CH. Ill] SUMMARY FOR SMALL CURRENT LIGHTS 



99 



4. Wire the Nernst lamp just 

 as the arc lamp is wired except 

 that no separate rheostat is 

 inserted. Wire the Nernst 

 lamp for alternating current 

 just as a Mazda incandescent 

 lamp is wired. 



5. Wire the Nernst lamp for 

 direct current with the positive 

 wire in the binding post marked 

 + or P, i. e., the same as a 

 direct current arc lamp is wired, 

 except that no separate rheostat 

 is included ( 141). 



6. Determine the polarity of 

 the supply wires with precision 

 and care ( 701-703). 



7. Let the Nernst lamp burn 

 during the entire exhibition, as 

 it takes from one to three 

 minutes for the light to reach 

 full brilliancy. 



8. Shut the light off the 

 screen when not needed, by the 

 objective shield (fig. 14). 



9. Handle the Nernst lamp 

 carefully, as it is easily injured. 



10. Manage the exhibition 

 with a Nernst lamp as with any 

 other light, remembering the 

 need of a dark room and a screen 

 picture of moderate size for this 

 relativelv weak light. 



4. Do not worry about polar- 

 ity in wiring the Nernst lamp 

 for an alternating current sys- 

 tem. 



5. For a direct current cir- 

 cuit, do not put the positive 

 wire in the negative binding 

 post of the Nernst lamp. 



6. Do not neglect the polarity 

 of the two wires on a direct 

 current circuit. 



7. Do not turn the Nernst 

 lamp out during an exhibition 

 for it takes too long to light it. 



8. Do not forget to use the 

 objective shield for shutting the 

 light off the screen when it is 

 not needed. 



9. Do not handle the Nernst 

 lamp roughly. It is delicate. 



10. Do not expect too much 

 of a Nernst lamp with the magic 

 lantern. One cannot have the 

 room so light, nor project such 

 large screen pictures, nor use 

 such dark lantern slides as with 

 the arc lamp. 



