342 



ELEMENTS OF ELECTRICAL ENGINEERING. 



An objection to the luminous-arc lamp is that a dense smoke 

 is produced by the condensation and oxidation of the metallic 

 vapors, so that the arc cannot be enclosed and the lamp cannot 

 be conveniently used indoors. 



The great advantage of the luminous-arc lamp is its high 

 efficiency. Such a lamp consumes from 0.8 to 1.2 watt per 

 spherical-candle of light flux, whereas an ordinary enclosed car- 

 bon-arc lamp consumes from 2.0 to 2.2 watts per spherical-candle. 



rig. i?o. 



In the luminous-arc lamp of Bremer the arc is formed between 

 carbon rods which are highly impregnated, chiefly with salts of 

 calcium. This lamp gives a brilliant yellow light which can be 

 made to approach a pure white by using salts of other metals. 



In the luminous-arc lamp of the General Electric Company 

 the arc is formed between a negative terminal (cathode) of iron 

 oxide and a positive terminal (anode) of metal, usually copper. 

 The iron oxide is contained in a thin sheet-iron tube and is fed 

 like the carbon rod of the carbon-arc lamp. The copper anode 

 is a rod which is held in a rigid support. 



