THE BANISHMENT OF NIGHT 



of success. But in 1898 Dr. Auer von Welsbach took 

 out patents, and in 1903 produced a lamp using an 

 osmium filament. Its advent marked the beginning 

 of the return to metal-filament lamps, although the 

 lamp itself did not prove to be very satisfactory and 

 was quickly displaced by a lamp invented by Messrs. 

 Siemens and Halske, having a tantalum filament. 

 On account of its ease to manufacture, its brilliant 

 light, and relatively low consumption of power, this 

 lamp gained great popularity at once, and for a single 

 year was practically without a rival. Then, in 1904, 

 patents were taken out by Just and Hanaman, Kuzel, 

 and Welsbach, for lamps using filaments of tungsten, 

 and the superiority of these lamps over the tantalum 

 lamps gave them an immediate popularity never attained 

 by either of the other metal-filament lamps. 



Needless to say there is good ground for this pop- 

 ularity, which may be explained by the simple state- 

 ment that the tungsten lamp gives more light with 

 much less consumption of power per candle power than 

 any of its predecessors. Unlike the carbon filament, 

 which projects in the familiar elongated horse-shoe 

 loop, or double loop, into the exhausted bulb, the tung- 

 sten filament is wound on a frame, so that several 

 filaments (usually eight or more) are used for producing 

 the light in each bulb. The chief defect of this lamp 

 is the fragility of the filament, which breaks easily when 

 subjected to mechanical vibration. On the other hand, 

 tungsten lamps can be used in places at a long distance 

 from the central generating plant, where the electric 

 current is too weak for carbon -filament lamps. 



[235] 



