Prof. E. Edlund on Unipolar Induction, 303 



suits accordant with the experiment. The principle on which 

 it rests, that the magnet acts upon the electric currents due to 

 the rotation of the conductor with respect to the magnet in 

 the same way as upon ordinary currents, this principle cannot, 

 as far as I can see, give occasion for any doubt. The only 

 objection which it would be possible to make to it would be 

 that, the velocity we are able to impart to the conductor being 

 relatively slight, these currents become so feeble that the 

 action of the magnet upon them is in reality inappreciable. 

 But to this remark it may be replied that the velocity of the 

 electric molecules in an ordinary galvanic current has never 

 been measured ; several physicists have assumed, upon good 

 grounds, that this velocity is in reality not very great ; it is 

 therefore not improbable that the velocity which it is possible 

 to impart mechanically to a conductor is comparable to that 

 of the electric molecules in a galvanic current of average in- 

 tensity. We must here carefully distinguish between the 

 velocity with which the electric movement is propagated from 

 place to place and that with which the molecules themselves 

 move. These two velocities have no relation with each other; 

 thus, as experiment shows, the former velocity may be ex- 

 tremely great, although the latter be insignificant *. 



As the electric molecules are carried along in the direction 

 in which the conductor is moved, it might perhaps seem, pre- 

 vious to mature reflection, that a cylindrical tube set in rota- 

 tion about its axis must exert an electro dynamic action in the 

 same manner as a coil through which a galvanic current passes. 

 Such an inference, however, is any thing but justified. If we 

 admit two electric fluids, one positive and one negative, it will 

 be noticed that both fluids are conveyed with the same velocity 

 and in the same direction during the movement of the con- 

 ductor ; therefore these curents mutually destroy their reci- 

 procal effects. Even if it be admitted that the electric phe- 

 nomena proceed from one fluid only, the above conclusion is 

 premature. But to prove this it is necessary to revert to the 

 principles of the theory as previously explained by mef. 



The phenomena of optics have led to the assumption that 

 the aether is attracted by ponderable matter. A material body 

 condenses the aether between its molecules until the attraction 

 exerted upon an aether molecule situated within the body by 

 the molecules of the body becomes equal to the repulsion ex- 

 erted by the already condensed aether upon the same aether 

 molecule. When this point is reached the material body is no 

 longer in a position to put in motion the external molecule of 

 aether. Besides that quantity of aether which may be regarded 

 * Thiorie des Phenomenes Electriques, p. 10. f Ibidem. 



