86 M. E. Edlund on the Nature of Electricity. 



Hence we shall obtain^ by the same process as before, the fol- 

 lowing expression for the attraction between the two bodies : — 



bb. 



r^ 



The attraction here, therefore, follows the known law. 



Let us now suppose that a body A, with excess of aether, acts 

 upon another body, B, originally in the normal condition, and 

 a good conductor of the sether. A having an excess of aether, 

 the repulsion upon all the aether molecules of B will be stronger 

 on the side opposite to A than on any other. The necessary 

 result of this will be, that the aether will collect on the side of B 

 which is not turned towards A, leaving a deficit on the side 

 facing A. 



If, on the contrary, A has a deficiency of aether, any molecule 

 whatever of the aether of B will necessarily be more strongly re- 

 pelled by the surrounding medium in the direction towards A 

 than in any other ; here, then, an excess of aether will be 

 formed, accompanied by a deficit on the opposite side. 



It is evident that, in both these cases of induction, attraction 

 must be produced between the two bodies ; for the distance be- 

 tween the excess of one and the deficit of the other is always less 

 than the distance between the two deficits or the two excesses. 



It is easy to demonstrate that the excess or deficit of aether 

 must place itself at the surface of the body. Let there be a 

 body. A, having a certain quantity of aether a-\-b, of which b is 

 the excess. It is evident that the aether of the surrounding space 

 and the quantity « in A must balance each other, and therefore 

 can exert no action upon a molecule of the excess b. With regard 

 to the distribution of the excess, it is just as if the whole of the 

 surrounding quantity of aether and the quantity « in A did not 

 exist ; the excess, then, must behave as if it alone existed ; and 

 in that case it would place itself at the surface, as Poisson has 

 demonstrated. 



That the deficit must equally place itself at the surface can be 

 demonstrated in the following manner. Let us at first suppose 

 that the body A contains the same quantity of aether as in the 

 normal condition. Then any molecule of the aether of A is in 

 equilibrium, seeing that all the repulsions annul one another, or, 

 in other terms, have a resultant = 0. It follows that the result- 

 ant of the repulsions of all the molecules of the surrounding 

 medium must be equal to the resultant of the repulsions of the 

 aether molecules within the body, and act in a direction opposed 

 to the latter. But we know that the aether molecules of the 

 body tend, in consequence of their mutual repulsion, to place 

 themselves at its surface. The resultant of the repulsion of all 



