ELECTKO-MAGNETISM. 1 51 



than this of the relation of the powers of mag- 

 netism and electricity ? Again, here is a little 

 piece of iron which is not yet magnetised. It 

 will not at present take up any one of these 

 nails ; but I will take a piece of wire and coil it 

 round the iron (the wire being covered with 

 cotton in every part it does not touch the iron), 

 so that the current must go round in this spiral 

 coil I am, in fact, preparing an electro-magnet 

 (we are obliged to use such terms to express our 

 meaning, because it is a magnet made by elec- 

 tricity, because we produce by the force of 

 electricity a magnet of far greater power than a 

 permanent steel one). It is now completed and 

 I will repeat the experiment which you saw the 

 other day, of building up a bridge of iron nails ; 

 the contact is now made and the current is 

 going through ; it is now a powerful magnet ; 

 here are the iron nails which we had the other 

 day, and now I have brought this magnet near 

 them they are clinging so hard that I can 

 scarcely move them with my hand (Jig. 53). 

 But when the contact is broken, see how they 

 fall. What can show you better than such an 

 experiment as this the magnetic attraction with 

 which we have endowed these portions of iron ? 



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