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, Malus 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 cale spar. The same 
experiment made with a glass reflector at the incidence 
of «bout 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 cale 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 cale 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, 
