188 



GENERAL SCIENCE 



other (Figure 154). These lines are parallel to the lines of force of 

 the magnet and may be said to represent them. Blueprint paper 

 may be used for this experiment, and if held in the sunlight while 



the filings are in place, will 

 give a permanent record of 

 their position, when devel- 

 oped. 



Perform the experiment 

 using two magnets with like 

 poles near each other (Figure 

 155). 



FIG. 154. Direction of the Lines of 

 Force Around a Bar Magnet. 



The magnetic field is 

 the region about a magnet 

 in which magnetic forces 

 can be detected. The 



above experiments show the direction of these forces 

 at every point in the plane cut by the sheet of paper. 

 Each little particle becomes a magnet by induction and 

 arranges itself so that it lies lengthwise in the direction 

 of the lines of force 

 at that point. 



Nature of Magne- 

 tism. Make a small 

 magnet by rubbing a 

 small piece of watch 

 spring on a bar mag- 

 net. Test its strength 

 on some filings or 

 small nails. Heat the 

 piece of watch spring 

 and again test its 

 magnetism. Make another such magnet and hammer it. 

 Its magnetism will be found to be much diminished. 

 Fill a small test tube with iron filings and stroke the 



FIG. 155. Showing the Direction of the 

 Lines of Force when the Like Poles of Two 

 Magnets are Brought Near Each Other. 



