If you magnetize a needle (holding it for awhile over a magnet), and attach it in the middle to a pivot in such a way that it can move freely around, and let it loose, it will turn with one end toward midday (south), and with the other toward midnight (north).

When the magnet was not known, people did not sail far out to sea. When they went out far into the sea, so that land was not to be seen, they could tell only by the stars and the sun where they had to sail. But when it was dark, and the sun or stars could not be seen, they did not know which way to sail. And a ship was borne by the winds and carried on rocks and wrecked.

So long as the magnet was not known, they did not sail far from the shore; but when the magnet was discovered, they made a magnetic needle on a pivot, so that it should move around freely. By this needle they could tell in which direction to sail. With the magnetic needle they began to sail farther away from the shores, and since then they have discovered many new seas.