16 ON MAGNETISM. 



balanced by its action on the other, and the united 

 frame is indifferent to terrestrial magnetism. But one 



Fig. 6. 



of the needles may be brought so near to the magnet 

 whose force is to be tried that the comparative in- 

 fluence on the more distant needle may sometimes 

 be neglected ; and the experiments on the action of the 

 magnet on the nearer needle will not differ much from 

 what they would have been if terrestrial magnetism 

 did not exist. 



12. Experimental examination of the action of a 

 large magnet on a small needle. Third Law of Mag- 

 netism ; the magnetism collected in or near each pole of 

 a magnet acts (as to sense) equally in all directions. 



Underneath a table, let a large magnet be placed 

 with its red pole north, at such a distance (determined 

 by trial with a small needle on the table) that on the 

 surface of the table the Earth's magnetism is sensibly 

 neutralized. Place in that region a magnet of mode- 

 rate size, carry round it a small compass, and register 

 the positions of its needle. A ^ ;ries of directions is 



