Magnetism 



197 



MAGNETIC ATTRACTION 



The positions of the iron filings show where 

 the bar magnet's attractive force lies. 



test the attraction of the N and S poles for each other, noting 



the result in each case. 



Bring into contact with each end of a bar magnet bits of string, 



steel, pasteboard, lead, iron and other materials. Notice which 



are attracted to the magnet. 

 Rub the blade of a pocket 



knife vigorously on a piece of 



lodestone, or on one end of a 



bar magnet, and afterwards 



touch bits of steel and other 



materials with it. Notice 



which objects touched are attracted to the blade. Touch the same 



objects with the blade of a knife which has not been magnetized 



and notice whether they are attracted to the blade. You will 



discover that bits of steel and iron are the only substances much 



attracted to magnetized objects. 

 Law of Magnetic Poles. 

 Experiments made with two 

 magnets of any kind or shape 

 show that the north pole of one 

 magnet will attract the south 

 pole of the other magnet, and 

 the south pole of one will attract 

 the north pole of the other ; but 

 the north pole of the one mag- 

 net will repel the north pole of 

 the other and the south pole of 

 the one will repel the south pole 

 of the other. From experiments 

 like these, the law of magnetic 

 poles has been formed: Like 

 poles repel each other and un- 

 like poles attract each other. 

 The Compass. The fact that a suspended magnet always 



points in a north and south direction was early discovered and 



led to the invention of the compass and of the dipping needle, 



the first of which is all important to seamen who direct 



THE MAGNETIC COMPASS 



It guides the traveler by means of 

 magnetism. 



