CH. V] 



DO AND DO NOT IN CHAPTER V 



135 



224. Summary of Chapter V: 

 Do 



i. For these relatively weak 



sources of light use a good 

 screen, and make the room dark 



( 



2. Use 

 slides. 



transparent lantern 



3. The objective to select is 

 one of large aperture for these 

 large sources ( 217, 855). 



4. Have perfect containers 

 for liquids and gases so that 

 none can escape into the room. 



5. For the petroleum light 

 and the alco-radiant use the 

 objective shield (fig. 62) as it 

 takes so long to get a good light. 



Do NOT 



1. Do not try to give an ex- 

 hibition with these weak lights 

 in a room with much stray light, 

 and do not use a dirty screen. 



2. Do not try to use opaque 

 lantern slides. 



3. Do not use an objective of 

 small aperture with these large 

 sources. 



4. Do not use leaky con- 

 tainers for the gases or liquids 

 used in this chapter. They are 

 all dangerous when out of their 

 proper containers. 



5. Do not turn off the alco- 

 radiant or the petroleum light 

 during the exhibition; it takes 

 too long to start them. 



6. Follow carefully the direc- 

 tions sent with the apparatus 

 by the manufacturers. 



6. Do not fail to read care- 

 fully and follow strictly the 

 directions sent out by the manu- 

 facturers. 



7. Do your part with great 

 care and even these weak lights 

 will give good projection within 

 their range of possibility, i. e., 

 for a screen two to three meters 

 (six to nine feet) square. 



7. Do not expect too much of 

 these weak sources, but give 

 them a chance to do their best. 



