MAGNETS. 



2-U 



each end of the iron alternately, an electric current will be established in 

 the wire. 



(3.) Referring to the first experiment, if we bring a needle in contact 

 with the iron horse-shoe, while the current is passing through the wire we 

 shall find that the needle has become a magnet ; i.e., that it will point due 

 north and south when suspended. 



We will now see what a Magnet is, and why it has obtained this 

 name. 



In Magnesia, in Lydia, in olden times was found a stone of peculiar 



Fig. 239. Magnetic attraction. 



attributes, which had the property of attracting small portions of iron. The 

 Chinese were acquainted with it, and nowadays it is found in many places. 

 In our childhood we have all read of it in the story of " Sinbad the Sailor." 

 Popularly it is known as the loadstone ; chemists call it magnetic oxide of 

 iron (F X O 3 ). This stone is a natural magnet. In Sweden it exists in great 

 quantities as " magnetic iron," for it has a great affinity for that metal. 



If we rub a piece of steel upon the loadstone we convert the former 

 into a magnet an artificial magnet as it is called, and the magnetic needle so 

 useful to us in our compasses and in the working of one form of the electric 

 telegraph is thus obtained. Let us see how this needle acts. 



Fig. 240. Simple touch. 



Fig. 241. Double touch. 



Take a magnetic needle and dust upon it some iron filings. You will 

 observe that the filings will be attracted to both ends of the magnet, but the 

 centre will remain uncovered. The ends of a magnet are termed " poles," 

 the centre the equator. So one end is north and the other south, and we 

 might, perhaps imagine that the same characteristics would abide in the bar 

 when it is cut in two. But we find that as when a worm is divided, each 

 portion gets a new head or tail, and makes a perfect worm, so in the magnet 

 each divided half becomes a perfect magnet with separate poles, one of which 

 always points to the north. 



