Method of treating Electrostatic Theorems. 19 



between them. Faraday pointed out that the result so 

 deduced, and confirmed by experiment, could be explained 

 by assuming the existence of an elastic medium, the straining 

 of which was electrification, and the consequent stress, elec- 

 trical force. The elastic constant of such a medium Maxwell 

 proposed to call the " coefficient of electric elasticity." Dr. 

 Lodge has used the idea with the best of results in his book 

 on * Modern Views of Electricity.' 



The reading of Dr. Lodge's book suggested to me the 

 working out of the results contained in this paper. 



The object of the paper is to draw attention to the advan- 

 tages that are to be derived, especially by the student, from 

 taking as hypothesis, not, as is usual, the law of the inverse 

 square, but the existence of this elastic medium. The hypo- 

 thesis may not be exactly true, but it is as nearly true, and in 

 the same manner true, as that a wave of sound may be repre- 

 sented by a wavy line. We have a3 much right to deduce 

 theorems of electrostatics from consideration of the behaviour 

 of this medium under stress, as to deduce the laws of the 

 interference of sound from the summation of waves on a dia- 

 gram. In both cases the whole truth is not presented, but 

 sufficient to ensure the accuracy of the deduction. 



Suppose, then, the existence of an incompressible perfect 

 fluid filling all space and all bodies — the aether. Suppose 

 that in some bodies — copper, silver, &c. — this fluid finds no 

 opposition to motion ; but that in others — air, glass, silk, 

 &c. — the particles of the body are so entangled or embedded 

 in the fluid that the fluid cannot move without carrying along 

 the particles with it ; and that whenever displacement of the 

 medium takes place, a force of restitution is called into play, 

 proportional to the displacement, to the amount of the moved 

 particles, and to a quantity depending on the nature of the 

 body in which the displacement occurs. This last quantity 

 is Maxwell's coefficient. 



In making these suppositions we are not laying upon that 

 maid-of-all-work, the aether, any burden other than those 

 she has for various purposes been already taught to bear. 



Suppose, further, that a positive charge of electricity cor- 

 responds to the forcing an extra quantity of aether into the 

 charged body, and a negative charge to the withdrawal of 

 part of the aether the body contains. 



Then it is easy to show that phenomena similar to those 

 ordinarily ascribed to the attractions and repulsions of elec- 

 trified particles must occur. 



1. Since the aether is incompressible and fills all space, if 

 aether be pumped into one of the first class of bodies (con- 



C2 



