VOLTAIC ELECTRICITY. 



245 



388. Luminous Effects. When the circuit of a 

 battery is closed or broken there is a spark at the point of 

 contact. Beautiful luminous effects may be produced by 

 winding the wire from one plate about the end of a file, 

 and drawing the other electrode along the side of the fiie, 

 thus rapidly closing and breaking the circuit. 



389. The Voltaic 

 Arc. The most bril- 

 liant luminous effect of 

 current electricity is the 

 Voltaic arc or electric 

 lamp. The electric lamp 

 consists essentially of 

 two pointed bars of gas 

 carbon placed end to 

 end in the circuit of a 

 very powerful current. 

 If the ends of the car- 

 bons be separated a 

 short distance while the 

 current is passing, the 

 carbon points become 

 incandescent and the 

 current "will not be in- 

 terrupted. W^^en the 

 carbons are thus sep- 

 arated, the space 'be- 

 tween is filled with 

 a luminous arc, the 

 'brilliancy of which 

 exceeds that of any 



THE BRUSH ELECTRIC LAMP. 



FIG. 190. 



