148 MALUS. 



and Biot. The report was presented by Lagrange, and 

 thus nothing was wanting duly to signalize the important 

 discovery of Malus. 



DISCOVERY OF POLARIZATION BY REFLEXION. 



We must go back to Erasmus Bartholimus to find the 

 first observations relative to the existence of double 

 refraction in Iceland spar, also called calc spar, or rhom- 

 boidal carbonate of lime. Huyghens had occupied him- 

 self with the study of these phenomena, and pointed out 

 a geometrical construction of a very simple and elegant 

 kind by which we can determine, in all directions and at 

 all incidences, the position of the extraordinary ray rela- 

 tive to the ray properly called the ordinary ray, whose 

 position is determined by the well-known law of the 

 sines, made known by Descartes. Huyghens arrived at 

 the discovery of this construction by means of an ellip- 

 soid, which, as he tells his readers, he derived from con- 

 siderations borrowed from the theory of waves. 



The reporter of the Academy on Malus's memoir of 

 the 12th December, 1808, entitled Memoir on a Prop- 

 erty of Light reflected by transparent Bodies, who was 

 no other than Laplace, wished that Huyghens had been 

 contented to have given his law as the result of experi- 

 ence only. But I may be permitted to ask, Is not the 

 hatred of theory carried too far when it leads to the sug- 

 gestion of dissimulation or the want of sincerity ? 



Newton contended for substituting other rules instead 

 of that of Huyghens ; but these have not been found 

 conformable to facts. 



Among modern observers, Wollaston was the first who 

 established the truth of the principles laid down by the 

 Dutch philosopher. To make this verification he availed 



