METHODS OF ELECTRICAL STIMULATION 57 



Evidently the induced current is of momentary 

 duration. 



Withdraw the magnet quickly. 



The meniscus will move in the opposite 

 direction. 



Insert the south pole. 



The induced current now has the direction 

 opposite to that of the current induced by the 

 insertion of the north pole. 



Withdraw the magnet quickly. 



The induced current has the direction opposite * 

 to that of the current induced by the withdrawal 

 of the north pole. 



These results may be thus expressed : the 

 moving of a magnet in the neighborhood of a 

 conductor, or of a conductor in the neighbor- 

 hood of a magnet, produces in the conductor an 

 electromotive force, which, on the circuit being 

 completed, creates a current that would impart 

 to the magnet or the conductor a movement in 

 the opposite direction. 



Magnetic Field. Lines of Force. The space 

 about a magnet in which the magnetic forces 

 act is called the " field " of the magnet. If very 

 fine iron filings are dusted through a muslin 

 cloth onto a thin card perforated near the centre 

 by a copper wire or other conductor, and a strong 

 current is passed through the wire, the filings will 



