80 EXPERIMENTS, &c. 



a direction, contrary to that which you gave it- 

 Should you, afterward, move your finger back 

 from right to left, and in like manner, if your 

 finger be moved from above downward, or from 

 below upward,- the shadow will always proceed 

 the contrary way. It is therefore manifest, 

 that the soul must here see objects inverted, as 

 their images in the eye truly are ; and that it- 

 refers impressions to those parts of the eye 

 where it feels them, and not to the places from 

 which the rays are emitted, as it does when it 

 possesses the means of rectifying its judgment. 

 Whence does this happen ? Doubtless, because 

 the luminous point has neither a high nor a 

 low, neither a right nor left side, nor any well- 

 enlightened object in its vicinity, to awaken 

 the attention of the soul ; in short, nothing 

 which can determine its judgment." 



I should scarcely have mentioned this experi- 

 ment, from any respect for the authority of its 

 author in optics ; but as-Haller* seems to assent 

 to the conclusion he draws from it, that the 

 soul sometimes sees objects inverted; and as 

 the Abbot Derochonf, a member of that learned 

 body, the Academy of Sciences of Paris, has 

 lately, but in my opinion unsuccessfully, at- 

 tempted to reconcile it to the commonly received 



* Eleraenta Physiologiae, Tom. v. p. 479- 

 f Memoires de Physique, p. 66. 



