838 Handbook of Nature-Study 



THE MAGNET 

 Teacher's Story 

 NTIL comparatively recent times, the power of the 

 mag-net was so inexplicable that it was regarded as the 

 working of magic. The tale of the Great Black Moun- 

 tain Island magnet described in the "Arabian Nights 

 Entertainments" — the story of the island that pulled 

 the nails from passing ships and thus wrecked them — 

 was believed by the mariners of the Middle Ages. Pro- 

 fessor George L. Burr assures me that this mountain 

 of lodestone and the fear which it inspired were potent factors in the 

 development of Medieval navigation. Even yet, with all our 

 scientific knowledge, the magnet is a mystery. We know what it 

 does, but we do not know what it is. That a force unseen by us is 

 flowing off the ends of a bar magnet, the force flowing from one end 

 attracted to the force flowing from the other and repellent to a force similar 

 to itself, we perceive clearly. We also know that there is less of this force 

 at a point in the magnet half-way between the poles ; and we know that the 

 force of the magnet acts more strongly if we offer it more surface to act 

 upon, as is shown in the experiment in drawing a needle to a magnet by 

 trying to attract it first at its point and then along its length. That this 

 force extends out beyond the ends of the magnet, the child likes to demon- 

 strate by seeing across how wide a space the magnet, without touching the 

 objects, can draw to it iron fihngs or tacks. That the magnet can impart 

 this force to iron objects is demonstrated with curious interest, as the child 

 takes up a chain of tacks at the end of the magnet ; and yet the tacks when 

 removed from the magnet have no such power of cohesion. That some 

 magnets are stronger than others is shown in the favorite game of "stealing 

 tacks," the stronger magnet taking them away from the weaker; it can also 

 be demonstrated by a competition between magnets, noting how many 

 tacks each will hold. 



One of the most interesting things about a magnet is that like poles repel 

 and opposite poles attract each other. How hard must we pull to separate 

 two magnets that have the south pole of one against the north pole of the 

 other ! Even more interesting is the repellent power of two similar poles, 

 which is shown by approaching a suspended magnetized needle with a 

 magnet. These attractive and repellent forces are most interestingly 

 demonstrated by the experiment in question 13 of the lesson. These 

 needles floating on cork join the magnet or flee from it, according to which 

 pole is presented to them. 



Not only does this power reside in the magnet, but it can be imparted to 

 other objects of iron and steel. By rubbing one pole of the magnet over a 

 needle several times, always in the same direction, the needle becomes a 

 magnet. If we suspend such a needle by a bit of thread from its center, and 

 the needle is not affected by the nearness of a magnet, it will soon arrange 

 itself nearly north and south. It is well to thrust the needle through a cork, 

 so it will hang horizontally, and then suspend the cork by a thread. The 

 magnetized needle will not point exactly north, for the magnet poles of the 

 earth do not quite coincide with the poles of the earth's axis. 



The direction assumed by the magnetized needle may be explained by 

 the fact that the earth is a great magnet, but the south pole of the great 



