Cox's timepiece is a

clock A clock or chronometer is a device that measures and displays time. The clock is one of the oldest Invention, human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, a ...

developed in the 1760s by James Cox. It was developed in collaboration with

John Joseph Merlin John Joseph Merlin (born Jean-Joseph Merlin, 6 September 1735 – 8 May 1803) was a Freemason, clock-maker, musical-instrument maker, and inventor from the Prince-Bishopric of Liège in the Holy Roman Empire. He moved to England in 1760. By 1766 ...

(with whom Cox also worked on developing

automata An automaton (; : automata or automatons) is a relatively self-operating machine, or control mechanism designed to automatically follow a sequence of operations, or respond to predetermined instructions. Some automata, such as bellstrikers i ...

). Cox claimed that his design was a true

perpetual motion machine Perpetual motion is the motion of bodies that continues forever in an unperturbed system. A perpetual motion machine is a hypothetical machine that can do work indefinitely without an external energy source. This kind of machine is impossible ...

, but as the device is powered from changes in

atmospheric pressure Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013. ...

via a mercury

barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

, this is not the case. The clock still exists, but was deactivated at the time of its relocation to the

Victoria and Albert Museum The Victoria and Albert Museum (abbreviated V&A) in London is the world's largest museum of applied arts, decorative arts and design, housing a permanent collection of over 2.8 million objects. It was founded in 1852 and named after Queen ...

in London.

Design and history

The clock is similar to other mechanical clocks, except that it does not need winding. The change of pressure in the

Earth's atmosphere The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weathe ...

acts as an external energy source and causes sufficient movement of the winding mechanism. This keeps the

mainspring A mainspring is a spiral torsion spring of metal ribbon—commonly spring steel—used as a power source in mechanical watches, some clocks, and other clockwork mechanisms. ''Winding'' the timepiece, by turning a knob or key, stores energy in ...

coiled inside the barrel. The clock is designed to enable the timepiece to run indefinitely and overwinding is prevented by a safety mechanism. The

prime mover Prime mover may refer to: Philosophy *Unmoved mover, a concept in Aristotle's writings Engineering * Prime mover (engine or motor), a machine that converts various other forms of energy (chemical, electrical, fluid pressure/flow, etc.) into ener ...

, encased in a finely detailed clock body, is a Fortin mercury barometer. The barometer contained 68

kilogram The kilogram (also spelled kilogramme) is the base unit of mass in the International System of Units (SI), equal to one thousand grams. It has the unit symbol kg. The word "kilogram" is formed from the combination of the metric prefix kilo- (m ...

s (150

pound Pound or Pounds may refer to: Units * Pound (currency), various units of currency * Pound sterling, the official currency of the United Kingdom * Pound (mass), a unit of mass * Pound (force), a unit of force * Rail pound, in rail profile * A bas ...

s) of mercury (approximately 5 litres).

Similar clocks

A similar design is

Cornelis Drebbel Cornelis Jacobszoon Drebbel (; 1572 – 7 November 1633) was a Dutch engineer and inventor. He was the builder of the first operational submarine in 1620 and an innovator who contributed to the development of measurement and control systems, opti ...

's circa 1610 device that told the time, date, and season. The gold machine was mounted in a globe on pillars and was powered by changes in air pressure (a sealed glass tub with liquid varied in volume through atmospheric pressure changes, rewinding constantly). It is unknown whether Cox was aware of Drebbel's device. The Atmos, manufactured by

Jaeger LeCoultre Manufacture Jaeger-LeCoultre SA, or simply Jaeger-LeCoultre (), is a Swiss luxury watch and clock manufacturer founded by Antoine LeCoultre in 1833 and is based in Le Sentier, Switzerland. Since 2000, the company has been a fully owned subsidiary ...

is a modern clock which is similar to Cox's clock although the main driving force is generated from temperature differential, instead of pressure differential.

References

External articles and further reading

Journals

* William Nicholson, "''Concerning those perpetual motions which are produced in machines by the rise and fall of the barometer or thermometrical variations in the dimensions of bodies''". Philosophical Journal. * William Nicholson, Philosophical Journal, vol I, 1799, p375

Books

* Arthur W. J. G. Ord-hume, "''Clockwork Music''", Allen & Unwin, London 1973. * John Joseph Merlin, "''The Ingenious Mechanick''". The Greater London Council, The Iveagh Bequest, Kenwood, Hampstead Lane, London, © 1985. *

Christoph Ransmayr Christoph Ransmayr (; born 20 March 1954) is an Austrian writer. Life Born in Wels, Upper Austria, Ransmayr grew up in Roitham near Gmunden and the Traunsee. From 1972 to 1978 he studied philosophy and ethnology in Vienna. He worked there as ...

, " Cox oder der Lauf der Zeit". Fischer, Frankfurt am Main 2016.

Radio

* *{{cite episode , series=The Engines of Our Ingenuity , series-link=The Engines of Our Ingenuity , credits=John H. Lienhard , network=NPR , station=KUHF-FM Houston , airdate=1991 , number=630 , transcript=John Joseph Merlin , transcript-url=http://www.uh.edu/engines/epi630.htm Perpetual motion Individual clocks in England