of Mr Charles Bell. 263 



eyeball instantly turns upward ; and he distinctly describes the 

 experiment by which he feels it move, by the application of 

 his finger to the ridge of the cornea. In opposition to this, I, 

 and other persons who have made the same experiment, find 

 that the eyeball remains at rest ; and we have the high authority 

 of Professor Soemmering of Gottingen in support of our re- 

 sult. If Mr Bell, therefore, has performed his own experi- 

 ment accurately, he has mistaken a casual motion of his own 

 eye for a general function ; and if that motion has, as he al- 

 leges, the effect of smoothing the accumulated ridge of the lu- 

 bricating fluid, he enjoys a privilege of vision which others are 

 not fortunate enough to possess. 



In the latter part of my former paper, I endeavoured to 

 show, that, even if the spectrum were immoveable, the notion 

 of position was actually acquired without the exercise of the 

 proper muscles. Against this position, which formed no part 

 of the philosophical argument, Mr Bell may make a stand ; 

 for it is here alone that refuge is to be found, among the phy- 

 siological sympathies — the never-failing strong-holds of hypo- 

 thesis and error. Even here, however, the argument may be 

 brought within the grasp of fixed principles, and the experi- 

 ment may be conducted as follows : 



Let the eye be supposed to be pushed by the finger from left 

 to right, through an arch of 10°, in a horizontal plane, then, 

 according to Mr Bell, the spectrum has not followed the mo- 

 tion of the eye, because the motion was brought about by the 

 finger, and not by the proper muscles, which alone have the 

 power of conveying the idea of change of place. 



Let the head be now placed so as to be capable of being 

 turned round through the same arch of 10°, by the pressure 

 of the finger upon the eye ; in this case, the spectrum does 

 follow the motion of the eye, and the head, though the proper 

 muscles are no more exerted in the one case, than in the other. 



It may perhaps be said, that the sensorium, being now 

 turned round along with the eye, has some how or other ob- 

 tained a notion of the change of position ; but such a suppo- 

 sition, besides being unintelligible, is hostile to Mr Bell's opin- 

 ion, unless the sensorium has acquired its knowledge from 

 an incipient action of the muscles, or rather from a disposition 



