212 R. B. Tolles on the Binocular Microscope. 
- Arr. XXVI.—NMethod of applying the binocular principle to 
eye-piece of a Microscope or Telescope; by Ropert B, TOLLES. 
To apply the binocular principle to the eye-piece of a micro 
scope or telescope, it is only necessary to make use of the erect 
correctly placed. +  - : 
the theory of the erecting eye-piece of common form were 
generally understood, no demonstration that binocularity can be 
given to such an eye-piece would be necessary. aa 
here by the appropriate prism, must be a very near! 
division of every particular pencil, and give a simi 
factory image of the entire field in each eye-tube. 1 
ficient expression of the whole theory of the binocular 
piece. 
It is, however, important in order to avoid pse 
effects, to adopt the proper form of dividing prism; 
e imm 
order in W 
image view 
m that which 
th rectangulat 
dell, does 2? 
rsion of P 
