152 Dr. W. F. G. Swarm on the Magnetic Field produced 



capacity. It will appear, however, (Section 2) that if part 

 of the space inside the coil is filled with dielectric material 

 of one kind, e. g. paraffin wax, and the other part with 

 dielectric material of another kind, e. g. a vacuum, a resultant 

 magnetic flux should be obtained through the coil, provided 

 that the specific inductive capacity is a quantity which may be 

 looked upon as continuous throughout the medium to w r hich it 

 refers. As will be shown later (Section 4), while the electron 

 theory satisfies the requirements of a hypothetical dielectric of 

 this kind, as far as the field outside it is concerned, nevertheless, 

 inside the dielectric, the condition of continuity is not satisfied; 

 and it will follow that on this view of dielectric action the 

 flux through the coil in all positions will be zero, so that 

 the absence of any effects of the kind sought in the experi- 

 ments to be presently described affords direct proof of the 

 discontinuous nature of the specific inductive capacity, and 

 shows that dielectric action is to be accounted for by the 

 presence of something of the nature of electric doublets, and 

 cannot be attributed to any other mysterious power of 

 twisting the tubes of force, which the dielectric might be 

 imagined to possess. 



Section 1. The total magnetic flux through a closed circuit 

 kept at constant potential, and due to the motion of a system 

 of charged bodies along with the closed circuit, is zero, when 

 the ivhole medium in the neighbourhood of the closed circuit 

 is filed with a substance of constant specific inductive 

 capacity K. 



B 



Let S (fig. 2) be the circuit (not necessarily a plane 

 circuit), and v its velocity in common with the system of 



