M. E. Edlund on the Nature of Electricity, 83 



elastic substance diffused throughout the universe, not only in 

 empty space, but also in the parts occupied by ponderable mat- 

 ter. We likewise assume that two molecules of aether, placed at 

 a distance one from the other, repel each other along their line 

 of junction and in the inverse ratio of the squares of the dis- 

 tances. The electric aether therefore most closely resembles an 

 ordinary gas. With respect to the relations of the aether to all 

 other matter, the only hypothesis we need to make is, that, in the 

 bodies called good conductors of electricity, the aether contained 

 in them (or at least a portion of it) moves with facility from one 

 point to another. We suppose further that, in imitation of what 

 takes place in an ordinary gas, the molecules of the electric 

 aether move readily — that is, can be displaced by the least effort. 

 In a nonconductor of electricity this mobility is arrested, and 

 depends on that of the molecules of the material substance which 

 contains the aether. If the nonconductor is a gas or a perfectly 

 fluid liquid, the aether particles conserve their mobility, trans- 

 porting themselves then with the gas or liquid particles. From 

 this mobility it necessarily follows that the hydrostatic pressure 

 must be equal in all directions, as in liquids and ordinary gases. 

 To the aether, therefore, can be applied the principle of Archi- 

 medes, that a body introduced into a fluid loses a quantity of 

 weight equal to the weight of the fluid displaced — although of 

 course we have here to do, not with gravity, but repulsion be- 

 tween the aether molecules. Much light has been thrown upon 

 the application of this principle to the question before us by 

 some of Pliicker^s well-known diamagnetic experiments. He 

 found that a magnetic body with a magnetic force inferior to 

 that of the liquid in which it was suspended was repelled by the 

 poles of the magnet, and that a diamagnetic body suspended in 

 a magnetic liquid was more strongly repelled by the same poles 

 than when it was in a less-magnetic liquid or gas*. An aether 

 molecule is at rest from the moment in which it is equally re- 

 pelled on all sides. A material body cannot be moved by elec- 

 trical action, if the aether contained in it is equally repelled on 

 all sides. If the repulsion is less on one side than on the other, 

 the body must, if free, move in the direction determined by the 

 resultant of the repulsive forces. To determine the motion pro- 

 duced in a body B in consequence of another body. A, being in 

 its vicinity, we may, without restricting in any degree the solu- 

 tion of the problem, regard A as fixed and motionless, and B 

 alone as free. It will then be necessary to take into consider 

 ration : — 



1, The action exerted directly between the aether of A and 

 that of B. 



* Pogg. Ann. vol. Ixxvii. p. 578. 

 G2 



