China was the earliest country to discover and use magnetic materials. Large-scale sifting and smelting of iron ores led to the discovery of magnets, while the booming navigation on the high seas called for direction-pointing instruments; these social demands motivated the progress of such instruments.
Over 2,000 years ago, in theWarring States Period(475-221BC), Chinese ancestors invented the earliestcompass-- Si Nan, also known as the South Pointer.
Different from the compass of today, Si Nan was composed of two parts: a spoon and a tray. The spoon was cut from an intact piece of natural loadstone, with its handle as the South Pole and its round, smooth bottom as the center of gravity. The tray, on the other hand, was made ofbronze, and at the center, there was a round, smooth groove. When the spoon was put into the groove, it would rotate. When
|Pointing-to-the-south fish made by Cheng Yuanliang of the Yuan Dynasty
the spoon stopped, its handle would point to the south, and its head to the north. This instrument was the predecessor of the magnetic compass. However, since it was easy for natural loadstone (magnetic iron oxide) to lose its magnetism, Si Nan could not be widely used.
During theNorthern Song Dynasty(960-1127), artificial magnetization was discovered, giving rise to the Pointing-to-the-South Fish, which was made from a piece of thin iron sheet cut into the shape of a fish, magnetized in a geomagnetic field, and put into water, floating and lying north-to-south. However, due to its weak magnetic field, Pointing-to-the-South Fish was not of much practical value.
Through magnetizing a steel needle by rubbing it on a natural magnet, people invented the earliest artificially magnetic compass, which pointed south when floated on water or suspended. Later it was attached to a bowl with directional points.