SPECTRAL ILLUSIONS. 37 



LETTER III. 



Subject of spectral illusions Recent and interesting case 

 of Mrs. A. Her first illusion affecting the ear Spectral 

 apparition of her husband Spectral apparition of a cat 

 Apparition of a near and living relation in grave- 

 clothes, seen in a looking-glass Other illusions, affecting 

 the ear Spectre of a deceased friend sitting in an easy- 

 chair Spectre of a coach-and-four filled with skeletons 

 Accuracy and value of the preceding cases State of 

 health under which they arose Spectral apparitions are 

 pictures on the retina The ideas of memory and imagi- 

 nation are also pictures on the retina General views of 

 the subject Approximate explanation of spectral appa- 

 ritions. 



THE preceding account of the different sources 

 of illusion to which the eye is subject is not 

 only useful as indicating the probable cause of 

 any individual deception, but it has a special im- 

 portance in preparing the mind for understanding 

 those more vivid and permanent spectral illusions 

 to which some individuals have been either occa- 

 sionally or habitually subject. 



In these lesser phenomena, we find the retina 

 so powerfully influenced by external impressions, 

 as to retain the view of visible objects long after 

 they are withdrawn : we observe it to be so ex- 

 cited by local pressures of which we sometimes 

 know neither the nature nor the origin, as to see 

 in total darkness moving and shapeless masses of 

 coloured light ; and we find, as in the case of Sir 



