Zhang Sixun (, fl. 10th century) was a Chinese

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...

and mechanical engineer from Bazhong, Sichuan during the early

Song Dynasty The Song dynasty (; ; 960–1279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou. The Song conquered the rest ...

(960–1279 AD).Liu, 577. He is credited with creating an

armillary sphere An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines of ...

for his

astronomical Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies ...

clock tower Clock towers are a specific type of structure which house a turret clock and have one or more clock faces on the upper exterior walls. Many clock towers are freestanding structures but they can also adjoin or be located on top of another buildi ...

that employed the use of liquid

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

(dripped periodically from a clepsydra clock).Needham, Volume 4, 469-471. The liquid mercury filled scoops of the

waterwheel A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buckets ...

would rotate and thus provide the effect of an

escapement An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to ...

mechanism in clockworks and allow the astronomical armillary sphere to rotate as needed.

Life and works

According to the '' History of Song'', Zhang Sixun passed the state examinations in astronomy and mathematics, for this he was appointed to service in the national astronomical observatory (Si Tian Jian), within two years of taking office he had finished construction of an armillary sphere either in 977 or 979. As a result, he was rewarded as assistant to the Astronomical Bureau. Zhang Sixun, although innovative, built upon the efforts of those before him. It was

Han dynasty The Han dynasty (, ; ) was an imperial dynasty of China (202 BC – 9 AD, 25–220 AD), established by Liu Bang (Emperor Gao) and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–207 BC) and a warr ...

scientist and engineer

Zhang Heng Zhang Heng (; AD 78–139), formerly romanized as Chang Heng, was a Chinese polymathic scientist and statesman who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, ma ...

(78–139 AD) who invented the first

hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...

-powered (i.e. with waterwheel and clepsydra) armillary sphere. In addition, it was the

Tang dynasty The Tang dynasty (, ; zh, t= ), or Tang Empire, was an Dynasties in Chinese history, imperial dynasty of China that ruled from 618 to 907 AD, with an Zhou dynasty (690–705), interregnum between 690 and 705. It was preceded by the Sui dyn ...

era

Buddhist Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha. It originated in northern India as a -movement in the 5th century BCE, and ...

monk A monk (, from el, μοναχός, ''monachos'', "single, solitary" via Latin ) is a person who practices religious asceticism by monastic living, either alone or with any number of other monks. A monk may be a person who decides to dedica ...

and engineer

Yi Xing Yi Xing (, 683–727), born Zhang Sui (), was a Chinese astronomer, Buddhist monk, inventor, mathematician, mechanical engineer, and philosopher during the Tang dynasty. His astronomical celestial globe featured a liquid-driven escapement, the ...

(683–727 AD) who invented the first hydraulic-powered armillary sphere that incorporated the

mechanism. Yet Zhang Sixun applied some innovative ideas of his own in order for his hydraulic-powered armillary sphere to function. His astronomical armillary sphere and clock was much like that of the later statesman

Su Song Su Song (, 1020–1101), courtesy name Zirong (), was a Chinese polymathic scientist and statesman. Excelling in a variety of fields, he was accomplished in mathematics, Chinese astronomy, astronomy, History of cartography#China, cartography, ...

(1020–1101 AD), incorporating the scoop-bearing driving-wheel and gearing, together with 19 clock jacks to report and sound the hours.Needham, Volume 4, 469.Needham, Volume 4, Part 2, 165. His device also employed the use of liquid mercury in the closed circuit of the clepsydra and waterwheel instead of water, because water would freeze easily during winter, while mercury could assure smooth and continual function and time-keeping during the cold seasons. Later

Ming dynasty The Ming dynasty (), officially the Great Ming, was an Dynasties in Chinese history, imperial dynasty of China, ruling from 1368 to 1644 following the collapse of the Mongol Empire, Mongol-led Yuan dynasty. The Ming dynasty was the last ort ...

clocks had the same concern in mind when they employed the use of falling sand grains to push the wheel drive.Needham, Volume 4, Part 2, 510–511. The later Su Song wrote that after Zhang's death, no one could replicate what he had achieved,Needham, Volume 4, 470. much like with Su Song himself and his astronomical

after his own death.

Historical texts

The later Song Dynasty historical text of the '' Song Shi'' (compiled in 1345 AD) records Zhang's work ( Wade-Giles spelling):

At the beginning of the Thai-Phing Hsing-Kuo reign-period (+976) the Szechuanese Chang Ssu-Hsun hang Sixun a student in the Bureau of Astronomy, invented an astronomical clock (lit. armillary sphere, ''hun i'') and presented the designs to the emperor Thai Tsung, who ordered artisans of the Imperial Workshops to construct it within the Palace. On a kuei-mao day in the first month of the 4th year (+979) the elaborate machine was completed, and the emperor caused it to be placed under the eastern drum-tower of the Wen-Ming Hall.Needham, Volume 4, 470-471.

The system of Chang Ssu-Hsun was as follows: they built a tower of three storeys (totalling) more than ten feet in height, within which was concealed all the machinery. It was round (at the top to symbolize) the heavens, and square (at the bottom to symbolize) the earth. Below there was set up the lower wheel (ti lun), lower shaft (ti chu), and the framework base (ti tsu). There were also horizontal wheels (heng lun), (vertical) wheels fixed sideways (tshe lun), and slanting wheels (hsieh lun, i.e. oblique gearing); bearings for fixing them in place (ting shen kuan), a central coupling device (chung kuan) and a smaller coupling device (hsiao kuan)(i.e. the escapement); with a main transmission shaft (thien chu). Seven jacks rang bells on the left, struck a large bell on the right, and beat a drum in the middle to indicate clearly the passing of the quarter(-hours).

Each day and night (each 24 hours) the machinery made one complete revolution, and the seven luminaries moved their positions around the ecliptic. Twelve other wooden jacks were also made to come out at each of the (double-)hours, one after the other, bearing tablets indicating the time. The lengths of the days and nights were determined by the (varying) numbers of the quarters (passing in light and darkness). At the upper part of the machinery there were the top piece (thien ting), upper gear(-wheel or -wheels)(thien ya), upper linking device (thien kuan; another part of the escapement), upper (anti-recoil) ratchet pin (thien chih), celestial (ladder?) gear-box (thien tho), upper framework beam carrying bearings (thien shu), and the upper connecting-chain (thien thiao). There were also (on a celestial globe?) the 365 degrees (to show the movement of) the sun, moon, and five planets; as well as the Purple Palace (north polar region), the lunar mansions (hsiu) in their ranks, and the Great Bear, together with the equator and the ecliptic which indicated how the changes of the advance and regression of heat and cold depend upon the measured motions of the sun.

The motive power of the clock was water, according to the method which had come down from Chang Heng hang Hengin the Han Dynasty through I-Hsing i Xingand Liang Ling-tsan in the Khai-Yuan reign period (+713 to +741)(of the Thang). But the bronze and iron (of their clocks) had long gone to rust (thung thieh chien se) and could no longer move automatically. Moreover, as during winter the water partly froze and its flow was greatly reduced, the machinery lost its exactness, and there was no constancy between the hot and cold weather. Now, therefore, mercury was employed as a substitute, and there were no more errors...The images of the sun and moon were also attached high up (to the globe) and according to the old method they had been moved by human hand (each day), but now success was attained in having them move automatically. This was a marvellous thing. (Chang) Ssu-Hsun was considered the equal of the Thang clock-makers and was made Special Assistant in charge of the Armillary Sphere (Engine)(Ssu-Thien Hun I Chheng).

Notes

References

*Liu, Heping
""The Water Mill" and Northern Song Imperial Patronage of Art, Commerce, and Science
" ''The Art Bulletin'' (Volume 84, Number 4, 2002): 566–595. *Needham, Joseph (1986). ''Science and Civilization in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering''. Taipei: Caves Books, Ltd.

External links

Mechanical Clock article with Zhang Sixun
{{DEFAULTSORT:Zhang, Sixun Year of birth unknown Year of death unknown 10th-century Chinese astronomers Chinese mechanical engineers Engineers from Sichuan People from Bazhong Scientists from Sichuan Song dynasty people

Life and works

Historical texts

See also

Notes

References

External links