The 1927 Bausch & Lomb catalog of Balopticons and Accessories describes this “Hand-feed Arc Lamp” for its magic lanterns in the following words:
“This lamp is carefully constructed, with screws and gears so as to prevent binding even after being thoroughly heated. The carbons can be fed independently or simultaneously. A wide range of adjustment is provided for by accurate centering screws, and all adjusting and feeding screws are carefully insulated. Either direct or alternating current can be used, although the former is desirable. A rheostat must always be used with this lamp.”
Direct Current provides a much brighter light on the positive carbon than can be obtained with Alternating Current, which supplies dimmer (but equal) light to both positive and negative carbons.
A rheostat or series resistor, like those wire coils commonly found in portable heaters, needs to be used with any carbon arc light to prevent its arc from shorting out the power source.
The “Hand-feed Arc Lamp” with a centering support was available for use in small lamp houses, the Model C type. It sold $21.50.
An arc lamp like the one above, but with long feeding and adjusting rods, was supplied for a large size lamp house for $30.00.
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