Helaine Selin, The origin of the magnetic compass is obscure

Medieval and Renaissance European compasses have been analyzed in detail, but until recently little work has been done on their history in non-Western cultures.

Most modern accounts place the birth of the magnetic compass in ancient China, but its inventors are unknown, its development unclear, and historians are divided over whether its later appearance in the West was independent, or borrowed from China through overland or Arabic maritime intermediaries. The Chinese compass seems to have been derived from a “south controlling spoon” (si nan shao) carved from lodestone (magnetite) and used in the early diviners’ boards the Han Dynasty (202 BCE–AD 220).

Just as in ancient Greece, Chinese philosophers were first aware of magnetic attraction; the ability of the lodestone to pick up iron was mentioned in the Lü Shi Chun Qiu (Master Lu’s Spring and Autumn Annals, third century BCE), the Lun Heng (Discourses Weighed in the Balance, AD 83), and a host of other Chinese annals between the third century BCE and the sixth century AD. The discovery of magnetic directivity (the tendency of magnets to point north and south) made the lodestone particularly important in geomancy and divination. Historian Joseph Needham argued that this was known publicly by the first century AD, and may have been a secret of court magicians as early as the second century BCE.

Between the first and sixth centuries AD, Chinese scholars discovered that magnetic directivity could be induced in small iron needles by stroking them on lodestones. These needles, when floated in bowls of water (sometimes hidden inside carved wooden fish), would then guide Chinese navigators by pointing to the north and south; these early “wet compasses” were the first type. The second variety, a “dry compass” consisting of a needle mounted on a pivot (often concealed inside a wooden turtle), was developed much later (early twelfth century). Chinese encyclopaedias such as the Taiping Yulan (Taiping Reign-Period Imperial Encyclopaedia) also mention “dry” compasses made by suspending a magnetic needle on a silk thread.

Chinese physicists may also have been first in discovering magnetic declination. The fact that the compass does not point exactly to the geographic north, but rather to the magnetic north a few degrees away, was mentioned in philosopher Shen Gua’s Meng Qi Bi Than (Dream Pool Essays) in 1088 AD. He says the compass needle “always inclines slightly to the east.” Knowledge of this effect was extremely important for ocean navigation. Chinese knowledge of declination goes back to the late Tang period (eighth–ninth centuries AD).

The development of the magnetic compass in India is highly uncertain. According to some scholars, the compass is mentioned in fourth century AD Tamil nautical books; moreover, its early name of macchayantra (fish machine) suggests a possible Chinese origin. In its Indian form, the wet compass often consisted of a fish-shaped magnet, floated in a bowl filled with oil.

The earliest references to the magnetic compass in Europe appear in the grammatical and philosophical treatises De Nominibus Utensilium and De Naturis Rerum of English monk Alexander Neckam (1157– 1217), French poet Guyot de Provins’ (fl. 1184–1210) La Bible, and the Historia Orientalis seu Hierosolymitana of French preacher Jacques de Vitry (ca. 1165– 1240). Based on these sources, historians have dated the European appearance of both dry and wet compasses to the middle of the twelfth century.

Among Arabic sources, the earliest descriptions of the magnetic compass occur in the thirteenth century. A Persian collection of stories, the Jāmi˓al-H. ikāyāt (ca. 1232) of Muh.ammad al-˓Awf ī says that sailors navigate using a piece of iron rubbed by a magnet, and the 1282 lapidary of Bailak al-Qabajaqi, the Kanz al-Tijar, mentions a wet compass seen in 1242. Some of these early treatises discuss the use of fish-shaped compass needles among Islamic navigators in the Indian Ocean, suggesting a possible borrowing from Indian sailors; but it is also possible that Arabs got the compass from Europeans (scholars arguing this hypothesis often point out the Arabic word for compass, al-kunbas, appears to come from Italian roots). Much more research needs to be done before this argument can be settled.


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