82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



THE OSMIUM LAMP 



Dr. Auer von Welsbach, the German scientist who had produced 

 the Welsbach gas mantle, invented an incandescent electric lamp 

 having a filament of the metal osmium. It was commercially intro- 

 duced in Europe in 1905 and a few were sold, but it was never 

 marketed in this country. It was generally made for 55 volts, two 

 lamps to burn in series on no- volt circuits, gave about 25 candle- 

 power and had an initial efficiency of about 5^ lumens per watt. It 

 had a very fair maintenance of candlepower during its life, having 

 an average efficiency of about 5 1-p-w. Osmium is a very rare and 



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Osmium Lamp, 1905. 



This incandescent lamp was used in Europe for a few years, but 

 was impractical to manufacture in large quantities as osmium is 

 rarer and more expensive than platinum. 



expensive metal, usually found associated with platinum, and is there- 

 fore very difficult to obtain. Burnt out lamps were therefore bought 

 back in order to obtain a supply of osmium. It is also a very brittle 

 metal, so that the lamps were extremely fragile. 



THE GEM LAMP 



Dr. Willis R. W'hitney, of Schenectady, N. Y., had invented an 

 electrical resistance furnace. This consisted of a hollow carbon 

 tube, packed in sand, through which a very heavy current could be 

 passed. This heated the tube to a very high temperature, the sand 

 preventing the tube from oxidizing, so that whatever was put inside 

 the tube could be heated to a very high heat. Among his various 



