CHRONOLOGY OF ELECTRIC LIGHT XIII 



1905-^Dr. Auer von Welsbach's invention of the osmium incandes- 

 cent lamp Commercially established, but only on a small scale 

 in Europe. The metal osmium, used for the filament which 

 operated in vacuum, is rarer and more expensive than plati- 

 num. 



1905 — Dr. Willis R. Whitney's invention of the Gem incandescent 

 lamp commercially established. The carbon filament had 

 been heated to a very high temperature in an electric resis- 

 tance furnace invented by him. The lamp was 25 per cent 

 more eflficient than the regular carbon lamp. 



1906 — Dr. Werner von Bolton's invention of the tantalum incandes- 

 cent lamp commercially established. 



1907 — Alexander Just and Franz Hanaman's invention of the tungs- 

 ten filament incandescent lamp commercially established. 



191 1 — Dr. William D. Coolidge's invention of drawn tungsten wire 

 commercially established. 



1913 — Dr. Irving Langmuir's invention of the gas-filled tungsten 

 filament incandescent lamp commercially established. 



