REMARKABLE OPTICAL ILLUSION. 117 



standing before me, I was surprised to observe, apparently 

 among my hair, and nearly straight above my head, and 

 far without the range of vision, a distinct image of one 

 of the candles inclined about 4.5 to the horizon, as shown 

 at A in Fig. 2. The image was as distinct and perfect 



as if it had been formed by reflexion from a piece oi 

 mirror glass, though of course much less brilliant, and 

 the position of the image proved that it must be formed 

 by reflexion from a perfectly fiat and highly-polished 

 surface. But where such a surface could be placed, 

 and how, even if it were fixed, it could reflect the image 

 of the candle up through my head, were difficulties not 

 a little perplexing. Thinking that it might be something 

 lodged in the eyebrow, I covered it up from the light, 

 but the image still retained its place. I then examined 

 the eyelashes with as little success, and was driven to the 

 extreme supposition that a crystallization was taking 

 place in some part of the aqueous humour of the eye, and 

 that the image was formed by the reflexion of the light 

 of the candle from one of the crystalline faces. In this 



