REMARKABLE OPTICAL ILLUSIONS. 35 



upon it whenever the image of the candle was 

 eclipsed. In this way I ascertained that the re- 

 flecting body was in the upper eyelash ; and I 

 found, that, in consequence of being disturbed, it 

 had twice changed its inclination, so as to repre- 

 sent a vertical candle in the horizontal position B, 

 and afterwards in the inverted position C. Still, 

 however, I sought for it in vain, and even with 

 the aid of a magnifier I could not discover it. 

 At last, however, Mrs. B., who possesses the 

 perfect vision of short-sighted persons, discovered, 

 after repeated examinations, between two eye- 

 lashes, a minute speck, which, upon being re- 

 moved with great difficulty, turned out to be a 

 chip of red wax not above the hundredth part of 

 an inch in diameter, and having its surface so 

 perfectly flat and so highly polished that I could 

 see in it the same image of the candle, by placing 

 it extremely near the eye. This chip of wax had 

 no doubt received its flatness and its polish from 

 the surface of a seal, and had started into my eye 

 when breaking the seal of a letter. 



That this reflecting substance was the cause of 

 the image of the candle, cannot admit of a doubt; 

 but the wonder still remains how the images which 

 it formed occupied so mysterious a place as to be 

 seen without the range of vision, and apparently 

 through the head. In order to explain this, let 

 m n, Fig. 2, be a lateral view of the eye. The 

 chip of wax was placed at m at the root of the 

 eyelashes, and being nearly in contact with the 

 outer surface of the cornea, the light of the candle, 

 which it reflected, passed very obliquely through 

 the pupil and fell upon the retina somewhere to 

 the left of n, very near where the retina ter- 

 D 2 



