PHILOSOPHICAL TRANSACTIONS. 
I. The Bakerian Lecture. — Contributions to the Physiology of Vision. — Part the 
Second. On some remarhahle, and hitherto unobserved, Phenomena of Binocular 
Vision (continued). By Charles WnY.\rs,'ro^^,F.R.S.,Professor of Experimental 
Philosophy in Kings College, London, Corresponding Member of the Academies of 
Science of Paris, Berlin, Brussels, Turin, Rome, Dublin, 8^c., of the Philosophical 
Society of Cambridge, the National Institute at Washington, 8^c. 
Received and read January 15, 1852. 
§ 17. 
In § 3 . of the first part of my “ Contributions to the Physiology of Vision,” published 
in the Philosophical Transactions for 1838, speaking of the stereoscope, I stated, 
“The pictures will indeed coincide when the sliding pannels are in a variety of dif- 
ferent positions, and consequently when viewed under different inclinations of the 
optic axes ; but there is only one position in which the binocular image will be im- 
mediately seen single, of its proper magnitude, and without fatigue to the eyes, 
because in this position only the ordinary relations between the magnitude of the 
pictures on the retina, the inclination of the optic axes, and the adaptation of the 
eye to distinct vision at different distances, are preserved. The alteration in the 
apparent magnitude of the binocular images, when these usual relations are disturbed, 
will be discussed in another paper of this series, with a variety of remarkable pheno- 
mena depending thereon.” 
In 1833, five years before the publication of the memoir just mentioned, these yet 
unpublished investigations were announced in the third edition of Herbert Mayo’s 
“Outlines of Human Physiology” in the following words: — “Mr. Wheatstone has 
shown, in a paper he is about to publish, that if by artificial means the usual relations 
which subsist between the degree of inclination of the optic axes and the visual angle 
which the object subtends on the retina be disturbed, some extraordinary illusions 
may be produced. Thus, the magnitude of the image remaining constant on the 
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