Time measurement in imperial China


June 2018

Time measurement in imperial China

According to legend (even though writing was not invented until 1800 years later), Chinese astronomy is thought to date from the 61st year of Huangdi’s reign, namely 2637 BC.

The calendar, attributed to the Chinese Emperor, the “Son of Heaven”

According to legend (even though writing was not invented until 1800 years later), Chinese astronomy is thought to date from the 61st year of Huangdi’s reign, namely 2637 BC. The legendary emperor, considered to be the founding father of the Chinese civilisation, is credited with the invention of the calendar. Initially lunar-based, the calendar became lunisolar around 1400 BC. This basic calendar was supplemented by a sexagesimal cycle, independent of astronomical phenomena and used for measuring the passing days and months.

Until the end of the Empire in 1911, the calendar was an attribute of imperial sovereignty. The monarch of the time, known as “Tian zi” or Son of Heaven, and considered a go-between between the Sky and the Earth, started his reign by introducing a new calendar based on the two complementary principles of Yin and Yang. Thenceforth holder of a “divine mandate”, the monarch’s task was to pass on information based upon the state of the heavens to ensure a harmonious earthly existence. Astronomy was thus elevated to the rank of state and government science.

Clepsydra, ancestor of the hydraulic astronomical clock

Alongside its work on vs, which were globally perceived as scientific instruments, China developed the clepsydra, examples of which were first witnessed back in around 500 BC. The in- or out-flow clepsydra was a cylindrical vase with an opening in its base. In order to improve its accuracy, the Chinese equipped the instrument with a system of siphons, followed by a series of reservoirs, each feeding into the other.

This culminated, towards the year 1000, in a model, which combining both methods. Appearing in the fifth century, balance clepsydras, composed of receptacles suspended from a balance beam, were used to measure short time intervals. In order to assist the Emperor in his mission, astronomers and mechanical engineers developed the hydraulic-powered armillary sphere.

To do this, they endeavoured to increase the minimal force of water in a clepsydra enough to be able to power a big machine. They achieved their aim thanks to the multiplying effect of the wheel.

In the year 124, Zang Heng presented the Emperor with a hydraulic-powered equatorial armillary sphere. The principle of combining a celestial globe with a water clock to create an astrarium was first attributed to Zang Heng.

Around 720, the Buddhist monk Yi-Xing compiled his “water-driven spherical bird’s eye view map of the heavens”. This latter was fitted with a regulator in the form of a wheel equipped with buckets in order to convert a continuous flow of water into a regular non-continuous movement.

Su Song's clock tower
Su Song’s clock tower

In 1086, the Emperor ordered Su Song, a Mandarin scientist, to rebuild the city clock. In 1094, he presented to the monarch his “tower for hydraulic-powered sphere and globe”. Housed within a 12-metre high construction, the armillary sphere, combined with a demonstrational celestial globe, depicted the orbits of the Sun, Moon and certain stars, as they were seen from Earth. The whole mechanism, complete with automata indicating the time audibly, was powered by a continuous power- transmission chain drive.

Su Song’s clock disappeared after its removal to Peking in 1127, since no-one was able to reassemble it. Nevertheless, it has been possible to reproduce it thanks to descriptions and diagrams recorded by its author in a treatise that has since been preserved.

Time measurement in imperial China Time measurement in imperial China

This “Dragon Boat vessel,” supported upon two wooden blocks was placed over a large flat copper or brass dish or platter. A thin string, usually of silk, having a small metal weight or bell attached at each end, was stretched across the top of the vessel at a point along the marked incense stick chosen by the sleeper when he wished to be aroused. The incense stick burned for the desired number of hours and when it reached the string, the string burned quickly and parted. As the small metal weights dropped into the dish, they made a brief tinkling sound, which presumably was sufficient to awaken the sleeper.

“Your son is not your son, but the son of his time”

In 11th century China, the water-powered astronomical clock with regulator logically ought to have been generating mechanical timepieces. However, astronomers were busy following another course, one that brought about the rift between Europe with its rise towards economic and technical supremacy and the Middle Kingdom with its protracted stagnation.

China was more preoccupied with improving observational astronomy than time measurement. The former attained an unparalleled degree of refinement between the 13th and 14th centuries thanks to the construction of oversized instruments permitting considerable improvements in accuracy.

The instrument built by the astronomer Guo Shoujing in 1276 close to the city of Dengfeng enabled him to measure the interval of a year to within 23 seconds. The fields of astronomy and watchmaking, the pursuit of which was prohibited, were the secret preserve of the Emperor and his scientists. Thus, when building a new astronomical clock, the watchmakers and astronomers considered competent for the job were required to learn everything again. This reminds us of a saying by Confucius: “Remember that your son is not your son, but the son of his time.”

It would be five centuries after Su Song’s long-since forgotten masterpiece of achievement had been completed before the Chinese would see any revolutionary new timepieces. These were the work of Westerners, for whom the clock was the ideal tool for gaining access to the Emperor and entering the Middle Empire for evangelisation purposes. Jesuits taught by Matteo Ricci arrived replete with a much more accurate knowledge of astronomy than that developed in China.

As a result, some of the costs they incurred were reimbursed by the authorities. Apart from globes and maps, Ricci gave his hosts never-before-seen chiming clocks. In addition to affording them private time, they entertained their new owners with their melodic chime features and the automata so beloved of the Asian people.

The Jesuit Matteo Ricci introduced watchmaking in China
The Jesuit Matteo Ricci introduced watchmaking in China

China, at the time, had a significant number of talented craftsmen and a population substantially equal to that of Europe. They thus provided an opportunity to develop a genuine watchmaking industry. Contrary to the basic principles underlying the Chinese civilisation, this path was not pursued to any significant extent. Although the calendar was of structural importance, never before had either life or work been organised on the basis of measured time. L’index de la Grande Bibliothèque of 1782 noted, in this respect, that while the practices of land surveying and irrigation were useful to the world’s populations, the other teachings of the West were nothing other than bizarrely complicated, conceived only for the pleasure of the senses and not satisfying a basic need.

Time-measurement did not satisfy a basic need

The population mainly lived off farming regulated to the rhythm of the seasons, day and night, and made do with these natural indicators. In towns and cities, the hours and public time were announced by chiming clock towers, or the beating of drums, as is still the case with the “Clock towers” and “Drum towers” of Beijing and Xi’an. Private time, however, was roughly indicated by vertical gnomons and combustion clocks with graduated wicks.

Under the Sung dynasty (960- 1279), incense clocks put in an appearance, based on the time it took for the material to burn. Although they provided random accuracy, these instruments were sufficient to meet the needs of the middle classes, while the water clocks were reserved for the authorities due to the encumbrances and constraints that they entailed.

A small number of watches, now preserved in the Forbidden City, illustrate the genius of European watchmakers in catering to the tastes of the Middle Kingdom.

Watchmaking was therefore the privilege of the Emperor and his dignitaries, who turned to Europe for their quality pieces. For 250 years, Peking had received as gifts, or purchased, a considerable number of watches, mantle or wall clocks from England, France and Switzerland. A small number of them, now preserved in the Forbidden City, illustrate the genius of European watchmakers in catering to the tastes of the Middle Kingdom.

The watches feature dials with a central seconds hand and richly engraved and gilded movement. Their cases, set with natural pearls and multi-coloured stones, sport painted decorations on enamel on a wide variety of themes. Chiming clocks are fitted with automata. They were all sold in pairs, with the decoration being mirrored in the most precious models. A symbol of integrity, the principle of twos stands for the notion of symmetry omnipresent in architecture, where Harmony is obtained by balancing the Yin and the Yang. According to this philosophy, any gifts given to the Emperor or a superior were always offered in pairs, a sacrosanct rule that no-one dared to break.

In 1911, it all changed with the Revolution. The Empire made way for the Republic. Although it was replaced in 1912 by the Gregorian system, wherein the calendar years were counted from the foundation of the Republic, the traditional calendar now co-exists unofficially with this system. This was the result of the last reform brought about by the Jesuit missionary, Adam Schall von Bell, imperial astronomer in Peking.