176 W. B. Rogers on Binocular Vision. 
while viewing the successive points of the arc presented to it, 
ing api 
ehicded all the directions which the optical axes assume in 
se dai arcs. In general terms ger the binocular resultant 
all such cases may be described as the curve line in which the 
Hu focer of the two visual cones Sioned one another 
It is only however under special conditions that the resultant 
thus formed is a plane curve. en the circular ares presented 
curvature are combined either with or without a stereoscope. 
ollows the figure and position of the roacileaet will 
be considered under the simplest conditions, viz.: when the cir- 
cular arcs have equal carvature and are so placed that the inter- 
secting conical surfaces are precisely alike. 
These conditions ar 
a ai in figs. 76 
77, where the ripe 
me ares ab and AB are 
respectively of — same 
and curvature as 
Wintel lines LA and RC... LM and RN, &e. ae egal 
and spores inclined to the plane of ABCD orabed. Hene 
each point of the resultant curve as7... »...or s, is pl 
