Voltaic Induction. 35 



polar surface, then, upon moving it upwards, the outer surface of 

 that margin will receive induction and establish a positive current 

 moving from the observer; but upon pulling it back again to its first 

 position, it is the inner surface that generates the magnetic circles 

 and the rotation, being obviously the reverse of the former, the pos- 

 itive current will move towards the observer. All these results are 

 fully confirmed by the currents actually formed. 



If, instead of a ring, we employ a flat coil, covered throughout 

 its length with silk or other non-conductor of electricity, the cur- 

 rent may be conducted either to the circumference or the centre, 

 by simply subjecting the opposite sides to the same kind of motion 

 before the magnet; but the inversion of the current is still only appa- 

 rent and the result always conforms with the magnetic rotation, as in- 

 dicated by theory. The mechanical construction of a flat coil is 

 such, that, when we look at the winding upon one side, which turns 

 from left to right, over, that, upon the other, becomes from right 

 to left, the opposite of the former. Hence it happens that a cur- 

 rent, always having the same direction, will pass to the centre of 

 the coil, if one side be exposed to the magnet, and to the circumfe- 

 rence, if we substitute the other. The current necessarily follows 

 the curvature of the wire in consequence of its insulation. Thus, 

 if we take a perpendicular wire conducting downwards the positive 

 current, and bend it either to the right or left, we give a correspond- 

 ing direction to the current, so that the rotating magnetic pole which 

 revolves horizontally from right to left across the near side, may be 

 made to turn over vertically, from above downwards or from below 

 upwards. The natural position of the transverse magnetic forces is 

 in planes parallel to each other, but, as the curvature of a coil or he- 

 lix necessarily destroys this condition, without any obvious diminu- 

 tion of intensity, we may infer that these magnetic circles have but 

 little action upon each other, laterally. 



Perhaps we could not have a better proof of the truth of the hy- 

 pothesis offered in this communication, than that furnished by exam- 

 ining the influence which a magnet exerts upon a flat coil, in its dif- 

 ferent positions. Thus, when the axis of motion is common to the 

 magnet and coil, so that both may be made to revolve singly or con- 

 jointly, the theory indicates that the magnetic circles, instead of distri- 

 buting themselves laterally either to the centre or circumference, so as 

 to form a continuous current, actually revolve in planes parallel to the 

 coil, and consequently the voltaic currents must circulate transversely 



