144 MALUS. 



mathematicians and physicists of the Emission School in 

 Europe, to afford a mathematical proof of the truth of 

 the emission theory. It is assuredly a singular thing that 

 there should be this perfect identity of refractive powers 

 calculated from angles of disappearance differing from 

 each other, and according to formulas very dissimilar be- 

 tween themselves. 



But what proof was there that the refractive powers 

 ought to be identical? Ought we to suppose that the 

 change from the solid to the fluid state in any substance 

 would be without influence on its refractive power? 

 Might we not cite cases in which heat modifies the re- 

 fractive power of bodies independently of their density ? 

 Again, were the temperature of the wax and its density 

 well ascertained at the moment of the experiment such 

 as Malus was obliged to make it ? Besides, would it be 

 strange to suppose that within those limits where the 

 action of bodies on light opei'ates, there are no sub- 

 stances truly opaque ! 



Now that the system of emission is overthrown without 

 hope of restoration, I endeavour to recall all the circum- 

 stances by which Malus might possibly have been misled. 

 But, for my own part, I feel sure that I do not deceive 

 myself in affirming that the memoir of which we are 

 speaking offers a new proof of the mathematical spirit 

 and experimental talent which Malus possessed in so 

 high a degree. We ought only to regret that the 

 conclusions in the report were so explicit that they 

 represented the atomic theory of light as completely 

 established ; and that such a decision, emanating from 

 individuals so competent as Laplace, Haiiy, and Gay- 

 Lussac, may perhaps have contributed to alienate our 

 illustrious associate from that experimental path which 



