340 



DRAWING WITH HOUSE CURRENT 



[Cn. X 



FIG. 189. SMALL ARC LAMP FOR DRAWING. 



Commencing at the left : 



Wi Supply wires 



So Lamp socket. 



K Key switch in the socket. 



Sp Separable attachment plug. 



W2 Wires to the arc lamp. 



W3 Wire to the binding post of the upper carbon. 



W4 Wire to the rheostat (R) and from the rheostat to the binding post 

 of the lower carbon. 



A Support of the arc lamp; the lamp can be raised or lowered on this 

 support. 



F Feeding screws for the carbons. 



H C, V C The horizontal and the vertical carbons. 



In In Insulation between the carbon holders and the remainder of the 

 lamp. This prevents the current from taking any path away from the carbons. 



Ch Chimney over the arc. 



T C The tube and the condenser in the movable inner tube. The con- 

 denser is at its focal distance from the crater, and therefore the rays are made 

 parallel. 



