SETS OF LENSES 



81 



And Small Photographic Lenses of 3", 2", and 1" 

 or 75, 50, and 25 mm. focal length. 



A battery sufficient for practically any purpose should 

 include 3" photographic lens. 



1|", f", Y, ', iV objectives, 

 with the following oculars : 

 X 12 Compensating. 

 x4 Projection. 

 X 6 and x 8 Huyghenian or Compensating. 



Convenient powers for less ambitious sets, but ample 

 for most workers, are 



(i) 3" planar, 1J", f", i", and T v" oil-immersion, with 

 X 4 and x 8 eyepieces. 



G 



