PHOSPHORESCENCE OF THE RETINA. 17 



spectator to keep up a continued view of it ; but 

 the disappearance and reappearance of its fainter 

 parts, and the change of shape which ensues, 

 will necessarily give it the semblance of a living 

 form, and if it occupies a position which is un- 

 approachable, and where animate objects cannot 

 find their way, the mind will soon transfer to it a 

 supernatural existence. In like manner a human 

 figure shadowed forth in a feeble twilight may 

 undergo similar changes, and after being dis- 

 tinctly seen while it is in a situation favourable 

 for receiving and reflecting light, it may suddenly 

 disappear in a position fully before, and within 

 the reach of, the observer's eye ; and if this 

 evanescence takes place in a path or road where 

 there was no side-way by which the figure could 

 escape, it is not easy for an ordinary mind to 

 efface the impression which it cannot fail to 

 receive. Under such circumstances we never 

 think of distrusting an organ which we have 

 never found to deceive us ; and the truth of the 

 maxim that " seeing is believing " is too uni- 

 versally admitted, and too deeply rooted in our 

 nature, to admit on any occasion of a single 

 exception. 



In these observations we have supposed that 

 the spectator bears along with him no fears or 

 prejudices, and is a faithful interpreter of the 

 phenomena presented to his senses ; but if he is 

 himself a believer in apparitions, and unwilling 

 to receive an ocular demonstration of their re- 

 ality, it is not difficult to conceive the picture 

 which will be drawn when external objects are 

 distorted and caricatured by the imperfect indi- 

 c 



