Marine chronometer

A marine chronometer is a timepiece that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of accurately measuring the time of a known fixed location, for example Greenwich Mean Time (GMT) and the time at the current location. When first developed in the 18th century, it was a major technical achievement, as accurate knowledge of the time over a long sea voyage is necessary for navigation, lacking electronic or communications aids. The first true chronometer was the life work of one man, John Harrison, spanning 31 years of persistent experimentation and testing that revolutionized naval (and later aerial) navigation and enabling the Age of Discovery and Colonialism to accelerate.

The term chronometer was coined from the Greek words chronos (meaning time) and meter (meaning counter) in 1714 by Jeremy Thacker, an early competitor for the prize set by the Longitude Act in the same year.[1] It has recently become more commonly used to describe watches tested and certified to meet certain precision standards. Timepieces made in Switzerland may display the word "chronometer" only if certified by the COSC (Official Swiss Chronometer Testing Institute).

Marine chronometer
Frodsham chronometer mechanism
A marine chronometer by Charles Frodsham of London, shown turned upside down to reveal the movement. Chronometer circa 1844-1860.
InventorJohn Harrison


Chronometer of Jeremy Thacker
The marine "Chronometer" of Jeremy Thacker used gimbals and a vacuum in a bell jar.

To determine a position on the Earth's surface, it is necessary and sufficient to know the latitude, longitude, and altitude. Altitude considerations can naturally be ignored for vessels operating at sea level. Until the mid-1750s, accurate navigation at sea out of sight of land was an unsolved problem due to the difficulty in calculating longitude. Navigators could determine their latitude by measuring the sun's angle at noon (i.e., when it reached its highest point in the sky, or culmination) or, in the Northern Hemisphere, to measure the angle of Polaris (the North Star) from the horizon (usually during twilight). To find their longitude, however, they needed a time standard that would work aboard a ship. Observation of regular celestial motions, such as Galileo's method based on observing Jupiter's natural satellites, was usually not possible at sea due to the ship's motion. The lunar distances method, initially proposed by Johannes Werner in 1514, was developed in parallel with the marine chronometer. The Dutch scientist Gemma Frisius was the first to propose the use of a chronometer to determine longitude in 1530.

The purpose of a chronometer is to measure accurately the time of a known fixed location, for example Greenwich Mean Time (GMT). This is particularly important for navigation. Knowing GMT at local noon allows a navigator to use the time difference between the ship's position and the Greenwich Meridian to determine the ship's longitude. As the Earth rotates at a regular rate, the time difference between the chronometer and the ship's local time can be used to calculate the longitude of the ship relative to the Greenwich Meridian (defined as 0°) using spherical trigonometry. In modern practice, a nautical almanac and trigonometric sight-reduction tables permit navigators to measure the Sun, Moon, visible planets, or any of 57 selected stars for navigation at any time that the horizon is visible.

The creation of a timepiece which would work reliably at sea was difficult. Until the 20th century, the best timekeepers were pendulum clocks, but both the rolling of a ship at sea and the up to 0.2% variations in the gravity of Earth made a simple gravity-based pendulum useless both in theory and in practice.

First marine chronometers

Christiaan Huygens, following his invention of the pendulum clock in 1656, made the first attempt at a marine chronometer in 1673 in France, under the sponsorship of Jean-Baptiste Colbert.[2][3] In 1675, Huygens, who was receiving a pension from Louis XIV, invented a chronometer that employed a balance wheel and a spiral spring for regulation, instead of a pendulum, opening the way to marine chronometers and modern pocket watches and wristwatches. He obtained a patent for his invention from Colbert, but his clock remained imprecise at sea.[4] Huygens' attempt in 1675 to obtain an English patent from Charles II stimulated Robert Hooke, who claimed to have conceived of a spring-driven clock years earlier, to attempt to produce one and patent it. During 1675 Huygens and Hooke each delivered two such devices to Charles, but none worked well and neither Huygens nor Hooke received an English patent. It was during this work that Hooke formulated what is known as Hooke's Law.[5]

The first published use of the term was in 1684 in Arcanum Navarchicum, a theoretical work by Kiel professor Matthias Wasmuth. This was followed by a further theoretical description of a chronometer in works published by English scientist William Derham in 1713. Derham's principal work, Physico-theology, or a demonstration of the being and attributes of God from his works of creation, also proposed the use of vacuum sealing to ensure greater accuracy in the operation of clocks.[6] Attempts to construct a working marine chronometer were begun by Jeremy Thacker in England in 1714, and by Henry Sully in France two years later. Sully published his work in 1726 with Une Horloge inventée et executée par M. Sulli, but neither his nor Thacker's models were able to resist the rolling of the seas and keep precise time while in shipboard conditions.[7]

In 1714, the British government offered a longitude prize for a method of determining longitude at sea, with the awards ranging from £10,000 to £20,000 (£2 million to £4 million in 2019 terms) depending on accuracy. John Harrison, a Yorkshire carpenter, submitted a project in 1730, and in 1735 completed a clock based on a pair of counter-oscillating weighted beams connected by springs whose motion was not influenced by gravity or the motion of a ship. His first two sea timepieces H1 and H2 (completed in 1741) used this system, but he realised that they had a fundamental sensitivity to centrifugal force, which meant that they could never be accurate enough at sea. Construction of his third machine, designated H3, in 1759 included novel circular balances and the invention of the bi-metallic strip and caged roller bearings, inventions which are still widely used. However, H3's circular balances still proved too inaccurate and he eventually abandoned the large machines.[8]

Harrison solved the precision problems with his much smaller H4 chronometer design in 1761. H4 looked much like a large five-inch (12 cm) diameter pocket watch. In 1761, Harrison submitted H4 for the £20,000 longitude prize. His design used a fast-beating balance wheel controlled by a temperature-compensated spiral spring. These features remained in use until stable electronic oscillators allowed very accurate portable timepieces to be made at affordable cost. In 1767, the Board of Longitude published a description of his work in The Principles of Mr. Harrison's time-keeper.[9]

Henry Sully clock with escapement and suspension mechanism

Henry Sully (1680-1729) presented a first marine chronometer in 1716.

H1 low 250

John Harrison's H1 marine chronometer of 1735.

Harrison H4 clock in The principles of Mr Harrison's time-keeper 1767

Drawings of Harrison's H4 chronometer of 1761, published in The principles of Mr Harrison's time-keeper, 1767.[10]

Marine watch no 3-CnAM 1388-IMG 1522-black

Ferdinand Berthoud marine chronometer no.3, 1763.

The modern chronometer

In France, 1748, Pierre Le Roy invented the detent escapement characteristic of modern chronometers.[11] In 1766, Pierre Le Roy created a revolutionary chronometer that incorporated a detent escapement, the temperature-compensated balance and the isochronous balance spring:[12] Harrison showed the possibility of having a reliable chronometer at sea, but these developments by Le Roy are considered by Rupert Gould to be the foundation of the modern chronometer.[12] The innovations of Le Roy made the chronometer a much more accurate piece than had been anticipated.[13]

Pierre Le Roy chronometer 1766

Pierre Le Roy marine chronometer, 1766. Photographed at the Musée des Arts et Métiers in Paris.

Harrison's Chronometer H5

Harrison's Chronometer H5 of 1772, now on display at the Science Museum, London.

Ferdinand Berthoud in France, as well as Thomas Mudge in Britain also successfully produced marine timekeepers.[11] Although none were simple, they proved that Harrison's design was not the only answer to the problem. The greatest strides toward practicality came at the hands of Thomas Earnshaw and John Arnold, who in 1780 developed and patented simplified, detached, "spring detent" escapements,[14][15] moved the temperature compensation to the balance, and improved the design and manufacturing of balance springs. This combination of innovations served as the basis of marine chronometers until the electronic era.

Berthoud clock 24 p1040260
Ferdinand Berthoud chronometer no. 24 (1782). This item is on display at the Musée des Arts et Métiers, Paris.

The new technology was initially so expensive that not all ships carried chronometers, as illustrated by the fateful last journey of the East Indiaman Arniston, shipwrecked with the loss of 372 lives.[16] However, by 1825, the Royal Navy had begun routinely supplying its vessels with chronometers.[17]

It was common for ships at the time to observe a time ball, such as the one at the Royal Observatory, Greenwich, to check their chronometers before departing on a long voyage. Every day, ships would anchor briefly in the River Thames at Greenwich, waiting for the ball at the observatory to drop at precisely 1pm.[18] This practice was in small part responsible for the subsequent adoption of Greenwich Mean Time as an international standard.[19] (Time balls became redundant around 1920 with the introduction of radio time signals, which have themselves largely been superseded by GPS time.) In addition to setting their time before departing on a voyage, ship chronometers were also routinely checked for accuracy while at sea by carrying out lunar[20] or solar observations.[21] In typical use, the chronometer would be mounted in a sheltered location below decks to avoid damage and exposure to the elements. Mariners would use the chronometer to set a so-called hack watch, which would be carried on deck to make the astronomical observations. Though much less accurate (and expensive) than the chronometer, the hack watch would be satisfactory for a short period of time after setting it (i.e., long enough to make the observations).

Although industrial production methods began revolutionizing watchmaking in the middle of the 19th century, chronometer manufacture remained craft-based much longer. Around the turn of the 20th century, Swiss makers such as Ulysse Nardin made great strides toward incorporating modern production methods and using fully interchangeable parts, but it was only with the onset of World War II that the Hamilton Watch Company in the United States perfected the process of mass production, which enabled it to produce thousands of its Hamilton Model 21 and Model 22 chronometers of World War Two for the United States Navy & Army and other Allied navies. Despite Hamilton's success, chronometers made in the old way never disappeared from the marketplace during the era of mechanical timekeepers. Thomas Mercer Chronometers still makes chronometers to the present day.

Without their accuracy and the accuracy of the feats of navigation that marine chronometers enabled, it is arguable that the ascendancy of the Royal Navy, and by extension that of the British Empire, might not have occurred so overwhelmingly; the formation of the empire by wars and conquests of colonies abroad took place in a period in which British vessels had reliable navigation due to the chronometer, while their Portuguese, Dutch, and French opponents did not.[22] For example: the French were well established in India and other places before Britain, but were defeated by naval forces in the Seven Years' War.

The most complete international collection of marine chronometers, including Harrison's H1 to H4, is at the Royal Observatory, Greenwich, in London, UK.

Mechanical chronometers

A chronometer mechanism diagrammed (text is in German). Note fusee to transform varying spring tension to a constant force

The crucial problem was to find a resonator that remained unaffected by the changing conditions met by a ship at sea. The balance wheel, harnessed to a spring, solved most of the problems associated with the ship's motion. Unfortunately, the elasticity of most balance spring materials changes relative to temperature. To compensate for ever-changing spring strength, the majority of chronometer balances used bi-metallic strips to move small weights toward and away from the centre of oscillation, thus altering the period of the balance to match the changing force of the spring. The balance spring problem was solved with a nickel-steel alloy named Elinvar for its invariable elasticity at normal temperatures. The inventor was Charles Édouard Guillaume, who won the 1920 Nobel Prize for physics in recognition for his metallurgical work.

The escapement serves two purposes. First, it allows the train to advance fractionally and record the balance's oscillations. At the same time, it supplies minute amounts of energy to counter tiny losses from friction, thus maintaining the momentum of the oscillating balance. The escapement is the part that ticks. Since the natural resonance of an oscillating balance serves as the heart of a chronometer, chronometer escapements are designed to interfere with the balance as little as possible. There are many constant-force and detached escapement designs, but the most common are the spring detent and pivoted detent. In both of these, a small detent locks the escape wheel and allows the balance to swing completely free of interference except for a brief moment at the centre of oscillation, when it is least susceptible to outside influences. At the centre of oscillation, a roller on the balance staff momentarily displaces the detent, allowing one tooth of the escape wheel to pass. The escape wheel tooth then imparts its energy on a second roller on the balance staff. Since the escape wheel turns in only one direction, the balance receives impulse in only one direction. On the return oscillation, a passing spring on the tip of the detent allows the unlocking roller on the staff to move by without displacing the detent. The weakest link of any mechanical timekeeper is the escapement's lubrication. When the oil thickens through age or temperature or dissipates through humidity or evaporation, the rate will change, sometimes dramatically as the balance motion decreases through higher friction in the escapement. A detent escapement has a strong advantage over other escapements as it needs no lubrication. An impulse from the escape wheel to the impulse roller is nearly dead-beat, meaning little sliding action needing lubrication. Chronometer escape wheels and passing springs are typically gold due to the metal's lower slide friction over brass and steel.

Chronometers often included other innovations to increase their efficiency and precision. Hard stones such as ruby and sapphire were often used as jewel bearings to decrease friction and wear of the pivots and escapement. Diamond was often used as the cap stone for the lower balance staff pivot to prevent wear from years of the heavy balance turning on the small pivot end. Until the end of mechanical chronometer production in the third quarter of the 20th century, makers continued to experiment with things like ball bearings and chrome-plated pivots.

Marine chronometers always contain a maintaining power which keeps the chronometer going while it is being wound, and a power reserve to indicate how long the chronometer will continue to run without being wound. Marine chronometers are the most accurate portable mechanical clocks ever made, achieving a precision of around a 0.1 second per day or less than one minute per year. This is accurate enough to locate a ship's position within 1–2 miles (2–3 km) after a month's sea voyage.

Chronometer rating

In strictly horological terms, "rating" a chronometer means that prior to the instrument entering service, the average rate of gaining or losing per day is observed and recorded on a rating certificate which accompanies the instrument. This daily rate is used in the field to correct the time indicated by the instrument to get an accurate time reading. Even the best-made chronometer with the finest temperature compensation etc. exhibits two types of error, (1) random and (2) consistent. The quality of design and manufacture of the instrument keeps the random errors small. In principle, the consistent errors should be amenable to elimination by adjustment, but in practice it is not possible to make the adjustment so precisely that this error is completely eliminated, so the technique of rating is used. The rate will also change while the instrument is in service due to e.g. thickening of the oil, so on long expeditions the instrument's rate would be periodically checked against accurate time determined by astronomical observations.


OMC ships clock
Omega 4.19 MHz Ships Marine Chronometer, French Navy issued

Ships and boats commonly use electronic aids to navigation, mostly the Global Navigation Satellite Systems. However celestial navigation, which requires the use of a precise chronometer, is still a requirement for certain international mariner certifications such as Officer in Charge of Navigational Watch, and Master and Chief Mate deck officers,[23][24] and supplements offshore yachtmasters on long-distance private cruising yachts.[25] Modern marine chronometers can be based on quartz clocks that are corrected periodically by GPS signals or radio time signals (see radio clock). These quartz chronometers are not always the most accurate quartz clocks when no signal is received, and their signals can be lost or blocked. However, there are quartz movements, even in wrist watches such as the Omega Marine Chronometer, that are accurate to within 5 or 20 seconds per year.[26] At least one quartz chronometer made for advanced navigation utilizes multiple quartz crystals which are corrected by a computer using an average value, in addition to GPS time signal corrections.[27][28]

See also


  1. ^ Sobel, Dava. Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. Penguin Books. pp. 56, 57. ISBN 0-14-025879-5. Dismissing other solutions to the longitude problem, Thacker wrote "In a word, I am satisfied that my Reader begins to think that the Phonometers, Pyrometers, Selenometers, Heliometers and all the Meters are not worthy to be compared to my Chronometer"
  2. ^ Heath, Byron (19 March 2018). "Discovering the Great South Land". Rosenberg. Retrieved 19 March 2018 – via Google Books.
  3. ^ The maze of ingenuity: ideas and idealism in the development of technology Arnold Pacey New p.133ff [1]
  4. ^ Matthews, Michael R. (31 October 2000). "Time for Science Education: How Teaching the History and Philosophy of Pendulum Motion Can Contribute to Science Literacy". Springer Science & Business Media. Retrieved 19 March 2018 – via Google Books.
  5. ^ "isbn:0330532189 - Google Search". Retrieved 19 March 2018.
  6. ^ Koberer, Wolfgang (May 2016). "Notes: On the First Use of the Term "Chronometer"". The Mariner's Mirror. United Kingdom: Society for Nautical Research. 102 (2): 203–205.
  7. ^ A Chronology of Clocks Archived 2014-03-25 at the Wayback Machine
  8. ^ A description concerning such mechanism as will afford a nice, or true, mensuration of time John Harrison, 1775, p.14 " ponderosity in a pendulum or a balance, can rightly or ever make up the want of velocity; and indeed velocity was very much wanting in my three large machines.."
  9. ^ Harrison, John; Maskelyne, Nevil; Great Britain. Commissioners of Longitude (19 March 1767). "The principles of Mr. Harrison's time-keeper; with plates of the same". London, Printed by W. Richardson and S. Clark and sold by J. Nourse. Retrieved 19 March 2018 – via Internet Archive.
  10. ^ The principles of Mr Harrison's time-keeper
  11. ^ a b Britten's Watch & Clock Makers' Handbook Dictionary & Guide Fifteenth Edition p.122 [2]
  12. ^ a b Macey, Samuel L. (19 March 1994). "Encyclopedia of Time". Taylor & Francis. Retrieved 19 March 2018 – via Google Books.
  13. ^ Usher, Abbott Payson (19 March 2018). "A History of Mechanical Inventions". Courier Corporation. Retrieved 19 March 2018 – via Google Books.
  14. ^ Landes, David S. (1983). Revolution in Time. Cambridge, Massachusetts: Belknap Press of Harvard University Press. p. 165. ISBN 0-674-76800-0. Pierre Le Roy had developed the detached spring detent escapement around 1748, but abandoned the concept.
  15. ^ Macey, Samuel L. (19 March 1994). "Encyclopedia of Time". Taylor & Francis. Retrieved 19 March 2018 – via Google Books.
  16. ^ Hall, Basil (1862). "Chapter XIV. Doubling the cape (from "Fragments of voyages and travels", 2nd series, vol. 2 (1832))". The Lieutenant and Commander. London: Bell and Daldy (via Project Gutenberg). OCLC 9305276. Retrieved 2007-11-09.
  17. ^ Britten, Frederick James (1894). Former Clock & Watchmakers and Their Work. New York: Spon & Chamberlain. p. 230. Retrieved 2007-08-08. Chronometers were not regularly supplied to the Royal Navy until about 1825
  18. ^ Golding Bird (1867). The Elements of Natural Philosophy; Or, An Introduction to the Study of the Physical Sciences. J. Churchill and Sons. p. 545. Retrieved 2008-09-24.
  19. ^ Tony Jones (2000). Splitting the Second. CRC Press. p. 121. ISBN 0750306408.
  20. ^ Nathaniel Bowditch, Jonathan Ingersoll Bowditch (1826). The New American Practical Navigator. E. M. Blunt. p. 179.
  21. ^ Norie, J. W. (1816). "To Find The Longitude of Chronometers or Time-Keepers". New and Complete Epitome of Practical Navigation. Archived from the original on 2015-09-07.
  22. ^ Alfred T. Mahan, The Influence of Sea Power on History:
  23. ^ "International Convention on Standards of Training, Certification and Watchkeeping for Seafarers, 1978". Admiralty and Maritime Law Guide, International Conventions. Retrieved 2007-09-22.
  24. ^ "International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (with amendments)". International Maritime Organization. Archived from the original on 2007-07-03. Retrieved 2007-09-22.
  25. ^ Yachting Chronometer and Sextant, Accessed 25 May 2013, publisher=Nautische Instrumente
  26. ^ Read, Alexander. "High accuracy timepieces that could be used as marine chronometer". Retrieved 2007-09-22.
  27. ^ Montgomery, Bruce G. "Keeping Precision Time When GPS Signals Stop". Cotts Journal Online. Archived from the original on 2011-06-09. Retrieved 2007-09-22.
  28. ^ "Precise Time and Frequency for Navy Applications: The PICO Advanced Clock". DoD TechMatch, West Virginia High Technology Consortium Foundation. Archived from the original on December 31, 2010. Retrieved 2007-09-22.

External links

1759 in Great Britain

Events from the year 1759 in Great Britain. This year was dubbed an "Annus Mirabilis" due to a succession of military victories in the Seven Years' War against French-led opponents.

1759 in science

The year 1759 in science and technology involved several significant events.

Balance wheel

A balance wheel, or balance, is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral torsion spring, the balance spring or hairspring. It is driven by the escapement, which transforms the rotating motion of the watch gear train into impulses delivered to the balance wheel. Each swing of the wheel (called a 'tick' or 'beat') allows the gear train to advance a set amount, moving the hands forward. The balance wheel and hairspring together form a harmonic oscillator, which due to resonance oscillates preferentially at a certain rate, its resonant frequency or 'beat', and resists oscillating at other rates. The combination of the mass of the balance wheel and the elasticity of the spring keep the time between each oscillation or ‘tick’ very constant, accounting for its nearly universal use as the timekeeper in mechanical watches to the present. From its invention in the 14th century until tuning fork and quartz movements became available in the 1960s, virtually every portable timekeeping device used some form of balance wheel.


Britglyph was a collaborative locative art and geoglyph project created by Alfie Dennen for ShoZu which took place between December 2008 and March 2009. Participants were instructed to travel to specific locations across the United Kingdom with a rock or stone taken from near where they live. Once at the designated spot, the participants would capture a photograph or video of themselves and the rock and upload that to the main website, leaving the rock at the location. As these media were added to the main site, the image of a watch and chain inspired by John Harrison's marine chronometer H5 was drawn on the main project website, with the rocks creating a geoglyph on the Earth's surface.

Charles Frodsham

Charles Frodsham (15 April 1810 – 11 January 1871) was a distinguished English horologist, establishing the firm of Charles Frodsham & Co, which remains in existence as the longest continuously trading firm of chronometer manufacturers in the world. In January 2018, the firm launched a new chronometer wristwatch, after sixteen years in development. It is the first watch to use the George Daniels double-impulse escapement.


Chronometer or chronoscope may refer to:

Chronometer of Loulie, a precursor to the metronome


Chronometer watch

Observatory chronometer, a device certified by an observatory to be extremely accurate

Marine chronometer, a timekeeper used for marine navigation

Railroad chronometer, a specialized timepiece once used for safe operation of trains

Chronoscope or time viewer, a fictional, oracle-like device occasionally employed in science fiction

Longines Chronoscope, an American television program (1951–1955)

Chronometer watch

A chronometer (from Ancient Greek χρονόμετρο) is a specific type of mechanical timepiece tested and certified to meet certain precision standards. In Switzerland, only timepieces certified by the Contrôle Officiel Suisse des Chronomètres (COSC) may use the word chronometer on them. Outside Switzerland, equivalent bodies (such as the Japan Chronometer Inspection Institute) have in the past certified timepieces to the same internationally recognised standards, although use of the term has not always been strictly controlled.

Glashütte Observatory

Glashütte Observatory is an observatory located in Glashütte, Saxony, Germany.

Hugo Müller led the way and supplied a plot of land in Dittersdorfer Weg for the construction of an observatory, which began construction when the foundation stone was set on 27 August 1906. When the observatory opened four years later in 1910, on 26 June, it cemented Glashütte as the hub of Germany's watchmaking industry.

It was furnished with a refracting telescope to precisely measure the Earth’s place in the Milky Way galaxy. It had some of the most accurate timepieces made at that time: a marine chronometer; and a donation from Glashütte's leading industrialist, Ludwig Trapp, a precision pendulum clock. Finally, German watchmakers had an exact reference to precisely quantify and further improve the accuracy of their craft.

As of early 2006, Wempe has established a Chronometer Observatory at Glashütte. Official Chronometer Certificates are now being issued under the auspices of the German standards (DIN) under government oversight and authority.

Hack watch

A hack watch is a watch whose movement offers a mechanism for stopping and setting the second hand of the watch, then restarting the watch the instant the time setting matches the time displayed by a reference timepiece.Hack watches are used on ships for astronomical sights for navigation and to synchronize the actions of personnel who may not be in direct communication (for example, personnel engaged in a military mission).

For navigational purposes, the hack watch is synchronized with the ship's marine chronometer. The use of a hack watch makes it easier to take sights, as the chronometer is normally in a fixed position in a ship – below decks and in gimbals to keep it level and protect it from the elements, while the hack watch is portable and can be carried on deck. Though not as accurate as the chronometer, the hack watch is accurate enough to be satisfactory over the relatively short time period between setting it from the chronometer and taking the sight.

For mission synchronization, several hack watches can be set alike, then set going at the same moment.

John Harrison

John Harrison (3 April [O.S. 24 March] 1693 – 24 March 1776) was a self-educated English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of calculating longitude while at sea.

Harrison's solution revolutionized navigation and greatly increased the safety of long-distance sea travel. The problem he solved was considered so important following the Scilly naval disaster of 1707 that the British Parliament offered financial rewards of up to £20,000 (equivalent to £3.09 million in 2019) under the 1714 Longitude Act.In 1730, Harrison presented his first design, and worked over many years on improved designs, making several advances in time-keeping technology, finally turning to what were called sea watches. Harrison gained support from the Longitude Board in building and testing his designs. Toward the end of his life, he received recognition and a reward from Parliament. Harrison came 39th in the BBC's 2002 public poll of the 100 Greatest Britons.

List of Cornish engineers and inventors

This is a list of engineers and inventors from Cornwall, England, United Kingdom.

John Arnold, watchmaker and pioneer of the marine chronometer

William Bickford, inventor of the safety fuse

Joseph Henry Collins, mining engineer, mineralogist and geologist

Sir John Coode, civil engineer

William Cookworthy, discoverer of china clay (kaolinite) in Cornwall

Sir Humphry Davy, scientist, inventor and President of the Royal Society

Sir Goldsworthy Gurney, inventor of limelight

Jonathan Hornblower, inventor of the compound engine and the steam valve

William Husband, civil and mechanical engineer

Thomas Brown Jordan, engineer

Michael Loam, inventor of the man engine

William Murdoch, engineer, inventor and sometime Cornish resident

Andrew Pears, inventor of transparent soap

Adrian Stephens, inventor of the steam whistle

Richard Tangye, engineer

John Taylor, inventor of the Cornish rolls

Joseph Thomas, architect and civil engineer

Joseph Treffry, engineer and industrialist

Henry Trengrouse, inventor of a rocket-powered maritime rescue system

Richard Trevithick, inventor, engineer and builder of the first steam locomotive

Robert Trewhella (1830-1909; it:Robert Trewhella), railway engineer and contractor

Andrew Vivian, Trevithick's cousin and collaborator, and captain of Dolcoath Mine

Arthur Woolf, inventor of the high pressure compound steam engine

List of watchmakers

This chronological list of famous watchmakers is a list of those who influenced the development of horology or gained iconic status by their creations. The list is sorted by the lifetimes of the watchmakers.

You can find following information:

Full name

Dates of birth and death, if known

Country of origin and profession

Field of activity (italics)

Macfarlane Observatory

At Glasgow University, the Macfarlane Observatory was established in 1757 with instruments donated by Alexander Macfarlane, a merchant in Jamaica. The instruments arrived to Glasgow in a deteriorated condition, and their suitability for mounting was in question before they were taken in hand by James Watt. Watt had been trained in London and upon returning to Glasgow served as instrument maker to the university.

The benefactor Alexander Macfarlane had graduated MA from the university in 1728. Beyond his successful commercial career in Jamaica, he was an assistant judge and a member of the Legislative Assembly of Jamaica. Macfarlane purchased the astronomical instruments of Colin Campbell after 1742. Macfarlane died in 1755. A portrait and biographical note appear on a Glasgow University site.The donation was opportune for Watt as well as the University. As Marshall writes

...within a month of [Watt’s] arrival in Glasgow, the University received a case of astronomical instruments...the sea voyage had thrown these delicate instruments out of gear, and they needed overhauling by an expert....In 1760 Alexander Wilson was installed as professor of practical astronomy. His interest in sun spots made Macfarlane Observatory an early contributor to solar physics as Wilson described the surface of the Sun. Observing the variation in width of the penumbra of a sunspot near the limb, he concluded the sunspots were depressions in the generally spherical photosphere. The phenomenon is called the Wilson effect to acknowledge his early observations.

In the eighteenth century, the social position of an observatory was greater than now: as Dava Sobel writes, "...The founding philosophy of the Royal Observatory, like that of the Paris Observatory before it, viewed astronomy as a means to an end. All the far-flung stars must be catalogued, so as to chart a course for sailors over the oceans of the earth."

An observatory represented a place of certitude of time and place, a place to set a marine chronometer for use at sea where longitude was found by the method of lunar distances. The establishment of the Macfarlane Observatory in 1757 was before the 1767 appearance of The Nautical Almanac based on the Prime Meridian at Royal Observatory, Greenwich.

Nautical almanac

A nautical almanac is a publication describing the positions of a selection of celestial bodies for the purpose of enabling navigators to use celestial navigation to determine the position of their ship while at sea. The Almanac specifies for each whole hour of the year the position on the Earth's surface (in declination and Greenwich hour angle) at which the sun, moon, planets and first point of Aries is directly overhead. The positions of 57 selected stars are specified relative to the first point of Aries.

In Great Britain, The Nautical Almanac has been published annually by HM Nautical Almanac Office, ever since the first edition was published in 1767.

In the United States, a nautical almanac has been published annually by the US Naval Observatory since 1852. It was originally titled American Ephemeris and Nautical Almanac. Since 1958, the USNO and HMNAO have jointly published a unified nautical almanac, the Astronomical Almanac for use by the navies of both countries. Almanac data is now available online from the US Naval Observatory.Also commercial almanacs were produced that combined other information. A good example would be Brown's — which commenced in 1877 – and is still produced annually, its early twentieth century subtitle being "Harbour and Dock Guide and Advertiser and Daily Tide Tables". This combination of trade advertising, and information "by permission... of the Hydrographic Department of the Admiralty" provided a useful compendium of information. More recent editions have kept up with the changes in technology – the 1924 edition for instance had extensive advertisements for coaling stations. Meanwhile, the Reeds Nautical Almanac, published by Adlard Coles Nautical, has been in print since 1932, and in 1944 was used by landing craft involved in the Normandy landings.The "Air Almanac" of the United States and Great Britain tabulates celestial coordinates for 10-minute intervals for use in aerial navigation. The Sokkia Corporation's annual "Celestial Observation Handbook and Ephemeris" tabulated daily celestial coordinates (to a tenth of an arcsecond) for the Sun and nine stars; it was last published for 2008.

To find the position of a ship or aircraft by celestial navigation, the navigator measures with a sextant the apparent height of a celestial body above the horizon, and notes the time from a marine chronometer. That height is compared with the height predicted for a trial position; the arcminutes of height difference is how many nautical miles the position line is from the trial position.


Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another. The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation.It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks. All navigational techniques involve locating the navigator's position compared to known locations or patterns.

Navigation, in a broader sense, can refer to any skill or study that involves the determination of position and direction. In this sense, navigation includes orienteering and pedestrian navigation.

Omega Marine Chronometer

The Omega Marine Chronometer was the first quartz wristwatch ever to be awarded certified status as a marine chronometer. The watch was made by Omega SA and developed by John Othenin-Girard and is one of the most accurate non thermo-compensated production watches ever made, keeping time to within 1 second per month

Pierre Le Roy

Pierre Le Roy (1717–1785) was a French clockmaker. He was the inventor of the detent escapement, the temperature-compensated balance and the isochronous balance spring. His developments are considered as the foundation of the modern precision clock. Le Roy was born in Paris, eldest son of Julien Le Roy, a clockmaker to Louis XV who had worked with Henry Sully, in which place Pierre Le Roy succeeded his father. He had three brothers: Jean-Baptiste Le Roy (1720-1800), a physicist; Julien-David Le Roy (1724–1803), an architect; and Charles Le Roy (1726–1779), a physician and Encyclopédiste.

Thomas Earnshaw

Thomas Earnshaw (4 February 1749 in Ashton-under-Lyne – 1 March 1829 in London) was an English watchmaker who, following John Arnold's earlier work, further simplified the process of marine chronometer production, making them available to the general public. He is also known for his improvements to the transit clock at the Royal Greenwich Observatory in London and his invention of a chronometer escapement and a form of bimetallic compensation balance.

In 1780, he devised a modification to the detached chronometer escapement, the detent being mounted on a spring instead of on pivots. This spring detent escapement was patented by Thomas Wright (for whom he worked) in 1783. Whilst initially the design was crude and unsuccessful, with modifications it later became the standard form in marine chronometers, following the invention of the detent escapement by Pierre Le Roy in 1748. John Arnold also invented a similar escapement in 1782.

In 1805, Earnshaw and Arnold were granted awards by the Board of Longitude for their improvements to chronometers; Earnshaw received £2500 and John Arnold's son John Roger Arnold received £1672. The bimetallic compensation balance and the spring detent escapement in the forms designed by Earnshaw have been used essentially universally in marine chronometers since then, and for this reason Earnshaw is generally regarded as one of the pioneers of chronometer development.Although he was principally a watchmaker, he did not shy away from building clocks. When asked by Nevil Maskelyne, he produced a clock for the Armagh Observatory. This clock incorporated Earnshaw's new design of escapement and had a number of novel features, including an airtight case (designed to reduce dust and draughts). It was highly praised by John Thomas Romney Robinson in the 19th century, who at that time believed it to be the most accurate clock in the world. In 1794, its purchase price was £100 and Earnshaw charged £100 to travel with it to Armagh and set it up in the new Observatory.The Observatory also purchased Earnshaw's second clock which was operated at sidereal rate with Edward Troughton's Equatorial Telescope.

Timeline of time measurement technology

Timeline of time measurement technology

270 BCE - Ctesibius builds a popular water clock, called a clepsydra

46 BCE - Julius Caesar and Sosigenes develop a solar calendar with leap years

11th century - Sets of hourglasses were maintained by ship's pages to mark the progress of a ship during its voyage

11th century - Large town clocks were used in Europe to display local time, maintained by hand

1335 - First known mechanical clock, in Milan

1502 - Peter Henlein builds the first pocketwatch

1582 - Pope Gregory XIII, Aloysius Lilius, and Christopher Clavius introduce a Gregorian calendar with an improved leap year system

1655 - Cassini builds the heliometer of San Petronio in Bologna, to standardise Solar noon.

1656 - Christiaan Huygens builds the first accurate pendulum clock

1676 - Motion works and minute hand introduced by Daniel Quare

1680 - Second hand introduced

1737 - John Harrison presents the first stable marine chronometer, thereby allowing for precise longitude determination while at sea

1850 - Aaron Lufkin Dennison starts in Roxbury, Mass.U.S.A. the Waltham Watch Company and develops the American System of Watch Manufacturing.

1884 - International Meridian Conference adopts Greenwich Mean Time for consistency with Nevil Maskelyne's 18th century observations for the Method of Lunar Distances

1893 - Introduction by Webb C. Ball of the General Railroad Timepiece Standards in North America: Railroad chronometers

1928 - Joseph Horton and Warren Morrison build the first quartz crystal oscillator clock

1946 - Felix Bloch and Edward Purcell develop nuclear magnetic resonance

1949 - Harold Lyons develops an atomic clock based on the quantum mechanical vibrations of the ammonia molecule

1982 - The Federation of the Swiss Watch Industry FH is founded by the merger of two previous organisations

1983 - Radio-controlled clocks become common place in Europe

1983 - First collection of 12 Swatch models went on sale on March 1, in Zurich - the first fashion watch

1994 - Radio-controlled clocks become common place in USA

Key concepts
Measurement and
  • Religion
  • Mythology
Philosophy of time
Human experience
and use of time
Time in
Related topics
International standards
Obsolete standards
Time in physics
Archaeology and geology
Astronomical chronology
Other units of time
Related topics
Classical simple machines
Compressors and pumps
External combustion engines
Internal combustion engines

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