South Pointing Chariot

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South Pointing Chariot
Traditional Chinese 指南車
Simplified Chinese 指南车
File:The Chinese-children instruction vehicle of Expo 2005 Aichi Japan.jpg
Reconstruction of a South Pointing Chariot, 2005
File:South-pointing chariot (Science Museum model).jpg
Model in the Science Museum in London

The South Pointing Chariot is widely regarded as one of the most complex geared mechanisms of the ancient Chinese civilization, and was continually used throughout the medieval period as well. According to legends it was supposedly invented sometime around 2600 BC in China by the mythical Yellow Emperor, yet the first valid historical version was created by Ma Jun (c. 200–265 AD) of Cao Wei during the Three Kingdoms. The chariot is a two-wheeled vehicle upon which is a pointing figure connected to the wheels by means of differential gearing. Through careful selection of wheel size, track and gear ratios, the figure atop the chariot will always point in the same direction, hence acting as a non-magnetic compass vehicle. Throughout history, many Chinese historical texts have mentioned the South Pointing Chariot, while some described in full detail the inner components and workings of the device.

Legend and history

Legend

Legend has it that Huang Di, credited as being the founder of the Chinese nation, lived in a magnificent palace in the Kunlun Mountains.

There was also at this time another tribal leader, Chi You, who was skilled at making weapons and waging war. He attacked the tribe of Yan Di, driving them into the lands of Huang Di. Huang Di was angered by this and went to war with Yan Di, initially suffering several defeats. At some stage in the fighting, Chi You conjured up a thick fog to confound Huang Di's men. However, the South Pointing Chariot was used to find their way and they were ultimately victorious.

History

Despite legend, it was recorded in the Sanguo Zhi (Records of the Three Kingdoms) that the 3rd century mechanical engineer Ma Jun from the Kingdom of Wei was the inventor of the South Pointing Chariot (also called the south-pointing carriage). After being mocked by Permanent Counsellor Caotang Long and the Cavalry General Qin Lang that he could not reproduce what they deemed a non-historical and nonsensical pursuit, Ma Jun retorted "Empty arguments with words cannot (in any way) compare with a test which will show practical results". After inventing the device and proving those who were doubtful wrong, he was praised by many, including his contemporary Fu Xuan, a noted poet of his age.

After Ma Jun, the South Pointing Chariot was re-invented by Zu Chongzhi (429–500 AD), after the details of its instructions had been lost temporarily in China. During the Tang Dynasty (618–907 AD) and Song Dynasty (960–1279 AD) the South Pointing Chariot was combined with another mechanical wheeled vehicle, the distance-measuring odometer.

Some early historical records states that the south pointing chariot was invented around the first millennium B.C.E., but such evidence is obscure.

Historical texts for the South Pointing Chariot

Earliest sources

The South Pointing Chariot, a differential mechanical-geared wheeled vehicle used to discern the southern cardinal direction (without magnetics), was given a brief description by Ma's contemporary Fu Xuan.[1] The contemporary 3rd century source of the Weilüe, written by Yuan Huan also described the South Pointing Chariot of Ma Jun.[2] The Jin Dynasty (265–420 AD) era text of the Shu Zheng Ji (Records of Military Expeditions), written by Guo Yuansheng, recorded that South Pointing Chariots were often stored in the northern gatehouse of the Government Workshops (Shang Fang) of the capital city.[2] However, the later written Song Shu (Book of Song) (6th century AD) recorded the South Pointing Chariot's design and use in further detail, as well as created background legend of the device's (supposed) use long before Ma's time, in the Western Zhou Dynasty (1050 BC–771 BC). The book also provided description of the South Pointing Chariot's re-invention and use in times after Ma Jun and the Three Kingdoms. The 6th century text reads as follows (in Needham's translation, the South Pointing Chariot is referred to as the south-pointing carriage):

“ The south-pointing carriage was first constructed by the Duke of Zhou (beginning of the 1st millennium BC) as a means of conducting homewards certain envoys who had arrived from a great distance beyond the frontiers. The country to be traversed was a boundless plain, in which people lost their bearings as to east and west, so (the Duke) caused this vehicle to be made in order that the ambassadors should be able to distinguish north and south. The Gui Gu Zi book says that the people of the State of Zheng, when collecting jade, always carried with them a 'south-pointer', and by means of this were never in doubt (as to their position). During the Qin and Former Han dynasties, however, nothing more was heard of the vehicle. In the Later Han period, Zhang Heng re-invented it, but owing to the confusion and turmoil at the close of the dynasty it was not preserved.[3] ”
“ In the State of Wei, (in the San Guo period) Gaotong Long and Qin Lang were both famous scholars; they disputed about the south-pointing carriage before the court, saying that there was no such thing, and that the story was nonsense. But during the Qing-long reign period (233–237 AD) the emperor Ming Di commissioned the scholar Ma Jun to construct one, and he duly succeeded. This again was lost during the troubles attending the establishment of the Jin Dynasty.[4] ”
“ Later on, Shi Hu (emperor of the Jie Later Zhao Dynasty) had one made by Xie Fei, and again Linghu Sheng made one for Yao Xing (emperor of the Later Qin dynasty). The latter was obtained by emperor An Di of the Jin in the 13th year of the Yi-xi reign-period (417 AD), and it finally came into the hands of emperor Wu Di of the Liu Song Dynasty when he took over the administration of Chang'an. Its appearance and construction was like that of a drum-carriage (odometer). A wooden figure of a man was placed at the top, with its arm raised and pointing to the south, (and the mechanism was arranged in such a way that) although the carriage turned round and round, the pointer-arm still indicated the south. In State processions, the south-pointing carriage led the way, accompanied by the imperial guard.[5] ”
“ These vehicles, constructed as they had been by barbarian (Qiang) workmen, did not function particularly well. Though called south-pointing carriages, they very often did not point true, and had to negotiate curves step by step, with the help of someone inside to adjust the machinery. The ingenious man from Fanyang, Zi Zu Chongzhi frequently said, therefore, that a new (and properly automatic) south-pointing carriage ought to be constructed. So towards the close of the Sheng-Ming reign period (477–479 AD) the emperor Shun Di, during the premiership of the Prince of Qi, commissioned (Zi Zu Chongzhi) to make one, and when it was completed it was tested by Wang Seng-qian, military governor of Tanyang, and Liu Hsiu, president of the Board of Censors. The workmanship was excellent, and although the carriage was twisted and turned in a hundred directions, the hand never failed to point to the south. Under the Jin, moreover, there had also been a south pointing ship.[5] ”

The last sentence of the passage is of great interest for navigation at sea, since the magnetic compass used for seafaring navigation was not used until the time of Shen Kuo (1031–1095). Although the Song Shu text describes earlier precedents of the South Pointing Chariot before the time of Ma Jun, this is not entirely credible, as there are no pre-Han or Han Dynasty era texts that describe the device.[6] In fact, the first known source to describe stories of its legendary use during the Zhou period was the Gu Jin Zhu book of Cui Bao (c. 300 AD), written soon after the Three Kingdoms era.[2] Cui Bao also wrote that the intricate details of construction for the device were once written in the Shang Fang Gu Shi (Traditions of the Imperial Workshops), but the book was lost by his time.[2]

Japan

The invention of the South Pointing Chariot also made its way to Japan by the 7th century. The Nihon Shoki (The Chronicles of Japan) of 720 AD described the earlier Chinese Buddhist monks Zhi Yu and Zhi You constructing several South Pointing Chariots for Emperor Tenji of Japan in 658 AD.[7] This was followed up by several more chariot devices built in 666 AD as well.[7]

South Pointing Chariot in the Song Shi

The South Pointing Chariot was also combined with the earlier Han Dynasty era invention of the odometer (also Greco-Roman), a mechanical device used to measure distance traveled, and found in all modern automobiles. It was mentioned in the Song Dynasty (960–1279 AD) historical text of the Song Shi (compiled in 1345) that between the engineers Yan Su (in 1027 AD) and Wu Deren (in 1107 AD) both created South Pointing Chariots, which it details as follows:[8]

“ In the 5th year of the Tian-Sheng reign period of the emperor Renzong (1027 AD), Yan Su, a Divisional Director in the Ministry of Works, made a south-pointing carriage. He memorialised the throne, saying, [after the usual historical introduction]: 'Throughout the Five Dynasties and until the reigning dynasty there has been, so far as I know, no one who has been able to construct such a vehicle. But now I have invented a design myself and have succeeded in completing it'.[8] ”
“ 'The method involves using a carriage with a single pole (for two horses). Above the outside framework of the body of the carriage let there be a cover in two stories. Set a wooden image of a xian (immortal) at the top, stretching out its arm to indicate the south. Use 9 wheels, great and small, with a total of 120 teeth, i.e. 2 foot-wheels (i.e. road-wheels, on which the carriage runs) 6 ft. high and 18 ft. in circumference, attached to the foot wheels, 2 vertical subordinate wheels, 2.4 ft. in diameter and 7.2 ft. in circumference, each with 24 teeth, the teeth being at intervals of 3 inches apart.[8] ”
“ '...Then below the crossbar at the end of the pole, two small vertical wheels 3 inches in diameter and pierced by an iron axle, to the left 1 small horizontal wheel, 1.2 feet in diameter, with 12 teeth, to the right 1 small horizontal wheel, 1.2 ft. in diameter, with 12 teeth, in the middle 1 large horizontal wheel, of diameter 4.8 ft. and circumference 14.4 ft., with 48 teeth, the teeth at intervals of 3 inches apart; in the middle a vertical shaft piercing the center (of the large horizontal wheel) 8 ft. high and 3 inches in diameter; at the top carrying the wooden figure of the xian'.[8] ”
“ 'When the carriage moves (southward) let the wooden figure point south. When it runs (and goes) eastwards, the (back end of the) pole is pushed to the right; the subordinate wheel attached to the right road-wheel will turn forward 12 teeth, drawing with it the right small horizontal wheel one revolution (and so) pushing the central large horizontal wheel to revolve a quarter turn to the left. When it has turned around 12 teeth, the carriage moves eastwards, and the wooden figure stands crosswise and points south. If (instead) it turns (and goes) westwards, the (back end of the) pole is pushed to the left; the subordinate wheel attached to the left road-wheel will turn forward with the road-wheel 12 teeth, drawing with it the left small horizontal wheel one revolution, and pushing the central large horizontal wheel to revolve a quarter turn to the right. When it has turned round 12 teeth, the carriage moves due west, but still the wooden figure stands crosswise and points south. If one wishes to travel northwards, the turning round, whether by east or west, is done in the same way'.[9] ”

After this initial description of Yan Su's device, the text continues to describe the work of Wu Deren, who crafted a wheeled device that would combine the odometer and South Pointing Chariot:

“ It was ordered that the method should be handed down to the (appropriate) officials so that the machine might be made. In the first year of the Da-Guan reign period (1107 AD), the Chamberlain Wu Deren presented specifications of the south-pointing carriage and the carriage with the li-recording drum (odometer). The two vehicles were made, and were first used that year at the great ceremony of the ancestral sacrifice.[10] ”
“ The body of the south-pointing carriage was 11.15 ft. (long), 9.5 ft. wide, and 10.9 ft. deep. The carriage wheels were 5.7 ft. in diameter, the carriage pole 10.5 ft. long, and the carriage body in two stories, upper and lower. In the middle was placed a partition. Above there stood a figure of a xian holding a rod, on the left and right were tortoises and cranes, one each on either side, and four figures of boys each holding a tassel. In the upper story there were at the four corners trip-mechanisms, and also 13 horizontal wheels, each 1.85 ft. in diameter, 5.55 ft. in circumference, with 32 teeth at intervals of 1.8 inches apart. A central shaft, mounted on the partition, pierced downwards.[10] ”
“ In the lower story were 13 wheels. In the middle was the largest horizontal wheel, 3.8 ft. in diameter, 11.4 ft. in circumference, and having 100 teeth at intervals of 2.1 inches apart. (On vertical axles) reaching to the top (of the compartment) left and right, were two small horizontal wheels which could rise and fall, having an iron weight (attached to) each. Each of these was 1.1 ft. in diameter and 3.3 ft. in circumference, with 17 teeth, at intervals of 1.9 inches apart. Again, to left and right, were attached wheels, one on each side, in diameter 1.55 ft., in circumference 4.65 ft., and having 24 teeth, at intervals of 2.1 inches.[10] ”
“ Left and right, too, were double gear-wheels (lit. tier-wheels), a pair on either side. Each of the lower component gears was 2.1 ft. in diameter and 6.3 ft. in circumference, with 32 teeth, at intervals of 2.1 inches apart. Each of the upper component gears was 1.2 ft. in diameter and 3.6 ft. in circumference, with 32 teeth, at intervals of 1.1 inches apart. On each of the road-wheels of the carriage, left and right, was a vertical wheel 2.2 ft. in diameter, 6.6 ft. in circumference, with 32 teeth at intervals of 2.25 inches apart. Both to left and right at the back end of the pole there were small wheels without teeth (pulleys), from which hung bamboo cords, and both were tied above the left and right (ends of the) axle (of the carriage) respectively.[10] ”
“ If the carriage turns to the right, it causes the small pulley to the left of the back end of the pole to let down the left-hand (small horizontal) wheel. If it turns to the left, it causes the small pulley to the right of the back end of the pole to let down the right (small horizontal) wheel. However, the carriage moves the xian and the boys stand crosswise and point south. The carriage is harnessed with two red horses, bearing frontlets of bronze.[10] ”

After the work of these various engineers, to put the device of the South Pointing Chariot into global perspective, the first true differential gear used in the Western world was by Joseph Williamson in 1720.[11] Joseph Williamson used a differential for correcting the equation of time for a clock that displayed both mean and solar time.[11] Even then, the differential was not fully appreciated in Europe until James White emphasized its importance and provided details for it in his Century of Inventions (1822).[11]

How it works

The South Pointing Chariot is a mechanical compass that transports a direction, given by the pointer, along the path it travels. The differential in the gear system integrates the difference in wheel rotation between the two wheels and thus detects the rotation of the base of the chariot. The mechanism compensates this rotation by rotating the pointer in the opposite direction.

Mathematically the device approximates parallel transport along the path it travels. In the Euclidean plane, the device performs parallel transport. On a curved surface it only approximates parallel transport. In the limit where the distance between the wheels tends to zero, the approximation becomes exact.

The chariot can be used to detect straight lines or geodesics. A path on a surface the chariot travels along is a geodesic if and only if the pointer does not rotate with respect to the base of the chariot.

Timeline

The South Pointing Chariot has been invented and reinvented at many times throughout Chinese history. Below is a partial timeline of the major events;

Year Event
2634 BC According to Legend, the Yellow Emperor designs the South Pointing Chariot. It is built for him by the craftsman Fang Bo.
1115 BC During the reign of the Duke of Chou, the duke gives five such devices (called Zhinan) to ambassadors of Yueshang to get them back home.
150 .. 100 BC Estimated construction of the Antikythera mechanism in ancient Greece.
120 .. 139 AD Zhang Heng might have reinvented the vehicle.
233 .. 237 Ma Jun constructs a working vehicle for Emperor Ming of Wei.
300 Cui Bao reports that the construction is described in a book (not preserved) named Shang Fang Ku Shih.
334 .. 349 Xie Fei makes one for emperor Shih Hu.
394 .. 416 Linghu Sheng makes one for Emperor Xiaowu of Jin China.
417 Linghu Sheng's vehicle is captured by Emperor An of Jin. It is reported that, at this time, there is no machinery, but only a man inside who turns the figure.
423 .. 452 Guo Shanming fails to make one for Emperor Taiwu of Northern Wei.
423 .. 452 Ma Yue succeeds, but he is killed by Guo Shanming.
478 Zu Chongzhi makes a new improved (bronze gears) vehicle for Emperor Shun of Liu Song.
658 Buddhist monk Chiyu constructs vehicle for Japanese Emperor Tenji
666 Monk Chiyu constructs another vehicle for Japanese Emperor Tenji.
806 .. 821 Jin Gongli presents a south-pointing carriage to Emperor Xianzong of Tang.
1027 Engineer Yan Su (member of the "Board of Works") describes his construction (5 cogged, 4 non-cogged gear wheels, 18 soldier-drivers).
1088 Su Song constructs a water wheel clock, using an escapement.
1107 Chamberlain Wu Deren presents a specification (24 cogged, 4 non-cogged gear wheels), which is successfully built twice.
1341 Chu Tê-Jun describes a jade figure as part of a miniature south-pointing carriage.
1720 Joseph Williamson uses a differential gear in a clock.
1834 Julius Klaproth writes to Alexander von Humboldt, noting the south-pointing chariot chih-nan-ch´ê, but assumes that a magnetic compass is hidden in the little doll.
1879 James Starley first uses a differential gear in a vehicle.
1909 Professor Giles points out that the directional property of the south pointing chariot was effected by a mechanical system, and not by magnetism.
1909 Professor Bertram Hopkinson (Cambridge) remarks that some mechanism would have been required to ensure that the gears connected to the chariot wheels at right and left were engaged or disengaged when the chariot turned right or left. After some years of study, he declares that Yen Su's specification is insufficient to build a working model.
1910 The first mechanical navigation aide, "Jones Live Map", is invented. Like in the south-pointing chariot, the movement of the road wheels is geared down, but this time to show the relative position of the vehicle on a map.
1924 Rev. A. C. Moule (Cambridge) proposes a realization of Wu Tê-Jen's specification, where the chariot is allowed to drive only in straight lines. For each turn it is stopped, a gear connected and the turn done on the spot, the pointer now being corrected automatically.
1924 K. T. Dykes is the first to propose a differential gearing, arguing that the clutch mechanism proposed by Moule is "slow and complicated to drive".
1932 Dr. J.B.Kramer discovers references to the mechanical nature of the south-pointing chariot and declares that the Chinese therefore did not invent the magnetic compass, unaware that the magnetic compass had been described by Shen Kuo about 200 years before its (re)invention in Europe.
1932 George Lanchester (chief engineer at Lanchester Motor Company) proposes that the ancient machines (Ma Jun notably) embodied some kind of differential gear. He builds a working model to prove his concept.
1937 Wang Zhenduo proposes a realization of Yan Su's specification and builds a working model from it.
1948 Bao Sihe proposes another reconstruction.
1955 F.W. Cousins introduces the Lanchester reconstruction to a broader public, namely the Meccano fans.
1956 J. Coales points out that by hanging a carrot from the emperor's hand, the south-pointing chariot would become self-steering!
1977 Professor André Wegener Sleeswyk publishes a scientific essay on the historic chariots. He proves their feasibility exactly to the words in the ancient texts.
1978 Dr. Alan Partridge starts a contest in Meccano Magazine for the design with the fewest gears. It is shown subsequently that no gears are necessary at all![citation needed]
1979 Dr. Noel C. Ta'Bois (LDS RCS Eng) publishes a concise treatise on the theoretical aspects. Working specimens are shown, which do not adhere to the "width equals wheel diameter" rule.
1979 Lu Zhiming produces three reconstructions based on differential gears.
1980 Mr. Don Frantz from New York re-discovers the south pointing chariot, builds models along the Lanchester path and manages to place them in the Museum of the Province of Xian.
1982 Yan Zhiren builds another model, stressing that only differential gears provide the accuracy reported by the old writings.
1991 Mr. M. Santander from Spain proposes to use the chariot to teach students the basic concepts of parallel transport and curvature. En passant a mathematical model is given for Mr. Nuttall's design.

Where they can be seen

While none of the historic South Pointing Chariots remain, full sized replicas can be found.

The History Museum in Beijing, China holds a replica based on the mechanism of Yen Su (1027). The National Palace Museum in Taipei, Taiwan holds a replica based on the Lanchester mechanism of 1932.

Referred to as the "Southern Pointing Man", two replicas can also be seen (and physically experimented with) at the Ontario Science Centre in Toronto Canada.

See also

Notes

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References

External links

de:Kompasswagen fr:Chariot pointant le sud ja:指南車 ru:Колесница, указывающая на юг fi:Mekaaninen kompassi vi:Chỉ Nam xa

zh:指南车
  1. ↑ Needham, Volume 4, Part 2, 40.
  2. ↑ 2.0 2.1 2.2 2.3 Needham, Volume 4, Part 2, 288
  3. ↑ Needham, Volume 4, Part 2, 286.
  4. ↑ Needham, Volume 4, Part 2, 286–287.
  5. ↑ 5.0 5.1 Needham, Volume 4, Part 2, 287.
  6. ↑ Needham, Volume 4, Part 2, 287–288.
  7. ↑ 7.0 7.1 Needham, Volume 4, Part 2, 289.
  8. ↑ 8.0 8.1 8.2 8.3 Needham, Volume 4, Part 2, 291.
  9. ↑ Needham, Volume 4, Part 2, 291–292.
  10. ↑ 10.0 10.1 10.2 10.3 10.4 Needham, Volume 4, Part 2, 292.
  11. ↑ 11.0 11.1 11.2 Needham, Volume 4, Part 2, 298.
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