CH. XXXV. 



AMPERE, 



345 



intellect. For a whole year he was almost an idiot, and it 

 was a long time before he could take up his mathematical 

 studies again. When he did, it was with his old love of 

 work, and he became a teacher first at Lyons, and afterwards 

 in Paris. 



Ampere's Experiments upon Magnetic and Electric 

 Currents, 1820. This was the man who heard of Oersted's 

 discovery in 1820. You can imagine the delight with which 

 he seized upon the new idea. He worked at it incessantly, as 

 he had done with his pebbles when a boy, and before a week 

 was over he had proved several new facts about electro- 

 magnetism. He found that it was quite true as Oersted had 

 said, that the magnet always lies across the electric current; 

 but he showed that the north pole of the magnet turns 

 different ways, according to the direction in which the 



FIG. 55. 



FIG. 56. 



Diagrams showing the direction of a Magnet acted upon by Electric Currents. 



a, b, c, d, Direction of current. 



current flows. Thus, if the current l flows from south to north 

 above the rhagnet, in the direction a b, Fig. 55, then the 

 north pole of the magnet turns towards the west ; but if it 

 runs from north to south above the magnet, in the direction 



1 You must bear in mind that there are always two currents, one 

 from the negative and the other from the positive pole of the battery ; 

 but to avoid confusion the positive current is always spoken of as ihe 

 current. 



