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, ]\Jalus 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 not 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 fall 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, 



