A water clock or clepsydra (Greek kleptein, to steal; hydor, water) is any timekeeper operated by means of a regulated flow of liquid into (inflow type) or out from (outflow type) a vessel where it is measured.

Water clock overview

Water clocks, along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the vertical gnomon and day-counting tally stick.^[1] Given their great antiquity, where and when they first existed are not known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC.^[2] The cantilever spar of this cable-stay bridge, the Sundial Bridge at Turtle Bay, forms the gnomon of a large garden sundial The gnomon is the part of a sundial that casts the shadow. ... Tally sticks are an ancient mnemonic device (memory aid) to record and document numbers or quantities even messages. ... For other uses, see Babylon (disambiguation). ... (5th millennium BC – 4th millennium BC – 3rd millennium BC - other millennia) Events City of Ur in Mesopotamia (40th century BC). ...

The Greek and Roman civilizations are credited for initially advancing water clock design to include complex gearing, which was connected to fanciful automata and improved accuracy. These advances were passed on through Byzantium and Islamic times, eventually making their way to Europe. Independently, the Chinese developed their own advanced water clocks, passing their ideas on to Korea and Japan. An automaton (plural: automata) is a self-operating machine. ... Byzantium (Greek: Βυζάντιον) was an ancient Greek city, which, according to legend, was founded by Greek colonists from Megara in 667 BC and named after their king Byzas or Byzantas (Βύζας or Βύζαντας in Greek). ... Islam (Arabic: ; ( ▶ (help· info)), the submission to God) is a monotheistic faith, one of the Abrahamic religions and the worlds second-largest religion. ... For other uses, see Europe (disambiguation). ... This article is about the Korean peninsula and civilization. ...

Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. It is important to point out that the need for the common person to 'know what time it is' largely did not exist until the Industrial Revolution, when it became important to keep track of hours worked. In the earliest of times, however, the purpose for using a water clock was for astronomical and astrological reasons. These early water clocks were calibrated with a sundial. Through the centuries, water clocks were used for timing lawyer's speeches during a trial, labors of prostitutes, night watches of guards, sermons and Masses in church, to name only a few. While never reaching the level of accuracy based on today's standards of timekeeping, the water clock was the most accurate and commonly used timekeeping device for millennia, until it was replaced by the more accurate pendulum clock in 17th century Europe. A Watt steam engine, the steam engine that propelled the Industrial Revolution in Britain and the world. ... For other uses, see Clock (disambiguation). ... For other uses, see Sundial (disambiguation). ... For the fish called lawyer, see Burbot. ... Prostitution is the sale of sexual services (typically manual stimulation, oral sex, sexual intercourse, or anal sex) for cash or other kind of return, generally indiscriminately with many persons. ... A pendulum clock uses a pendulum as its time base. ...

Egypt

The oldest water clock of which there is physical evidence dates to c. 1400 BC and was used in the Temple of Amen-Re.^[3] The oldest documentation of the water clock is the tomb inscription of the 16th century BC Egyptian court official Amenemhet, which identifies him as its inventor.^[4][5] These simple water clocks, which were of the outflow type, were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom. There were twelve separate columns with consistently spaced markings on the inside to measure the passage of "hours" as the water level reached them. The columns were for each of the twelve months to allow for the variations of the seasonal hours. These clocks were used to determine hours at night, but may have been used in daylight as well. Map of the Amun-Re Temple First pylon of Karnak The Precinct of Amun-Re, located near Luxor, Egypt, is one of the four main enclosed areas that make up the immense Karnak Temple Complex. ... Look up Month in Wiktionary, the free dictionary. ...

Babylon

In Babylon, water clocks were of the outflow type and were cylindrical in shape. Use of the water clock as an aid to astronomical calculations dates back to the Old Babylonian period (c. 2000 BC–c. 1600 BC).^[6] Old Babylonian is a term used to describe the period of Mesopotamian history between the end of the Third Dynasty of Ur (c. ...

While there are no surviving water clocks from the Mesopotamian region, most evidence of their existence comes from writings on clay tablets. Two collections of tablets, for example, are the Enuma-Anu-Enlil (1600–1200 BC) and the MUL.APIN (7th century BC).^[7] In these tablets, water clocks are used in reference to payment of the night and day watches (guards). MUL.APIN are ancient cuneiform tablets that were created around the 1400s BC to catalog the constellations of the day. ...

These clocks were unique, as they did not have an indicator such as hands (as are typically used today) or grooved notches (as were used in Egypt). Instead, these clocks measured time "by the weight of water flowing from" it.^[8] The volume was measured in capacity units called qa. The weight, mana (the Greek unit for about one pound), is the weight of water in a water clock.

It is important to note that during Babylonian times, time was measured with temporal hours. So, as seasons changed, so did the length of a day. "To define the length of a 'night watch' at the summer solstice, one had to pour two mana of water into a cylindrical clepsydra; its emptying indicated the end of the watch. One-sixth of a mana had to be added each succeeding half-month. At equinox, three mana had to be emptied in order to correspond to one watch, and four mana were emptied for each watch of the winter solstitial night."^[8]

India

N. Kameswara Rao suggests that pots excavated from Mohenjodaro might have been used as water clocks; they are tapered at bottom, have a hole on the side, and are similar to the utensil used to perform abhishekam (pour holy water) on shivalingam.^[9] Mohenjo-daro (literally, mound of the dead), like Harappa, was a city of the Indus Valley civilization. ... Linga worship (Estate of Cynthia and Harlen Welsh) Lingam or Linga (Sanskrit: Gender as in purusha-linga : male sexual organ) is used as a symbol for the worship of the Hindu God Shiva. ...

N. Narahari Achar^[10] and Subhash Kak^[11] suggest that the use of the water clock in ancient India is mentioned in the Atharvaveda from the 2nd millennium BC. Subhash Kak (सुभाष काक) (born March 26, 1947, Srinagar, Kashmir) is Delaune Distinguished Professor of Electrical Engineering and Professor in the Asian Studies and Cognitive Science Programs at Louisiana State University, Baton Rouge. ... Ancient India may refer to: The ancient History of India, which generally includes the ancient history of the whole Indian subcontinent (South Asia) Indus Valley Civilization — during the Bronze Age Vedic period — the period of Vedic Sanskrit, spanning the late Bronze Age and the earlier Iron Age Mahajanapadas — during the... The Atharvaveda (Sanskrit: अथर्ववेद, , a tatpurusha compound of , a type of priest, and meaning knowledge) is a sacred text of Hinduism, and one of the four Vedas, often called the fourth Veda. According to tradition, the Atharvaveda was mainly composed by two groups of rishis known as the Bhrigus and the...

Ghati or Kapala (clepsydra or water clock) is referred to in Jyotisha Vedanga, where the amount of water that measures a nadika (24 minutes) is mentioned. A more developed form of the clepsydra is described in chapter xiii, 23 of the Suryasiddhanta.^[12] Jyotisha (, in Hindi and English usage Jyotish; sometimes called Hindu astrology, Indian astrology, and/or Vedic astrology) is the Hindu system of astrology, one of the six disciplines of Vedanga, and regarded as one of the oldest schools of ancient astrology to have had an independent origin, affecting all other... The Vedanga (IAST , member of the Veda) are six auxiliary disciplines for the understanding and tradition of the Vedas. ...

At Nalanda, a Buddhist university, four hours a day and four hours at night were measured by a water clock, which consisted of a copper bowl holding two large floats in a larger bowl filled with water. The bowl was filled with water from a small hole at its bottom; it sank when completely filled and was marked by the beating of a drum at daytime. The amount of water added varied with the seasons and this clock was operated by the students of the university.^[13] This article is about the ancient town and university. ... A replica of an ancient statue found among the ruins of a temple at Sarnath Buddhism is a philosophy based on the teachings of the Buddha, Siddhārtha Gautama, a prince of the Shakyas, whose lifetime is traditionally given as 566 to 486 BCE. It had subsequently been accepted by...

The description of a water clock in astrologer Varahimira's Pancasiddhantika (505) adds further detail to the account given in the Suryasiddhanta. The description given by mathematician Brahmagupta in his work Brahmasphutasiddhanta matches with that given in the Suryasiddhanta. Astronomer Lallacharya describes this instrument in detail.^[14] In practice, the dimensions were determined by experiment. Brahmagupta (ब्रह्मगुप्त) ( ) (589–668) was an Indian mathematician and astronomer. ...

China

The water powered mechanism of Su Song's astronomical clock tower.

In China, as well as throughout eastern Asia, water clocks were very important in the study of astronomy and astrology. The oldest reference dates the use of the water-clock in China to the 6th century BC.^[15] From about 200 BC onwards, the outflow clepsydra was replaced almost everywhere in China by the inflow type with an indicator-rod borne on a float.^[15] Seeing the water powered mechanism through the second floor window of Su Songs Water Clock. ... Seeing the water powered mechanism through the second floor window of Su Songs Water Clock. ... Su Song 蘇頌 (1020 – 1101), style Zirong 子容, was a Chinese engineer. ... For other uses, see Astronomy (disambiguation). ... Hand-coloured version of the anonymous Flammarion woodcut (1888). ...

Huan Tan (40 BC–30 AD), a Secretary at the Court in charge of clepsydrae, wrote that he had to compare clepsydras with sundials because of how temperature and humidity affected their accuracy, demonstrating that the effects of evaporation, as well as of temperature on the speed at which water flows, were known at this time.^[16] In 976, Zhang Sixun addressed the problem of the water in clepsydrae freezing in cold weather by using mercury instead.^[17] Centuries: 2nd century BC - 1st century BC - 1st century Decades: 90s BC 80s BC 70s BC 60s BC 50s BC - 40s BC - 30s BC 20s BC 10s BC 0s BC 10s BC Years: 45 BC 44 BC 43 BC 42 BC 41 BC 40 BC 39 BC 38 BC 37... Events The Sermon on the Mount (according to proponents of the 33 theory) April 7 - Crucifixion of Jesus (suggested date, but it is also suggested that he died on April 3, AD 33) Births Quintus Petillius Cerialis, brother-in-law of Vespasian Deaths April 7 - Judas Iscariot, disciple of Jesus... An artists interpretation of the astronomical clock tower of Su Song (1020-1101) Zhang Sixun (Chinese: ; pinyin: ; Wade-Giles: chang ssu hsün) was a 10th century Chinese astronomer and engineer during the Song Dynasty (960-1279 AD). ...

The use of clepsydrae to drive mechanisms illustrating astronomical phenomena began with Zhang Heng in 125.^[18] This led to the invention by Yi Xing and Liang Lingzan in 725 of a clock driven by a water-wheel linkwork escapement.^[19] The same mechanism would be used by Su Song in 1088 to power his astronomical clock tower.^[20] Su Song's clock tower, over 30 feet tall, possessed a bronze power-driven armillary sphere for observations, an automatically rotating celestial globe, and five front panels with doors that permitted the viewing of changing manikins which rang bells or gongs, and held tablets indicating the hour or other special times of the day. For other uses, see Zhang Heng (disambiguation). ... Yi Xing (Yi-xing) (一行) (683 – 727) was a Chinese astronomer and buddhist monk of the Tang Dynasty. ... A simple escapement. ... Su Song 蘇頌 (1020 – 1101), style Zirong 子容, was a Chinese engineer. ... Assorted ancient Bronze castings found as part of a cache, probably intended for recycling. ... Chinese history, astronomers have created celestial globes to assist the observation of the stars. ... A pair of mannequins A mannequin (alternately, manikin, mannikin, manakin, dummy, or form) is a life-size, articulated doll mainly used to display clothing. ...

Greco-Roman world

In Ctesibius's clepsydra from the 3rd century BC, the human-shaped hour pointer ascends as water flows in. Outflow drives a series of gears that rotates a cylinder bearing hour lengths appropriate for each day's date.

In Greece, a water clock was known as a clepsydra (water thief). A commonly used water clock was the simple outflow clepsydra. This small earthenware vessel had a hole in its side near the base. In both Greek and Roman times, this type of clepsydra was used in courts for allocating periods of time to speakers. In important cases, when a person's life was at stake for example, it was filled. But, for more minor cases, it was only partially filled. If proceedings were interrupted for any reason, such as to examine documents, the hole in the clepsydra was stopped with wax until the speaker was able to resume his pleading.^[21] Image File history File linksMetadata No higher resolution available. ... Image File history File linksMetadata No higher resolution available. ...

Between 270 BC and 500 AD, Hellenistic (Ctesibius, Hero of Alexandria, Archimedes) and Roman horologists and astronomers were developing more elaborate mechanized water clocks. The added complexity was aimed at making the flow more constant by regulating the pressure, and at providing fancier displays of the passage of time. For example, some water clocks rang bells and gongs, while others opened doors and windows to show figurines of people, or moved pointers, and dials. Some even displayed astrological models of the universe. Centuries: 4th century BC - 3rd century BC - 2nd century BC Decades: 320s BC 310s BC 300s BC 290s BC 280s BC 270s BC - 260s BC 250s BC 240s BC 230s BC 220s BC 275 BC 274 BC 273 BC 272 BC 271 BC - 270 BC - 269 BC 268 BC 267... Events Possible date for the Battle of Mons Badonicus: Romano-British and Celts defeat an Anglo-Saxon army that may have been led by the bretwalda Aelle of Sussex (approximate date; suggested dates range from 490 to 510) Note: This battle may have influenced the legend of King Arthur. ... The term Hellenistic (derived from Héllēn, the Greeks traditional self-described ethnic name) was established by the German historian Johann Gustav Droysen to refer to the spreading of Greek culture over the non-Greek people that were conquered by Alexander the Great. ... Ctesibius or Ktesibios or Tesibius (Greek Κτησίβιος) (flourished 285–222 BC) was a Greek[1] inventor and mathematician in Alexandria. ... ‹ The template below (Expand) is being considered for deletion. ... For other uses, see Archimedes (disambiguation). ... Ancient Rome was a civilization that grew from a small agricultural community founded on the Italian Peninsula circa the 9th century BC to a massive empire straddling the Mediterranean Sea. ... Horology is the study of the science and art of timekeeping devices. ... An astronomer or astrophysicist is a person whose area of interest is astronomy or astrophysics. ... A bell is a simple sound-making device. ... A gong is one of a wide variety of metal percussion instruments. ... Hand-coloured version of the anonymous Flammarion woodcut (1888). ...

A Greek astronomer, Andronicus of Cyrrhus, supervised the construction of his Horologion, known today as the Tower of the Winds, in the Athens marketplace (or Agora) in the first half of the 1st century BC. This octagonal structure showed scholars and shoppers both sundials and mechanical hour indicators. It featured a 24-hour mechanized clepsydra and indicators for the eight winds from which the tower got its name, and it displayed the seasons of the year and astrological dates and periods. Andronicus of Cyrrhus was a Greek astronomer who flourished about 100 BC. He built a horologium at Athens, the so-called Tower of the Winds, a considerable portion of which still exists. ... The frieze of the tower showing the Greek wind gods Boreas (north wind, on the left) and Skiron (northwesterly wind, on the right). ... This article is about the capital of Greece. ... Stoa of the ancient agora de Thessaloniki An agora (αγορά), translatable as marketplace, was a public space and an essential part of an ancient Greek polis or city-state. ... (2nd millennium BC - 1st millennium BC - 1st millennium) The 1st century BC started on January 1, 100 BC and ended on December 31, 1 BC. An alternative name for this century is the last century BC. The AD/BC notation does not use a year zero. ... For other uses, see Octagon (disambiguation). ... For other uses, see Sundial (disambiguation). ... The hour (symbol: h) is a unit of time. ... This article or section is in need of attention from an expert on the subject. ...

Korea

Scaled model of Jang Yeong-sil's Self-striking water clock.

In Korea, timekeeping was both a royal duty and a royal prerogative from its Three Kingdom Period (c. 37 BC) onwards. In 1434 during the Choson (or Joseon) Dynasty, Chang Yongsil (or Jang Young Sil), Palace Guard and later Chief Court Engineer, constructed the Chagyongnu (self-striking water clock or striking clepsydra) for King Sejong. What made the Chagyongnu self-striking (or automatic) was the use of jack-work mechanisms, by which three wooden figures (jacks) struck objects to signal the time. This innovation no longer required the reliance of human workers, known as "rooster men", to constantly replenish it. By 554, the water clock spread from Korea to Japan. Water clocks were used and improved upon throughout Asia well into the 15th century. Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... This article is about the Korean peninsula and civilization. ... For other uses, see Three Kingdoms (disambiguation). ... Centuries: 2nd century BC - 1st century BC - 1st century Decades: 80s BC 70s BC 60s BC 50s BC 40s BC - 30s BC - 20s BC 10s BC 0s 10s 20s Years: 42 BC 41 BC 40 BC 39 BC 38 BC 37 BC 36 BC 35 BC 34 BC 33 BC... Joseon or Chosun (Korean: 조선; Hanja: 朝鮮; Revised: Joseon; McCune-Reischauer: Chosŏn; Chinese: Cháoxiǎn; Japanese: Chōsen) is a name for Korea, as used in the following cases: As part of the name of several ancient kingdoms (including Gojoseon, Gija Joseon, and Wiman Joseon); During most of the Joseon... Jang Yeong-sil was a Korean scientist and inventor during the Joseon Dynasty under King Sejong. ... King Sejong the Great (May 6, 1397 - May 18, 1450), born I Do, was the fourth ruler of the Joseon Dynasty of Korea from 1418 to 1450. ... Events The Byzantine general Narses reconquers all of Italy. ... (14th century - 15th century - 16th century - other centuries) As a means of recording the passage of time, the 15th century was that century which lasted from 1401 to 1500. ...

Islamic and Arabic water clocks

Al-Jazari's elephant water clock (1206).^[22]

In Islamic times (632 - 1280), the use of the water clock has its roots from Archimedes during the rise of Alexandria and continues on through Byzantium. Al-Jazari, however, is credited for going "well beyond anything" that had preceded it. Hill, speaking on al-Jazari's treatise, states that "the invention of the basic machinery and a single time-recording device was indeed made by Archimedes."^[23] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Diagram from The Book of Knowledge of Ingenious Mechanical Devices by al-Jazari. ... The reproduction elephant clock in the Ibn Battuta Mall, Dubai. ... Islam (Arabic: ; ( ▶ (help· info)), the submission to God) is a monotheistic faith, one of the Abrahamic religions and the worlds second-largest religion. ... This article is about the city in Egypt. ... Byzantium (Greek: Βυζάντιον) was an ancient Greek city, which, according to legend, was founded by Greek colonists from Megara in 667 BC and named after their king Byzas or Byzantas (Βύζας or Βύζαντας in Greek). ... Diagram from The Book of Knowledge of Ingenious Mechanical Devices by al-Jazari. ...

In al-Jazari's treatise, he describes one of his water clocks, the elephant clock. The clock recorded the passage of temporal hours, which meant that the rate of flow had to be changed daily to match the uneven length of days throughout the year. To accomplish this, the clock had two tanks, the top tank was connected to the time indicating mechanisms and the bottom was connected to the flow control regulator. Basically, at daybreak the tap was opened and water flowed from the top tank to the bottom tank via a float regulator that maintained a constant pressure in the receiving tank.^[24] The reproduction elephant clock in the Ibn Battuta Mall, Dubai. ... In automatic control, a regulator is a device which has the function of maintaining a designated characteristic. ...

Modern water clock designs

Bernard Gitton's Time-Flow clock.

Today, few water clocks exist. In 1979, French scientist Bernard Gitton began creating his Time-Flow Clocks, which are a modern-day approach to water clocks. His unique glasstube design can be found in over 30 locations throughout the world, including the Children's Museum in Indianapolis, Indiana, and the Shopping Iguatemi in São Paulo, Brasil. Also, there are some other modern designs of water clocks, including the Royal Gorge water clock in Colorado and the Woodgrove Mall in Nanaimo, British Columbia. Today overall, the use of water flow to power a clock is a rarely practiced and forgotten art, where its purpose has become more for show and novelty than for functional accuracy. Image File history File links Metadata Size of this preview: 450 × 600 pixelsFull resolution (1536 × 2048 pixel, file size: 1. ... Image File history File links Metadata Size of this preview: 450 × 600 pixelsFull resolution (1536 × 2048 pixel, file size: 1. ... The Indianapolis skyline Indianapolis is the capital of the U.S. state of Indiana. ... Official language(s) English Capital Indianapolis Largest city Indianapolis Area  Ranked 38th  - Total 36,418 sq mi (94,321 km²)  - Width 140 miles (225 km)  - Length 270 miles (435 km)  - % water 1. ... This article is about the city. ... Royal Gorge (also Grand Canyon of the Arkansas) is a canyon on the Arkansas River near Cañon City, Colorado. ... Official language(s) English Capital Denver Largest city Denver Largest metro area Denver-Aurora Metro Area Area  Ranked 8th  - Total 104,185 sq mi (269,837 km²)  - Width 280 miles (451 km)  - Length 380 miles (612 km)  - % water 0. ... Nanaimo (2004 pop. ... Motto: Splendor Sine Occasu (Latin: Splendour Without Sunset (diminishment)) Capital Victoria Largest city Vancouver Official languages English Government - Lieutenant-Governor Iona Campagnolo - Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament - House seats 36 - Senate seats 6 Confederation July 20, 1871 (6th province) Area  Ranked 5th - Total 944,735...

Notes

David Edwin Pingree (1933-2005), late University Professor and Professor of History of Mathematics and Classics at Brown University, was one of Americas foremost historians of the exact sciences in antiquity. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 131st day of the year (132nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 131st day of the year (132nd in leap years) in the Gregorian calendar. ... Subhash Kak (सुभाष काक) (born March 26, 1947, Srinagar, Kashmir) is Delaune Distinguished Professor of Electrical Engineering and Professor in the Asian Studies and Cognitive Science Programs at Louisiana State University, Baton Rouge. ... Diagram from The Book of Knowledge of Ingenious Mechanical Devices by al-Jazari. ... Donald Routledge Hill (1922–1994) was an engineer and historian of science. ...

Bibliography

David Landes is professor emeritus of economics and retired professor of history at Harvard University. ... Abraham Rees (1743–1825), compiler of Reess Cyclopaedia (45 vols. ... Otto E. Neugebauer (May 26, 1899 – February 19, 1990) was an Austrian-American mathematician and historian of science who became known for his research on the history of astronomy and the other exact (i. ... Derek John de Solla Price (January 22, 1922 – September 03, 1983) was a science historian and information scientist, credited as the father of scientometrics. ... Joseph Terence Montgomery Needham (December 9, 1900 – March 24, 1995) was a British biochemist and pre-eminent authority on the history of Chinese science. ... Joseph Terence Montgomery Needham (December 9, 1900 – March 24, 1995) was a British biochemist and pre-eminent authority on the history of Chinese science. ... Joseph Terence Montgomery Needham (December 9, 1900 – March 24, 1995) was a British biochemist and pre-eminent authority on the history of Chinese science. ... Donald Routledge Hill (1922–1994) was an engineer and historian of science. ... Donald Routledge Hill (1922–1994) was an engineer and historian of science. ...

See also

Armillary sphere An armillary sphere (variations known as a spherical astrolabe, armilla, or armil) is a model of the celestial sphere, invented by the ancient Greek Eratosthenes in 255 BC. Its name comes from the Latin armilla (circle, bracelet), since it has a skeleton made of graduated metal circles linking... A 16th century astrolabe. ... The reproduction elephant clock in the Ibn Battuta Mall, Dubai. ... The cantilever spar of this cable-stay bridge, the Sundial Bridge at Turtle Bay, forms the gnomon of a large garden sundial The gnomon is the part of a sundial that casts the shadow. ... For other uses, see Hourglass (disambiguation). ... For other uses, see Sundial (disambiguation). ... A Hydrochronometer is a Water clock. ...

External links