A LECTURE ON MAGNETISM. 365 



right in your left hand, and cause the test-needle to ap- 

 proach the lower end of your strip ; one end is attracted, 

 the other is repelled. Raise your needle along the strip ; 

 its oscillations, which at first were quick, become slower ; 

 opposite the middle of the strip they cease entirely ; neither 

 end of the needle is attracted ; above the middle the test- 

 needle turns suddenly round, its other end being now at- 

 tracted. Go through the experiment thoroughly ; you thus 

 learn that the entire lower half of the strip attracts one end 

 of the needle, while the entire upper half attracts the oppo- 

 site end. Supposing the north end of your little needle to 

 be that attracted below, you infer that the entire lower half 

 of your magnetized strip exhibits south magnetism, while 

 the entire upper half exhibits north magnetism. So far, 

 then, you have determined the distribution of magnetism in 

 your strip of steel. 



You look at this fact, you think of it ; in its suggestive- 

 ness the value of the experiment chiefly consists. The 

 thought arises, " What will occur if I break my strip of 

 steel across in the middle ? Shall I obtain two magnets, 

 each possessing a single pole ? " Try the experiment ; 

 break your strip of steel, and test each half as you tested 

 the whole. The mere presentation of its two ends in suc- 

 cession to your test-needle suffices to show you that you 

 have not a magnet with a single pole, that each half pos- 

 sesses two poles with a neutral point between them. And 

 if you again break the half into two other halves, you will 

 find that each quarter of the original strip exhibits precisely 

 the same magnetic distribution as the strip itself. You 

 may continue the breaking process ; no matter how small 

 your fragment may be, it still possesses two opposite poles 

 and a neutral point between them. Well, your hand ceases 

 to break where breaking becomes a mechanical impossi- 

 bility ; but does the mind stop there ? No : you follow 

 the breaking process in idea when you can no longer realize 



