164 Scientific Proceedings, Royal Dublin Society. 



charge produced no force in its neighbourhood. There is another 

 way of looking at this question, and one that leads to another view 

 of the reason for this limiting velocity. It depends on the theory 

 put forward by Professor Poynting that the energy given out at 

 any point in an electric circuit is transferred there through the ether, 

 and as energy is transferred through the ether with the velocity of 

 light, it cannot keep up with a moving body that moves with a 

 greater velocity than this. This completes the very remarkable 

 analogy between the way in which the rate of motion of a piston 

 by a gas is limited by the rate of propagation of energy in the gas, 

 and the rate of motion of electric engines is limited by the rate of 

 propagation of energy in the ether. 



