On Electric Phenomena. 27 



magnet, then a current is formed in an opposite direction. 

 Naturally, the same occurs, when the magnet is at rest, and 

 the coil in motion. This is most efficiently acquired, when 

 two coils are set in quick rotation before the end of a magnet 

 in the form of a horse-shoe. As the coils alternately approach 

 and retreat from the end of the magnet, a quantity of com- 

 pressed induced currents are produced, which are conveyed 

 outwardly by trailing springs. 



The efPect is essentially increased, if we put in the coils 

 a piece of soft iron curved like a horse-shoe, which must be 

 !set in motion with the coils. Through the approach of the 

 soft iron towards the magnet and its retreat from it, it be- 

 comes alternately magnetic and non-magnetic, and through 

 fthis appearing and disappearing of magnetism, induced 

 currents are also produced in the coils. In this manner 

 the magneto - electric rotation macliine is formed, which 

 is used for medical purposes, and which we often see 

 at fairs, where everybody for a small sum can have the 

 pleasure of trying the wonderful effects of electricity on his 

 : own person. 



The effect of induction through the rise and disappearance 

 of magnetism, can be united with the first kind of induction 

 through the closing and opening of a permanent current. If 

 we, for example, put a piece of soft iron in the first coil, it 

 will become magnetic, if the current be closed, and the ma- 

 gnetism ceases as soon as the current is opened. In this 

 manner, the induced current in the second coil is greatly 

 strengthened. Apparatuses of this kind are principally used 

 medicinally. Through the faciHty, with which it stimulates 

 the nerves and muscles, medical science has not only obtained 

 an important remedy for curing the diseases of these organs, 



(149) 



