140 THE ELECTRIC ARC 



A more recent comparison of direct-current arc lamps 

 has been given by Ryan 1 in which the following lamps 

 were compared. 



(1) The carbon open arc, 9.6 amperes, 50 volts, consum- 

 ing in practice from 450 to 500 watts, commercially rated 

 at 480 watts, equipped with clear globe and no reflector. 

 Electrode life of from 16 to 18 hours. This lamp is nor- 

 mally designated as 2000 c.p., which, however, is regarded 

 as merely a trade name. 



(2) Enclosed carbon arc, requiring 6.6 amperes and from 

 70 to 75 volts, consuming in practice from 450 to 500 watts, 

 commercially rated at 480 watts, equipped with light opal 

 inner, clear outer globe and street reflector. Electrode life 

 of from 100 to 150 hours. 



(3) Magnetite arc, requiring 4 amperes and from 75 to 80 

 volts, consuming in practice from 300 to 320 watts, com- 

 mercially rated at 310 watts, equipped with clear outer 

 globe, internal concentric diffuser and magnetite electrode. 

 Electrode life of from 150 to 200 hours. 



(4) Magnetite arc, requiring 6.6 amperes, 75 to 80 volts, 

 consuming in practice from 495 to 530 watts, commercially 

 rated at 510 watts, equipped with clear globe, internal 

 concentric diffuser and magnetite electrode. Electrode life 

 of from 75 to 125 hours (large unit). 



(5) Boston flaming arc, requiring from 6.6 amperes and 

 from 75 to 80 volts, consuming in practice from 495 to 530 

 watts, commercially rated at 510 watts, equipped with 

 26-in. concentric diffuser and light opal outer globe. 

 Electrode life of from 20 to 25 hours. 



The following are the data which he gives concerning 

 these. 



1 Paper presented before the N. E. L. A., at St. Louis, 1910. 



