NO. 2 



HISTORY OF ELECTRIC LIGHT SCTIROEDER 



71 



THE NERNST LAMP 



Dr. Walther Nernst, of Germany, investigating the rare earths used 

 in the Welsbach mantle, developed an electric lamp having a burner, 

 or " glower " as it was called, consisting of a mixture of these oxides. 



Nernst Lamp, 1900. 



The burners consisted mainly of zirconium oxide which had to be 

 heated before current could go through them. 



I'he main ingredient was zirconia, and the glower operated in the open 

 air. It is a non-conductor when cold, so had to be heated before cur- 

 rent would flow through it. This was accomplished by an electric 

 heating coil, made of platinum wire, located just above the glower. 

 As the glower became heated and current flowed through it, the heater 

 was automatically disconnected by an electro-magnet cut-out. 



The resistance of the glower decreases with increase in current, 

 so a steadying resistance was put in series with it. This consisted of 



