W. B. Rogers on Binocular Vision. 185 
bined action of both kinds of adjustment, we perceive the result- 
ant in a direction which is the binocular direction both as regards 
athe vertical and the horizontal plane. ; 
* In the above experiments the effects described are obtained by 
_ferossing the axes, and so as to form the resultant in front of the 
picture, but similar phenomena present themselves when the com- 
pa bination is made behind the picture. Any further reference to the 
latter is therefore: unnecessary. 
33. Why the height of the resultant is a mean of the heights 
of the component figures. 
87. 
a a ac o 
hd. poten elre 
a 
et ieee 
If in combining a with e, (fig. 87,) by the process before de- 
scribed, we also keep in view the lateral images of these lines 
formed one in each eye we find that the resultant takes a position 
midway in vertical as well as in horizontal direction between the 
linesa. , c, thus laterally seen, and a similar effect occurs in 
uniting 6 with d, and when the difference of level of these lines 
18 so small as to allow the vertical adjustments to be made in 
quick succession we perceive both resultants apparently at the 
Same time in their positions of midway elevation as shown in 
the lines a ¢ 
trally seen appear to occupy but one place, viz., that of re af 
Sltant, it follows that ¢ laterally viewed must appear higher, an 
@ similarly seen, lower, than this resultant. — 
cau 
If now a 
made the upper and lower f :. 
8 ies 
oe Bichon tat 
EE See 
