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The south-pointing chariot is a Chinese invention that functioned in a similar way to a compass. The compass, which is regarded as one of the Four Great Inventions of the Chinese civilisation, functions based on the Earth’s magnetic field. The south-pointing chariot, on the other hand, worked based on mechanics.
Several figures from Chinese history have been credited with the invention of the south-pointing chariot. According to one legend, the south-pointing chariot was invented during the reign of the mythical Yellow Emperor, or Huangdi, who is credited also with a range of other inventions, including the calendar, astronomy, and cuju (an ancient Chinese football game). The story goes that the Yellow Emperor was at war with Chi You, the leader of the Nine Li tribe. During the Battle of Zhuolu, Chi You produced a fog that darkened the sky, thus causing the Yellow Emperor and his army to lose their sense of direction. In order to counter Chi You’s fog, the Yellow Emperor had his minister, Feng Hou, invent the south-pointing chariot. This invention allowed the Yellow Emperor and his troops to find their way through the fog, and defeat the enemy.
Model of a Chinese South Pointing Chariot, an early navigational device using a differential gear. (CC by SA 3.0 )
Another story claims that the south-pointing chariot was created during the early part of the Zhou Dynasty. During this time, the King of Zhou (either the first king, Wu, or his successor, Cheng) received an embassy from a tribe from far beyond the borders of his kingdom. This tribe wished to pay tribute to the Zhou king, which was accepted. In return, the envoys of this tribe were given gifts to bring home. Amongst these were a number of south-pointing chariots, which had been built by Duke Wen of Zhou. These devices were supposed to have guided the envoys back home.
It may be mentioned briefly that other figures credited with the invention of this device include the Zhang Heng, a polymath who lived during the Han Dynasty, and the famous mechanical engineer Ma Jun, who lived in the state of Cao Wei during the succeeding Three Kingdoms period.
Unfortunately, if the south-pointing chariot had indeed been invented by any one of these famous Chinese figures, its technical specifications have not survived through the passage of time. According to one source, the earliest preserved description of a south-pointing chariot’s form and construction dates to the reign of the Emperor Renzong, the fourth ruler of the Song Dynasty. This description, which may be found in the Song Shi , provides us with the details of how the south-pointing chariot was made by Yan Su and Wu Deren, engineers who were in the service of the Song court.
A South-pointing Chariot ( Internet Archive Book Images / Flickr )
Based on the technical description of Yan Su and Wu Deren’s south-pointing chariot, scholars are able to have an understanding of the way this device worked. In essence, the south-pointing chariot consists of a system of gears that was connected to a pointing figure. This figure could be set to point in any direction, and would continue to point in the same direction regardless of where the chariot moved. It is generally accepted it was the differential (a type of gear train), that made this possible. The best known use of this gear system today is in wheeled vehicles, such as cars. The differential allows the outer drive wheel to rotate faster than the inner drive wheel during a turn, which would allow traction to be maintained.
Replica of the South-pointing chariot in the China Court of the Ibn Battuta Mall, Dubai ( CC by SA 4.0 )
As a navigator device, the south-pointing chariot would not have been quite accurate, unless it was regularly adjusted to correct the errors that arose over time. Nevertheless, if such a device was used for ceremonial purposes, for instance, to lead an imperial procession down a winding street, it would certainly have had an awe-inspiring effect on onlookers, who would probably have attributed the machine’s functioning to magic, rather than mechanics.
Ancient Chinese Technology - PowerPoint PPT Presentation
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The Wheels of War: Evolution of the Chariot
For one thousand years, chariots rolled through the Middle East, terrifying armies, destroying infantry lines and changing the face of war. Sumerians used heavy battlewagons with solid wheels drawn by wild asses around 2600 B.C. Until the innovation of spoked wheels, the weight of the battlewagons hindered their utility in war. The domestication of the horse inspired further chariot innovation as horses increased chariot mobility and speed. Drawn by horses, with lighter carts and spoked wheels, chariots gained their status as an elite weapon and transport. Two wheeled war chariots carrying an archer and a driver, combined with the use of the composite bow, fully revamped military tactics around 1700 B.C. Chariots spread to Greece, Asia Minor, Iran, India and China. Chariot use in war declined slowly, beginning around 1000 B.C. With the advent of mounted cavalry however, chariot use ended in the Middle East circa 500 to 300 B.C.
The First Chariots: Battlewagons
The antecedent of the chariot was the ox cart in Mesopotamia, used to transport trade goods and agricultural products. Not long after, Mesopotamians created wagons to carry a ruler and his soldiers to the battlefield. These battlewagons with four solid wheels were heavy, but on the battlefield, they provided a platform from which archers and spearmen could shoot and throw missiles at the enemy. The Standard of Ur shows battlewagons in the War panel. Pulled by wild asses, these battlewagons carried two men, a spear man and a driver. Both dismounted to fight.
Scholars believe that people of the steppes—a wild grassy plain running from Hungary to China through Central Asia—domesticated the horse and created the first spoked-wheel chariot around 2000 B.C. North-south trade routes brought both horses and spoked wheels to the Near East cultures of Mesopotamia, Iran, Syria, Persia and Egypt. Spoked wheels were a major improvement on the heavier solid wheels, allowing a lighter, speedier vehicle.
Uses of Chariots on the Battlefield
Different armies used chariots in a variety of ways. The Hittites, for instance, built heavier chariots that were used to crash into infantry lines. More often, chariots were lighter, created to be a platform for archers. Masses of chariots were then used to get close to the enemy and decimate them with arrows. Egypt’s armies used chariots for speedy transport on the battlefield and as all-purpose war machines. The Persians added the innovation of scythed chariot wheels, long blades that stuck out from the hubs, killing enemy foot soldiers in the hundreds. Rome kept chariots for racing, hunting and ceremonies while India used them as platforms for archers.
The Composite Bow/Chariot Combination
The introduction of the composite bow around 2000 B.C. and its employment by charioteers (1700 B.C.) made the chariot an essential war machine. Composite bows were made by gluing wood, horn and sinew together, creating a vastly superior weapon over the self bow made of wood alone. Archers using composite bows could now fire much faster, with more striking power with at least twice the range of the self bow. Archers mounted on chariots could fire an arrow every six seconds with good accuracy. Formations of chariots carrying bowmen became an army’s deadliest weapon.
Chariots, however, were expensive to make and maintain. They required flat ground to be effective, needed constant maintenance and broke down often. Chariot repair teams traveled right with the army, ready to do maintenance when required. The Assyrian army had a special logistical branch just for chariots and cavalry. Men and horses had to be trained in its use, which gave rise to the first warrior elites, the charioteers. These men were the first warriors to be selected for their skills and not by birth.
Concept Art, Xuan Yuan the Yellow Emperor and Chi You the God of War
Since the announcement of Mulan, I have been noticing a renewed interest in the Chinese Pantheon on this subreddit. It motivated me to create this piece of concept art, my visual interpretations of two Chinese mythical figures I am most interested in- Xuan Yuan, the yellow emperor and Chi You, the god of war.
Xuan Yuan, more commonly known as the yellow emperor, mythical founder of the Chinese culture and the first mortal to ascend to heaven. After making an alliance with the flame emperor, the yellow emperor led his army to fight an epic battle that lasted for 10 years against the army of Chi You. Upon receiving the aid of Xuan Nu, the lady of nine heavens, the yellow emperor defeated Chi You, built an utopian society, lived to the age of 118 and ascended to godhood.
There were many variations of Chi You’s legend. Aside from being worshipped as the god of war, he had the supernatural power to breathe out fog, some described him as a beast-like creature with multiple limbs and eyes. Certain versions even considered him and the flame emperor to be the same person.
-Xing Tian, a subordinate of the flame emperor at the time, was decapitated by the yellow emperor.
-Jing Wei’s father was also a flame emperor, likely a descendant of the said flame emperor (there were supposedly 17 flame emperors in Chinese history)
-The reign of “Three Sovereigns and Five Emperors” was the beginning of the Chinese mytho-history. When different sources disagree with who these eight individuals are, the yellow emperor was often considered to be one of five emperors while some considered Nu Wa to be one of the three sovereigns.
-The yellow emperor invented the “south-pointing chariot” (prototype compass) which helped him to find his way on the fogged battlefield.
Most interpretations of the yellow emperor I found depicts a traditional ancient Chinese king with the golden robe. My personal take, as you can see here, is drastically different. I think he should be more barbaric and prehistoric, he was a warrior tribal leader from 2500 BC afterall. Moreover, The dragon robe wasn’t really adopted by Chinese kings until the Tang dynasty (618-907AD). I also think it is quite fitting to have the “dragon” wearing a tiger pelt (that also keeps the yellow color scheme and the barbaric theme)
Chi You, on the other hand, was often depicted either as a human warlord with horned armor or a satan-like demonic creature. My version of him is meant to be a glass-cannon mage, hence the magical floating arms with blood strings and the lean body type, also I was trying to set him apart from the many multi-arm indian gods.
I am not qualified to comment on anything balanced-related really, so I will just throw out some vague ideas of what I imagined these characters could do, if they sound silly it is because I have no idea what I am talking about. just having fun here.
Warrior, has a kit that is supportive of his teammates but also forces them to work around him. For example, a strong AOE heal and/or buff ultimate abilities that also self-root while casting, forcing teammates to protect him. something along those lines.
Mage who shoots Laser-beams out of his multiple arms, holding a key to create converging beams to form a shield, release and it turns into a single sniper-shot, other abilities include close-range shotgun blast beams, anti-air homing beams, ricochet beams, etc…you got the idea.
A more lore-related ability would be to breathe out fog that creates an area blind.
Isn’t Guan Yu the Chinese god of war?
Not quite, a more literal translation of Guan Yu’s title would be “The saint of military/martial arts” ranked the same as Confucious, “The saint of culture/literature”
Also, It is actually a shortened version of his full title, that is …. and I kid you not "Guan the Holy Great Deity God of War Manifesting Benevolence, Bravery and Prestige Protector of the Country and Defender of the People Proud and Honest Supporter of Peace and Reconciliation Promoter of Morality, Loyalty and Righteousness"
I have heard of the yellow emperor, but who is Xuan Yuan, is that his name?
It is believed that the yellow emperor’s full name was Ji Xuan Yuan (Ji being the last name),
Apparently, Xuan Yuan is also a legit 2-character Chinese surname, people with such surname were likely the descendants of the yellow emperor. I have also found a source saying that Xuan and Yuan referred to the vertical and horizontal beam of a cart-wheel, suggesting he might have been a carpenter.
That’s all. If you have read through this entire post, I thank you for your patience. I am only quasi-familiar with the source material so you are welcome to point out any information in this post that I might have got wrong.
If this post is received well I may start doing more of this. Kushinada-hime and Shuten-doji of the Japanese pantheon are pretty high up in my priority list.
Shemot: The Book of Exodus
The next significant annual Torah reading is the parashah called Shemot, number thirteen on the reading list. Just as Bereshit described the events of the Book of Genesis, Shemot deals explicitly with the Book of Exodus, wherein the Israelites suffered in Egypt. Shemot is also broken into seven sections. It opens with the coming of the descendants of Jacob, the son of Isaac and Rebekah and considered the father of the Israelites, to Egypt. The rise of a new Pharaoh during their time in Egypt led to the Egyptians forcing the Israelites into slavery. Meanwhile the new Pharaoh also demanded the death of all male children by Hebrew women, in an attempt to control the population of the Israelites. It is believed that the children were not killed out of a fear of God and compassion.
Into this tumultuous scene Moses is born, discovered on the banks of the Nile and later adopted by the Pharaoh’s daughter. The remainder of Shemot goes on to dictate the story of Moses: his killing of an Egyptian in vengeance for the beating of another Hebrew, the bounty placed on his head by the Pharaoh, and his escape to the life of a shepherd. It was during his time living as a shepherd, married to a woman named Zipporah, that God spoke to Moses from the Burning Bush and instructed him to rescue the Israelites in Egypt. With the rod of God, Moses goes to the Pharaoh and attempts to have his people freed, but is sorely rejected by the Pharaoh who does not believe in the power of God.
Depiction of Moses being found by the river, from a fresco at the Dura Europos synagogue. The story is part of the Shemot, or the Book of Exodus. ( Public domain )
The First Compass
The magnetic compass is actually an old Chinese invention, probably first made in China during the Qin dynasty (221–206 BCE). Back then, the Chinese used lodestones (which align themselves in a north-south direction) to construct fortune-telling boards. Eventually, someone noticed that the lodestones were better at pointing out real directions, which led to the creation of the first compasses.
The earliest compasses were designed on a square slab that had markings for the cardinal points and the constellations. The pointing needle was a spoon-shaped lodestone device with a handle that would always point south. Later on, magnetized needles were used as direction pointers instead of the spoon-shaped lodestones. These appeared in the eighth century CE—again in China—and from 850 to1050.
Ancient Chinese Warfare
In ancient China warfare was a means for one region to gain ascendancy over another, for the state to expand and protect its frontiers, and for usurpers to replace an existing dynasty of rulers. With armies consisting of tens of thousands of soldiers in the first millennium BCE and then hundreds of thousands in the first millennium CE, warfare became more technologically advanced and ever more destructive. Chariots gave way to cavalry, bows to crossbows and, eventually, artillery stones to gunpowder bombs. The Chinese intelligentsia may have frowned upon warfare and those who engaged in it and there were notable periods of relative peace but, as in most other ancient societies, for ordinary people it was difficult to escape the insatiable demands of war: either fight or die, be conscripted or enslaved, win somebody else's possessions or lose all of one's own.
Attitudes to Warfare
The Chinese bronze age saw a great deal of military competition between city-rulers eager to grab the riches of their neighbours, and there is no doubt that success in this endeavour legitimised reigns and increased the welfare of the victors and their people. Those who did not fight had their possessions taken, their dwellings destroyed and were usually either enslaved or killed. Indeed, much of China's history thereafter involves wars between one state or another but it is also true that warfare was perhaps a little less glorified in ancient China than it was in other ancient societies.
The absence of a glorification of war in China was largely due to the Confucian philosophy and its accompanying literature which stressed the importance of other matters of civil life. Military treatises were written but, otherwise, stirring tales of derring-do in battle and martial themes, in general, are all rarer in Chinese mythology, literature and art than in contemporary western cultures, for example. Even such famous works as Sun-Tzu's The Art of War (5th century BCE) warned that, "No country has ever profited from protracted warfare” (Sawyer, 2007, 159). Generals and ambitious officers studied and memorised the literature on how to win at war but starting from the very top with the emperor, warfare was very often a policy of last resort. The Han Dynasty (206 BCE - 220 CE) was notable for its expansion, as were some Tang Dynasty emperors (618-907 CE) but, in the main, a strategy of paying off neighbours with vast tributes of silver and silk, along with a parallel exportation of “civilising” culture was seen as the best way to defend imperial China's borders. Then, if war ultimately proved unavoidable, it was better to recruit foreign troops to get on with it.
Joining the intellectuals with their disapproval of warfare were also the bureaucrats who had no time for uncultured military men. No doubt, too, the vast majority of the Chinese peasantry were never that keen on war either for it was they who had to endure conscription, heavy taxes in kind to pay for costly campaigns, and have their farms invaded and plundered.
With the emperors, the landed gentry, intellectuals and farmers all well-aware of what they could lose in war, it was, then, somewhat disappointing for them all that China, in any case, had just as many conflicts as anywhere else in the world in certain periods. One cannot ignore the common presence of fortifications in the bronze age, such chaotic centuries as the Autumn and Spring Period (722-481 BCE) with its one hundred plus rival states, the Warring States Period (481-221 BCE) with its incredible 358 separate conflicts or the fall of the Han when war was once again incessant between rival Chinese states. Northern steppe tribes were also constantly prodding and poking at China's borders and emperors were not averse to the odd foreign folly such as attacking ancient Korea.
The great weapon of Chinese warfare throughout its history was the bow. The most common weapon of all, skill in its use was also the most esteemed. Employed since the Neolithic period, the composite version arrived during the Shang Dynasty (c. 1600-1046 BCE) and so became a much more useful and powerful component of an army's attack strategy. Bowmen often opened up the battle proceedings by firing massed volleys into the enemy and then protected the flanks of the infantry as they advanced, or their rear when they retreated. Bowmen also rode in chariots and bows were the main weapon of cavalry.
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Perhaps the most distinctive and symbolic weapon of Chinese warfare was the crossbow. Introduced during the Warring States Period it set China apart as a nation capable of technical innovation and the training necessary to use it effectively. The Han used it to great effect against “barbarian” tribes to expand their empire, their disciplined crossbow corps even seeing off opposing cavalry units. As with bowmen, crossbowmen were usually stationed at the flanks of infantry units. Over the centuries new designs made the crossbow lighter, able to be cocked using one hand, fire multiple bolts and fire them further, more accurately and with more power than before. Artillery versions were developed which could be mounted on a swivel base. Apart from its potential as an offensive weapon, the crossbow became a much-used means of defending well-fortified cities.
Swords only appeared relatively late on Chinese battlefields, probably from around 500 BCE, and never quite challenged the bow or crossbow as the prestige weapons of Chinese armies. Developing from long-bladed daggers and spearheads which were used for stabbing, the true sword was made from bronze and then, later, iron. During the Han period they became more effective with better metalworking techniques giving stronger blades with sharper cutting edges. Other weapons used by Chinese infantry included the ever-popular halberd (a mix of spear and axe), spears, javelins, daggers, and battle-axes.
Artillery was present from the Han period when the first stone-throwing, single-armed catapults were used. They were probably mostly restricted to siege warfare but were employed by both attackers and defenders. The more powerful counter-weighted catapult was not used in China until the 13th century CE. Artillery fired stones, missiles made of metal or terracotta, incendiary bombs using naphtha oil of “Greek fire” (from the 10th century CE) and, from the Sung Dynasty (960-1279 BCE), bombs using gunpowder. The oldest text reference to gunpowder dates to 1044 CE while a silk banner describes its use in the 9th century CE (if its dating is accurate). Gunpowder was never fully exploited in ancient China and devices using it were restricted to missiles made with a soft casing of bamboo or paper which were designed to start fires on impact. The true bomb, which dispersed lethal fragments on explosion, was not seen until the 13th century CE.
With arrows and crossbow bolts becoming ever more lethal, it is no surprise that armour made leaps forward in design to better protect warriors. The earliest armour was undoubtedly the most impressive - tiger skins, for example - but also the least effective and by the Shang Dynasty hardened leather was being worn to cover the chest and back in a more serious effort to dampen and deflect blows. By the Zhou Dynasty (1046-256 BCE) more flexible armour tunics were being produced made of rectangles of tanned and lacquered leather or bronze linked together with hemp or riveted. Examples of this type can be seen in the Qin warriors of the Terracotta army of the 3rd century BCE. From the Han period, iron was used more and more in armour.
Additional protection was provided by shields, the earliest being made only of bamboo or leather but then, like body armour, they began to incorporate metal elements. Helmets followed the same path of material evolution and usually protected the ears and back of the neck. Helmets and armour, on occasion, were decorated with plumes, engravings and paintings of fearsome creatures or beautified with additions in precious metal or ivory. Specialised armour developed for warriors in chariots who did not need to move so much and could wear full-length armoured coats. There was, too, heavy cavalry where the legs of the rider and the whole horse were protected.
Chariots & Cavalry
Chariots were used in Chinese warfare from around 1250 BCE but were seen in the greatest numbers between the 8th and 5th century BCE. First as a commander's status symbol and then as a useful shock weapon, the chariot usually carried a rider, bowman and spearman. They were very often deployed in groups of five. Pulled by two, three or four horses, they came in different versions - light and fast for moving troops around the battlefield, heavy bronze and armoured versions for punching holes in enemy ranks, those converted to carry fixed heavy crossbows, or even towered versions for commanders to better view the battle proceedings. The chariot corps could also pursue an army in retreat. Needing a wide area to turn and flat ground to function, the limitations of chariots meant they were eventually replaced by cavalry from the 4th century BCE onwards.
Cavalry was probably an innovation from the northern steppe tribes which the Chinese realised offered much more speed and mobility than chariots. The problem was to acquire the skill not only to ride the horses but also to fire weapons from them when the saddle was not much more than a blanket and the stirrup had yet to be invented. For these reasons, it was not until the Han period that cavalry became an important component of a field army. Cavalry riders were armed with a bow, lance, sword or halberd. Like chariots, cavalry was used to protect the flanks and rear of infantry formations, as a shock weapon and as a means to harass an enemy on the move or conduct hit-and-run raids.
Surrounding a settlement with a protective ditch (sometimes flooded to make a moat) dates back to the 7th century BCE millennium BCE in China and the building of fortification walls using dried earth dates to the late Neolithic period. Siege warfare was not a common occurrence in China, though, until the Zhou Dynasty when warfare entailed the total destruction of the enemy as opposed to just their army. By the Han period, city walls were commonly raised to a height of up to six metres and made of compacted earth. Crenellations, towers and monumental gates were another addition to a city's defence. Walls also became more weather resistant by covering the lower parts in stone to withstand local water sources being re-directed by an attacking force in order to undermine the wall. Another technique to strengthen walls was to mix in pottery sherds, plant material, branches and sand with the earth. Ditches up to 50 metres wide, often filled with water, and even a double ring of circuit wall were other techniques designed to ensure a city could withstand attack long enough for a relieving force to arrive from elsewhere.
Not only cities but state frontiers were protected by high walls and watchtowers. The earliest may have been in the north from the 8th century BCE but the practice became a common one in the Warring States Period when many different powerful states vied for control of China. Most of these structures were dismantled by the victor state, what would become the Qin Dynasty from 221 BCE, but one wall was greatly expanded to become the Great Wall of China. Extended again by subsequent dynasties, the wall would eventually stretch some 5,000 km from Gansu province in the east to the Liaodong peninsula. The structure was not continuous but it did, for several centuries, help protect China's northern frontier against invasion from nomadic steppe tribes.
Organisation & Strategies
China's history is an extremely long one and each time period and dynasty saw its own practices and innovations in warfare. Still, some themes run through the history of warfare in China. Officers were often professionals (although they commonly inherited their status), ordinary troops were conscripts or captured soldiers convicts could also be pressed into service. There were also volunteers, typically young men from noble families who joined as cavalrymen looking for adventure and glory. The organisation of an army in the field into three divisions had a long tradition. So, too, did the five-man unit, typically applied to infantry where squads were composed of two archers and three spearmen. By the Warring States period, an army was typically divided into five divisions, each represented by a flag which denoted its function:
- Red Bird - Vanguard
- Green Dragon - Left Wing
- White Tiger - Right Wing
- Black Tortoise - Rear Guard
- Great Bear Constellation - Commander & Bodyguard
When the crossbow became more common troops proficient with that weapon often formed an elite corps and other specific units were used as shock troops to help out where needed or confuse the enemy. As already noted above, archers and cavalry protected the flanks of heavier infantry and chariots, when used, could fulfill the same function or bring up the rear. Such positions, which are described as ideals in the military treatises, are confirmed by the Terracotta Army of Shi Huangti. Flags, unit banners, drums and bells were used on the battlefield to better organise troops and deploy them in the manner the commander wished.
Supporting the soldiers were dedicated officers responsible for logistics and supplying the army with the necessary food (millet, wheat and rice), water, firewood, fodder, equipment and shelter they needed while on campaign. Material was transported by river whenever possible and if not, on ox carts, horses and even wheelbarrows from the Han period onward. From the Warring States Period, and especially the Han period, portions of armies were set the task of farming so as to acquire the necessary vitals that foraging, confiscation from locals or capture from the enemy could not supply. The establishment of garrisons with their own food production and improvements in supply roads and canals also went a long way to lengthening the time an army could effectively stay in the field.
Full-on infantry battles, cavalry skirmishes, reconnaissance, espionage, subterfuge, and ambush were all present in Chinese warfare. Much was made of gentlemanly etiquette in war during the Shang and Zhou periods but this was likely an invention of later writers or at best an exaggeration. Certainly, when warfare became more mobile and the stakes made higher from the 4th century BCE, a commander was expected to win with and by any means at his disposal.
One final theme which runs through much of China's history is the use of expert diviners who could study omens, observe the movement and position of celestial bodies, gauge the meaning of natural phenomena and consult calendars all in order to determine the most auspicious time and place to engage in warfare. Without these considerations, it was believed, the best weapons, men and tactics would not be enough to bring final victory.
Porcelain was not a sudden invention, and an ancient form of porcelain existed during the Shang dynasty (1600 BC–1046 BC). It was perfected during the Tang dynasty and was exported to the Middle East. During the Song dynasty (960–1279 AD), the manufacture of porcelain became highly organized and reached new heights. By the time of the Ming dynasty (1368–1644 AD) porcelain was being exported to Europe, Africa, and Asia via the Silk Road.
Early life Edit
Born in the town of Xi'e in Nanyang Commandery (north of the modern Nanyang City in Henan province), Zhang Heng came from a distinguished but not very affluent family.    His grandfather Zhang Kan had been governor of a commandery and one of the leaders who supported the restoration of the Han by Emperor Guangwu (r. 25–57), following the death of the usurping Wang Mang of the Xin (AD 9–23).     When he was ten, Zhang's father died, leaving him in the care of his mother and grandmother. 
An accomplished writer in his youth, Zhang left home in the year 95 to pursue his studies in the capitals of Chang'an and Luoyang.  While traveling to Luoyang, Zhang passed by a hot spring near Mount Li and dedicated one of his earliest fu poems to it.  This work, entitled "Fu on the Hot Springs" (Wēnquán fù 溫泉賦), describes the throngs of people attending the hot springs, which later became famous as the "Huaqing Hot Springs", a favorite retreat of imperial concubine Yang Guifei during the Tang dynasty.  After studying for some years at Luoyang's Taixue, he was well-versed in the classics and friends with several notable persons, including the mathematician and calligrapher Cui Yuan (78–143), the official and philosophical commentator Ma Rong (79–166), and the philosopher Wang Fu (78–163).   Government authorities offered Zhang appointments to several offices, including a position as one of the Imperial Secretaries, yet he acted modestly and declined.  
At age 23, Zhang returned home with the title "Officer of Merit in Nanyang", serving as the master of documents under the administration of Governor Bao De (in office from 103–111).    As he was charged with composing inscriptions and dirges for the governor, he gained experience in writing official documents.  As Officer of Merit in the commandery, he was also responsible for local appointments to office and recommendations to the capital of nominees for higher office.  He spent much of his time composing rhapsodies on the capital cities. When Bao De was recalled to the capital in 111 to serve as a minister of finance, Zhang continued his literary work at home in Xi'e.    Zhang Heng began his studies in astronomy at the age of 30 and began publishing his works on astronomy and mathematics. 
Official career Edit
In 112, Zhang was summoned to the court of Emperor An (r. 106–125), who had heard of his expertise in mathematics.  When he was nominated to serve at the capital, Zhang was escorted by carriage—a symbol of his official status—to Luoyang, where he became a court gentleman working for the Imperial Secretariat.   He was promoted to Chief Astronomer for the court, serving his first term from 115–120 under Emperor An and his second under the succeeding emperor from 126–132.  As Chief Astronomer, Zhang was a subordinate of the Minister of Ceremonies, one of Nine Ministers ranked just below the Three Excellencies.  In addition to recording heavenly observations and portents, preparing the calendar, and reporting which days were auspicious and which ill-omened, Zhang was also in charge of an advanced literacy test for all candidates to the Imperial Secretariat and the Censorate, both of whose members were required to know at least 9,000 characters and all major writing styles.   Under Emperor An, Zhang also served as Prefect of the Majors for Official Carriages under the Ministry of Guards, in charge of receiving memorials to the throne (formal essays on policy and administration) as well as nominees for official appointments.  
When the government official Dan Song proposed the Chinese calendar should be reformed in 123 to adopt certain apocryphal teachings, Zhang opposed the idea. He considered the teachings to be of questionable stature and believed they could introduce errors.  Others shared Zhang's opinion and the calendar was not altered, yet Zhang's proposal that apocryphal writings should be banned was rejected.  The officials Liu Zhen and Liu Taotu, members of a committee to compile the dynastic history Dongguan Hanji ( 東觀漢記 ), sought permission from the court to consult Zhang Heng.  However, Zhang was barred from assisting the committee due to his controversial views on apocrypha and his objection to the relegation of Gengshi Emperor's (r. 23–25) role in the restoration of the Han Dynasty as lesser than Emperor Guangwu's.   Liu Zhen and Liu Taotu were Zhang's only historian allies at court, and after their deaths Zhang had no further opportunities for promotion to the prestigious post of court historian. 
Despite this setback in his official career, Zhang was reappointed as Chief Astronomer in 126 after Emperor Shun of Han (r. 125–144) ascended to the throne.   His intensive astronomical work was rewarded only with the rank and salary of 600 bushels, or shi, of grain (mostly commuted to coin cash or bolts of silk).   To place this number in context, in a hierarchy of twenty official ranks, the lowest-paid official earned the rank and salary of 100 bushels and the highest-paid official earned 10,000 bushels during the Han.  The 600-bushel rank was the lowest the emperor could directly appoint to a central government position any official of lower status was overseen by central or provincial officials of high rank. 
In 132, Zhang introduced an intricate seismoscope to the court, which he claimed could detect the precise cardinal direction of a distant earthquake.  On one occasion his device indicated that an earthquake had occurred in the northwest. As there was no perceivable tremor felt in the capital his political enemies were briefly able to relish the failure of his device,  until a messenger arrived shortly afterwards to report that an earthquake had occurred about 400 km (248 mi) to 500 km (310 mi) northwest of Luoyang in Gansu province.    
A year after Zhang presented his seismoscope to the court, officials and candidates were asked to provide comments about a series of recent earthquakes which could be interpreted as signs of displeasure from Heaven.  The ancient Chinese viewed natural calamities as cosmological punishments for misdeeds that were perpetrated by the Chinese ruler or his subordinates on earth. In Zhang's memorial discussing the reasons behind these natural disasters, he criticized the new recruitment system of Zuo Xiong which fixed the age of eligible candidates for the title "Filial and Incorrupt" at age forty.  The new system also transferred the power of the candidates' assessment to the Three Excellencies rather than the Generals of the Household, who by tradition oversaw the affairs of court gentlemen.  Although Zhang's memorial was rejected, his status was significantly elevated soon after to Palace Attendant, a position he used to influence the decisions of Emperor Shun.   With this prestigious new position, Zhang earned a salary of 2,000 bushels and had the right to escort the emperor. 
As Palace Attendant to Emperor Shun, Zhang Heng attempted to convince him that the court eunuchs represented a threat to the imperial court. Zhang pointed to specific examples of past court intrigues involving eunuchs, and convinced Shun that he should assume greater authority and limit their influence.  The eunuchs attempted to slander Zhang, who responded with a fu rhapsody called "Fu on Pondering the Mystery", which vents his frustration.  Rafe de Crespigny states that Zhang's rhapsody used imagery similar to Qu Yuan's (340–278 BC) poem "Li Sao" and focused on whether or not good men should flee the corrupted world or remain virtuous within it.  
While working for the central court, Zhang Heng had access to a variety of written materials located in the Archives of the Eastern Pavilion.  Zhang read many of the great works of history in his day and claimed he had found ten instances where the Records of the Grand Historian by Sima Qian (145–90 BC) and the Book of Han by Ban Gu (AD 32–92) differed from other ancient texts that were available to him.   His account was preserved and recorded in the 5th century text of the Book of Later Han by Fan Ye (398–445).  His rhapsodies and other literary works displayed a deep knowledge of classic texts, Chinese philosophy, and histories.  He also compiled a commentary on the Taixuan ( 太玄 , "Great Mystery") by the Daoist author Yang Xiong (53 BC–AD 18).   
Xiao Tong (501–531), a crown prince of the Liang Dynasty (502–557), immortalized several of Zhang's works in his literary anthology Selections of Refined Literature (Wen xuan 文選 ). Zhang's fu rhapsodies include "Western Metropolis Rhapsody" (Xī jīng fù 西京賦 ), "Eastern Metropolis Rhapsody" (Dōng jīng fù 東京賦 ), "Southern Capital Rhapsody" (Nán dū fù 南都賦 ), "Rhapsody on Contemplating the Mystery" (Sī xuán fù 思玄賦 ), and "Rhapsody on Returning to the Fields" (Guī tián fù 歸田賦 ).  The latter fuses Daoist ideas with Confucianism and was a precursor to later Chinese metaphysical nature poetry, according to Liu Wu-chi.  A set of four short lyric poems (shi 詩) entitled "Lyric Poems on Four Sorrows" (Sì chóu shī 四愁詩 ), is also included with Zhang's preface. This set constitutes some of the earliest heptasyllabic shi Chinese poetry written.   While still in Luoyang, Zhang became inspired to write his "Western Metropolis Rhapsody" and "Eastern Metropolis Rhapsody", which were based on the "Rhapsody on the Two Capitals" by the historian Ban Gu.  Zhang's work was similar to Ban's, although the latter fully praised the contemporaneous Eastern Han regime while Zhang provided a warning that it could suffer the same fate as the Western Han if it too declined into a state of decadence and moral depravity.  These two works satirized and criticized what he saw as the excessive luxury of the upper classes.  Zhang's "Southern Capital Rhapsody" commemorated his home city of Nanyang, home of the restorer of the Han Dynasty, Guangwu. 
In Zhang Heng's poem "Four Sorrows", he laments that he is unable to woo a beautiful woman due to the impediment of mountains, snows and rivers.   Rafe de Crespigny, Tong Xiao, and David R. Knechtges claim that Zhang wrote this as an innuendo hinting at his inability to keep in contact with the emperor, hindered by unworthy rivals and petty men.   This poem is one of the first in China to have seven words per line.  His "Four Sorrows" reads:
In Taishan stays my dear sweetheart,
But Liangfu keeps us long apart
Looking east, I find tears start.
She gives me a sword to my delight
A jade I give her as requite.
I'm at a loss as she is out of sight
Why should I trouble myself all night?
In another poem of his called "Stabilizing the Passions" (Dìng qíng fù 定情賦) — preserved in a Tang Dynasty (618–907) encyclopedia, but referred to earlier by Tao Qian (365–427) in praise of Zhang's lyrical minimalism — Zhang displays his admiration for an attractive and exemplary woman.  This simpler type of fu poem influenced later works by the prominent official and scholar Cai Yong (132–192).  Zhang wrote:
Ah, the chaste beauty of this alluring woman!
She shines with flowery charms and blooming face.
She is unique among all her contemporaries.
She is without a peer among her comrades.
Zhang's long lyrical poems also revealed a great amount of information on urban layout and basic geography. His rhapsody "Sir Based-On-Nothing" provides details on terrain, palaces, hunting parks, markets, and prominent buildings of Chang'an, the Western Han capital.   Exemplifying his attention to detail, his rhapsody on Nanyang described gardens filled with spring garlic, summer bamboo shoots, autumn leeks, winter rape-turnips, perilla, evodia, and purple ginger.  Zhang Heng's writing confirms the size of the imperial hunting park in the suburbs of Chang'an, as his estimate for the circumference of the park's encircling wall agrees with the historian Ban Gu's estimate of roughly 400 li (one li in Han times was equal to 415.8 m, or 1,364 ft, making the circumference of the park wall 166,320 m, or 545,600 ft).  Along with Sima Xiangru (179–117 BC), Zhang listed a variety of animals and hunting game inhabiting the park, which were divided in the northern and southern portions of the park according to where the animals had originally came from: northern or southern China.  Somewhat similar to the description of Sima Xiangru, Zhang described the Western Han emperors and their entourage enjoying boat outings, water plays, fishing, and displays of archery targeting birds and other animals with stringed arrows from the tops of tall towers along Chang'an's Kunming Lake.  The focus of Zhang's writing on specific places and their terrain, society, people, and their customs could also be seen as early attempts of ethnographic categorization.  In his poem "Xijing fu", Zhang shows that he was aware of the new foreign religion of Buddhism, introduced via the Silk Road, as well as the legend of the birth of Buddha with the vision of the white elephant bringing about conception.  In his "Western Metropolis Rhapsody" ( 西京賦 ), Zhang described court entertainments such as juedi ( 角抵 ), a form of theatrical wrestling accompanied by music in which participants butted heads with bull horn masks. 
With his "Responding to Criticism" (Ying jian 應間 ), a work modeled on Yang Xiong's "Justification Against Ridicule",  Zhang was an early writer and proponent of the Chinese literary genre shelun, or hypothetical discourse. Authors of this genre created a written dialogue between themselves and an imaginary person (or a real person of their entourage or association) the latter poses questions to the author on how to lead a successful life.  He also used it as a means to criticize himself for failing to obtain high office, but coming to the conclusion that the true gentleman displays virtue instead of greed for power.  In this work, Dominik Declercq asserts that the person urging Zhang to advance his career in a time of government corruption most likely represented the eunuchs or Empress Liang's (116–150) powerful relatives in the Liang clan.  Declercq states that these two groups would have been "anxious to know whether this famous scholar could be lured over to their side", but Zhang flatly rejected such an alignment by declaring in this politically charged piece of literature that his gentlemanly quest for virtue trumped any desire of his for power. 
Zhang wrote about the various love affairs of emperors dissatisfied with the imperial harem, going out into the city incognito to seek out prostitutes and sing-song girls. This was seen as a general criticism of the Eastern Han emperors and their imperial favorites, guised in the criticism of earlier Western Han emperors.  Besides criticizing the Western Han emperors for lavish decadence, Zhang also pointed out that their behavior and ceremonies did not properly conform with the Chinese cyclical beliefs in yin and yang.  In a poem criticizing the previous Western Han Dynasty, Zhang wrote:
Those who won this territory were strong
Those who depended on it endured.
When a stream is long, its water is not easily exhausted.
When roots are deep, they do not rot easily.
Therefore, as extravagance and ostentation were given free rein,
The odor became pungent and increasingly fulsome.
For centuries the Chinese approximated pi as 3 Liu Xin (d. AD 23) made the first known Chinese attempt at a more accurate calculation of 3.1457,  but there is no record detailing the method he used to obtain this figure.   In his work around 130,  Zhang Heng compared the celestial circle to the diameter of the earth, proportioning the former as 736 and the latter as 232, thus calculating pi as 3.1724.  In Zhang's day, the ratio 4:3 was given for the area of a square to the area of its inscribed circle and the volume of a cube and volume of the inscribed sphere should also be 4 2 :3 2 .  In formula, with D as diameter and V as volume, D 3 :V = 16:9 or V= 9 16
In his publication of AD 120 called The Spiritual Constitution of the Universe (靈憲, Ling Xian, lit. "Sublime Model"),   Zhang Heng theorized that the universe was like an egg "as round as a crossbow pellet" with the stars on the shell and the Earth as the central yolk.   This universe theory is congruent with the geocentric model as opposed to the heliocentric model. Although the ancient Warring States (403–221 BC) Chinese astronomers Shi Shen and Gan De had compiled China's first star catalogue in the 4th century BC, Zhang nonetheless catalogued 2,500 stars which he placed in a "brightly shining" category (the Chinese estimated the total to be 14,000), and he recognized 124 constellations.   In comparison, this star catalogue featured many more stars than the 850 documented by the Greek astronomer Hipparchus (c. 190–c.120 BC) in his catalogue, and more than Ptolemy (AD 83–161), who catalogued over 1,000.  Zhang supported the "radiating influence" theory to explain solar and lunar eclipses, a theory which was opposed by Wang Chong (AD 27–97).  In the Ling Xian, Zhang wrote:
The Sun is like fire and the Moon like water. The fire gives out light and the water reflects it. Thus the moon's brightness is produced from the radiance of the Sun, and the Moon's darkness is due to (the light of) the sun being obstructed. The side which faces the Sun is fully lit, and the side which is away from it is dark.
The planets (as well as the Moon) have the nature of water and reflect light. The light pouring forth from the Sun does not always reach the moon owing to the obstruction of the earth itself—this is called 'an-xu', a lunar eclipse. When (a similar effect) happens with a planet (we call it) an occultation when the Moon passes across (the Sun's path) then there is a solar eclipse.
Zhang Heng viewed these astronomical phenomena in supernatural terms as well. The signs of comets, eclipses, and movements of heavenly bodies could all be interpreted by him as heavenly guides on how to conduct affairs of state.  Contemporary writers also wrote about eclipses and the sphericity of heavenly bodies. The music theorist and mathematician Jing Fang (78–37 BC) wrote about the spherical shape of the Sun and Moon while discussing eclipses:
The Moon and the planets are Yin they have shape but no light. This they receive only when the Sun illuminates them. The former masters regarded the Sun as round like a crossbow bullet, and they thought the Moon had the nature of a mirror. Some of them recognized the Moon as a ball too. Those parts of the Moon which the Sun illuminates look bright, those parts which it does not, remain dark. 
The theory posited by Zhang and Jing was supported by later pre-modern scientists such as Shen Kuo (1031–1095), who expanded on the reasoning of why the Sun and Moon were spherical.  The theory of the celestial sphere surrounding a flat, square Earth was later criticized by the Jin-dynasty scholar-official Yu Xi (fl. 307-345). He suggested that the Earth could be round like the heavens, a spherical Earth theory fully accepted by mathematician Li Ye (1192-1279) but not by mainstream Chinese science until European influence in the 17th century. 
Extra tank for inflow clepsydra Edit
The outflow clepsydra was a timekeeping device used in China as long ago as the Shang Dynasty (c. 1600–c. 1050 BC), and certainly by the Zhou Dynasty (1122–256 BC).  The inflow clepsydra with an indicator rod on a float had been known in China since the beginning of the Han Dynasty in 202 BC and had replaced the outflow type.  The Han Chinese noted the problem with the falling pressure head in the reservoir, which slowed the timekeeping of the device as the inflow vessel was filled.  Zhang Heng was the first to address this problem, indicated in his writings from 117, by adding an extra compensating tank between the reservoir and the inflow vessel.   Zhang also mounted two statuettes of a Chinese immortal and a heavenly guard on the top of the inflow clepsydra, the two of which would guide the indicator rod with their left hand and point out the graduations with their right.  Joseph Needham states that this was perhaps the ancestor of all clock jacks that would later sound the hours found in mechanical clocks by the 8th century, but he notes that these figures did not actually move like clock jack figurines or sound the hours.  Many additional compensation tanks were added to later clepsydras in the tradition of Zhang Heng. In 610 the Sui Dynasty (581–618) engineers Geng Xun and Yuwen Kai crafted an unequal-armed steelyard balance able to make seasonal adjustments in the pressure head of the compensating tank, so that it could control the rate of water flow for different lengths of day and night during the year.  Zhang mentioned a "jade dragon's neck", which in later times meant a siphon.  He wrote of the floats and indicator-rods of the inflow clepsydra as follows:
Bronze vessels are made and placed one above the other at different levels they are filled with pure water. Each has at the bottom a small opening in the form of a 'jade dragon's neck'. The water dripping (from above) enters two inflow receivers (alternately), the left one being for the night and the right one for the day.
On the covers of each (inflow receiver) there are small cast statuettes in gilt bronze the left (night) one is an immortal and the right (day) one is a policeman. These figures guide the indicator-rod (lit. arrow) with their left hands, and indicate the graduations on it with their right hands, thus giving the time. 
Water-powered armillary sphere Edit
Zhang Heng is the first person known to have applied hydraulic motive power (i.e. by employing a waterwheel and clepsydra) to rotate an armillary sphere, an astronomical instrument representing the celestial sphere.    The Greek astronomer Eratosthenes (276–194 BC) invented the first armillary sphere in 255 BC. The Chinese armillary sphere was fully developed by 52 BC, with the astronomer Geng Shouchang's addition of a permanently fixed equatorial ring.  In AD 84 the astronomers Fu An and Jia Kui added the ecliptic ring, and finally Zhang Heng added the horizon and meridian rings.   This invention is described and attributed to Zhang in quotations by Hsu Chen and Li Shan, referencing his book Lou Shui Chuan Hun Thien I Chieh (Apparatus for Rotating an Armillary Sphere by Clepsydra Water). It was likely not an actual book by Zhang, but a chapter from his Hun I or Hun I Thu Chu, written in 117 AD.  His water-powered armillary influenced the design of later Chinese water clocks and led to the discovery of the escapement mechanism by the 8th century.  The historian Joseph Needham (1900–1995) states:
What were the factors leading to the first escapement clock in China? The chief tradition leading to Yi Xing (AD 725 ) was of course the succession of 'pre-clocks' which had started with Zhang Heng about 125. Reason has been given for believing that these applied power to the slow turning movement of computational armillary spheres and celestial globes by means of a water-wheel using clepsydra drip, which intermittently exerted the force of a lug to act on the teeth of a wheel on a polar-axis shaft. Zhang Heng in his turn had composed this arrangement by uniting the armillary rings of his predecessors into the equatorial armillary sphere, and combining it with the principles of the water-mills and hydraulic trip-hammers which had become so widespread in Chinese culture in the previous century. 
Zhang did not initiate the Chinese tradition of hydraulic engineering, which began during the mid Zhou Dynasty (c. 6th century BC), through the work of engineers such as Sunshu Ao and Ximen Bao.  Zhang's contemporary, Du Shi, (d. AD 38) was the first to apply the motive power of waterwheels to operate the bellows of a blast furnace to make pig iron, and the cupola furnace to make cast iron.   Zhang provided a valuable description of his water-powered armillary sphere in the treatise of 125, stating:
The equatorial ring goes around the belly of the armillary sphere 91 and 5/19 (degrees) away from the pole. The circle of the ecliptic also goes round the belly of the instrument at an angle of 24 (degrees) with the equator. Thus at the summer solstice the ecliptic is 67 (degrees) and a fraction away from the pole, while at the winter solstice it is 115 (degrees) and a fraction away. Hence (the points) where the ecliptic and the equator intersect should give the north polar distances of the spring and autumn equinoxes. But now (it has been recorded that) the spring equinox is 90 and 1/4 (degrees) away from the pole, and the autumn equinox is 92 and 1/4 (degrees) away. The former figure is adopted only because it agrees with the (results obtained by the) method of measuring solstitial sun shadows as embodied in the Xia (dynasty) calendar. 
Zhang Heng's water-powered armillary sphere had profound effects on Chinese astronomy and mechanical engineering in later generations. His model and its complex use of gears greatly influenced the water-powered instruments of later astronomers such as Yi Xing (683–727), Zhang Sixun (fl. 10th century), Su Song (1020–1101), Guo Shoujing (1231–1316), and many others. Water-powered armillary spheres in the tradition of Zhang Heng's were used in the eras of the Three Kingdoms (220–280) and Jin Dynasty (266–420), yet the design for it was temporarily out of use between 317 and 418, due to invasions of northern Xiongnu nomads.  Zhang Heng's old instruments were recovered in 418, when Emperor Wu of Liu Song (r. 420–422) captured the ancient capital of Chang'an. Although still intact, the graduation marks and the representations of the stars, Moon, Sun, and planets were quite worn down by time and rust.  In 436, the emperor ordered Qian Luozhi, the Secretary of the Bureau of Astronomy and Calendar, to recreate Zhang's device, which he managed to do successfully.  Qian's water-powered celestial globe was still in use at the time of the Liang Dynasty (502–557), and successive models of water-powered armillary spheres were designed in subsequent dynasties. 
Zhang's seismoscope Edit
From the earliest times, the Chinese were concerned with the destructive force of earthquakes. It was recorded in Sima Qian's Records of the Grand Historian of 91 BC that in 780 BC an earthquake had been powerful enough to divert the courses of three rivers.  It was not known at the time that earthquakes were caused by the shifting of tectonic plates in the Earth's crust instead, the people of the ancient Zhou Dynasty explained them as disturbances with cosmic yin and yang, along with the heavens' displeasure with acts committed (or the common peoples' grievances ignored) by the current ruling dynasty.  These theories were ultimately derived from the ancient text of the Yijing (Book of Changes), in its fifty-first hexagram.  There were other early theories about earthquakes, developed by those such as the ancient Greeks. Anaxagoras (c. 500–428 BC) believed that they were caused by excess water near the surface crust of the earth bursting into the Earth's hollows Democritus (c. 460–370 BC) believed that the saturation of the Earth with water caused them Anaximenes (c. 585–c. 525 BC) believed they were the result of massive pieces of the Earth falling into the cavernous hollows due to drying and Aristotle (384–322 BC) believed they were caused by instability of vapor (pneuma) caused by the drying of the moist Earth by the Sun's rays. 
During the Han Dynasty, many learned scholars—including Zhang Heng—believed in the "oracles of the winds".  These oracles of the occult observed the direction, force, and timing of the winds, to speculate about the operation of the cosmos and to predict events on Earth.  These ideas influenced Zhang Heng's views on the cause of earthquakes.
In 132, Zhang Heng presented to the Han court what many historians consider to be his most impressive invention, the first seismoscope. A seismoscope records the motions of Earth's shaking, but unlike a seismometer, it does not retain a time record of those motions.  It was named "earthquake weathervane" (hòufēng dìdòngyí 候風地動儀),  and it was able to roughly determine the direction (out of eight directions) where the earthquake came from.   According to the Book of Later Han (compiled by Fan Ye in the 5th century), his bronze urn-shaped device, with a swinging pendulum inside, was able to detect the direction of an earthquake hundreds of miles/kilometers away.   This was essential for the Han government in sending quick aid and relief to regions devastated by this type of natural disaster.    The Book of Later Han records that, on one occasion, Zhang's device was triggered, though no observer had felt any seismic disturbance several days later a messenger arrived from the west and reported that an earthquake had occurred in Longxi (modern Gansu Province), the same direction that Zhang's device had indicated, and thus the court was forced to admit the efficacy of the device. 
To indicate the direction of a distant earthquake, Zhang's device dropped a bronze ball from one of eight tubed projections shaped as dragon heads the ball fell into the mouth of a corresponding metal object shaped as a toad, each representing a direction like the points on a compass rose.  His device had eight mobile arms (for all eight directions) connected with cranks having catch mechanisms at the periphery.  When tripped, a crank and right angle lever would raise a dragon head and release a ball which had been supported by the lower jaw of the dragon head.  His device also included a vertical pin passing through a slot in the crank, a catch device, a pivot on a projection, a sling suspending the pendulum, an attachment for the sling, and a horizontal bar supporting the pendulum.  Wang Zhenduo (王振鐸) argued that the technology of the Eastern Han era was sophisticated enough to produce such a device, as evidenced by contemporary levers and cranks used in other devices such as crossbow triggers. 
Later Chinese of subsequent periods were able to reinvent Zhang's seismoscope. They included the 6th-century mathematician and surveyor Xindu Fang of the Northern Qi Dynasty (550–577) and the astronomer and mathematician Lin Xiaogong of the Sui Dynasty (581–618).  Like Zhang, Xindu Fang and Lin Xiaogong were given imperial patronage for their services in craftsmanship of devices for the court.  By the time of the Yuan Dynasty (1271–1368), it was acknowledged that all devices previously made were preserved, except for that of the seismoscope.  This was discussed by the scholar Zhou Mi around 1290, who remarked that the books of Xindu Fang and Lin Xiaogong detailing their seismological devices were no longer to be found.  Horwitz, Kreitner, and Needham speculate if Tang Dynasty (618–907) era seismographs found their way to contemporary Japan according to Needham, "instruments of apparently traditional type there in which a pendulum carries pins projecting in many directions and able to pierce a surrounding paper cylinder, have been described." 
Hong-sen Yan states that modern replicas of Zhang's device have failed to reach the level of accuracy and sensitivity described in Chinese historical records.  Wang Zhenduo presented two different models of the seismoscope based on the ancient descriptions of Zhang's device.  In his 1936 reconstruction, the central pillar (du zhu) of the device was a suspended pendulum acting as a movement sensor, while the central pillar of his second model in 1963 was an inverted pendulum.  According to Needham, while working in the Seismological Observatory of Tokyo University in 1939, Akitsune Imamura and Hagiwara made a reconstruction of Zhang's device.   While it was John Milne and Wang Zhenduo who argued early on that Zhang's "central pillar" was a suspended pendulum, Imamura was the first to propose an inverted model.  He argued that transverse shock would have rendered Wang's immobilization mechanism ineffective, as it would not have prevented further motion that could knock other balls out of their position.  On June 13, 2005, modern Chinese seismologists announced that they had successfully created a replica of the instrument. 
Anthony J. Barbieri-Low, a Professor of Early Chinese History at the University of California, Santa Barbara, names Zhang Heng as one of several high-ranking Eastern-Han officials who engaged in crafts that were traditionally reserved for artisans (gong 工), such as mechanical engineering.  Barbieri-Low speculates that Zhang only designed his seismoscope, but did not actually craft the device himself. He asserts that this would most likely have been the job of artisans commissioned by Zhang.  He writes: "Zhang Heng was an official of moderately high rank and could not be seen sweating in the foundries with the gong artisans and the government slaves. Most likely, he worked collaboratively with the professional casters and mold makers in the imperial workshops." 
The Wei (220–265) and Jin Dynasty (266–420) cartographer and official Pei Xiu (224–271) was the first in China to describe in full the geometric grid reference for maps that allowed for precise measurements using a graduated scale, as well as topographical elevation.   However, map-making in China had existed since at least the 4th century BC with the Qin state maps found in Gansu in 1986.  Pinpointed accuracy of the winding courses of rivers and familiarity with scaled distance had been known since the Qin and Han Dynasty, respectively, as evidenced by their existing maps, while the use of a rectangular grid had been known in China since the Han as well.   Historian Howard Nelson states that, although the accounts of Zhang Heng's work in cartography are somewhat vague and sketchy, there is ample written evidence that Pei Xiu derived the use of the rectangular grid reference from the maps of Zhang Heng.  Rafe de Crespigny asserts that it was Zhang who established the rectangular grid system in Chinese cartography.  Needham points out that the title of his book Flying Bird Calendar may have been a mistake, and that the book is more accurately entitled Bird's Eye Map.  Historian Florian C. Reiter notes that Zhang's narrative "Guitian fu" contains a phrase about applauding the maps and documents of Confucius of the Zhou Dynasty, which Reiter suggests places maps (tu) on a same level of importance with documents (shu).  It is documented that a physical geography map was first presented by Zhang Heng in 116 AD, called a Ti Hsing Thu. 
Odometer and south-pointing chariot Edit
Zhang Heng is often credited with inventing the first odometer,   an achievement also attributed to Archimedes (c. 287–212 BC) and Heron of Alexandria (fl. AD 10–70). Similar devices were used by the Roman and Han-Chinese empires at about the same period. By the 3rd century, the Chinese had termed the device the jili guche ( 記里鼓車 , "li-recording drum carriage" (the modern measurement of li = 500 m/1640 ft). 
Ancient Chinese texts describe the mechanical carriage's functions after one li was traversed, a mechanically driven wooden figure struck a drum, and after ten li had been covered, another wooden figure struck a gong or a bell with its mechanically operated arm.  However, there is evidence to suggest that the invention of the odometer was a gradual process in Han Dynasty China that centered on the "huang men"—court people (i.e. eunuchs, palace officials, attendants and familiars, actors, acrobats, etc.) who followed the musical procession of the royal "drum-chariot".  There is speculation that at some time during the 1st century BC the beating of drums and gongs was mechanically driven by the rotation of the road wheels.  This might have actually been the design of Luoxia Hong (c. 110 BC), yet by at least 125 the mechanical odometer carriage was already known, as it was depicted in a mural of the Xiao Tang Shan Tomb. 
The south-pointing chariot was another mechanical device credited to Zhang Heng.  It was a non-magnetic compass vehicle in the form of a two-wheeled chariot. Differential gears driven by the chariot's wheels allowed a wooden figurine (in the shape of a Chinese state minister) to constantly point to the south, hence its name. The Song Shu (c. AD 500 ) records that Zhang Heng re-invented it from a model used in the Zhou Dynasty era, but the violent collapse of the Han Dynasty unfortunately did not allow it to be preserved. Whether Zhang Heng invented it or not, Ma Jun (200–265) succeeded in creating the chariot in the following century. 
Science and technology Edit
Zhang Heng's mechanical inventions influenced later Chinese inventors such as Yi Xing, Zhang Sixun, Su Song, and Guo Shoujing. Su Song directly named Zhang's water-powered armillary sphere as the inspiration for his 11th-century clock tower.  The cosmic model of nine points of Heaven corresponding with nine regions of earth conceived in the work of the scholar-official Chen Hongmou (1696–1771) followed in the tradition of Zhang's book Spiritual Constitution of the Universe.  The seismologist John Milne, who created the modern seismograph in 1876 alongside Thomas Gray and James A. Ewing at the Imperial College of Engineering in Tokyo, commented in 1886 on Zhang Heng's contributions to seismology.   The historian Joseph Needham emphasized his contributions to pre-modern Chinese technology, stating that Zhang was noted even in his day for being able to "make three wheels rotate as if they were one."  More than one scholar has described Zhang as a polymath.     However, some scholars also point out that Zhang's writing lacks concrete scientific theories.  Comparing Zhang with his contemporary, Ptolemy (83–161) of Roman Egypt, Jin Guantao, Fan Hongye, and Liu Qingfeng state:
Based on the theories of his predecessors, Zhang Heng systematically developed the celestial sphere theory. An armillary constructed on the basis of his hypotheses bears a remarkable similarity to Ptolemy's earth-centered theory. However, Zhang Heng did not definitely propose a theoretical model like Ptolemy's earth-centered one. It is astonishing that the celestial model Zhang Heng constructed was almost a physical model of Ptolemy's earth-centered theory. Only a single step separates the celestial globe from the earth-centered theory, but Chinese astronomers never took that step. Here we can see how important the exemplary function of the primitive scientific structure is. In order to use the Euclidean system of geometry as a model for the development of astronomical theory, Ptolemy first had to select hypotheses which could serve as axioms. He naturally regarded circular motion as fundamental and then used the circular motion of deferents and epicycles in his earth-centered theory. Although Zhang Heng understood that the sun, moon and planets move in circles, he lacked a model for a logically structured theory and so could not establish a corresponding astronomical theory. Chinese astronomy was most interested in extracting the algebraic features of planetary motion (that is, the length of the cyclic periods) to establish astronomical theories. Thus astronomy was reduced to arithmetic operations, extracting common multiples and divisors from the observed cyclic motions of the heavenly bodies. 
Poetic literature Edit
Zhang's poetry was widely read during his life and after his death. In addition to the compilation of Xiao Tong mentioned above, the Eastern Wu official Xue Zong (d. 237) wrote commentary on Zhang's poems "Dongjing fu" and "Xijing fu".  The influential poet Tao Qian wrote that he admired the poetry of Zhang Heng for its "curbing extravagant diction and aiming at simplicity", in regards to perceived tranquility and rectitude correlating with the simple but effective language of the poet.  Tao wrote that both Zhang Heng and Cai Yong "avoided inflated language, aiming chiefly at simplicity", and adding that their "compositions begin by giving free expression to their fancies but end on a note of quiet, serving admirably to restrain undisciplined and passionate nature". 
Posthumous honors Edit
Zhang was given great honors in life and in death. The philosopher and poet Fu Xuan (217–278) of the Wei and Jin dynasties once lamented in an essay over the fact that Zhang Heng was never placed in the Ministry of Works. Writing highly of Zhang and the 3rd-century mechanical engineer Ma Jun, Fu Xuan wrote, "Neither of them was ever an official of the Ministry of Works, and their ingenuity did not benefit the world. When (authorities) employ personnel with no regard to special talent, and having heard of genius neglect even to test it—is this not hateful and disastrous?" 
In honor of Zhang's achievements in science and technology, his friend Cui Ziyu (Cui Yuan) wrote a memorial inscription on his burial stele, which has been preserved in the Guwen yuan.  Cui stated, "[Zhang Heng's] mathematical computations exhausted (the riddles of) the heavens and the earth. His inventions were comparable even to those of the Author of Change. The excellence of his talent and the splendour of his art were one with those of the gods."  The minor official Xiahou Zhan (243–291) of the Wei Dynasty made an inscription for his own commemorative stele to be placed at Zhang Heng's tomb. It read: "Ever since gentlemen have composed literary texts, none has been as skillful as the Master [Zhang Heng] in choosing his words well . if only the dead could rise, oh I could then turn to him for a teacher!" 
Several things have been named after Zhang in modern times, including the lunar crater Chang Heng,  the asteroid 1802 Zhang Heng,  and the mineral zhanghengite. In 2018, China launched a research satellite called China Seismo-Electromagnetic Satellite (CSES) which is also named Zhangheng-1 (ZH-1).