174 J. LeConte on Binocular Vision. 
is the result of horizontal displacement of the two images in 
opposite directions, and therefore the two images may be brought 
together by bringing the doubled portion of the vertical line 
rotation on the optic axes. But I have also proved this by 
direct experiment. 
If two lines, one white on black and the other black on 
white (fig. 14) be drawn at an angle of 13 degrees with the 
14, 
are brought in perfect coincidence. The accom- 
panying figure (fig. 15) in which OO are the 
eyes, A the point of sight, aH, aH and a'H, 
a'H’ are the lines in the two positions, will ex- 
place in each case. The 
| Horopter. This experiment is difficult to pe 
mine the inclination of the horopteric line for different degrees” 
