432 THE POPULAR SCIENCE MONTHLY. 



trie cuiTent, and light is instantaneously produced. At first Jablosh- 

 koff lighted his candle directly by supporting on the tips of the two 

 wicks a piece of charcoal which he soon afterwai'd removed ; thus 

 the voltaic arc was produced as in electric lamps, by beginning with 

 contact, and then placing the two carbons at the required distance 

 from each other. But it was necessary to devise some method for 

 lighting the candle from a distance, and this fresh diificulty M. 

 Jabloshkoif has overcome by a very simple device. He places be- 

 tween the two carbons a little bit of graphite, of the diameter used 

 in lead-pencils; this acts as a conductor between the two wicks of the 

 candle. On the current entering it, the bit of graphite soon becomes 

 red-hot, and is burned up ; there is then a break of continuity be- 

 tween the wicks, and the electric arc is produced. Instead of graphite, 

 a fine metallic wire, or a bit of lead, can be used. 



Relighting. As we have stated, the insulating strip between the 

 wicks is fused at the points near the voltaic arc, and so disappears 

 gradually in proportion to the waste of the carbon-points. But this 

 fusion of the insulator is attended with another consequence that but 

 few of our readers would have anticipated. That which in its solid 

 state is an insulator becomes in its liquid state a conductor, and allows 

 of a longer span of the electric arc than could be had in the free air. 

 Owing to this conductivity of the strip of kaolin, the circuit may be 

 opened for a moment and the candle lighted again without any need 

 of resorting to any of the contrivances already described under the 

 head of " Lighting." But after a certain length of time, as the sub- 

 stance cools, it loses its conductivity, and then the candle cannot be 

 relighted by simply closing the circuit again. We may extinguish 

 the candle for nearly two seconds, and relight it by simply closing the 

 circuit. Hence the electric candle may be used for transmitting tele- 

 graphic signals according to the Morse alphabet, by means of flashes 

 of greater or less duration, divided by longer or shorter periods of 

 eclipse. For such use the candle is better adapted than the electric 

 lamp, as it is more readily relighted, producing at once a perfect vol- 

 taic arc, whereas in the lamp the arc is produced gradually. 



Division of the Light. Hitherto a separate pile, or a separate 

 machine, has been necessary for the production of each electric light, 

 and it has been found impossible to place two lamps in one circuit. 

 This is readily understood when we consider the mechanism of the 

 regulating apparatus. In electric lamps the approximation and the 

 separating of tlie carbons are controlled by an electro-magnet, which 

 itself follows the variations of resistance in the circuit produced by 

 changes in the length of the voltaic arc. As the arc lengthens the re- 

 sistance of the circuit is increased, and the electro-magnet is weakened, 

 and allows the carbons to approximate. It is easily understood that 

 if there are two lamps and two voltaic arcs in one circuit, and if only 

 one of these arcs is lengthened, both electro-magnets will act and 



