Rotational Optical Activity in Isotropic Media. 997 



polarization intensity, the coefficients being in general 

 complex functions of the light disturbance considered. This 

 relation is of the form 



wherein 2' denotes a sum taken only over the electrons con- 

 tained in the actual active molecules and perhaps only over 

 some of them. 



Lorentz writes this relation in the form 

 E=«P + /3curlP, 

 without giving any account of the constants «, /3; our theorv 

 shows that J 



1_ V ae V m ^' be 2 /m 



4 n 2 + innr'—n* A n / + inn r '-n? 



We can now obtain the required constitutional relation to 

 complete the scheme of equations for our medium. We 

 know in fact that 



D = P + E, 

 and thus 



E(l + «)-£ Curl E = «D-/3 Curl D . . (2) 

 is the required relation. 



Now let us examine the propagation of a plane homo- 

 geneous beam of light in a medium where these relations 

 are satisfied. The direction of propagation is taken to be 

 the axis of z ma rectangular coordinate system so that the 

 components of E, D, H all involve the coordinates of space 



and time only by the exponential factor /^"^ wherein a 

 is in general a complex constant, a function ' of n, the 

 frequency of the light used. 



Since all differentials with respect to fa y) vanish, the 

 general equations (1) reduce to 



_l^H* = dE,, _ldH l _ dE x 



c dt ~ ~&z c dt "~ d~ > H,=0, 



and 



1^D £= ^H_ ldB y _ _^H X 



c dt '" 3* ' c <fc "~ "§7"' Dr = 0, 



( H -H,) = <? (E„-E Z ) 



= ? 2 (£r, E„). 



P/w7. 1%. S. 6. Vol. 27. No. 162. June 1914. 3 U 



