7O THE A B C OF PHOTO MICROGRAPHY 



in any of the procedures from those already 

 shown. The lighting must be even more care- 

 fully looked after and the focusing is much 

 more delicate and exacting. But it may be 

 truthfully said that one who masters the art of 

 making a good photo-micrograph with low or 

 medium powers can do as well with the high- 

 est amplifications if he has the necessary ap- 

 pliances and uses them carefully. A sub- 

 stage condenser is among these, and homo- 

 geneous oil immersion lenses for the greatest 

 amplifications. A serious loss of light from 

 any radiant less powerful than the electric arc 

 is unavoidable, which must be compensated 

 for as far as possible by increased care and 

 exposures. The modern oil immersion objec- 

 tives are a boon, indeed, since they utilize 

 about all the light that enters them. If we take 

 a student's iV oil immersion, and carefully 

 study its lighting of an object on the screen 

 at say +1000, then replace it with the best 

 obtainable dry -J-, under the same amplification, 

 (obtained by increasing the camera's length or 

 by higher eyepiecing), we will find the illumi- 

 nation by the former to be greatly superior 

 to that of the i, notwithstanding the much 

 greater actual aperture of the latter lens, there 

 being no loss of light from either refraction 



