CHAPTER XIII. 



ON POLARIZED LIGHT. 



" IF we transmit/' says Dr. Brewster, " a beam of the sun's 

 light through a circular aperture into a dark room, and if we 

 reflect it from any crystallized or uncrystallized body, or trans- 

 mit it through a thin plate of either of them, it will be re- 

 flected and transmitted in the very same manner and with the 

 same intensity, whether the surface of the body is held above 

 or below the beam, or on the right side or left, or on any other 

 side of it, provided that in all these cases it falls upon the 

 surface in the same manner, or, what amounts to the same 

 thing, the beam of solar light has the same properties on all 

 its ,'ides; and this is true, whether it is white light as directly 

 emitted from the sun, or whether it is red light, or light of 

 any other color. 



" The same property belongs to light emitted from a candle, 



Me. 



or any burning or self-luminous body, and all such light is 

 called common light. A section of such a beam of light will 



