32 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 



76 



arc being started by a thin piece of carbon across the tips of the car- 

 bons. Current burned this bridge, starting the arc. The early carbons 

 were about five inches long, and the positive carbon was twice as 

 thick as the negative to compensate for the unequal consumption on 

 direct current. This, however, did not work satisfactorily. Later 

 the length of the carbons was increased, the carbon made of equal 



Jablochkoff " Candle," 1876. 



This simple arc consisted of a pair of carbons held together side by 

 side and insulated from each other by kaolin. Several boulevards in 

 Paris were lighted with these arc lights. This arc lamp is in the 

 collection of the Smithsonian Institution. 



thickness and burned on alternating current of about eight or nine 

 amperes at about 45 volts. He made an alternating current generator 

 which had a stationary exterior armature with interior revolving field 

 poles. Several " candles," as they were called, were put in one fixture 

 to permit all night service and an automatic device was developed, 

 located in each fixture, so that shottld one " candle " go otit for any 

 reason, another was switched into service. 



In 1876 many of these ''candles" were installed and later several 

 of the boulevards in Paris were lip;hted with them. This was the 



