﻿Unipolar Induction. 941 



surface of the inner cylinder by the radial component of 



- [V'H], which diminishes the result by about 5 per cent., 



c 



and for the effect of floor and ceiling, which might further 



diminish it by as much as 10 per cent. The value thus 



obtained for the total charge on the outer cylinder when 



earthed was 0*008 electrostatic CJ.GT.S. unit, and for the 



deflexion on reversal of the magnetization, 41*0 divisions. 



In order to check this very rough calculation, the metal 

 case around the solenoid was divided into several insulated 

 sections, and both it and the outer cylinder were charged by 

 means of a potentiometer to known potentials • by connecting 

 Ihe outer cylinder to the electrometer (previously earthed), 

 deflexions were obtained in imitation of the main experiment, 

 some of them while the magnet was in rotation. From these 

 observations and the corrections described above, the theore- 

 tical value of the deflexion was found to be 36*0 divisions. 



From these two values it was decided, after considering 

 the degree of accuracy of each observation and approxima- 

 tion in turn, that the deflexion required by the Moving Force 

 Line Theory w r as probably about 37 '0 divisions, pretty 

 certainly greater than 31*0, and could not have been less 

 than 26*0 divisions. 



The Moving Force Line Theory is thus disproved. Tn 

 future, whenever the electromotive intensitv due to electro- 

 magnetic induction is assumed to be proportional to motion 

 relative to magnetic force lines, these force lines must be 

 supposed to be always stationary, at least as regards any 

 rotation of the magnetic system about an axis of magnetic 

 symmetry. That is, a, rotating magnet does not " carry its 

 force lines " around with it. 



It is thus rendered probable that electromagnetic induction 

 caused by motion depends on absolute motion— that is, on 

 motion relative to the aether, not on motion relative to 

 material bodies. The result thus tends to support Lorentz/s 

 theory ; but the method is not capable of distinguishing, for 

 instance, between the theories of Lorentz and of Hertz, so 

 that it leads only to a partial solution of the problem. It is 

 the author's hope that a further investigation by another 

 method, which is now under way, will lead to a complete 

 solution. 



In conclusion, I wish to express my gratitude to Prof. J.. 

 S. Townsend, for his assistance and advice, without which 

 the experiment could never have become an actuality. 



