ee oe ee Ae 
“ceeds that of HK from AB. 
_ ‘Seconp Segis, Vol XX, No. 58.—July, 1855. 18 
W. B. Rogers on Binocular Vision. - 97 
of it but at unequal distances from it, will form Separate virtual 
foci on HK. The former will of course be seen united by the 
natural process of vision as if the coincident foci were real ob- 
require for their union the convergence of the axes to some point 
either nearer or more remote than the pair of images, at the same 
time that the refractive power of the eyes is maintained in its ad- 
justment to the distance at which the images are placed, 
8, 
R $ 
placed at PQ. In this adjustment the images of L and M will 
be optically united on HK at a point z on the left of the centre 
of the line and at a distance equal to the radius of the circle, and 
the images of N and O will be united at a point y at an equal 
distance from the middle of HK towards the right. All the other 
corresponding points of the two exterior circles will be optically 
united in the vertical plane of HK, so as to form an equal resuilt- 
ant circle in that plane, having its centre in VR. Turning now 
to the smaller circles it is obvious that the corresponding points 
@ and b form separate images at m and n respectively which in 
Virtue of the forced or unusual adjustment are united at 7, In 
the same way we are presented with the resultant image of ¢ and 
datsina symmetrical position on the opposite side of VR, and 
thus the resultants of all the corresponding points of the two 
smaller circles unite to form a circular image in the position rs 
parallel to and behind the resultant circle at ry. The diameter 
of this image is greater than that of the component circles ab or 
cd in the same proportion as its distance from the eyes at AB ex- 
iar 
tes 
"eth. 
iss 
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