88 THE FAIRY-LAND OF SCIENCE. 
on this white cardboard, have been rubbed along a 
magnet until they have become magnets themselves, 
and I can attract and lift up a needle with any one of 
them. But if I try to lift one bar with another, I can 
only do it by bringing certain ends together. I have 
tied a piece of red cotton (c, Fig. 21) round one end 
of each of the magnets, and if I bring two red ends 
together they will not cling together but roll apart. 
If, on the contrary, I put a red end against an 
end where there is no cotton, then the two bars cling 
Fig. 21. 
A B 
c 
Bar magnets attracting and repelling each other. 
c, Cotton tied round the north pole of the magnet. 
together. This is because every magnet has two 
poles or points which are exactly opposite in character. 
One of these is called the north pole of the magnet, 
because, if the rod hangs freely, that end will point to 
the north, and the other is the south pole, pointing to 
the south. Now, when I bring two red ends, that is, 
two north poles together, they drive each other away. 
See ! the magnet I am not holding runs away from 
the other. The same will happen if I bring two 
south poles together. But if I bring a red end and 
