J. LeConte on Binocular Vision. 167 
balance each other and there is no rotation, Below 45° the 
action of the superior oblique predominates and the eye there- 
fore rotates inward, In turning the visual plane upward and 
converging strongly, the action of the inferior oblique predomi- 
hates more and more 
apparent vertical. 2. Prof. Helmholtz’s difference is a con- 
stant one, viz, 14°; ours varies from 11° to 20’ and robably 
to zero, 3, According to Prof. Helmholtz the relation of the 
‘pparent vertical to the apparent horizontal is a constant one, 
viz: an angle of about 882° ; our experiments prove that this 
. 5° 
It is certain, therefore, that the law of Listing is far from 
true in strong convergence. Evidently the reason is that 
cles are used in strong convergence is easily shown as follows : 
allel with 
both eyes at the same time so as to look at this point. 
strain is experienced in producing convergence even much short 
Of this, The eyes are turned from side to side, parallel to each 
te 
The law of Donders is equally untrue for strong convergence. 
This law asserts that the position of the eye is :igorously con- 
Stant for every position of the visual line. But in the experi- 
ment represented by figure 9 the eye II, although the direction 
% its visual line is unchanged, rotates on its axis when the 
