NO. 2 



HISTORY OF ELECTRIC LIGHT — SCHROEDER 



31 



the upper part of which was in circuit. As this part burned out, the 

 rod was automatically pushed up so that a fresh portion then was in 

 circuit. It operated in a vacuum. None of these lamps was com- 

 mercial as they blackened rapidly and were too expensive to maintain. 



Bouliguine's Incandescent Lamp, 1876. 



A long graphite rod, the upper part of which only was in circuit, 

 operated in vacuum. As this part burned out, the rod was auto- 

 matically shoved up, a fresh portion then being in the circuit. 



THE JABLOCHKOFF CANDLE 



Paul Jablochkoff was a Russian army officer and an engineer. In 

 the early seventies he came to Paris and developed a novel arc light. 

 This consisted of a pair of carbons held together side by side and 

 insulated from each other by a mineral known as kaolin which vapo- 

 rized as the carbons were consumed. There was no mechanism, the 



