Maxwell. 309 



the same equation of motion for the medium; but, owing to 

 the differences in the surface-terms, they yield different con- 

 ditions at the boundary of the medium, and consequently give 

 rise to different theories of reflexion. 



The assumptions involved in Maxwell's treatment of the 

 magnetic rotation of light were such as might scarcely be 

 justified in themselves ; but since the discussion as a whole 

 proceeded from sound dynamical principles, and its conclu- 

 sions were in harmony with experimental results, it was fitted 

 to lead to the more perfect explanations which were afterwards 

 devised by his successors. At the time of Maxwell's death, 

 which happened in 1879, before he had completed his forty- 

 ninth year, much yet remained to be done both in this and in 

 the other investigations with which his name is associated; 

 and the energies of the next generation were largely spent in 

 extending and refining that conception of electrical and optical 

 phenomena whose origin is correctly indicated in its name of 

 Maxwell's Theory. 



