diam” ‘ #3 
as = ; : 
“ wee 
, oie — : 
326 W. B. Rogers on Binocular Vision. Bes 
In viewing the pefspective resultant CD ” 
of the lines A and , each of y 
tions ,in whigh the components are seen 
without binocular combination. So when 
ing nearly united perspective lines, each of 
them appears in a position nearly midway | _ 
» between those of the components. In this & c 
experiment the place of the resultant, that is the binocular place 
of both A and B, is in the vertical mesial plane of view, w ile t at 
of A seen by the left eye singly is an oblique plane diverging to 
the left, and that of B seen by the right eye singly is in a similar 
plane diverging to the right. 
By covering or omitting a part of one of 
the components as in fig. 30, and combining 
them by the usual binocular effort, we have 
a resultant consisting of a perspective line 
ED due to the union of A and the corres- 
ponding part of D, and a line EC not per- 
Spective but parallel to B and equal to the re- 
siduary part of it. Here by the binocular 
combination the upper half of B is made to 
appear in a direction different from the lower 
half not thus combined and therefore differ- 
ent from the direction in which it would itself appear independ- 
ently of the combination. 
That the same influence operates in ordinary vision with both 
eyes is shewn .by the following experiment. (Fig. 31.) Let 
31. : 
b 
a line or thin rod be held at the limit of distinct vision in a per- 
spective position between the two eyes, while by a card attached 
laterally we hide the near half of the rod from the right eye. 
If now we direct both eyes upon the rod, it will appear not as 
a straight line but as composed of two parts making an angle in 
the middle, the remote half lying in the mesial direction of our 
view, and the near half deflected a little to the right. ‘The re- 
Pe Rc = oe ES ee ee Se er aes ae eer ee 
40% 
