14 



ON MAGNETISM. 



ously in its position ; and, if it is drawn aside for a 

 moment, it returns rapidly to that position. Lower 1$ 

 gradually : at a certain elevation of B, the needle A 

 will become indifferent to position, and if drawn aside 

 will not return to its former direction. Lower B still 

 more, and A will reverse its position, its red end 

 pointing to the south, as in Figure 4. 



Fig. 4. 



A 



O- 



It is evident here that, at the second or inter- 

 mediate position of B, the action of B is sensibly 

 neutralized by the Earth's action. But, as we have 

 remarked in the last article, the action of B may be 

 neutralized by that of another magnet, at a proper 

 distance, with its red pole to the south. Consequently, 

 the Earth's action is exactly the same as that of a 

 magnet whose red pole is south, and for magnetic 



