120 LETTERS ON NATURAL MAGIC. 



LETTER III. 



Subject of spectral illusions Recent and interesting case of Mrs. A. 

 Her first illusion a/ecting the ear Spectral apparition of Jier 

 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 ivith 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 imagination are also pictures on the 

 retina General views of the subject Approximate explanation of 

 spectral apparitions. 



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 importance in preparing the mind for understand- 

 ing those more vivid and permanent spectral illusions to 

 which some individuals have been either occasionally or 

 habitually subject. 



In these lesser phenomena we find the retina so power- 

 fully influenced by external impressions as to retain the 

 view of visible objects long after they are withdrawn ; wo 

 observe it to be so excited 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 Isaac 

 Newton and others, that the imagination has the power 

 of reviving the impressions of highly-luminous objects, 

 months and even years after they were first made. From 

 such phenomena, the mind feels it to be no violent transi- 



