Prof. W. B. Rogers on Binocular Vision. 387 
Arr. XXXV.—Some experiments and inferences in regard to 
Binocular Vision; by Prof. Witiam B. Rogers, 
In the theory of binocular vision which has been so ably ex- 
pounded by Sir David Brewster, Briicke, and others, it is con- 
tended that no part of an object is seen single and distinctly, but 
that to which the optic axes are for the moment directed, and 
that “the unity of the perception is obtained by the rapid survey 
which the eyes take of every part of the object.” According to 
this view our perception of an object in its solidity and relief, 
instead of being the simple and direct result of the pictures 
ormed at any one moment in the two eyes, is acquire 
cumulative process, in which the optic axes are successively con- 
verged upon every point of the object within view. __ 
an experimental discussion of some points in binocular 
vision published in the Am. Journ. of Science several years ago,* 
was led to conclude that the phenomena of the stereoscopic 
resultant do not necessarily or even usually conform to these - 
conditions, and that “the perception of a perspective resultant 
r 
_ line or of a physical line in the same attitude does not require 
_ the successive convergence of the axes to every point he 
grounds of this conclusion were,—first that the perspectiveness of 
the resultant although not perceived when the axes are steadily 
maintained at any one convergence, appears as soon as they are 
allowed sufficient freedom of motion to wnite a few contiguous 
points of the component lines, and that it then effects the whole 
extent of the resultant; and—second that the resultant presents 
4 perspective attitude even when the component lines, instead of 
being united into one, are brought together so as to intersect at 
a — angle, each of the intersecting lines in this case appearing tn 
relie 
Satisfied from these considerations that the perceived single- 
ness and relief of the resultant are to be ascribed rather toa 
In this vi i jecting the theory of successive vision in 
the ne brag aa fina els propounded, I still considered 
Some degree of motion of the axes as 8s of on hel by which 
Ww i i f the binocular resultant. 
" iasdolbdardea ecpeetada intended still further to test the 
theory of the successive combination of corresponding points 
* This Journal, [2], xx, 86, 204, 818, and xxi, 80, 173, 489. 
