J. LeConte on Binocular Vision. * 165 
vision both monocular and binocular. The law of visible 
direction does indeed explain all the ordinary phenomena of 
single vision with two eyes; for in all ordinary cases of single 
vision—in all ordinary voluntary acts of binocular sight—in all 
cases of vision of objects ccc in = horopter —- this be 
a line or a pease since ray rom an object or radiant 
single. Thus single visio assoanee is ches cases a necessary 
result of the law of direction, and the law of corresponding 
points becomes only a particular case of the more general law 
of direction 
ut in all cases of double images, the apparent position of 
these to the binocular observer is always different, and in some 
cases very different from the true position of the object which 
they represent. The difference may amount even to 45°. For 
example: The binocular field of view in my own case is about 
100° in a horizontal direction. By strong convergence I can 
almost wholly obliterate this common field. In such case the 
images of objects lying near the extreme margins of the com- 
mon field, and therefore at least 90° apart, are brought together 
front; while objects really in front are doubled and _ their 
images are separated 90° from each other, and each 45° from 
the hag position of the object which they represent. 
. 3 represents the actual position of parts in this experi- 
eos ‘Band L being the right and left eye respectively, N the 
3. 4. 
root of the nose, a a’ objects in the | gees line 45° to the right 
and left, MN the median line and M a object in front; and 
gure 4 is the visual result represented by my method. It 
will be seen by comparing the two figures that the two eyes 
and L are combined and rectified to form the single binocular 
eye K, the visual lines Ra and La’ become the common visual 
