HERMANN VON HELMHOLTZ 



in the sense that two electrified particles starting 

 with a finite velocity would, within a finite dis- 

 tance, acquire infinite speed, and therefore infinite 

 energy. ... It remains, however, to discuss the 

 case where k was equal to or greater than zero. 

 The most interesting part of this investigation was 

 the application of the generalised formula to the 

 propagation of electrical and magnetic disturbances 

 through bodies capable of electrical or magnetic 

 polarisation. These properties were treated inde- 

 pendently. . . . Both longitudinal and transversal 

 electric disturbances can be propagated in unmagnet- 

 isable dielectrics. The velocity of the transversal 

 undulations in air depends on the absolute suscepti- 

 bility of the medium. If this is very large the 

 velocity is the same as that of light. The velocity 

 of the longitudinal waves is equal to that of the 

 transversal waves multiplied by the factor i/^, and 

 by a constant which depends on the magnetic con- 

 stitution of the air. In conductors the waves are 

 rapidly damped. If the insulator is magnetisable, the 

 magnetic longitudinal oscillations have an infinite 

 velocity, the transversal magnetic oscillations are per- 

 pendicular to the transversal electrical oscillations, 

 and are propagated with the same velocity. In the 

 particular cases when k = o the longitudinal waves 

 of electricity have also an infinite velocity, and the 

 theory is then in close accord with that of Maxwell, 

 provided that the absolute specific inductive capacity 

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