154 MALUS. 



Such was the state of our knowledge on this delicate 

 and singular branch of optics, when, one day, in his 

 house in the Rue d Enfer, Mains happened to examine 

 through a doubly refracting crystal, the rays of the sun 

 reflected by the glass panes of the windows of the Lux 

 embourg Palace. Instead of the two bright images 

 which he expected to see, he perceived only one, the 

 ordinary, or the extraordinary, according to the position 

 which the crystal occupied before his eye. This singular 

 phenomenon struck him much ; he tried to explain it by 

 supposing some particular modifications which the solar 

 light might undergo in traversing the atmosphere. But 

 when night came, he caused the light of a taper to fall 

 on the surface of water, at an angle of 36, and found, 

 by the test of a double refracting crystal, that the light 

 reflected from the water was also polarized, just as if it 

 had emerged from a crystal of calc spar. The same 

 experiment made with a glass reflector at the incidence 

 of about 35, gave the same result. From that moment 

 it was thus proved that .double .refraction is riot the sole 

 means of polarizing light, or of making it lose the prop 

 erty of dividing itself constantly into two pencils on 

 traversing calc spar. Reflexion at the surface of trans 

 parent bodies a phenomenon occurring every instant, 

 and as ancient as the world possessed the same prop 

 erty, without being hitherto suspected by any one. Ma- 

 lus, however, did not stop here ; he caused an ordinary 

 and an extraordinary ray from calc spar to fail simulta 

 neously on the surface of water, and observed that at the 

 incidence of 36 these two rays acted in a very different 

 manner. 



When the ordinary ray underwent a partial reflexion, 

 the extraordinary ray was not reflected at all, that is, 



