ses tioaeas 
W. Bt Rogers on Binocular Vision. 327 
sult of this simple experiment would be inferred from what has 
~ been said under a Te head, but it is so striking 4s at first to 
create some sur 
Since the binnootae direction of an object is not that in which 
“it appears to either eye separately, it follows that tw@Mnes having 
similar attitudes to the two eyes respectively, may ade to ap- 
pear in very dissimilar positions by combining a third line with 
one of them and not with the other. 
Thus if we place fig. 32 on the up- 
per stage so that a shall be opposite the 
left and 6 and ¢ opposite the right gh. 
and if then we combine ¢ with a, 
shall have a perspective indies (fig. 33) 
lying obliquely on the left of 6. Now 
this oblique resultant is the binocular 
place of a as well as of c, and thus the 
binocular combination has caused a 
82, 
a 
& 
S 
in a vertical visual plane to appear in an oblique visual plane 
fi 
receding from that of 6 downwards towards the left. 
A 
elt eae 
<------.. 8 
Using fig. 34 in which a and c¢ are equally and oppositely 
inclined to the vertical, and placing @ opposite the left, and } and 
_ € opposite the right eye, we have, on combining @ with c, a result- 
ant lying in the mesial vce! plane, (fig. 35). Here the binoc- 
ular position of aand c is in avertical visual plane parallel to that 
of 6, and when projected binocularly on the plane of the paper, 
will appear to have a position parallel to 6. : 
With lines related as in fig. 36, the ed = 
effect is still more interesting. Here a 
and ¢ when united form a perspective 
line which springs wey the plane of the : 
paper at the lower end of 4 and ascends Be 
obliquely towards oe left (fig. 37). If 
ay 
& 
oe 
pause in the convergence will unite a 
