NO. 2 



HISTORY OF ELI-XTRIC LIGHT SCHROEDER 



79 



The dry battery was made in small units of 2, 3 and 5 cells, so 

 that lamps of about -| to i candlepower were made for 2h, 33 and 

 (4 volts, for portable flashlights. It was not however until the 

 tungsten filament was developed in 1907 that these flashlights became 

 as popular as they now are. For ornamental lighting, lamps were 

 supplied in round and tuljular bulbs, usually frosted to soften the 

 light. 



The AFoork Tube Light, 1904. 



This consisted of a tube about i}i inches in diameter and having 

 a length up to 200 feet, in which air at about one thousandth part of 

 atmospheric pressure was made to glow by a very high voltage alter- 

 nating current. 



THE MOORE TUBE LIGHT 



Geissler, a German, discovered sixty odd years ago, that a high 

 voltage alternating current would cause a vacuum tube to glow. This 

 light was similar to that obtained by Hawksbee over two hundred 

 years ago. Geissler obtained his high voltage alternating current by a 

 spark coil, which consisted of two coils of wire mounted on an iron 

 core. Current from a primary battery passed through the primary 



