ELEMENTARY LESSONS ON [CHAP. n. 



so as to have neither external field nor poles ; or rather 

 any point in it may be regarded as a N. pole and a S. 

 pole, so close together that they neutralise one another's 

 forces. 



That poles of opposite name do neutralise one another 

 may be shown by the well-known experiment of hanging 

 a small object a steel ring or a key to the N. pole of 

 a bar magnet. If now the S. pole of another bar magnet 

 be made to touch the first the two poles will neutralise 

 each other's actions, and the ring or key will drop down. 



1O6. Breaking a Magnet. We have already stated 

 that when a magnet is broken into two or more parts, each 

 is a complete magnet, possessing poles, and each is 

 nearly as strongly magnetised as the original magnet. 

 Fig. 48 shows this. If the broken parts be closely joined 





Fig. 48. 



these adjacent poles neutralise one another and disappear, 

 leaving only the poles at the ends as before. If a magnet 

 be ground to powder each fragment will still act as a 

 little magnet and exhibit polarity. A magnet may there- 

 fore be regarded as composed of many little magnets 



put together, so that their like poles all face one way. 

 Such an arrangement is indicated in Fig. 49, from which 

 it will be seen that if the magnet be broken asunder across 

 any part, one face of the fracture will present only N. 



