RELATION OF MAGNETISM TO ELECTEICITY. 149 



(Jig. 51) , and though connected with one extreme 

 end of the battery, you see that before the circuit 

 is completed it has no power over the magnet. 

 But observe it when I make contact ; watch the 

 needle, see how it is swung round, and notice 

 how indifferent it becomes if I break contact 

 again ; so you see we have this wire evidently 

 affecting the magnetic needle under these cir- 

 cumstances. Let me show you that a little 

 more strongly. I have here a quantity of wire 

 which has been wound into a spiral, and this 

 will affect the magnetic needle in a very curious 

 manner, because, owing to its shape, it will act 

 very like a real magnet. The copper spiral has 

 no power over that magnetic needle at present ; 

 but if I cause the electric current to circulate 

 through it, by bringing the two ends of the bat- 

 tery in contact with the ends of the wire which 

 forms the spiral, what will happen ? Why one 

 end of the needle is most powerfully drawn to 

 it ; and if I take the other end of the needle it 

 is repelled ; so yoii see I have produced exactly 

 the same phenomena as I had with the bar 

 magnet, one end attracting and the other 

 repelling. Is not this then curious to see that 

 we can construct a magnet of copper? Further- 



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