Atom and the Charge of Electricity carried by it. 519 



Faraday tubes, and also to the direction in which they are 

 moving, the magnitude of the force varying as the product 

 of the " polarization " and the velocity of the tubes at right 

 angles to their direction (see ' Recent Researches in Elec- 

 tricity and Magnetism,' by J. J. Thomson, p. 8). On this 

 view the energy per unit volume in the magnetic field when 

 the tubes are moving at right angles to themselves is (see 

 ' Recent Researches,' p. 9) 



f 1 pay 2 



8 



IT 



where /li is the magnetic permeability, P the polarization, and 

 V the translatory velocity of the tubes. This expression 

 would represent the kinetic energy due to the translatory 

 motion of the tubes if the expression for the effective mass of 

 the tubes contained a term proportional to the square of the 

 "polarization/' Now if we have a vortex column moving 

 about in a fluid which is subject to other disturbances, the 

 following considerafions would seem to show that the ex- 

 pression for its effective mass would contain a term propor- 

 tional to the square of the vorticity in the vortex column. 

 The lines of flow when the vortex column is stationary in a 



Fio-. 2. 



liquid moving so that at an infinite distance its velocity is 

 uniform and horizontal are represented in fig. 2. 



