Some of the properties of magnets were known from very early times. For example, it was known over 2,000 years ago that the mineral magnetite, an oxide of iron, possesses the property of attracting iron. The Chinese, earlier than 2,500 B.C., knew that if a piece of magnetite is suspended so that it can turn freely in a horizontal plane it will set in a definite direction and can therefore be used as a primitive compass. Later it was found that if a bar of iron is rubbed with a piece of magnets, which are made by various artificial processes.
Magnets today are usually made of special alloys of steel. A steel magnet differs from ordinary steel and from all other substances in three important respects: It attracts iron filings, it sets in a definite direction when freely suspended, and it converts iron and steel bars in its neighbourhood into magnets. If we place a bar magnet in iron filings it will emerge with a cluster of filings attached to each end, showing that there is a center of magnetic force at each end of the bar. These centers are called the oleos of the magnet. A bar magnet suspended horizontally in a paper stirrup will always set with the line joining its poles along a north and south line; in other words, the magnet has a north-seeking pole and a south-seeking pole. A bar magnet floating on a cork will set roughly north and south but it will not move either bring the north pole of one magnet close to the south pole of another magnet, the unlike poles attract one another, but if we bring two north poles or two south poles into proximity we find that like poles repel one another.