On Orthoseopie and Pseudoscopio Effects. By Prof. E. Ahhe. 211 



always arise, if the right half of the left circle or the left half of 

 the right circle is suppressed. We have, therefore, two other 

 arrangements for either kind of stereoscopic eflfect, which are 

 equivalent to and P of Fig. 36, respectively — as represented in 

 Fig. 38. 



Fig. 38. 



o I o a 



r 



J 



O I O 



In view of the considerations here advanced, it must be quite 

 immaterial in the action of the binocular arrangement how the 

 rays are brought to the oculars and whether these oculars yield 

 erect or inverted images. And as the only conditions of stereo- 

 scopic vision — two images of opposite perspective projection — are 

 fulfilled by the method pointed out above, exactly in the same 

 degree as with binoculars on the ordinary system, there is no 

 rational ground for presuming that the effect must be inferior in 

 regard to the reality of orthoscopic or pseudoscopic impressions. 

 In fact, a few experiments with the binocular eye-piece described 

 in the paper quoted above (or with any similar arrangement) will 

 prove the validity of the principle here developed. 



