ENCLOSED SERIES ALTERNATING CURRENT ARC LAMPS
The simplicity of the constant current transformer soon drove the constant direct-current dynamo from the market. An enclosed arc lamp was therefore developed for use on alternating constant current. Two sizes of lamps were made; one for 6.6 amperes consuming 450 watts and having an efficiency of about 4½ lumens per watt, and the other 7.5 amperes, 480 watts and 5 l-p-w (clear glassware). These lamps soon superseded the direct current series arcs. They have now been superseded by the more efficient magnetite arc and tungsten filament incandescent lamps.