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 which 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 
