THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



APRIL 1881. 



XXXIII. On the Electric and Magnetic Effects produced by the 

 Motion of Electrified Bodies. By J. J. Thomson, B. A., 

 Fellow of Trinity College, Cambridge* . 



§ 1. T~N the interesting experiments recently made by Mr. 

 J- Crookes (Phil. Trans. 1879, parts 1 and 2) and Dr. 

 Goldstein (Phil. Mag. Sept. and Oct. 1880) on " Electric 

 Discharges in High Vacua," particles of matter highly charged 

 with electricity and moving with great velocities form a pro- 

 minent feature in the phenomena ; and a large portion of the 

 investigations consists of experiments on the action of such 

 particles on each other, and their behaviour when under the 

 influence of a magnet. It seems therefore to be of some 

 interest, both as a test of the theory and as a guide to future 

 experiments, to take some theory of electrical action and find 

 what, according to it, is the force existing between two moving 

 electrified bodies, what is the magnetic force produced by such 

 a moving body, and in what way the body is affected by a 

 magnet. The following paper is an attempt to solve these 

 problems, taking as the basis Maxwell's theory that variations 

 in the electric displacement in a dielectric produce effects 

 analogous to those produced by ordinary currents flowing 

 through conductors. 



For simplicity of calculation we shall suppose all the moving 

 bodies to be spherical. 



* Communicated by the Author. 

 Phil. Mag. S. 5. Yol. 11. No. 68. April 1881. S 



