THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[FOURTH SERIES.] 



NOVEMBER I860. 



XLII. On a new Species of Stereoscopic Fhcenomeno n. 

 By F. August*. 



[With a Plate.] 



THE object of this paper is to communicate an experiment 

 which seems to have an important bearing on the theory 

 of binocular vision. 



Wheatstone, it will be rememberedf, has called in question 

 the doctrine of identical retina-points, on certain grounds con- 

 nected with stereoscopic vision. A body of suitable dimensions, 

 especially at the distance of distinct vision, will, he says, appear 

 simply solid, though it is obviously impossible that the corre- 

 sponding points of the images received by the two eyes can fall 

 on the corresponding points of the retinse. This objection, how- 

 ever, has not prevailed on physiologists to abandon the doctrine 

 of corresponding retina-points, since that doctrine is confirmed 

 by many other considerations. Briicke, indeed, has advanced J 

 an explanation of stereoscopic vision which has hitherto been 

 generally regarded as sufficient, and which at first sight appears 

 to afford a solution of the difficulty. According to Briicke, the 

 eyes during vision are never at rest, but are constantly making 

 small movements, by means of which the images of continually 

 different points of the body regarded fall successively in the two 

 eyes on corresponding points of the retina?; and thus single 

 vision arises, since the images of points which fall on parts of the 

 eyes that do not correspond escape consciousness, because in 

 general the recognition of double impressions is resisted. The 

 impressions, however, perceived by corresponding retina-points 



* Translated from Poggendorff's Annalen for 1860, by F. Guthrie, Esq. 

 t Phil. Trans. 1838, vol. ii. p. 371. Pogg. Ann. Suppl. vol. i. p. 1. 

 X Muller's Archiv, 1841. 

 Phil. Mag. S. 4. Vol. 20. No. 134. Nov. 1860. Z 



