page_title: History of timekeeping devices
section_title: Early mechanical clocks and watches
hierarchical_section_title: History of timekeeping devices / Timekeeping innovations in medieval and pre-modern periods / Early mechanical clocks and watches
caption_attribution_description: English: The miniature represents Richard of Wallingford, Abbot of St Albans. He is pointing to a clock, referring to his gift to the abbey, and his face is disfigured by leprosy Title of Work: Golden Book of St Albans Author: Walsingham, Thomas; Wylum, William de, scribe Illustrator: Strayler, Alan Production: England [St Albans]; 1380 Language: Latin
context_page_description: For thousands of years, devices have been used to measure and keep track of time. The current sexagesimal system of time measurement dates to approximately 2000 BC from the Sumerians.
  The Egyptians divided the day into two 12-hour periods, and used large obelisks to track the movement of the sun. They also developed water clocks, which were probably first used in the Precinct of Amun-Re, and later outside Egypt as well; they were employed frequently by Persians and the Ancient Greeks, who called them clepsydrae. The Zhou dynasty is believed to have used the outflow water clock around the same time, devices which were introduced from Mesopotamia as early as 2000 BC.
  Other ancient timekeeping devices include the candle clock, used in ancient China, ancient Japan, England and Mesopotamia; the timestick, widely used in Persia, India and Tibet, as well as some parts of Europe; and the hourglass, which functioned similarly to a water clock. The sundial, another early clock, relies on shadows to provide a good estimate of the hour on a sunny day. It is not so useful in cloudy weather or at night and requires recalibration as the seasons change.
context_section_description: The earliest medieval European clockmakers were Catholic monks. Medieval religious institutions required clocks because they regulated daily prayer- and work-schedules strictly, using various types of time-telling and recording devices, such as water clocks, sundials and marked candles, probably in combination. When mechanical clocks came into use, they were often wound at least twice a day to ensure accuracy. Monasteries broadcast important times and durations with bells, rung either by hand or by a mechanical device, such as by a falling weight or by rotating beater.
  Although the mortuary inscription of Pacificus, archdeacon of Verona, records that he constructed a night clock (horologium nocturnum) as early as 850, his clock has been identified as being an observation tube used to locate stars with an accompanying book of astronomical observations, rather than a mechanical or water clock, an interpretation supported by illustrations from medieval manuscripts.
  The religious necessities and technical skill of the medieval monks were crucial factors in the development of clocks, as the historian Thomas Woods writes:
  The monks also counted skillful clock-makers among them. The first recorded clock was built by the future Pope Sylvester II for the German town of Magdeburg, around the year 996. Much more sophisticated clocks were built by later monks. Peter Lightfoot, a 14th-century monk of Glastonbury, built one of the oldest clocks still in existence, which now sits in excellent condition in London's Science Museum.
  The appearance of clocks in writings of the 11th century implies that they were well known in Europe in that period. In the early 14th-century, the Florentine poet Dante Alighieri referred to a clock in his Paradiso; the first known literary reference to a clock that struck the hours. Giovanni da Dondi, Professor of Astronomy at Padua, presented the earliest detailed description of clockwork in his 1364 treatise Il Tractatus Astrarii. This has inspired several modern replicas, including some in London's Science Museum and the Smithsonian Institution. Other notable examples from this period were built in Milan (1335), Strasbourg (1354), Rouen (1389), Lund (c. 1425) and Prague (1462).
  Salisbury Cathedral clock, dating from about 1386, is one of the oldest working clocks in the world, and may be the oldest.  It still has most of its original parts, although its original verge and foliot timekeeping mechanism is lost, having been converted to a pendulum, which was replaced by a replica verge in 1956.  It has no dial, as its purpose was to strike a bell at precise times. The wheels and gears are mounted in an open, box-like iron frame, measuring about 1.2 metres (3.9 ft) square. The framework is held together with metal dowels and pegs.  Two large stones, hanging from pulleys, supply the power. As the weights fall, ropes unwind from the wooden barrels. One barrel drives the main wheel, which is regulated by the escapement, and the other drives the striking mechanism and the air brake.
  Note also Peter Lightfoot's Wells Cathedral clock, constructed c. 1390. The dial represents a geocentric view of the universe, with the Sun and Moon revolving around a central fixed Earth. It is unique in having its original medieval face, showing a philosophical model of the pre-Copernican universe. Above the clock is a set of figures, which hit the bells, and a set of jousting knights who revolve around a track every 15 minutes. The clock was converted to pendulum-and-anchor escapement in the 17th century, and was installed in London's Science Museum in 1884, where it continues to operate.  Similar astronomical clocks, or horologes, survive at Exeter, Ottery St Mary, and Wimborne Minster.
  One clock that has not survived is that of the Abbey of St Albans, built by the 14th-century abbot Richard of Wallingford. It may have been destroyed during Henry VIII's Dissolution of the Monasteries, but the abbot's notes on its design have allowed a full-scale reconstruction. As well as keeping time, the astronomical clock could accurately predi
caption: The astronomical clock of St Albans Abbey, built by its abbot, Richard of Wallingford, circa 1380. British Library, London.
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