Ch. Ill] 



BINOCULAR MICROSCOPES 



85 



While more or less successful efforts had long been made to produce 

 binocular microscopes with a single objective, the optical requirements 



Ocular 1 



Fig. 53. Ives Binocular Arrangement for All Powers. 

 (Journal of the Franklin Institute, Dec. 1902). 



Objective The single objective. 



pb The prism box at the lower end of the tube. 



a, b, c The prisms dividing the light equally from each point to the two eyes. 



a, b The transparent silvered surface in the prism allowing half the light to 

 pass through and half to be reflected to the right. 



c Prism at the right reflecting the light upward to the right eye, as, ad- 

 justing screw to tilt the prism c, at the correct angle for the position of the 

 right ocular. 



apd Adjustment for the pupillary distance. 



Ocular, 1, Ocular 2 The oculars for the right and the left eye. 



Axis 1 The principal optic axis for the left eye. 



Axis 2 The principal optic axis for the right eye. 



Due to the length of the prism c, this axis is optically of the same length as 

 Axis 1 for the left eye. 



were not fully grasped. Recently, however, Mr. Frederic E. Ives 

 has stated the optical principles witji great clearness, and shown how 

 binocular microscopes using a single objective can be constructed. 



