94 W. B. Rogers on Binocular Vision. 
If the arcs be of unequal convexity the resultant curve will 
no longer have the perpendicular altitude, but will incline a a 
to the one or other side according to circumstances. ‘Thus 
6 be more convex than a the resultant curve will turn its ape 
eee — left, and if a be more convex than 6 it will turn it 
wards right. 
salto ee curvatures of @ and 6 are turned the same way the 
depth of the relief will storia be proportional to the differ- 
ence of the convexities of the two arcs. With equal curvatures 
they will form a resultant arc sea to either 70. 
component and having no relief. When they é 
unequal convexity as in fig. 70, the re 
position. If, asin the figure, b should have the 
greater curvature of the two, the apex of the ; 
resultant curve will incline towards the right ; £ 
if that of a should be the greater the apex will ‘ ed 
turn towards the left. ‘ 
ith arcs of no greater curvature than those of the last figure, 
but lie in a curved su To prove this we have only to use 
arcs of much greater ineectesiot as in fig. 71. Here when we 
form the resultant in front of the dia- +. . 
we find it to consist of a curved 
surface bounded by the resultant eas 
and a vertical straight line d the 
union of the two chords. Daghaning at 
the near edge formed by this vertical 
line, the surface recedes with a concave 
sweep, at first rapidly, and then more 
gently towards the apex or farthest point. When the combinat 
is made beyond the plane of the paper, the curved surface traced 
from the vertical edge, approaches the observer in a conver sweep, 
rapidly at first, but more slowly towards the a 
When the curves which are united are a ci? ae ‘and an ellipse 
whose vertical axis is equal to the diameter of the circle, or when 
they are two rere ¥. Sar vertical diameters, the resultant 
curve lies wholly 
On conbiniae: tha alli 
a with the circle of ¢ : 
72, we have for the resu 
