﻿86 Dr. AV. F. G. Swann on the 



motion, which would mean that the effects produced by that 

 motion would depend on the elastic properties of the material, 

 which of course, on our present view, are entirely determined 

 by the nature of the electronic motions. As a matter of 

 fact, this is really what might be expected to be the case, 

 were it not for the fact that no matter what material is used 

 in the apparatus, no experiment so far devised to detect an 

 effect due to the earth's motion through space has given a 

 positive result, which drives us to the somewhat unsatis- 

 iactory conclusion that, on the electron theory of matter, 

 though the orbital velocities are almost certainly not small, 

 the motions in any molecule probably combine together to 

 produce, at external points, the equivalent of slow orbital 

 motions, somewhat after the analogy of beats in sound. It 

 would, I think, be interesting if the Michelson and Morley 

 experiment could be repeated with the body of the apparatus 

 made of some strongly magnetic material, such as iron, for 

 Ave know that in such a material the orbital motions are 

 capable of making themselves very evident. 



It may be remarked, that since expressions (15) are exactly 

 true however large W or v may be, the equilibrium of the 

 moving system studied follows absolutely when the electrons 

 are considered simply as singularities moving in accordance 

 with the eleclromagnetic scheme. This apparent avoidance of 

 the difficulty is illusory, however (as I propose to show in 

 the communication following), owing to the fact that in this 

 method of treatment it is vitally essential to consider the whole 

 transition from the fixed to the moving state of the system. 



University of Sheffield, 

 April 28th, 1911. 



VI. The Fitz Gerald Lorentz Contraction, and an Examina- 

 tion of the Method of Determining the Motions of Electrons, 

 ichen considered simply as Singularities, moving so as to 

 satisfy the Electromagnetic Scheme. By W. F. G. Swann, 

 D.Sc, A.F.C.S., Assistant Lecturer in Physics at the 

 University of Sheffield *. 



IK his ' iEther and Matter/ Sir Joseph Larmor develops 

 the consequences of the view that matter is an assem- 

 blage of electrons, in secular equilibrium under the influence 

 of their mutual fields. In considering the laws which must 

 determine the motions of the electrons, he points out that all 

 idea of forces must be abolished, and the problem must be 



'. * Communicated by" the Author, 



