10 



MAGIC LANTERN WITH DIRECT CURRENT [Cfl. I 



Condenser 



Arc La 



KS 



FIG. i. SIMPLEST FORM OF MODERN MAGIC LANTERN WITH ARC 



LAMP 



It consists of an arc lamp with suitable connections to the current supply, 

 a rheostat and a table switch; a double condenser, lantern-slide holder and 

 projection objective. 



Arc Lamp This is a mechanism for holding and feeding the carbons. 



h c Horizontal (upper) and 



v c Vertical (lower) carbons. 



5 5 Set screws for holding the carbons in place. 



In In Insulation between the carbon holders, and the rest of the lamp to 

 prevent a short circuit. 



/ 5 Feeding mechanism for moving the carbons. 



d Clamp for fixing the lamp in any position on its vertical support. 



SW Supply wires to the lamp socket or wall receptacle. 



So Lamp socket. 



K Key of the socket switch. 



5 P Separable attachment plug. 



L W Supply wires from the cap of the attachment plug to the table switch. 



K S Double-pole knife switch on the table for turning the current off and 

 on the arc lamp. 



Rheostat for controlling the current. It is inserted in one wire. 



Condenser In this simple form it is composed of two plano-convex lenses 

 with the convexities facing each other. 



I 2 The two elements of the condenser. 



L S Lantern slide close to the plane face of the 2d condenser lens. 



Axis Axis The straight line passing from the source of light along the 

 optic axis of the condenser and the objective to the image screen. 



Objective The projection objective for giving a clear image of the lantern 

 slide on the screen. 



c The center of the objective where the rays from the condenser should 

 cross. 



Image Screen The white screen upon which the image of the lantern slide 

 is projected by the objective. 



If the principles governing the magic lantern are mastered, and 

 one gains skill in handling it, the more difficult forms of projection 

 will offer no great obstacles. 



