History of Chinese Invention - Invention of the Magnetic Compass

As found in the Encyclopedia Britannica, 1999 "Sometime in the 12th century, mariners in China and Europe made the discovery, apparently independently, that a piece of lodestone, a naturally occurring magnetic ore, when floated on a stick in water, tends to align itself so as to point in the direction of the polestar. This discovery was presumably quickly followed by a second, that an iron or steel needle touched by a lodestone for long enough also tends to align itself in a north-south direction." and further that the "Chinese were using the magnetic compass around AD 1100, western Europeans by 1187, Arabs by 1220, and Scandinavians by 1300." This apparently is not a thorough investigation into the origins of the compass, but rather a single observation perhaps from the English scholar Alexander Neckam, who wrote of sailors using a magnetic compass to assist navigation in 1190, De Utensilibus (On Instruments).

Some speculate that in 101 BCE Chinese ships reached the east coast of India for the first time with help from the navigational compass pioneered by the Chinese. They had discovered the orientating effect of magnetite, or lodestone as early as the 4th century BCE. 

The figure to the right shows a working model of the first instrument known to be a compass. The spoon is of magnetic loadstone, and the  plate is of bronze. Rather than navigation, these simple direction pointers were likely used for geomancy, the technique of aligning buildings according to forces of nature.

 

The bowl of water with edge markings (to the left) shows a simple mariner's compass, with a floating magnetized needle pointing north and south.By the time of the T'ang dynasty (7-8th century CE) , Chinese scholars had devised a way to magnetize iron needles, by rubbing them with magnetite, and then suspending them in water (early 11th century). They also had observed that needles cooled from red heat and held in the north-south orientation (the earth's axis) would become magnetic. These more refined needle compasses could then be floated in water (wet compass), placed upon a pointed shaft (dry compass) or suspended from a silk thread. Consequently, they were much more useful for navigation purposes since they were now much more portable (and smaller). A further refinement in the box compass (to the right) is from about 1200 CE, and is much more suitable for navigation. It retains markings of the heaven's plate around its circumference, in a simplified form. Compass markings generally had an inner circle with the eight trigrams and an outer circle with 24 directions based on azimuth points.