190 THE MICROSCOPIST. 



C, D, Fig. 59, of common light. Hence we infer, that a beam 

 of common light consists of two beams of polarized light, 

 whose planes of polarization, or whose diameters of similar 

 properties, are at right angles to one another." 



There are other means of polarizing light besides that of 

 double refraction, just mentioned. M. Malus discovered, in 

 1810, that a beam of common light, reflected from glass at an 

 angle of 56, or from water at an angle of 53 became polar- 

 ized. 



In order to explain the phenomena of polarized light when 

 produced by reflection from glass, let C, D, Fig. 61, represent 



Fig. 61. 



T> 



two tubes, one turning within the other. A, B, are plates of 

 glass capable of turning on their axis, so as to form different 

 angles with the axis of the tube. 



If a beam of light, r s, from a candle or hole in the window- 

 shutter, fall upon A at the polarizing angle of 56 45', it will 

 be reflected through the tubes, and will fall upon the second 

 plate, B, also at an angle of 56 45'. If, however, this plate 

 be so placed that its plane of reflection is at right angles to 

 the plane of reflection of the first plate, A, the ray of light 

 will not suffer reflection from B, or will be so fainb as to be 

 scarcely visible. If we now turn round the tube, D, carrying 

 the plate, B, without moving the tube C, the reflected ray, E, 



