one tenth the cost of the automatic lamp. The apparatus merely consists of a bar A (see illustration) to which is fixed a clamp B. Travelling along A is a similar clamp for the carbon C, adjusted by a rack D and ratchet wheel E, worked by the wheel F. An opal reflector G is fixed as shown and receives the rays of light, reflecting them into the larger drum H, which in turn throws the light on the figure. The drum is made to turn somewhat tightly in I at J. A counter-balance L is fixed as shown, and the whole swings from the ceiling at M. By means of the ball socket at K the lamp may be instantly placed in any position. Wires N and 0 convey the current to the carbons V and Q. Of course, the clamps carrying the carbons must be insulated from the rest of the apparatus.

For this purpose the grip of the clamps is generally made in sections with sheets of mica between.

Electric Arc Lamp for Portraiture.