292 Prof. E. Edlund on Unipolar Induction. 



an element of current, which law, as is known, is formulated 

 as follows : — A single magnetic pole acts on a current-element 

 ils with a force directly proportional to the product of the 

 magnetic moment M of the pole, the intensity i of the current, 

 and the sine of the angle X between the current-element and 

 the straight line joining the pole of the magnet to the same 

 element, and inversely proportional to the square of the dis- 

 tance r between these last. The force in question may there- 

 fore be expressed by § • ^he point of application of 



the force is situated in the current-element ; and its direction 

 is perpendicular to the plane which passes through the mag- 

 netic pole and the current-element. The sense in which the 

 force acts upon the said direction depends, moreover, on the 

 direction of the current and the nature of the pole. 



When the cylinder is put in rotation about the fixed mag- 

 net, the electric fluid or the two fluids (if we admit two) put 

 themselves in rotation in the same direction. They form, then, 

 currents with a horizontal circulation round the vertical mag- 

 net ; and their intensity will be proportional to the velocity of 

 the rotation. 



The sole difference between these currents and ordinary 

 galvanic currents is, that the two fluids (if they are two in 

 number) follow the same direction, while in ordinary galvanic 

 currents they take opposite directions. But, according to the 

 usual ideas, the action of the magnet upon the negative cur- 

 rent is the same as its action upon a positive current going in 

 the opposite direction. Now the poles of the magnet act, in 

 virtue of the law above cited, upon the currents produced by 

 the rotation of the cylinder ; and the consequence of this will 

 be that the cylinder will receive an excess of sether (electro- 

 positive fluid) at its two extremities, and a deficiency of aether 

 (electronegative fluid) in the centre, or vice versa, according 

 to the direction of the rotation and the position of the poles. 

 In a conducting wire, one of the extremities of which is in 

 contact with the centre, and the other with one of the edges 

 of the cylinder, there will necessarily arise a galvanic current. 

 The direction of the current thus produced and the augmen- 

 tation of its intensity with that of the velocity of rotation are 

 perfectly like what takes place in experiment. 



In opposition to this view the following objection may now 

 be raised : — If the rise of the unipolar induced current depends 

 on the electric molecules commencing to move round the 

 magnet at the same time as the conductor in which they are 

 present, a similar induced current should also arise if, the con- 

 ductor and the electric molecules remaining at rest, the mag- 



