208 Transactions of the Society. 



depends solely on the manner in which the impression of the de^th is 

 conceived (conformable or unconformable to the true depth), and is 

 entirely independent of the manner in which the aspect of an object, 

 in regard to its lateral dimensions, may be changed in observation. 

 Therefore, any projection which affords right-eye perspective in 

 regard to the solid image of the Microscope, will always afford 

 right-eye perspective in regard to the object likewise, et vice versa. 

 Hence the following conclusion : — 



The image of an object, which is delineated by a pencil in- 

 clined to the riyht hand at its emergence from the ocular, will 

 always yield right-eye perspective of the object, and the other 

 image left-eye perspective, in orthoscopic vision. 



All rays which have been gathered by the objective must, at 

 their final emergence from the ocular, pass through the image of 

 the objective's clear aperture, which is projected by all subsequent 

 lenses. This is the Eamsden circle, visible above the eye-piece. 

 The right-hand portion of any emergent pencil will be transmitted, 

 therefore, by the right-hand half of the Kamsden circle, the other 

 portion by the other half. The above inference may therefore be 

 expressed thus: — 



The character of right-eye perspective in orthoscopic vision 

 always adheres to that image which is admitted to the 

 observer's eye by the right half of the Eamsden circle, and 

 vice versa. 



According to the foregoing deduction, the perspective character 

 of the projections which are obtained with incident pencils of 

 opposite obliquity, does not directly depend on the rays having 

 entered the right or the left half of the objective. The result 

 is found to be independent of this. In fact, the pencil r, which 

 gives the perspective of right-eye vision, in comparison to the 

 pencil I, may be conjugate to (or the continuation of) the incident 

 pencil R or L. Both cases are equally possible. The first case is 

 met with, when the entire cone of rays emanating from any point 

 of the object is transmitted through the optical system without 

 inversion ; the other case, when there is an inversion of the pencils 

 of light in their passage to the conjugate points of the final image. 

 The obvious criterion of the former is an erect position of the 

 Kamsden circle, and of the latter an inverted position in regard to 

 the objective's clear aperture, which is depicted by the said circle. 

 My deduction implies, therefore, this general inference : — 



Eight-eye perspective (in regard to orthoscopic vision) 

 adheres to the image projected by the right-hand part of the 

 objective, whenever the Microscope transmits the delineating 



