MAGNETIC ATTK ACTION. 115 



it attracts these keys, two or three in succession, 

 and it will attract a very large piece of iron. 

 That then is a very different thing indeed to 

 what you saw in the case of the shellac, for that 

 only attracted a light ball, but here I have 

 several ounces of iron held up. And if we come 

 to examine this attraction a little more closely, 

 we shall find it presents some other remarkable 

 differences ; first of all, one end of this bar (fig. 

 37) attracts this key, but the middle does not 

 attract. It is not then the whole of the sub- 

 stance which attracts. If I place this little key 

 in the middle it does not adhere; but if I place 

 it there, a little nearer the end, it does, though 

 feebly. Is it not then very curious to find that 

 there is an attractive power at the extremities 

 which is not in the middle ! to have thus in 

 one bar two places in which this force of attrac- 

 tion resides. If I take this bar and balance it 

 carefully on a point, so that it will be free to 

 move round, I can try what action this piece of 

 iron has on it. Well, it attracts one end, and 

 it also attracts the other end, just as you saw 

 the shellac and the glass did, with the exception 

 of its not attracting in the middle. But if now, 

 instead of a piece of iron, I take a magnet, and 



