142 MALUS. 
this point then, they would say, that Wollaston was de- 
ceived. The object which Malus proposed in his memoir 
was to submit this point to a decisive experimental test. 
He chose a substance, beeswax, whose refractive power 
could be measured in the transparent state, and in the 
opaque state by the method of Wollaston. He applied 
to the angles of disappearance corresponding to these two 
conditions, and sufficiently different one from the other, 
the formulas of the Mécanique Oéleste, and he found there 
would result refractive powers perfectly identical. This 
For refraction; by an analogous construction, the circles which 
spread in the denser medium are smaller than those in the first, the 
radii being diminished in the ratio of the velocities or inversely as the 
densities. Thus when the new wave originating at o/ has spread to v/, 
that from o will have spread to double the same radius at v. The com- 
mon tangent or front of the refracted waves will be inclined at an angle 
otv, which is easily determined by drawing the parallel through ¢ of 
the incident light, whence we have (7 and 7 being the angles of inci- 
dence and refraction) wu t=o ¢ sin. i, andov=otsin. r; but ovand wt 
being the radii of waves in the two media, are in the constant ratio of ~ 
the densities =u; hence sin. i =y sin. r, which is the experimental 
law of refraction. 
