CH. II 



MAGIC LATERN WITH DIRECT CURRENT 



Condenser 



H C 



FIG. 2. MAGIC LANTERN WITH TRIPLE CONDENSER AND 

 WATER-CELL. 



H C, V C Horizontal or upper and vertical or lower carbon of an arc lamp. 

 The upper carbon furnishes the light. 



D + C Supply wires for the electric current. The positive wire (+) goes 

 to the upper carbon (H C), and the negative wire ( ) comes from the lower 

 carbon (V C). The arrows indicate the direction of the electric current. 



F Fuses where the supply wires for the lamp connect with the main line. 



L Incandescent lamp with wire guard. It is connected with the supply 

 wires before the table switch (S) and the resistor (R), hence it can be used 

 while the arc lamp is running or when it is turned off (See also fig. 4). 



S Double-pole, knife switch for turning the current on or off the arc lamp. 



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



A Ammeter to indicate the amount of current being used. It is inserted 

 in one wire. 



Condenser This consists of a meniscus next the arc light, and of two plano- 

 convex lenses with a water-cell between them. The lenses must be arranged 

 as here indicated. 



W Water-cell placed between the plano-convex lenses of the condenser. 

 It absorbs much of the radiant heat. 



L S Lantern slide close to the condenser. 



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

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



Objective Projection objective serving to give a clear image of the lantern 

 slide on the screen. 



C Center of the objective where the rays from the condenser should cross. 



Screen Image The image of the lantern slide formed by the objective on 

 the white screen. 



carbons is used and the upper carbon is enough larger than the 

 lower one, so that the two shorten at the same rate. 



In our experience it is more satisfactory to have both carbons 

 with soft cores, but some advocate and use a large soft-cored carbon 

 above and a smaller solid carbon below (fig. 299). 



