THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOUKNAL OF SCIENCE. 



[FIFTH SERIES.] 



MARCH 1878. 



XXIY. On Reflection of Polarized Light from the Equatorial 

 Surface of a Magnet. By John Kerb, LL.D., Mathema- 

 tical Lecturer of the Free- Church Training College, Glasgow* 



IN trying to carry forward the magneto-optic inquiry which 

 formed the subject of my last communication to this 

 Magazine f, I proceeded to examine a lateral face of an in- 

 tensely magnetized iron bar as a reflector, and had the pleasure 

 of obtaining good effects in the first trial. I have lately 

 performed a series of careful experiments on the subject ; and 

 I propose to give an account of these and of their very inter- 

 esting results in the present paper. I mean to describe the 

 experiments at sufficient length, for the guidance of any one 

 who would like to repeat them. Most of them are, I think, 

 rather easier and more satisfactory than those described in my 

 former paper. 



1. Apparatus. — The electromagnet is the same upright horse- 

 shoe that was used in my former experiments, a small but 

 effective instrument constructed by Mr. Ladd. Each coil 

 contains about 200 turns of thick double wire. The coils are 

 put into circuit, through a good Ruhmkorff's commutator, 

 with a series of six Grove's elements, the connexions being 

 made in the usual way as for magnetization of the horseshoe. 



The reflecting bar is a rectangular prism of soft iron, 7 

 inches long, 2 wide, f thick. The iron was selected and 

 specially forged ; and its structure is homogeneous and very 



* Communicated by the Author. 



t " On Rotation of the Plane of Polarization by Reflection from the Pole 

 of a Mag-net," May, 1877. 



Phil. Mag. S. 5. Vol. 5. No. 30. March 1878. M 



