86 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. ']6 



The two laboratory assistants in 1905 finally succeeded in getting 

 their invention taken up by a Hungarian lamp manufacturer. By the 

 end of the year lamps were made that were a striking success for they 

 could be operated at an efficiency of 8 lumens per watt. They were 

 put on the American market in 1907, the first lamp put out being the 

 lOO-watt size for iio-volt circuits. This was done by mounting 

 several hair pin loops in series to get the requisite resistance, tungsten 

 having a low specific resistance. The issue of the American patent 



Tungsten Lamp, 1907. 



The original 100 watt tungsten lamp was nearly three times as effi- 

 cient as the carbon lamp, but its " pressed " filament was very fragile. 

 This lamp is in the exhibit of Edison lamps in the Smithsonian 

 Institution. 



was delayed owing to an interference between four different parties, 

 each claiming to be the inventor. After prolonged hearings, one 

 application having been found to be fraudulent, the patent was finally 

 granted to Just and Hanaman on February 27, 1912. 



This " pressed " tungsten filament was quite fragile, but on account 

 of its relatively high efficiency compared with other incandescent 

 lamps, it immediately became popular. Soon after its introduction 

 it became possible to make finer filaments so that lamps for 60, 40 



