246 ON THE REFLEXION AND REFRACTION OF LIGHT. 



problems that relate to the motions of systems composed of an 

 immense number of particles mutually acting upon each other. 

 One of the advantages of this method, of great importance, is, 

 that we are necessarily led by the mere process of the calcu- 

 lation, and with little care on our part, to all the equations 

 and conditions which are requisite and sufficient for the com- 

 plete solution of any problem to which it may be applied. 



The present communication is confined almost entirely to the 

 consideration of non-crystallized media; for which it is proved, 

 that the function due to the molecular actions, in its most general 

 form, contains only two arbitrary coefficients, A and B-, the 

 values of which depend of course on the unknown internal con- 

 stitution of the medium under consideration, and it would be 

 easy to shew, for the most general case, that any arbitrary dis- 

 turbance, excited in a very small portion of the medium, would 

 in general give rise to two spherical waves, one propagated 

 entirely by normal, the other entirely by transverse, vibrations, 

 and such that if the velocity of transmission of the former wave 

 be represented by *JA, that of the latter would be represented 

 by *JB. But in the transmission of light through a prism, 

 though the wave which is propagated by normal vibrations were 

 incapable itself of affecting the eye, yet it would be capable 



of giving rise to an ordinary wave of light propagated by 





 transverse vibrations, except in the extreme cases where -5=0, 



r IB ~ a ver y l ar e quantity ; which, for the sake of simplicity, 



may be regarded as infinite; and it is not difficult to prove 

 that the equilibrium of our medium would be unstable unless 

 A. 4. 

 5 > 3 ' ^ e are therefore compelled to adopt the latter value of 



A 



-g , and thus to admit that in the luminiferous ether, the velocity 



of transmission of waves propagated by normal vibrations is 

 very great compared with that of ordinary light. 



The principal results obtained in this paper relate to the 

 tensity of the wave reflected at the common surface of two 



