Shen Kuo Describes the Magnetic Compass

Around 1088, the former Northern Song statesman and military general Shen Kuo completed an encyclopedic collection of notes known as the Dream Pool Essays. Having fallen from political grace following a Song military defeat against the Western Xia dynasty in the early 1080s, Shen lived in enforced retirement at his estate near modern Zhenjiang in Jiangsu province. Stripped of official responsibilities, he channeled decades of technical inquiry, administrative service, and natural observation into a wide-ranging manuscript. Writing in relative seclusion, he produced an expansive record of eleventh-century Chinese intellectual, artisanal, and scientific life.

The scope of the work extended across medicine, optics, mathematics, architecture, civil engineering, metallurgy, and early archaeology. Among its most prominent technological entries is Shen's description of a needle rubbed with lodestone that points south but deviates slightly to the east, one of the earliest known records of magnetic declination. He also preserved the sole contemporary account of the artisan Bi Sheng, who developed movable type printing between 1041 and 1048 by firing carved clay characters and setting them onto an iron frame with melted resin and wax. In addition, the text preserved China's first recorded description of a drydock used to repair boats out of the water.