If a piece of iron is put on the magnet, then the iron also begins to attract other pieces of iron. And if a steel needle is laid on a magnet and kept there for some time, then the needle itself becomes a magnet, and is able to attract iron to itself.
If two magnets are laid side by side, two of the ends or poles will repel each other; the other two will attract each other. If a magnetic needle be broken in two, then again each half will attract at one pole and repel at the other. And if it be broken again, the same thing will happen; and no matter how many times it is broken, it will be always the same—like poles repelling one another, unlike poles attracting one another; just as if the magnet pushed with one end and pulled with the other.
And, however often you break it, one pole will always push and the other draw.
It is exactly like a pine cone: no matter where it is broken off, one end is always convex, the other hollow. And if they are put end to end, the convex fits into the hollow; but the convex will not fit the convex, nor the cup the cup.
3
If a needle is magnetized by being left some time in contact with a magnet, and is balanced on a point in such a way that it will move freely on the point, then no matter in which direction the magnetic needle is turned, as soon as it is set free, it will come to rest with one pole pointing to the south, the other pointing to the north.
Before the magnet was discovered men did not dare to sail very far out on the sea. Whenever they sailed out of sight of land, then they could judge only by the sun and the stars where they were going. But if it was stormy, and the sun and stars were hid, then they had no way of telling where their course lay; and the vessel would drift before the wind, and be dashed on the rocks and go to pieces.
