{ | J. LeConte on Binocular Vision. 493 
like that which takes place, in natural vision, in looking suc- 
cessively at nearer and more distant objects, or nearer and more 
distant parts of the same object, gives a distinct perception of 
relief. 
No one who has carefully analyzed his visual impressions, 
either in natural vision or in stereoscopic combination of pie- 
tures, can for a moment doubt that there is in all cases @ change 
i ears 
idea of a complete mental combination of dissimi- 
| lar images, though still supported Oy great names, is certainly 
: n my ou 
a stereoscopic Bese: or of a natural solid object; and that 
in insisting, against Wheatstone, on the impossibility of com- 
plete union of all parts of a stereoscopic picture of an object 
Wwe can distinctly perceive stereoscopic relief by the arath an 
* Arago, (Euvres complete, tome 4, p. 70. + This Jour., ITI, vol. i, p. 15. 
Am. Jour. Sct.—Tutrp Series, Vou. II, No. 12.—Dec., 1871. 
28 
