164 J. LeConte on Binocular. Vision. 
found the result precisely the same when the point of sight 
was at the same distance, viz: twelve inches, In the next 
diagram which I constructed the verticals inclined 14 degrees 
aud the horizontals 50 minutes, the difference being therefore 
25 minutes. In this case both seemed to combine perfectly 
when the point of sight was distant 75 inches, The next dia- 
gram tried had the verticals inclined 5° and the horizontals 
3° 45’, the difference being 17 degrees. In this case both ver- 
ticals and horizontals combined perfectly at the distance of 
2-2 inches. I then tried one in which the verticals inclined 
10°. this case I could not make perfect coincidence of 
both verticals and horizontals until the difference of inclina- 
tion was made as great as 5°. The diagram used is shown 
reduced in the figure (fig, 10). The point of sight in this 
joining the optit 
centers, or about one-quarter inch from the root of the nose. 
I attribute these phenomena to a slight distortion of the 
ocular globe under the action of the oblique muscles—a dis- 
tortion which increases with the degree of optic convergence. 
e will refer to this again, 
In all the experiments described above the greatest care was 
taken that the visual plane should be in the primary directio0, 
1. €,, at right angles to the line of the face, and especially that 
downward 45° from its primary position, and that the rotatio® 
increased as the plane was elevated toward the eyebrows. 
7 
Toe 
