THE MAGICIAN 3 M1EROR. 



59 



pher thoroughly acquainted with the modern dis- 

 covery of the polarisation of light by reflexion. 

 Without seeking for so profound an explanation 

 of the phenomenon, we may readily understand 

 how a silver mirror may instantly lose its reflect- 

 ing power in a damp atmosphere, in consequence 

 of the precipitation of moisture upon its surface, 

 and may immediately recover it when transported 

 into drier air. 



One of the simplest instruments of optical de- 

 ception is the plane mirror, and when two are 

 combined for this purpose it has been called the 

 magician's mirror. An observer in front of a 

 plane mirror sees a distinct image of himself; but 

 if two persons take up a mirror, and if the one 

 person is as much to one side of a line perpen- 

 dicular to the middle of it as the other is to the 

 other side, they will see each other, but not them- 

 Fig. 3. 



L 



selves. If we now suppose MC, CD, NC, CD to 

 be the partitions of two adjacent apartments let 

 square openings be made in the partitions at A 



