FUNCTION OF THE DIELECTRICAL MEDIUM. 87 



CHAPTER VI. 



ON DIELECTRICS. 



99. FUNCTION OF THE DIELECTRICAL MEDIUM. We have 

 hitherto reasoned on the hypothesis that the actions between elec- 

 trified bodies take place at a distance, and have considered the 

 dielectric as an inert medium, through which the forces act, but 

 as destitute itself of any active properties. 



It appears now to be well proved that heat is a vibratory motion, 

 the propagation of which takes place through the intervention of an 

 elastic medium. Now, we have seen that the problem of electrical 

 equilibrium, and that of heat in the permanent state, are characterized 

 by the same mathematical properties. 



May we not then suppose that the analogy in the two cases is 

 closer ; that it may be followed into the mechanism of the elementary 

 actions ; and that there is no other difference in the two orders of 

 phenomena than that which we ourselves introduce into the physical 

 interpretation of the laws ? If this is the case, it should be possible 

 to explain the production of the electrical forces by the action of 

 the medium only. 



Such is the idea which Faraday sought to elucidate, and which 

 constantly guided him in his researches. This is not the place to 

 attempt to prove, or to disprove, the exactitude of one or the other 

 of these points of view, but simply to show their equivalence in 

 explaining phenomena. 



We shall commence by establishing some theorems on the 

 relations between forces and electrostatic pressure. 



100. EXPRESSION OF FORCE AS A PRESSURE. We have already 

 considered as evident, that the action which is exerted on a conductor 

 is the resultant of the electrical pressures on the whole of its sur- 

 face ; but it may be useful to consider this theorem from another 

 point of view. 



