134 



THE TANTALUM LAMP. 



twenty-four books the thin tantalnni wire is drawn np and down be- 

 tween the two disks. This is believed to be the first metallic incan- 

 descent lamp for nearly 110 volts Avhich, like the common carbon 

 glow lamp, can burn in any position whatsoever. This lamp sup- 

 plied about 30 Hefner candlepower on a 04-volt circuit at 1 "5 wattg 

 per candlepower. It lasted for 2()0 hours, and lost during that time 

 9 '5 per cent of its illuminating power. 



After this first practical success we redoul)led our eiforts to improve 

 the lamp further. As far l)ack as about the middle of October, 1903, 



Hf? 



Fig. 1.— Lamp with cor- 

 rugated filament. 



Fig. 2. — Early type of 

 tantalum lamp. 



Fig. 3.— Tantalum lamp with 

 filaments fixed obliquely. 



we succeeded in making the first 200-voIt tantalum lamp, which was 

 of a design similar to the lamp just described, but with eighteen arms 

 on each disk and with a greater distance between the two disks. I 

 may add at once that it is of interest only as a curiosity, for it has 

 served no practical purpose. The length of its filament was 1,350 

 millimeters and the illuminating value about 60 Hefner candle- 

 power. In the course of further development the form of the frame 

 of wire filament for the 110- volt lamp went through different stages, 

 the principle of subdivision being always followed. Among other 

 constructions, we tried some in which, instead of one long fihuuent. 



