590 SIGHT. 



certain sound, the idea is immediately suggested to the un- 

 derstanding, which custom had united with it." Dr. Wells, in 

 1792 ' l , extended this principle of Berkeley's, and proved that 

 the apparent direction also of an object which sends its picture 

 to any given point of the retina depends upon the state of 

 action existing at the same time in the muscles of the eye ; 

 and he adduced many and convincing proofs that it cannot be 

 altered except by a change in the state of that action. Thus, 

 an ocular spectrum impressed on any part of the retina does 

 not appear to alter its position, when it is forcibly pressed aside 

 in any direction; but, whenever the voluntary muscles act, 

 it is referred by the mind to a different point of external space. 

 That the apparent distances and positions of objects are sug- 

 gested to the mind by sensations accompanying the motion of 

 the muscles of the eyes, is a principle then clearly stated both 

 by Berkeley and Wells. It has, however, by many been con- 

 sidered the discovery of Sir C. Bell, because he reproduced it, 

 in 1823, above a century after Berkeley and thirty years after 

 Wells, though he has not advanced a single original argument in 

 its favour, and has unpardonably suppressed all reference to the 

 philosophers by whose reasonings and researches it had been 

 established. k 



Prof. Wheatstone has recently made a series of curious expe- 

 riments, from which it appears that the sensations which accom- 

 pany the converging and the parallel motions of the eyes are so 

 dissimilar, that it is highly improbable that these two sets of 

 motions are effected by the same muscles. He is of opinion that 

 the parallel motions of the eyes are governed by the straight 



1 An Essay upon Single Vision with Two Eyes. 1792. p. 56. sq. p. 70. sqq. of 

 an edition of this and some other writings, with his autobiography, 1818. 



k Let any one read Wells (pp. 55 57.) and Sir C. Bell (pp. 318 323. ), 

 and his eyes will rise most expressively, by the action, I presume, of the superior 

 straight muscles. 



Too many of the anatomical and physiological papers in the Philosophical 

 Transactions, from the time of the first contributions of the glorious burner of 

 John Hunter's precious and voluminous manuscripts to the present, reflect no 

 credit upon those medical members of the council of the Royal Society who re- 

 commended their publication. But the poverty or errors of papers disfigure 

 the Transactions, to my view, less than the parade of old facts and opinions as 

 new, without the slightest reference to their authors ; and this is a greater 

 reflection upon the medical members of the council, when the real authors 

 were distinguished Fellows of the Royal Society. 



