Faraday's Discoveries 



variometer wire, and its equator with the other 

 end, electricity rushes round the galvanometer 

 from the rotating magnet. He remarks upon 

 the "singular independence" of the magnetism 

 and the body of the magnet which carries it. 

 The steel behaves as if it were isolated from its 

 own magnetism. 



And then his thoughts suddenly widen, and 

 he asks himself whether the rotating earth does 

 not generate induced currents as it turns round 

 its axis from west to east. In his experiment 

 with the twirling magnet the galvanometer wire 

 remained at rest; one portion of the circuit was 

 in motion relatively to another portion. But in 

 the case of the twirling planet the galvanometer 

 wire would necessarily be carried along with the 

 earth; there would be no relative motion. What 

 must be the consequence ? Take the case of a 

 telegraph wire with its two terminal plates 

 dipped into the earth, and suppose the wire to lie 

 in the magnetic meridian. The ground under- 

 neath the wire is influenced like the wire itself by 

 the earth's rotation; if a current from south to 

 north be generated in the wire, a similar current 

 from south to north would be generated in the 

 earth under the wire; these currents would run 

 against the same terminal plates, and thus neu- 

 tralize each other. 



This inference appears inevitable, but his 

 profound vision perceived its possible invalidity. 

 He saw that it was at least possible that the dif- 

 ference of conducting power between the earth 

 17 



