The Binocular Microscope. By F. Jentzsch. 



15 



a semicircular diaphragm* in order to obtain all the desired effects! 

 With normal microscopic observation, however, this is the spot where 

 the " entrance-pupil " of the observer's eye should be placed so 

 that inconvenience with the eye would be unavoidable ; this would 



Q P 1 



Pupil of eye, \ 



Ramsden disk | 



Eye-lens 



Eye-piece diaphragm 



Field-lens of eye-piece 





JB §SU- 



Upper focal plane of \ 

 objective. / 



j Eye (turned out of the 

 \ microscopical axis). 



r 



Ocular. 



> Objective. 



Object. 



also be the case, for instance, with Abbe's stereoscopic eye-pieces. 

 For a stereoscopic Microscope it would therefore be better to pro- 

 duce another image of the Ramsden disk between the objective and 

 eye-lens of the ocular, and to do the screening there. This neces- 



* It may be interesting to note that F. H. Wenhani already in 1854 made a 

 proposal of this kind. Quart. Journ. Micr. Sci., ii., pp. 132-4. 



