174 Dr. J. Kerr on Reflection of Polarized Light 



two other lines of experiment which I have tried without effect, 

 and which ought to be briefly noticed. 



(1) The mirror, as formerly, an equatorial face of a magne- 

 tized bar, the plane of incidence perpendicular to the lines of 

 magnetic force, and the incidence varying from near normal 

 to near grazing. The arrangements were of course somewhat 

 different from those already described ; but they were not more 

 difficult, and were made with equal care ; and I think that the 

 experiments were altogether as delicate as any of the preceding. 

 Working in this way at different times, I saw no appearance 

 of optical effect of magnetization. 



(2) The mirror an equatorial face of a magnet, the incidence 

 normal, and the inclination of the plane of incidence to the 

 lines of magnetic force varying from 0° to 90°. As the normal 

 incidence was obtained by the employment of a mirror of un- 

 silvered glass, the light was a good deal weaker than formerly ; 

 but otherwise the experiment was as delicate as any of the 

 preceding. Nothing like an optical effect of magnetization 

 was observed in any instance. 



From these experiments, and from all that I have seen upon 

 the subject, I think it probable, in the highest degree, that 

 magnetization of a reflector even to saturation would be abso- 

 lutely without optical effect in the cases now exemplified (that 

 is, in the case of normal incidence upon an equatorial face), and 

 in any case where the fronts of the incident and reflected waves 

 are parallel to the lines of magnetic force. 



I return now to the consideration of our first arrangement, 

 where the lines of magnetic force are parallel to the intersection 

 of the reflecting surface and the plane of incidence. 



22. Law of the optical action of magnetism at incidences 

 near grazing. 



Whatever be the angle of incidence between grazing and 

 principal, the effect of magnetization of the mirror, when sen- 

 sible, is to turn the plane of polarization of the reflected light 

 through a very small angle, in a direction always contrary to 

 that of the Amperean currents ; for, whatever be the angle of 

 incidence between grazing and principal, the two laws stated 

 in art. 13 hold true throughout the first four experiments with- 

 out exception. 



(1) The right-handed current conspires with a right-handed 

 rotation of the second JSicol. But the effect of a right-handed 

 rotation of the second Mcol (before magnetization of the 

 mirror) is virtually to turn the reflected ray lefthandedly, or 

 to displace its plane of polarization lefthandedly, with reference 

 to the principal section of the analyzer. And since the right- 

 handed current conspires with the right-handed rotation of the 



