Mr. E. Matthey. Further Contri/xitlnn* [Jan. 8, 



The boundary conditions are : continuity of magnetic indnction and 

 electric displacement perpendicular to the reflecting surface, the 

 of which is equivalent to continuity of magnetic force perpen- 

 dicular to the plane of incidence; continuity of magnetic force along 

 the line of intersection of the plane of incidence with the reflecting 

 surface ; continuity of the rate at which energy flows across the 

 reflecting surface. Now the refracted light consists of two waves, 

 circularly polarised in opposite directions, and the reflected light is 

 elliptically polarised; we have, therefore, four equations to determine 

 the amplitudes of the two refracted waves, and the amplitudes of the 

 two components of the reflected wave. 



The results of the paper agree with Dr. Kerr's experiments in the 

 following particulars : 



(i.) The reflected light is elliptically polarised. 



(ii.) When the magnetisation is parallel to the reflecting surface, 

 no effect is produced when the incidence is normal, or when the plane 

 of incidence is perpendicular to the direction of magnetisation. 



(iii.) When the plane of incidence is parallel to the direction of 

 magnetisation, and the light is polarised tn the plane of incidence, 

 the magnetic term increases from grazing incidence to a maximum 

 value, and then decreases to normal incidence. 



The principal point of disagreement is, that in all cases the inten- 

 sity of the reflected light is unchanged when the direction of the 

 magnetising current is reversed. 



I do not think that the results of the theory cnn be considered 

 altogether unsatisfactory, since they certainly explain some of Dr. 

 Kerr's experimental results ; and I am disposed to think that the 

 disagreement is due to the disturbing influence of metallic reflection. 

 At the same time, the question is one which can only be decided by 

 experiment, and it is therefore most desirable that experiments on 

 magnetised solutions should be made. 



IV. " Further Contributions to the Metallurgy of Bismuth." 

 By EDWARD MATTHEY, F.S.A., F.C.S., Assoc. Roy. Sch. 

 Mines. Communicated by Sir G. G. STOKES, Bart., F.R.S. 

 Received December 22, 1890. 



In October, 1837, I read a paper before the Royal Society* upon 

 a new method which I incidentally discovered while working with 

 a view to separate copper from bismuth, by fusion with bismuth 

 sulphide. 



' Roy. Soc. Proc.,' vol. 43, p. 172. 



