The Sciences

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The Sciences

Magnetism. The Chinese were the first to study theories of magnetism: polarity (the condition of opposite properties); induction (the process by which an object becomes magnetized); retentivity (the capacity for retaining magnetism); and variation (the measurement of change in magnetism). These theories were identified much earlier in China than in Europe, although Europeans performed the first experiments relating to electric charges and magnetism in the seventeenth century. Chinese notions about magnetic phenomena were connected with cosmic theories that probably made their influence felt in Europe by the eighteenth century. The magnetic North Pole is about 1,200 miles from the geographical true north of the earth. The difference between the true geographical North Pole and the magnetic North Pole was identified as the angle of declination. (It is not constant and frequently shifts.) By the ninth century the Chinese had discovered this magnetic declination. The oldest, most accurate, and completely clear description of the declination appeared in an eleventh-century poem on the magnet written by Wang Chi, founder of the Fujian school of geomancers (scholars who performed divination by means of figures, lines, or geographic features). The magnetic compass and the polarity of the earth’s field were not discussed in any Western literature until the end of the twelfth century. In addition, the Chinese had described explicitly the induction of remanent or residual magnetism in iron by the eleventh century, referring to a fish-shaped magnet.

Archaeology. The twelfth-century discovery of antique objects such as bronzes and jades in the area of Anyang, the last capital of the Shang dynasty (circa 1766-circa 1122 B.C.E.), spurred widespread interest in archaeology. In turn, increased enthusiasm for antiques contributed to a rise in epigraphy, the study of inscriptions. Archaeological Plates, a scientific classification and dating of the bronzes of the second and first millennia B.C.E., was published in 1092. By the end of the twelfth century Ancient Coins, the first book on numismatics in Chinese history, was available.

Astronomy. In 1090 an important development occurred in the field of astronomy. Su Song produced an astronomical clock actuated by an escapement system, cogs, and transmission chains. The machine had a wheel turned by the successive filling of pivoting cups fed by a tank with a constant level. This clock was the most precise thus far developed, and it was one of the oldest mechanisms in the history of the world, with a slow, regular, continuous rotation.

Equatorial Instrument. Astronomical observatories helped Chinese scientists to understand the positions of stars. The Arabs first invented an astronomical instrument that improved upon the ancient Greek armillary sphere (a device for representing the great circles of the heavens with the horizon, meridian, equator, tropics, polar circles, and an ecliptic hoop). With this Arab instrument all the various rings were not nested together in a single sphere but were mounted on a set of struts. In 1270 astronomer Guo Shoujing adapted this instrument to the equatorial system of the Chinese but with all the Arab ecliptic components left out. In this regard he anticipated the equatorial mounting so extensively used in contemporary telescopes.

Star Map. Chinese cartographers used the cylindrical projection centuries before the sixteenth-century German scholar Gerardus Mercator devised his projection map (a type of map that allows for the globe’s surface to be projected onto a flat surface). By 940 they created the first star map with the cylindrical technique. The sky was divided into twenty-eight regions, which were similar to the sections of an orange. They were lunar mansions—stages of the moon’s progress through the sky—with the pole as their base. In the star map the sections were represented as long rectangles centered on the equator and extremely distorted

in the direction of the poles. In 1094 Su Song illustrated this type of map in his book New Design for a Mechanized Armillary Sphere and Celestial Globe.

Quantitative Cartography. Two important maps were created in the eleventh century. (Both were carved in stone, and they currently reside in the Pei Lin Museum in Xi’an.)The “Map of the Paths of Yu the Great” has a rectangular grid laid over it. Superior to the other map with reference to the coastal details, this map includes the Shandong Peninsula. The other map, however, has more precise information on the southwestern rivers. In 1320 the Daoist and geographer Zhu Siben published a reliable map in an atlas. The map was not printed again until 1555, when it appeared in the Enlarged Terrestrial Atlas. This map was prepared with a network of squares that presented an accu-rate geographic picture. If the map was divided and then reassembled, the individual parts in the East and West fitted together perfectly. The grid was used successfully to reduce the size of the map in a manner similar to presentday photographic decrease. However, the map was seven feet long and thus difficult to unroll.

Geobotanical Prospecting. The use of botanical observation to find minerals is known as geobotanical prospecting. The Chinese were the first people to become aware of and use the link between the types of vegetation that grow in certain regions and the minerals to be discovered under-ground at the same area. In the first half of the sixth century there were no less than three guidebooks dealing with systematic accounts of geobotanical mineral prospecting and listing different kinds of plants and their related minerals. Duan Chengshi in his Miscellany of the Yuyang Mountain Cave (800) is the first to propose the relationship between plant types and mineral deposits. In 1062 Su Song published his Illustrated Pharmacopoeia, which maintains that a specific plant of purslane contained sufficient mercury for the metal to be extracted from it by careful beating, ventilation, and natural organic decay. In 1421 a book called Signs of Metals and Minerals was published claiming that mineral trace elements could be found in and could be taken out of certain plants. Gold was found in the rape turnip; silver in a type of weeping willow; lead and tin in

MAGNETIC COMPASS

Below is an account of the use of the magnetic compass for navigation from a book by Zhu Yu, son of a former port official and governor of Canton. The book is called Pingchoiv Table Talk and dates from 1117. Zhu writes:

According to the government regulations concerning sea-going ships, the larger ones can carry several hundred men and the small ones may have more than a hundred men on board.. . . The ship’s 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.

Source: Robert Temple, The Genius of China: 3,000 Years of Science, Discovery, and Invention (New York: Simon oc Schuster, 1986).

chestnut, barley, and wheat; and copper in Indian sorrel. Europeans did not understand geobotanical concepts until the seventeenth century.

Geology. In 1086 the great scientist Shen Kuo published his book Dream of Pool Essay in which the principle of modern geology was included. In his work Shen discussed erosion of mountains and lofty peaks and described sedimentary deposition. Although Shen Kuo was not the first person to have these ideas, he explained them thoroughly and included his personal observations in the field.

Natural Luminescence. The Chinese became interested in natural luminescence as early as the third century. They observed the relationship between the bioluminescence of fireflies and the glowing of certain kinds of rotting vegetation. This discovery resulted in the use of natural luminescence in the manufacturing of phosphorescent paints in the eleventh century, if not earlier. In 1596 Li Shizhen correctly distinguished glowworms, whose glowing tails were able to be seen at night over long distances, from fireflies and other evidently luminous insects, such as mayflies or midges infected with luminous bacteria. Luminescence and phosphorescence called “Yin fire” enthralled the Chinese for centuries, and they collected naturally luminescent pearls and glowing minerals. The West did not make any phosphorescent substance until 1768, when John Canton utilized oyster shells to prepare a mixed calcium sulfide by calcining the carbonate with sulfur.