THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 

 APRIL 1852. 



XXXVI. Contributions to the Physiology of Vision. — Part the 

 First. On some remarkable, and hitherto unobserved, Pheno- 

 mena of Binocular Vision. By Charles Wheatstone, F.R.S., 

 Professor of Experimental Philosophy in King's College, 

 London*. 



[With Two Plates.] 



§1- 



WHEN an object is viewed at so great a distance that the 

 optic axes of both eyes are sensibly parallel when directed 

 towards it, the perspective projections of it, seen by each eye 

 separately, are similar, and the appearance to the two eyes is 

 precisely the same as when the object is seen by one eye only. 

 There is in such case no difference between the visual appear- 

 ance of an object in relief, and its perspective projection on a 

 plane surface; and hence pictorial representations of distant 

 objects, when those circumstances which would prevent or disturb 

 the illusion are carefully excluded, may be rendered such perfect 

 resemblances of the objects they are intended to represent as to 

 be mistaken for them; the Diorama is an instance of this. But 

 this similarity no longer exists when the object is placed so near 

 the eyes that to view it the optic axes must converge ; under 

 these conditions a different perspective projection of it is seen 

 by each eye, and these perspectives are more dissimilar as the 

 convergence of the optic axes becomes greater. This fact may 

 be easily verified by placing any figure of three dimensions, an 

 outline cube, for instance, at a moderate distance before the 

 eyes, and while the head is kept perfectly steady, viewing it with 



* From the Philosophical Transactions for 1838, part ii. ; having been 

 rci rived and read bv the Royal Society June 21, 1838. 



PhU. Mag. S. 4. Vol. J5. No. 18. April 1852. R 



