( 669 ) 
Physics. — H. A. Lorentz. “The rotation of the plane of pola- 
rization in moving media.” 
(Communicated in the meeting of March 29, 1902). 
§ 1. In my , Versuch einer Theorie der electrischen und optischen 
Erscheinungen in bewegten Körpern” (Leiden, 1895) I examined the 
propagation of light in transparent bodies having a constant trans- 
lation with velocity p, the aether being supposed to remain at rest, 
and tried to find, in how far optical phenomena may be affected by 
this motion. In the case of the rotation of the plane of polarization 
in optically active substances, I had to leave the question undecided. 
Indeed, the relation between the electric force € and the electric 
moment MW, to which I was led by certain general principles (linear 
form of the equations, isotropy of structure and reversibility of the 
motions) does not only contain the coefficient j, which determines 
the rotation in the quiescent medium; there is besides a second 
coefficient £, which is multiplied by the velocity p, and whose ratio 
to j I could not determine, because I wished to refrain from special 
hypotheses as to the mechanism of the phenomenon. 
The equation in question is *) 
CS oO MOED EAT. oly. eee (1) 
and the rotation for unit length was found to be?) 
i ie 
Best B 
if the body is at rest, and 
on (1+ <P) jb op np ky hy AM 
if it has a translation along the axis of z, the light travelling in 
the same direction. In these formulae n’ is the frequency, i.e. the 
number of vibrations in the time 2z, for an observer, moving with 
the medium, W the mean of the velocities of right-handed and 
left-handed circularly polarized rays in the medium at rest, and c 
the velocity of light in the aether. 
The two terms with p, would annul each other, if 
J 
eee . « ° ° e e ° ° e (3) 
I saw however no reason to admit this relation. 
§ 2. Mr. LARMOR has published 5) some objections to my in- 
1) 1 c., p. 80. « is the coefficient which determines the index of refraction. 
sale, ps 118. 
8) J. Larmor, Aether and Matter, Cambridge, 1900, 
