NEGATIVE MAKING 7 1 



or reflection with the homogenous objec- 

 tive. 



High powers are chiefly useful in bacterio- 

 logical work; for the resolution of diatoms and 

 other test objects ; in photographing blood ; the 

 pus corpuscles and all subjects requiring great 

 amplifications. But higher powers than are 

 absolutely necessary should not be used simply 

 to exhibit a specimen made big as possible. 

 Well and clearly shown under a moderate 

 magnification it would be infinitely more in- 

 structive and pleasing. Could we see every- 

 thing in nature without a microscope we cer- 

 tainly would not need to use one. Let us 

 make a couple of negatives of this class, how- 

 ever, and see what we can do. 

 : The first subject I have chosen is a kary- 

 okinetic figure in a leucocyte or white blood 

 corpuscle, a rather rare specimen, by the way. 

 Radiant and condenser are first centered with 

 a low power, and it will be well to find our 

 object, at the same time bringing it and the 

 flame into focus together, the latter appearing 

 as a brilliant vertical line of light in the field 

 of view. Then removing this lens and putting 

 a drop of cedar oil on the front of a iV horn. 

 objective (a Powell and Lealand Apochromat 

 of 1.40 N.A.), we attach, latter to microscope 



