Shen Kuo Describes the Magnetic Compass Needle

1088

In his Dream Pool Essays, the retired polymath Shen Kuo provided the world's first explicit description of a magnetized needle - suspended on silk thread or floated on water - and noted that magnetic north deviated slightly from true north. This observation of magnetic declination, made almost casually amid hundreds of other entries on astronomy, geology, and medicine, would eventually underpin the navigational revolution that made oceanic exploration possible.