244 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1908. 



are fixed to them, if these are threaded through a ring P with a small 

 but finite mass and the system caused to rotate round A and B, the 

 effort of the ring to get away from the axis of rotation will cause 

 A and B to approach each other, and the law of approach may easily 

 be shown to be the same as if there was a force between them vary- 

 ing inversely as the square of the distance. 



The result mentioned on page 236 that the potential energy of a 

 system charged with electricity is equal to the kinetic energy of the 

 mass of ether bound to the system when moving with the velocity 

 of light is another example of potential energy, being in reality the 

 kinetic energy of an associated system, and indeed, as I have endeav- 

 ored to bring before you this evening, the study of the problems 

 brought before us by recent investigations leads us to the conclusion 

 that ordinary material systems must be connected with invisible 

 systems which possess mass whenever the material systems contain 

 electrical charges. If we regard all matter as satisfying the condi- 

 tion we are led to the conclusion that the invisible universe — the 

 ether — is to a large extent the workshop of the material universe, and 

 that the phenomena of nature as we see them are fabrics woven in the 

 looms of this unseen universe. 



