W. B. Rogers on Binocular Vision, 177 
at the apex of an isosceles triangle DrB... NuM...orCsA 
formed by the lower segments of the visual lines. 
! 77. 
ee 
a Let us now assume a line zy midway between M and N and 
Parallel to tangents at these points, and let us imagine a vertical 
Plane including this line to extend indefinitely upwards. Since 
* 1s vertically over the middle of MN andr... s and the other 
ns of the’ resultant rvs are similarly situated in regard to 
i 
v 
x 
Nes parallel to M N and connecting the two arcs, it follows that 
"+1... 8, &e., are situated vertically above the line Ly, and 
therefore that the resuliant curve lies in the before-mentioned j 
tical plane. 
ver 
In Combinations of t 
and circular 
Be 
Ae? ite a3. 
es aryl 
EB 
ure is an hyperbola. But if we suppose the component arcs 
Sxoom Sznizs, Vol. XXI, No. 62.—March, 1856. 23 
