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The magnetic compass

The Chinese may have been aware of magnetism since the second millenium BC, since houses of the Shang dynasty are aligned with magnetic north, but the first mention in writing is from the fourth century BC:

'When the people of Cheng go out to collect jade, they carry a south-pointer with them so as not to lose their way.'
The Book of the Devil Valley Master, quoted by Robert Temple, The Genius of China, p.151

The earliest compass was a piece of naturally-magnetic lodestone. The idea of temporarily magnetising a needle by stroking it with a lodestone came later, and the induction of remanent (persistent) magnetism later again. Dr Joseph Needham reckoned that the use of the compass at sea probably started between 850 and 1050 AD, and mentioned that the French scholar Saussure, himself a keen sailor:

'... pointed out that the use of the compass in navigation depended to some extent upon metallurgical procedures for the production of steel. Soft iron does not retain its magnetism long, or show it strongly; for extended voyages magnetized needles of good steel would have been desirable. De Saussure considered that the Chinese narratives of deep-water sailing, which we have from the thirteenth century AD, such as the embassy to Cambodia, would not have been possible without steel needles... It may well be... that good steel needles were available to the Chinese several centuries before Europe had them... failing them, lodestones had to be carried on board every ship for remagnetization, as Bromehead has described, quoting from a book on navigation of 1597.'
Robert Temple, The Genius of China, p.150.

The induction of remanent magnetism in iron was described in 1044, with the magnetic 'fish' being distinguished from the south-pointing carriage, which was a non-magnetic mechanical device:

'When troops encountered gloomy weather or dark nights, and the directions of space could not be distinguished, they let an old horse go on before to lead them, or else they made use of the south-pointing carriage or the south-pointing fish to identify the directions. Now the carriage method has not been handed down, but in the fish method a thin leaf of iron is cut into the shape of a fish two inches long and half an inch broad, having a pointed head and tail. This is then heated in a charcoal fire, and when it has become thoroughly red-hot, it is taken out by the head with iron tongs and placed so that its tail points due north. In this position it is quenched with water in a basin, so that its tail is submerged for several tenths of an inch. It is then kept in a tightly closed box. To use it, a small bowl filled with water is set up in a windless place, and the fish is laid as flat as possible on the water surface so that it floats, whereupon its head will point south.'
Tseng Kung-Liang, Compendium of Important Military Techniques, 1044AD, quoted by Robert Temple, The Genius of China, p.155.

The tightly closed box is thought to have had a lodestone base. The practice of 'nourishing the needle' to strengthen its magnetism by additional contact with a lodestone has continued into modern times.

Magnetic deviation was recorded by the Chinese in the eighth or ninth century, according to Needham, and compass roses of the eleventh century certainly incorporate the necessary adjustments from magnetic to true north.

Regulations and navigation for Chinese sea-going ships were described in 1117 AD by Zhu Yu, son of Zhu Fu who had in 1098-1106 been a high port official and then governor of Guangzhou:

'According to the government regulations concerning sea-going ships, the larger ones can carry several hundred men, and the smaller ones more than a hundred men on board... The ships' pilots are acquainted with the configuration of the coasts; at night they steer by the stars, and in the day-time by the sun. In dark weather they look at the south-pointing needle. They also use a line a hundred feet long with a hook at the end, which they let down to take samples of mud from the sea-bottom; by its appearance and smell they can determine their whereabouts.'
Zhu Yu, Pingzhou Ketan (Pingzhou chats), 1117 AD, quoted by Robert Temple, The Genius of China, p.150; Shen Fuwei, Cultural flow between China and the outside world, p.220; text of Pingzhou Ketan shown in The Maritime Silk Route, 1996, p.88.

- and further descriptions were given in the next few years:

'During the night it is often not possible to stop because of wind or current drift, so the pilot has to steer by the stars and the Great Bear. If the night is overcast then he uses the south-pointing floating needle to determine south and north.'
Hsü Ching, Illustrated record of an embassy to Korea in the Hsüan Ho reign period, 1124 AD, quoted by Robert Temple, The Genius of China, p.150.

'During dark or rainy days, and when the nights are overclouded, sailors rely on the compass. The Mate is in charge of this.'
Meng Yuan-Lao, Dreams of the Glories of the Eastern Capital, 1126 AD, quoted by Robert Temple, The Genius of China, p.150.

The compass was first mentioned by a European in 1190AD:

'The sailors, moreover, as they sail over the sea, when in cloudy weather they can no longer profit by the light of the sun, or when the world is wrapped up in the darkness of the shades of night, and they are ignorant to what point of the compass their ship's course is directed, they touch the magnet with a needle. This then whirls round in a circle until, when its motion ceases, its point looks direct to the north.'
Alexander Neckam, De Naturis Rerum, quoted by Robert Temple, The Genius of China, p.149

Arabic references to the compass start in about 1232, and refer to a fish-shaped piece of iron rubbed with a magnet [Temple, p.149]; the fish shape was typically Chinese.

The first version of this page has been compiled from Robert Temple's summary of the work of Dr Joseph Needham, but references have been given with each quotation, as they may be replaced in due course by translations of the primary sources, or supplemented with additional references.

Shen Fuwei, Cultural flow between China and the outside world, Foreign Languages Press, Beijing, 1996. ISBN 7-119-00431-X.

Robert Temple, The Genius of China: 3000 years of science, discovery and invention (described by Dr Joseph Needham as a 'brilliant distillation' of his multi-volume Science and Civilisation in China). Prion, UK, 1986. ISBN 1-85375-078-6

The Maritime Silk Route, 2000 years of trade on the South China Sea, ed. Joseph S.P. Ting, Hong Kong Museum of History, 1996. ISBN 962-7039-34-9.

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