ELECTRO-MAGNETIC ENGINES. 715 



passes out through the piece h to k. , At starting, a and 

 c are thus south poles, and b and d north poles ; repulsion 

 therefore takes place between a and c and between b 

 and d, that is, the straight magnet will begin to rotate 

 in the direction of the arrow ; c approaches #, and d 

 approaches a. This motion would cease as soon as c is 

 close and opposite to i, and d to a, for contrary poles 

 are then in juxtaposition, and the attraction is greatest ; 

 but at the moment when the movable magnet is thus 

 in a straight line between the two legs of the horse -shoe, 

 the free ends of the spiral around it reach the inter- 

 vening space between the metal pieces h and //, and 

 are no longer in contact with a metallic conductor; 

 hence the current is interrupted, and the attraction be- 

 tween c and b on one side, and d and a on the other, 

 ceases instantaneously. The consequence of this is that 

 c does not really stop when opposite to 6, but by its 

 inertia moves a little beyond b, while in the same way 

 d does not stop opposite to a, but continues its motion 

 until it is a little in front of a. In this position, how- 

 ever, the free ends of the spiral are again brought in 

 contact with the pieces h and #, but now the free end 

 which proceeds from d is in contact with 7i, the free 

 end from c touches//; the current is again closed, but 

 it traverses the spiral of the movable magnet in a 

 direction exactly opposite to that which it had at first ; 

 it enters at the end c, making c a north pole, and leaves 

 the spiral at 6?, making d a south pole. Since b re- 

 mains a north pole, and c, which is a little behind it, 

 has now also become a north pole, c is repelled farther 

 away from b, that is, the motion is continued in the 

 direction of the arrow. Repulsion with similar effect 



