CH. Ill] MAGIC LANTERN WITH NERNST LIGHT 



93 



WI 



W2 



FIG. 54. NERNST LAMP FOR THE MAGIC LANTERN (REICHERT). 



This is on a support and has a rack and pinion for raising and lowering the 

 lamp. It is automatic. 



Gl The three filaments or glowers with this lamp. 

 S 3^ The two supply wires from the house circuit. 

 T t Pinion and milled head of the rack work. 

 W It W 2 , W 3 The three ballast tubes. 



142. Centering and distance from the condenser with the 

 Nernst lamp. The lamp must be centered with the condenser and 

 objective as described in Ch. I ( 51+). It must have some form 

 of support with means of raising and lowering the lamp. The 

 distance of the lamp from the condenser which gives the best 

 illumination can be determined as follows: Light the lamp, put a 

 good lantern slide in the lantern, then move the lamp up toward 

 the condenser, shifting it back and forth until the best screen image 

 is produced. In general, it will be found that this results when the 

 glower is at about the principal focal distance from the condenser. 

 When the best position is found the place should be clearly marked, 

 then the lamp can be put in this position quickly at any time. 



143. Connecting the lamp with the house circuit ; alternating 

 current. This is done by means of a flexible conductor connected 



