THEORY OF MAGNETISM 479 



pended magnet, as was done in Experiment 148. Is each half a 

 full magnet or only half a magnet ? Break these halves again and 

 test. .What effect does breaking a magnet have upon the magnet? 



In Experiment 151 it was found that if a magnet is broken 

 in two, each half is a perfect magnet. If these halves are 

 broken, each piece is a perfect magnet, and so on as long 

 as the division is kept up. It is also found that if a magnet 

 is heated or suddenly jarred or pounded it loses its magnet- 

 ism. If a magnet is filed into filings and these filings are 

 put into a glass tube, the tube will have no magnetic prop- 

 erties but will act to a magnet like an ordinary 

 iron bar. 



If now the tube is held vertically and tapped 

 several times on a strong magnet, the tube will 

 be found to have acquired the properties of a 

 magnet. The tapping joggled the particles so 

 that they could arrange themselves under the 

 influence of the magnetic pole and when they be- 

 came so arranged a magnet was the result. If the 

 filings are now poured out of the tube and then 

 put back again, there will be no magnetization. I 



It was the arrangement of the tiny magnetized particles 

 which must have caused the contents of the tube to be- 

 come magnetic. It would therefore seem probable that 

 magnetism must be a property of the exceedingly small 

 particles or molecules of which the iron or steel as well as 

 all other substances are supposed to be composed. 



It is supposed that when a bar of steel becomes magnet- 

 ized the molecules arrange themselves in definite directions, 

 as do the filings in the tube. The molecules of magnetic 

 substances are supposed to be separate little magnets. In 

 the unmagnetized bar (Figure 151) their poles point in all 



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