124 



GALVANIC ELECTRICITY. 



Explain the 

 figure. 



stant circulation, the direction being dependent on the 

 position in which the magnet is held. In the case of 

 a magnet whose north pole is directed north, the di- 

 rection is from west to east across the upper surface, 

 and of course, in the contrary direction on the under 

 side. The earth acts on a magnet, or a floating coil, 

 as one helix acts on another. The north and south 

 direction of the magnetic needle is a consequence of 

 this action. 



296. THE THEORY ILLUSTRATED. In 

 illustration of this theory, let a globe be 

 coiled with a wire, carrying a current, as indicated in 

 the figure. Let the current flow from east to west 

 through the coil. A small magnetic needle placed at 

 different points on the surface 

 of the globe, however the po- 

 sition of the latter may be 

 changed, will always point to 

 "its north pole. It is under- 

 stood, in this experiment, that 

 the current is strong enough 

 to overcome the influence of 

 the earth itself on the mag- 

 net. A freely movable coil through which a current 

 was passing, would, in this case also, act precisely like 

 a magnet. 



297. MAGNETIC TELEGRAPH. The ex- 



Explain the . . 



principle of planation of the mechanism of the mag- 

 netic tele g, ra P h belongs to Natural Philoso- 

 phy. The principle of its operation may 



