W. B. Rogers on Binocular Vision. 93 
to the other we have the opportunity of alternating these stereo- 
scopic effects 
In these experiments the apparent magnitude of the resultant 
exceeds that of the drawings when the upper stage of the instru- 
nent is used, and falls short of it when the. drawings are placed 
on the lower stage, the change in both cases being determined by 
the relative distance of the resultant and the. drawings from the 
eyes. 
4. Of the unusual adaptation of teat ee and refractive 
power by which we see the resultant im 
A feature of great interest in the preceding win. i is 
clearness and precision of the resultant image. ( 
true whether the image be formed between the eyes and 1 
gram or at a greater distance than the latter. In the One case 
the lines are more slender and in the other case broader than in 
the drawings, but this is only a part of the eo dancin 
or enlarging influence due to the relative dista the resultant 
and the drawings from the eyes, and does net affect the distinct- 
ness of the combined image. 
In order that each point of th ng figure may be thus 
clearly seen, the eyes must be in condition sttited to the accurate 
convergence of the ra s falling upon them from the correspond- 
jis points of the ings; that is, they must for the time be ad- 
usted in refractive power to the distance of the diagrams and not 
to he distance at which the binocular resultant is seen. At the 
me time the convergence of the optic axes to a point nearer or 
more remote than the. pictures has the effect of determining our 
perception of the combined image at that point. 
