66 



DO AND DO NOT WITH THE MAGIC LANTERN 



[Cn. I 



14. Make sure that the con- 

 denser is arranged with the 

 proper lens next the radiant. 

 If a three-lens condenser, the 

 meniscus should face the source 

 of light ; if a two-lens condenser, 

 it is the lens in a special mount- 

 ing (fig. 36 B), or if there is no 

 special mounting, it is the one 

 of shorter focus usually, i. e., of 

 15 to 19 cm. (6-7^ in.), while 

 the one next the objective is 

 often of longer focus. 



15. Mark or "spot" the lan- 

 tern slides so that they may be 

 inserted in the lantern correctly 

 ( 23, fig. 7, 8, 13) and arrange 

 the slides as desired before the 

 exhibition ( 21). 



1 6. Make sure that every- 

 thing is in working order, the 

 room properly darkened, and 

 the proper amount of current 

 available (10 to 15 amperes). 



1 7 . Light the arc lamp before 

 the room lights are turned off 

 ( 33)- 



1 8. Keep the arc lamp burn- 

 ing until the room lights are 

 turned on (34). 



19. After the last slide, show 

 simply a lighted screen ( 34). 



14. Do not reverse the ends 

 of the condenser and thus have 

 the wrong lens next the light 

 and the wrong one next the 

 objective. 



15. Do not try to exhibit 

 slides that are not in order and 

 not marked for insertion in he 

 carrier. 



1 6 . Do not attempt an exhibi- 

 tion unless the room is properly 

 darkened, and the apparatus in 

 working order. 



17. Do not let the room get 

 dark, but turn on the arc lamp 

 before the room lights are out. 



1 8. Do not turn out the arc 

 lamp until the room lights are 

 turned on. 



19. Do not keep the last 

 slide in the holder too long, but 

 show a light screen to indicate 

 that the last slide has been 

 shown. 



