176 J, LeConte on Binocular Vision. 
increases or decreases with distance would depend upon the law 
of increase of rotation with increasing convergence. If it in- 
creases with distance then it is possible that when we look at 
the ground before us the Horopter may be a line lying along 
the ground, as maintained by Helmholtz. 
I next tried the same experiments with the eyes inclined 
et forward. T conclude therefore that in this posi 
tion ae horopteric line inclines less to the visual plane than it~ 
t cannot fall on correspon ct wheres the 
two retinee. AS to the form of this surface, I sss — une- 
qual to th ditse 
mentai investigation presents , 1 believe, es diffic 
— have seen that the eye in convergence rotates on the OP or 
The question naturally occurs, is this rotation to be 
here in the light of an imperfection, of the instrument cf 
which there are several examples in the structure and mecbal- — 
ism of the eye,) and should the a of Listing be regarded % — 
ted in note gave In my 0W2 
sone total terett sala meaner seta 
ual plane, becomes zero, ei even is converted into an snward rotation; 1? 
inclination of the Horopter, Sette a decreases, Sectias' icular and vee 
” ; a Ir a the outward rotation Pencreance wiatee 
; in this case, tame Sadicntoes ion 0 Horopter 
as stated by Meissner, sere — 
