J26 LETTERS ON NATURAL MAGIC. 



candle from which they proceeded would not be 

 visible, or they would not suffer reflexion from 

 the plates C, D. At all other angles the light 

 would be reflected and the candles visible. Now 

 the plate D is placed at an angle of 53 11' and 

 C at an angle of 56 45', so that when a film of 

 water is breathed upon them the light will be 

 reflected from the latter, and none from the 

 former; that is, the act of breathing upon the 

 plates will restore the invisible and extinguish the 

 visible image. 



