Doublets and Triplets in the Spectrum. 55 



One statement in Prof. Reynolds's paper I must protest 

 against ; on page 147 he says of me : " showing that he has 

 in no way realised the point of Clausius's paper which he 

 quotes — showing, in fact, that he cannot even have read it." 

 I am sorry that without just cause Prof. Reynolds should 

 disfigure a scientific discussion with an assertion such as the 

 last part of this. 



While disclaiming the errors that Prof. Reynolds would 

 saddle me with, I must confess that the theory of my paper 

 is far less complete than I should like to see it, hut I have a 

 partial excuse in that I cut the space devoted to the bare 

 essentials of the theory down to a minimum, seeing that its 

 applications made a demand on your space which, it appeared 

 to me, might jeopardize their being published at all. 



Yours obediently, 



Melbourne, 19th April, 1897. WlLLIAM SUTHERLAND. 



VII. Doublets and Triplets in the Spectrum produced by 

 External Magnetic Forces. By Dr. P. Zeeman *. 



1. /~\N a former occasion! I have remarked that the elemen- 

 V_J tary treatment of the general idea of the Lorentz 

 theory of the magnetic broadening of the spectral lines 

 indicates that the broadened line must in some cases be 

 broken up into a triplet. I have examined this subject 

 somewhat more in detail. Further consideration shows that 

 with a very strong magnetic field, a magnetically broadened 

 line must be broken up into doublets or triplets according as 

 the light is emitted in a direction parallel or perpendicular 

 respectively to the lines of force. With a smaller intensity of 

 the field, the line will be simply widened. The prediction of 

 Lorentz with regard to the polarization of the edges of the 

 broadened lines having been fulfilled, it seemed worth while 

 to pursue still further the study of the polarization of the 

 lines. Even with magnetic forces insufficient to break up 

 the line into a triplet, it might be possible to learn something 

 more about the constitution of the widened line. It seemed 

 to me to be of interest to investigate this point, and to see 

 whether the explanation formerly given, intended as the 

 very first sketch of the motion of ions according to the theory 

 of Lorentz, was further confirmed by experiment. 



Prof. Oliver Lodge \ has suggested that, under some sup- 



* Communicated by Prof. Oliver Lodge. 



t Phil. Mag. for March 1897. 



\ < The Electrician ' for February 28, 1897, p. 569 



