DOUBLE REFRACTION. 147 
MALUS GAINS THE PRIZE PROPOSED BY THE ACAD- 
EMY FOR A MATHEMATICAL THEORY OF DOUBLE 
REFRACTION. 
On the 4th January, 1808, the Academy proposed, as 
the subject for a prize in physical science to be decided 
in 1810, the following question :— 
“'To give a mathematical theory, confirmed by experi- 
ment, of the double refraction which light undergoes in 
passing through different crystallized bodies.” 
The memoir of Malus received the prize. Doubtless 
fearing lest he should be forestalled by some of the com- 
petitors, in the discovery of the singular properties of 
light which he had observed, this eminent physicist com- 
municated the most essential parts of his researches to 
the Academy on the 12th December, 1808, without 
waiting for the period at which, according to the pro- 
gramme, the competition was to be closed. It is then to 
the end of the year 1808 that the immortal discoveries 
belong of which I proceed immediately to give you an 
analysis. The commission appointed to judge of the com- 
petitors was composed of Lagrange, Haiiy, Gay-Lussac, 
of the Méc. Céleste by which this conclusion can be considered as 
established. 
Malus observed by Wollaston’s method the angles at which the dis- 
appearance took place in wax, solid and in fusion. These angles were 
different; and calculated in the usual way, the indices of refraction 
resulted different also (as seen in the above tabular view). 
The same observed angles, however, calculated by Laplace’s for- 
mula gave the resulting index the same in both cases. 
Now Laplace, Malus, and the emissionists, considered the identity 
of refractive power thus resulting to be a necessary truth—why so, we 
do not see; it is obviously, at best, a mere consequence of the asswmp- 
tion made at the first. The result is no proof of its truth, and decides 
nothing either way. Arago’s laboured remarks therefore seem super- 
fluous.— Translator. ° 
