CH. II] ALTERNATING AND DIRECT CURRENT LANTERNS 71 



more disagreeable than from a direct current supply of the same 

 voltage. 



FIG. 40. 



MAGIC LANTERN SHOWING THE WIRING AND THE RELATION 

 OF THE PARTS. 



Supply Wires Wires from the electric supply to the outlet box. 



Outlet box The iron box receiving the supply wires and containing fuses of 

 the cartridge form, a double-pole knife switch and the wires extending to the 

 wall receptacle. 



P W R Polarized wall receptacle from which is taken the current to supply 

 the arc lamp of the magic lantern. As this receptacle is polarized the cap can 

 be put on but one way, and hence the polarity will always be the same if 

 the current is direct. With alternating current this form of connection is 

 also good. 



Arc Supply The wires extending from the wall receptacle to the table 

 switch and the arc lamp. 



Switch The double-pole, knife switch on the lantern table. 



W f The wire extending from the switch to the upper carbon. 



W 2 W 3 Wire from the table switch through the rheostat to the lower 

 carbon. 



Arc Lamp Hand-feed, right-angle carbon arc lamp. 



F S Feeding screws for the carbons. 



V A Fine adjustment for moving the source of light vertically. 



L A Fine adjustment for moving the source of light laterally. 



in in Insulation between the carbon holder and the rest of the arc lamp so 

 that the current will keep to the carbons instead of short circuiting through the 

 lamp. 



5 5 Set screws for holding the carbons in place, etc. 



Lamp-House The metal box enclosing the arc lamp. The feeding and fine 

 adjustment screws project through the back end of the lamp-house. 



V Ventilator of the lamp-house. 



Condenser The three-lens condenser. 



Water Cell The vessel of water in the path of the beam. 



