W. B. Rogers on Binocular Vision. 183 
are reversed. From what I have noticed in the experience of 
other observers I am disposed to conclude that a like inequality 
of adjusting movement is of common occurrence, having in some 
cases the same relation to the right and left eyes as that above 
described, and in others the reverse. The effect of the vertical 
adjusting power however, is obviously the same whether we con- 
sider it under either of these conditions or as having equal range 
above and below a perfectly horizontal line. 
In order more completely to study its action in producing the 
apparent coincidence of figures of unequal height, I use the sys- 
tem of parallel lines shown in fig. 84, Holding this at a distance 
84, 
d 
| etic Sante 
= eae yan 
in such position that all the lines shall be visually horizontal and 
bringing together the parts of the figure by cross vision, I remark 
that the lines of either of the pairsad... be. . ¢fto which 
lines become coincident, while a takes a position slightly below : - 
d, and ¢ above f; and so when I unite cf each of the other pai : 
32. Explanation of these phenomena by a vertical tation a8 
Soctated with the converying movement of the eyes. ten. 
© show in what manner the hypothesis of a vertical ro — 
of one or both eyes may be applied to explain these phenomena, 
let us Suppose m and m to be the central points of the retinas of 
