CH. IX] DO AND DO NOT IN MICRO-PROJECTION 



315 



1 6. Use a hood on the objec- 

 tive to aid in centering the light 

 and in placing the objective the 

 right distance from the conden- 

 ser ( 372); a light shield 

 beyond the objective to stop 

 stray light is also an advantage 

 ( 373)- 



1 6. Do not forget the advan- 

 tages of an objective hood for 

 centering the light and prevent- 

 ing glare; and do not omit the 

 light shield to cut off stray light. 



17. It is of the utmost im- 

 portance that every part be 

 accurately centered for micro- 

 projection ( 375), and that the 

 parts should be separated from 

 one another the right distance 

 ( 376, 382). 



17. Do not fail to have all 

 parts accurately centered, and 

 the correct distance apart. 



1 8. Remember that it is a 

 pure waste to use too great an 

 amperage ( 378). 



1 8. Do not use a greater cur- 

 rent than necessary. 



19. As the same object is to 

 be shown entire and with magni- 

 fied details and different objects 

 require different magnifications, 

 it is convenient to have two, 

 three or four objectives of 

 different powers in a revolving 

 nose-piece ( 379). 



20. For exhibition purposes 

 it is a great advantage to use 

 carbons whose ends have been 

 shaped by previous burning in 

 the lamp ( 380). 



19. Do not show all objects 

 with the same objective, but 

 have two or three on a revolving 

 nose-piece so that different 

 powers can be used with the 

 minimum of trouble. 



20. Do not forget to shape 

 the ends of the carbons by burn- 

 ing them awhile in the arc lamp 

 before anv formal exhibition. 



