MAGNETS 245 



other, and especially not in contact, because the stronger 

 of the two will weaken, reverse, or completely destroy 

 the magnetism of the other, or else make secondary poles. 



168. How to Magnetize Steel. The simplest method 

 of magnetizing a small piece of steel is to draw the steel 

 slowly across one end of a magnet. The end of the steel 

 leaving the magnet will have a pole opposite that of the 

 end of the magnet across which 



the steel was drawn. The second 



method is to lay the steel on the sT N 



table and take a bar magnet in each MAGNETIZING A PIECE OF 



hand and touch opposite poles, N 



and S, together on the middle of the piece of steel and 



then slowly draw the magnets apart toward the ends of 



the piece of steel. 



169. The Earth a Magnet. We have learned that mag- 

 nets attract each other if unlike poles are placed near to- 

 gether, and repel each other if like poles are placed near 

 together, and that magnets do not attract or repel objects 

 which are not magnets or which cannot be made magnets 

 by induction, that is, magnets do not attract or repel glass, 

 paper, and similar substances. Hence we may say that 

 magnets only attract or repel poles of magnets or poles 

 of substances which are made temporary magnets by in- 

 duction. This being true, there must be a magnetic pole 

 somewhere in the north which attracts one pole of a 

 balanced magnet, such as a .compass needle, and repels 

 the other pole, which in turn is attracted by a magnetic 

 pole somewhere near the south geographic pole. 



We have also found that the needle of a small compass 

 places itself parallel with the lines of force coming from 

 the N pole and going to the S pole of a bar magnet. 

 Since a compass acts on the earth the same as it does 



