on SUR cath t i <> le eee 
‘A ee a See egke ae es" 
as SBS 2d ae 
mat j . es “e. oe ak ’ oat 8 
a W. B. Rogers on Binocular Visions = = 319 
. 
s 
. “These changes usually go on until the lines assume the greatest 
amount of relief and the least angle of intersection of which 
m their positions in the diagram they are susceptible, and then 
the opposite changes supervene. If but slightly inclined in the 
diagram, they acquire the perspective position almost as soon as 
they are brought to intersect. Their inclination to the plane of 
the paper then rapidly augments, they grow longer and the inelud- 
ed angle lessens, until in many cases it becomes imperceptible, 
and for a moment the two lines seem to melt into a single result- 
ant. But as we look at this we see it again resolving itself into 
~ two intersecting lines varying continually in apparent length, mu- 
tual inclination and amount of relief. The relation of these va- 
rious appearances to one another and to the visual conditions in 
which they occur will be more clearly understood by referring to 
fig. 27. 
27. 
LORE MEG, ee, 
= x K = a ¥ 
In this diagram R and L denote the centres of the right and 
left eyes AM, and BN, the two lines which are to be combined, 
and RCED LCEFD the planes in which the axes of the right and 
left eyes respectively revolve while directed to successive points 
of AM, BN. Since CD is the intersection of the two optical 
planes, it is obvious that the axes directed to corresponding points 
o N will always meet in that line. Hence A and B will 
be seen united at D, M and N at C, and so other points of AM, BN 
will be combined at some determinate place in CD. This line 
is therefore the locus of all the points due to the binocular com- 
verge: of the corresponding points of the component lines 
M BN. 
If we begin our observations by converging the axes through 
M and N to Cand hold them in this inclination, AM and BN 
will appear in the position and of the magnitude represented by 
A’C BG. If then reducing the convergence of the axes we di- 
rect them through A and B to D, the components will appear in 
DE DF. The resultant figures A’C B’ and DEF being in 
planes parallel to that of the diagram AM BN, their lines will 
