ILLUSIONS AND HALLUCINATIONS. 637 



the chief factors in determining the character of the hallucina- 

 tion, but as they acted through association it is not so clear to what 

 its externalization is to be ascribed. Perhaps the hurlyburly of 

 the storm outside had something to do with it ; probably the 

 drowsy, disordinated condition of the percipient favored the 

 formation of the apparition, but of the details of the process one 

 can not speak with confidence. 



In the hallucinations of which the crystal vision is the type 

 we have a form intermediate between the true hallucination and 

 the illusion. Prolonged staring into a mirror, a glass of water, a 

 crystal, a piece of glass, or even fixation of the gaze upon a point 

 will induce in some persons brilliantly colored hallucinations. 

 While they are certainly peripherally initiated by the prolonged 

 staring, their special character is nearly always centrally deter- 

 mined usually, indeed, they simply reproduce old memories. 

 Susceptibility to these hallucinations is by no means uncommon ; 

 I have tried about a hundred persons myself, and found that 

 about one in four saw something. Similar hallucinations of hear- 

 ing can be produced by listening to the " sound of waves " in a 

 large shell, to the sound of water running from a spigot, etc. 

 The stories of ghosts seen in mirrors probably all rest upon this 

 principle. For example : * 



" The first hallucination which I was in a position clearly to 

 recognize as such occurred during the Indian mutiny. Several 

 members of our family were in danger. One night on which we 

 had all been talking late of them, after we had parted and gone 

 upstairs to bed, I stood before my dressing table, plaiting my hair, 

 when my attention was arrested by a faint spot in the center of 

 the mirror; this, to my amazement, gradually enlarged (as a 

 grease spot spreads with heat) till the whole surface was covered, 

 and then, in the center of this veil, came through the face of 

 one of the near relatives above mentioned, as plain as might 

 have been his living reflection. I noted the day and hour, 

 and ascertained, six weeks later, that the relative seen had in- 

 curred no sort of danger at that date." This misty discoloration 

 of the glass is significant, for many of my subjects describe the 

 glass as becoming milky or cloudy just before the hallucination 

 appears. Occasionally it is possible by means of an indeter- 

 minate stimulus of this sort to raise a thought to sensory inten- 

 sity. Thus Miss X saw in the polished surface of a piano a 



scene of which she was thinking. \ I have met with one analogous 

 experience, but it seems to be rare. 



Many interesting questions arise as to the relation that exists 



* Proceedings of the Society for Psychical Research, vol. x, p. 407. 

 f Ibid., vol. v, p. 512. 



