W. B. Rogers on Binocular Vision. . oe 
Arr, XXII.— Observations on Binocular Vision; by Professor 
Wituram B. Rocers. 
(Concluded from page 95.) 
29. Of the form of the curve resulting from the binocular union 
of a straight line with a circular arc or of two equal circular 
arcs with one another. 
A. Binocular resultant of a straight line and a circular are. 
Assuming the optical centres of the two eyes L and R, figs. 
74 and 75, as fixed during the act 14. 
of combination, it is evident that 
the centre of the eye directed to 
the circular arc a b or AB may be 
regarded as the vertex of a cone 
whose surface includes ail the po- 
Sitions of the optical axis of that 
different points of the arc. This 
2 
- 
bo 4 
@ 
° 
eo 
on 
a) 
S 
oO 
Ss 
fae] 
bee 
5 
_ 
pat) 
=| 
og 
= 
gg 
> 
8 
= 
Which during the binocular com- 
bination intersects the conical sur- 
ace, in an attitude depending on the distance between the opti- 
cal centres, the place of the diagram, and the position of the 
Component lines, ab, cd... or AB, CD. O°. ee IE 
Points of the vertical line and the arc, as m, %...+ 
or M, N meet in the coni 
€xperiment will be seen more clearly by considering separately 
each f the following cases which pain together include all the 
Variations that can occur. — 
First. When the arc is conver towards the right line and the 
two are combined by directing the optic axes beyond the plane 
of the diagram. 
