OTHER MAGNETS 83 



other end of the magnet to the clock spring. You should not 

 see any difference in the result. 



b. Touch one end of the clock spring to one end of the mag- 

 net, and then touch the other end of the clock spring to the 

 other end of the magnet. This magnetizes the clock spring. 

 Support the clock spring as before, and repeat (a). Do this 

 several times and make a complete statement of your ob- 

 servations. 



c. Remove all magnets and iron from near the clock spring 

 and it will take a definite direction due to the earth's mag- 

 netism. How does this compare with the direction of the 

 true north? 



62. OTHER MAGNETS 



Besides the earth, there are other magnets, some natural 

 and some which are made by man. A certain ore of iron, 

 called magnetite, on account of its peculiarity, has a weak 

 attraction for iron and steel. Suitable pieces of this ore are 

 sometimes mounted with iron ends, and are capable of holding 

 up a mass of iron which is equal to their own weight. Power- 

 ful magnets are made from steel bars which have received their 

 magnetism through the agency of electricity. If a wire covered 

 with cotton, silk, or some other material through which elec- 

 tricity does not readily pass, is wound around a piece of iron, 

 and a current of electricity allowed to pass through the wire, 

 the iron will become a strong magnet, attracting other pieces 

 of iron and steel with considerable force. As soon as the 

 electricity ceases to pass through the wire around the iron, 

 the iron loses its magnetism. If, on the other hand, a simi- 

 lar electric current is passed around steel, the magnetism 

 remains in the steel, after the electric current has been dis- 

 continued. Therefore a steel magnet is called permanent. 



