LETTER FROM YOUNG TO MALUS. 159 



Council of the Royal Society of London had awarded to 

 him the Rumford Medal. 



So little was the progress which had been made in 

 England in these new theories, that Young requested 

 Malus to assure him whether a ray polarized by reflexion 

 from glass, was really not reflected by a second glass 

 suitably placed, as Malus had announced. In the opinion 

 of the learned Secretary of the Royal Society, the rays 

 which after a first reflexion were incapable of reflexion 

 at a second surface ought to be absorbed or rendered inert. 



Again we read in this same letter : " Your experi- 

 ments demonstrate the insufficiency of a theory (that of 

 interferences) which I had adopted, but they do not prove 

 its falsity." 



Malus, who was a declared and immovable partisan of 

 the theory of emission, accepted with great joy the 

 declaration of Young on the insufficiency of the doctrine 

 of interferences. He always held out the opinion of the 

 celebrated Secretary of the Royal Society to those who 

 entreated him to examine, with his superior genius, the 

 hypothesis in favour of Avhich such men as Huyghens 

 and Euler stood so openly committed. He did not 

 remark that Young, in admitting the insufficiency of 

 that theory in 1811, had the caution to add that nothing 

 up to that time, even after the discovery of polarization, 

 had proved its falsity.* 



* It may illustrate further the want of due appreciation of the value 

 of Malus's discovery on its first announcement, if, besides the letter 

 of Young here quoted, we refer to several other passages in his cor- 

 respondence, from which it appears how entirely the discovery of 

 polarization was regarded as something if not quite at variance with 

 the theory of waves, yet as wholly incapable of representation by its 

 principles. 



Young, himself, went so far as to predict that it was a problem 



