Su Song
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Su Song (蘇頌, Wade-Giles: Su Sung, style Zirong 子容) (AD 1020 – 1101) was a Chinese statesman, astronomer, horologist, pharmaceutical naturalist, and engineer of the Song Dynasty.
Su Song was the engineer of a water-driven astronomical clock tower in medieval Kaifeng, which employed the use of an early escapement mechanism, the verge escapement (known in Europe from about 1275).[1][2] Although Su made use of the escapement mechanism, it had been previously invented by Buddhist monk Yi Xing and government official Liang Ling-zan in 723 (or 725, see armillary sphere). Su Song's treatise about the clock-tower, the Hsin I Hsiang Fa Yao (Wade-Giles, Pinyin: Xin Yi Xiang Fa Yao), has survived, and has been analyzed by historians such as Joseph Needham. However, the clock itself was dismantled by the invading Jurchen army in AD 1127, and although attempts were made to reassemble the clock-tower, it was never successfully reinstated.
Interestingly enough, Su Song's treatise on astronomical clockwork was not the only one made in China during his day, as the Song Shi records the written treatise of Shui Yun Hun Thien Chi Yao (Pinyin: Shui Yun Hun Tian Ji Yao; lit. Essentials of the [Technique of] making Astronomical Apparatus revolve by Water-Power), written by Juan Tai-fa. However, this treatise itself no longer survives.[3]
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[edit] Life and Works
Su Song was born in modern-day Fujian, near medieval Chuanzhou. Like his brilliant contemporary Shen Kuo (discoverer of magnetic true north for a compass), Su Song was something of a polymath. It was written by Ye Meng De that in his youth, the young Su Song mastered the provincial exams (see Imperial Examination), who came at the top of the examination list for writing the best essay on general principles and structure of the Chinese calendar. From an early age, his interests in astronomy and calendrical science would lead him onto a distinguished path as a state bureaucrat.
In matters of administrative government, he had risen to the rank of Ambassador and President of the Ministry of Personnel at the capital of Kaifeng (known also as an expert in administration and finance). Eventually, he also rose to the post of Vice President of the Chancellery Secretariat. At court, he chose to distance himself from the political rivalries of the Conservatives (led by Prime Minister Sima Guang) and the Reformists (led by Prime Minister Wang Anshi), although many of his associates were of the Conservative faction. In 1077 he was dispatched on a diplomatic mission to the Liao Dynasty of the Khitan people to the north. In an embarrassing event, Su Song admitted to the emperor that the calendar of the Khitan people was in fact a bit more accurate than their own, resulting in the fining and punishment of officials in the Bureau of Astronomy and Calendar. Among many honorable positions and titles conferred upon him, Su Song was also one of the Deputy Tutors of the Heir Apparent.
In 1070, Su Song and a team of scholars compiled the Ben Cao Tu Jing (Illustrated Pharmacopoeia), which was a groundbreaking treatise on pharmaceutical botany, zoology, and minerology. This treatise documented a wide range of pharmaceutical practices, including the use of ephedrine as a drug.[4] This treatise also includes valuable information of steel and iron metallurgy and industries during 11th century China.
Su Song compiled one of the greatest Chinese horological treatises of the Middle Ages, surrounding himself with an entourage of notable engineers and astronomers to assist in various projects. The Hsin I Hsiang Fa Yao (lit. Essentials of a New Method for [Mechanizing the Rotation] of an [Armillary] Sphere and a [Celestial] Globe), written in 1092, was the final product of his life's achievements in horology and clockwork (below).
Su Song's greatest project was the 40-foot-tall water-powered astronomical clock-tower constructed in Kaifeng, completed in 1088 (during the reign of Emperor Zhezong of Song). The emperor had previously commissioned Han Gong-lian, Acting Secretary of the Ministry of Personnel, to head the project, but the leadership position was instead handed down to Su Song. The emperor ordered in 1086 for Su to reconstruct the 'armillary clock' ('hun-yi') for a new clock-tower ('he-tai') in the capital city. Su continued to have the aid of Han Gong-lian, who applied his extensive knowledge of mathematics to the construction of the clock-tower. A small-scale wooden model was first crafted by Su Song, testing its intricate parts before applying it to an actual full-scale clock tower.[5] In the end, the clock-tower had many impressive features, such as the water-powered, rotating armillary sphere crowning the top-level (weighing some 10 to 20 tons),[5] a bronze celestial globe located in the middle that was 4.5 feet in diameter,[5] mechanically-timed and rotating manikins that would exit miniature opening doors to announce the time of day (on designated plaques, ringing bells and gongs), a sophisticated use of oblique gears and an escapement mechanism, as well as an exterior facade of a fanciful Chinese pagoda. Upon its completion, the tower was called the Shui Yun Yi Xiang Tai (Tower for the Water-Powered Sphere and Globe). Joseph Needham writes:
After the invention of the escapement in ~AD 725 (Tang Dynasty), there was a great flourishing of gear-wheels in clockwork and jackwork, culminating in the bronze and iron of Su Song's elaborate masterpiece in ~AD 1088.[6]
Years after Su's death, the capital city of Kaifeng was besieged and captured in 1127 by the Jurchens of the Manchurian-based Jin Dynasty. The clock-tower was dismantled piece by piece by the Jurchens, who carted its components back to their own capital in modern-day Beijing. However, due to the complexity of the tower, they were unable to successfully piece it back together. The new Emperor Gaozong of Song instructed Su's son, Su Xie, to construct a new astronomical clock-tower in its place, and Su Xie set to work studying his father's texts with a team of other experts. However, they were also unsuccessful in creating another clock tower, as Su Xie was convinced that Su Song had purposefully left out essential components in his written work and diagrams (so that others would not steal his ideas).
[edit] Su Song's Escapement Mechanism
The mechanical clockworks for Su Song's astronomical tower featured a great driving-wheel (shu lun) that was 11 feet in diameter, carrying 36 scoops (shou shui hu) on its circumference, into each of which water would pour at uniform rate from the 'constant-level tank' (phing shui hu) (Needham, Fig. 653). The main driving shaft of iron (thieh shu chu), with its cylindrical necks (yuan hsiang) supported on iron crescent-shaped bearings (thieh yang yueh), ended in a pinion (ti ku) which engages (po) with a gear-wheel at the lower end of the main vertical transmission-shaft (thien chu).[7]
Joseph Needham gives a general description of the clock-tower itself:
(Su Song's) clockwork, driven by a water-wheel, and fully enclosed within the tower, rotated an observational armillary sphere on the top platform and a celestial globe in the upper story. Its time-announcing function was further fulfilled visually and audibly by the performances of numerous jacks mounted on the eight superimposed wheels of a time-keeping shaft and appearing at windows in the pagoda-like structure at the front of the tower. Within the building, some 40 ft. high, the driving-wheel was provided with a special form of escapement, and the water was pumped back into the tanks periodically by manual means. The time-annunciator must have included conversion gearing, since it gave 'unequal' as well as equal time signals, and the sphere probably had this. Su Sung's treatise on the clock, the Hsin I Hsiang Fa Yao, constitutes a classic of horological engineering.[8]
That was figure Fig. 650, while Fig. 656 displays the upper and lower norias with their tanks and the manual wheel for operating them.
Fig. 657 displays a rather miniature and scaled-down pic for the basics of the escapement mechanism in an illustration (from Su's book), with Needham's caption here in this quote: "The 'celestial balance' (thien heng) or escapement mechanism of Su Sung's clockwork (Hsin I Hsiang Fa Yao, ch. 3, p. 18b),".[9] The latter figure carefully labels:
A) a right upper lock B) upper link C) left upper lock D) axle or pivot E) long chain F) upper counterweight G) sump H) checking fork of the lower balancing lever I) coupling tongue J) main (ie. lower) counterweight.[9]
Figure 658. displays a more intricate and most-telling half-page scale drawing of Su Song's large escapement mechanism, labeling these individual parts as they interact with one another (in numeric order):
1. arrested spoke (fu)
2. left upper lock (tso thien so)
3. scoop (shou shui hu) being filled by
4. water jet from constant-level tank
5. small counterweight
6. checking fork (ko chha) tripped by a projection pin on the scoop, and forming the near end of
7. the lower balancing lever (shu heng) with
8. its lower counterweight (shu chhuan)
9. coupling tongue (kuan she), connected by
10. the long chain (thien thiao) with
11. the upper balancing lever (thien heng), which has at its far end
12. the upper counterweight (thien kuan), and at its near end
13. a short length chain (thien kuan) connecting it with the upper lock beneath it;
14. right upper lock (yu thien so)[10]
[edit] Transmission of Su's Text (Throughout Time)
When Su Song's Hsin I Hsiang Fa Yao was written in 1092 and the horological monograph finalized and presented in 1094, his work was published and widely printed in the north (see woodblock printing and movable type of Bi Sheng). In the south, printing and circulation of his work was not widely distributed until Shi Yuan-zhi of Jiangsu had it printed there in 1172.[2]
The later Ming Dynasty/Qing Dynasty scholar Qian Zeng (1629 - 1699) held an old volume of Su's work, which he faithfully reproduced in a newly-printed edition (taking extra special care in avoiding any rewording or inconsistencies with the original text).[2] Again, it was later reprinted by Zhang Xi-zu (1799 - 1844).[2]
In the realm of modern research, the deceased British biochemist and historian of Chinese science Joseph Needham (1900 - 1995) (known as Li Yuese in China) has done extensive research and analysis of Su Song's texts and various achievements in his Science and Civilization in China book series. Joseph Needham had also related many detailed passages from Su's contemporary medieval Chinese sources on the life of Su and his achievements known in his day.
[edit] See also
- Clock tower
- Water clock
- Pin-lever watch
- Grasshopper escapement
- Richard of Wallingford
- Villard de Honnecourt
- De'Dondi
- John Harrison
- Thomas Tompion
- George Graham
[edit] Notes
[edit] References
- Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 2. Taipei: Caves Books, Ltd.
