Marine chronometer
Encyclopedia
A marine chronometer is a clock 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 celestial navigation
. When first developed in the eighteenth 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 test that revolutionized naval (and later aerial) navigation enabling the Age of Discovery
and Colonialism
to accelerate.
The term chronometer (apparently coined in 1714 by Jeremy Thacker
, an early competitor for the prize set by the Longitude Act in the same year) is used more recently to describe wristwatches tested and certified
to meet certain precision standards. Timepiece
s made in Switzerland
may only display the word 'chronometer' if certified by the COSC (Official Swiss Chronometer Testing Institute)
.
, longitude
and altitude
. Altitude considerations can of course 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
). 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 Distance 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 navigational almanac and trigonometric sight-reduction tables permit navigators to measure the Sun
, Moon
, visible planet
s, or any of 57 navigational stars 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 clock
s, but the rolling of a ship at sea made a simple gravity-based pendulum useless.
in 1656, made the first attempt at a marine chronometer in 1673 in France
, under the sponsorship of Jean-Baptiste Colbert
. 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.
More attempts were made by Jeremy Thacker
in England in 1714, and Henry Sully
in France in 1716, who published his work in 1726 with Une Horloge inventée et executée par M. Sulli, but these inventions remained unable to resist the rolling of the high seas and keep time precisely enough.
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 (several million pounds in modern 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 .
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 oscillator
s allowed very accurate portable timepieces to be made at affordable cost. Harrison published his work with The Principles of Mr. Harrison's time-keeper in 1767.
About the same time in France, Pierre Le Roy
invented in 1748 the detent escapement characteristic of modern chronometers. In 1766, Pierre Le Roy created a revolutionary chronometer that incorporated a detent escapement
, the temperature-compensated balance
and the isochronous balance spring
: 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. The innovations of Le Roy made the chronometer a much more accurate piece than had been anticipated.
Ferdinand Berthoud
in France, as well as Thomas Mudge
in Britain also successfully produced marine timekeepers. Although none was 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" escapement
s, moved the temperature compensation to the balance, and improved the design and manufacturing of balance spring
s. This combination of innovations served as the basis of marine chronometers until the electronic era.
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
. However by 1825, the Royal Navy
had begun routinely supplying its vessels with chronometers.
It was common for ships at the time to observe a time ball
, such as the one at 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. This practice was responsible for the subsequent adoption of Greenwich Mean Time
as an international standard. (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
or solar 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 US perfected the process of mass production
, which enabled them to produce thousands of their superb Hamilton Model 21 & Hamilton 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. Mercer of St. Albans in Britain, for instance, continued to produce high-quality chronometers by traditional production methods well into the 1970s.
Without their accuracy and the accuracy of the feats of navigation that marine chronometers enabled, it is quite likely the ascendancy of the Royal Navy
, and by extension that of the British Empire
, would not have occurred; 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. 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 National Maritime Museum, Greenwich, Britain.
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 Edouard Guillaume
, who won the 1920 Nobel Prize for physics in recognition for his metallurgical work (the only Nobel that has been granted for work related to horology
).
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.
Chronometers often included other innovations to increase their efficiency and precision. Hard stones such as ruby and sapphire were often used as jewel bearing
s to decrease friction and wear of the pivots and escapement. 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 tenth of a second per day. This is accurate enough to locate a ship's position within 4600 feet (1,402.1 m) after a month's sea voyage.
s. 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,
and supplements offshore yachtmasters on long-distance private cruising yachts.
Modern marine chronometers can be based on quartz clock
s that are corrected periodically by GPS
signals or radio time signal
s (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, that are accurate to within 10 or 20 seconds per year.
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.
Time standard
A time standard is a specification for measuring time: either the rate at which time passes; or points in time; or both. In modern times, several time specifications have been officially recognized as standards, where formerly they were matters of custom and practice. An example of a kind of time...
; it can therefore be used to determine longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
by means of celestial navigation
Celestial navigation
Celestial navigation, also known as astronavigation, is a position fixing technique that has evolved over several thousand years to help sailors cross oceans without having to rely on estimated calculations, or dead reckoning, to know their position...
. When first developed in the eighteenth century it was a major technical achievement, as accurate knowledge of the time over a long sea voyage is necessary for navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
, lacking electronic or communications aids. The first true chronometer was the life work of one man, John Harrison
John Harrison
John Harrison was a self-educated English clockmaker. He invented the marine chronometer, a long-sought device in solving the problem of establishing the East-West position or longitude of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age...
, spanning 31 years of persistent experimentation and test that revolutionized naval (and later aerial) navigation enabling the Age of Discovery
Age of Discovery
The Age of Discovery, also known as the Age of Exploration and the Great Navigations , was a period in history starting in the early 15th century and continuing into the early 17th century during which Europeans engaged in intensive exploration of the world, establishing direct contacts with...
and Colonialism
Colonialism
Colonialism is the establishment, maintenance, acquisition and expansion of colonies in one territory by people from another territory. It is a process whereby the metropole claims sovereignty over the colony and the social structure, government, and economics of the colony are changed by...
to accelerate.
The term chronometer (apparently coined in 1714 by Jeremy Thacker
Jeremy Thacker
Jeremy Thacker was an 18th century writer and watchmaker, who coined the word chronometer for precise clocks designed to find longitude at sea. He himself created a marine chronometer positioned on gimbals and within a vacuum, but it was a failure. The idea of a vacuum for a marine clock had...
, an early competitor for the prize set by the Longitude Act in the same year) is used more recently to describe wristwatches tested and certified
Chronometer watch
A chronometer watch is a specific type of watch tested and certified to meet certain precision standards. In Switzerland, only timepieces certified by the COSC may use the word 'Chronometer' on them....
to meet certain precision standards. Timepiece
Clock
A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...
s made in Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
may only display the word 'chronometer' if certified by the COSC (Official Swiss Chronometer Testing Institute)
COSC
COSC aka C.O.S.C. is Contrôle Officiel Suisse des Chronomètres, the Official Swiss Chronometer Testing Institute, which is the institute responsible for certifying the accuracy and precision of wristwatches in Switzerland.-Background:...
.
History
To determine a position on the Earth's surface, it is necessary and sufficient to know the latitudeLatitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
, longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
and altitude
Altitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
. Altitude considerations can of course be ignored for vessels operating at sea level. Until the mid 1750s accurate navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
at sea
Sea
A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...
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
Culmination
In astronomy, the culmination of a planet, star, constellation, etc. is the altitude reached when the object transits over an observer's meridian....
). To find their longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
, 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
Jupiter's natural satellites
Jupiter has 64 confirmed moons, giving it the largest retinue of moons with "reasonably secure" orbits of any planet in the Solar System. The most massive of them, the four Galilean moons, were discovered in 1610 by Galileo Galilei and were the first objects found to orbit a body that was neither...
, was usually not possible at sea due to the ship's motion. The Lunar Distance Method
Lunar distance (navigation)
In celestial navigation, lunar distance is the angle between the Moon and another celestial body. A navigator can use a lunar distance and a nautical almanac to calculate Greenwich time...
, initially proposed by Johannes Werner
Johannes Werner
Johann Werner was a German parish priest in Nuremberg and a mathematician...
in 1514, was developed in parallel with the marine chronometer. The Dutch scientist Gemma Frisius
Gemma Frisius
Gemma Frisius , was a physician, mathematician, cartographer, philosopher, and instrument maker...
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
Greenwich Mean Time
Greenwich Mean Time is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London. It is arguably the same as Coordinated Universal Time and when this is viewed as a time zone the name Greenwich Mean Time is especially used by bodies connected with the United...
(GMT). This is particularly important for navigation. Knowing GMT at local noon
Noon
Noon is usually defined as 12 o'clock in the daytime. The word noon is also used informally to mean midday regarding the location of the sun not the middle of a persons day. Although this is a time around the middle of the day when people in many countries take a lunch break...
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 navigational almanac and trigonometric sight-reduction tables permit navigators to measure the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, visible planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s, or any of 57 navigational stars 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 clock
Pendulum clock
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a resonant device; it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates...
s, but the rolling of a ship at sea made a simple gravity-based pendulum useless.
First marine chronometers
Christiaan Huygens, following his invention of the pendulum clockPendulum clock
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a resonant device; it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates...
in 1656, made the first attempt at a marine chronometer in 1673 in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, under the sponsorship of Jean-Baptiste Colbert
Jean-Baptiste Colbert
Jean-Baptiste Colbert was a French politician who served as the Minister of Finances of France from 1665 to 1683 under the rule of King Louis XIV. His relentless hard work and thrift made him an esteemed minister. He achieved a reputation for his work of improving the state of French manufacturing...
. In 1675, Huygens, who was receiving a pension from Louis XIV, invented a chronometer that employed a balance wheel
Balance wheel
The balance wheel 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 spring, the balance spring or hairspring...
and a spiral spring
Balance spring
A balance spring, or hairspring, is a part used in mechanical timepieces. The balance spring, attached to the balance wheel, controls the speed at which the wheels of the timepiece turn, and thus the rate of movement of the hands...
for regulation, instead of a pendulum, opening the way to marine chronometers and modern pocket watches and wristwatches. He obtained a patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
for his invention from Colbert, but his clock remained imprecise at sea.
More attempts were made by Jeremy Thacker
Jeremy Thacker
Jeremy Thacker was an 18th century writer and watchmaker, who coined the word chronometer for precise clocks designed to find longitude at sea. He himself created a marine chronometer positioned on gimbals and within a vacuum, but it was a failure. The idea of a vacuum for a marine clock had...
in England in 1714, and Henry Sully
Henry Sully
Henry Sully was an English clockmaker. He lived for many years in France.-Marine clock:He invented a marine clock to determine longitude accurately, a sophisticated pendulum clock. He presented a first Montre de la Mer in 1716 to the French Académie des Sciences. He was the first to develop...
in France in 1716, who published his work in 1726 with Une Horloge inventée et executée par M. Sulli, but these inventions remained unable to resist the rolling of the high seas and keep time precisely enough.
In 1714, the British government offered a longitude prize
Longitude prize
The Longitude Prize was a reward offered by the British government for a simple and practical method for the precise determination of a ship's longitude...
for a method of determining longitude at sea, with the awards ranging from £10,000 to £20,000 (several million pounds in modern terms) depending on accuracy. John Harrison
John Harrison
John Harrison was a self-educated English clockmaker. He invented the marine chronometer, a long-sought device in solving the problem of establishing the East-West position or longitude of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age...
, 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
Centrifugal force
Centrifugal force can generally be any force directed outward relative to some origin. More particularly, in classical mechanics, the centrifugal force is an outward force which arises when describing the motion of objects in a rotating reference frame...
, 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
Bi-metallic strip
A bimetallic strip is used to convert a temperature change into mechanical displacement. The strip consists of two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases brass instead of copper. The strips are joined together...
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 .
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 oscillator
Electronic oscillator
An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. They are widely used in innumerable electronic devices...
s allowed very accurate portable timepieces to be made at affordable cost. Harrison published his work with The Principles of Mr. Harrison's time-keeper in 1767.
The modern chronometer
Pierre Le Roy
Pierre Le Roy 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 chronometer...
invented in 1748 the detent escapement characteristic of modern chronometers. In 1766, Pierre Le Roy created a revolutionary chronometer that incorporated a detent escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
, the temperature-compensated balance
Balance wheel
The balance wheel 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 spring, the balance spring or hairspring...
and the isochronous balance spring
Balance spring
A balance spring, or hairspring, is a part used in mechanical timepieces. The balance spring, attached to the balance wheel, controls the speed at which the wheels of the timepiece turn, and thus the rate of movement of the hands...
: Harrison showed the possibility of having a reliable chronometer at sea, but these developments by Le Roy are considered by Rupert Gould
Rupert Gould
Rupert Thomas Gould , was a Lieutenant Commander in the British Royal Navy noted for his contributions to horology .-Life:...
to be the foundation of the modern chronometer. The innovations of Le Roy made the chronometer a much more accurate piece than had been anticipated.
Ferdinand Berthoud
Ferdinand Berthoud
Ferdinand Berthoud was a Swiss chronometer-maker.-Career:He was born at Plancemont, Neuchâtel, Switzerland. Having served his apprenticeship with his brother, Jean-Henri, a pendulum maker, he set up a clockmaking business in Paris in 1745 and gained a great reputation for the excellence and...
in France, as well as Thomas Mudge
Thomas Mudge (horologist)
Thomas Mudge was an English horologist who invented the lever escapement, the greatest single improvement ever applied to pocket watches.-Early life:...
in Britain also successfully produced marine timekeepers. Although none was 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
Thomas Earnshaw
Thomas Earnshaw 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...
and John Arnold
John Arnold
John Arnold was an English watchmaker and inventor.John Arnold was the first to design a watch that was both practical and accurate, and also brought the term "Chronometer" in to use in its modern sense, meaning a precision timekeeper...
, who in 1780 developed and patented simplified, detached, "spring detent" escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
s, moved the temperature compensation to the balance, and improved the design and manufacturing of balance spring
Balance spring
A balance spring, or hairspring, is a part used in mechanical timepieces. The balance spring, attached to the balance wheel, controls the speed at which the wheels of the timepiece turn, and thus the rate of movement of the hands...
s. This combination of innovations served as the basis of marine chronometers until the electronic era.
Arniston (ship)
The Arniston was an East Indiaman ship that was wrecked on 30 May 1815 during a storm at Waenhuiskrans, near Cape Agulhas, South Africa with the loss of 372 lives and only 6 survivors...
. However by 1825, the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
had begun routinely supplying its vessels with chronometers.
It was common for ships at the time to observe a time ball
Time ball
A time ball is a large painted wooden or metal ball that drops at a predetermined time, principally to enable sailors to check their marine chronometers from their boats offshore...
, such as the one at Greenwich
Greenwich
Greenwich is a district of south London, England, located in the London Borough of Greenwich.Greenwich is best known for its maritime history and for giving its name to the Greenwich Meridian and Greenwich Mean Time...
, to check their chronometers before departing on a long voyage. Every day, ships would anchor briefly in the River Thames
River Thames
The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...
at Greenwich, waiting for the ball at the observatory to drop at precisely 1pm. This practice was responsible for the subsequent adoption of Greenwich Mean Time
Greenwich Mean Time
Greenwich Mean Time is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London. It is arguably the same as Coordinated Universal Time and when this is viewed as a time zone the name Greenwich Mean Time is especially used by bodies connected with the United...
as an international standard. (Time balls became redundant around 1920 with the introduction of radio time signals
Time signal
A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible 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
Lunar distance (navigation)
In celestial navigation, lunar distance is the angle between the Moon and another celestial body. A navigator can use a lunar distance and a nautical almanac to calculate Greenwich time...
or solar 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
Ulysse Nardin
Ulysse Nardin is a watch manufacturer founded in 1846 in Le Locle, Switzerland. Historically Ulysse Nardin was best known for being a manufacturer of marine chronometers, but today Ulysse Nardin produces complicated mechanical watches.-History:...
made great strides toward incorporating modern production methods and using fully interchangeable parts, but it was only with the onset of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
that the Hamilton Watch Company
Hamilton Watch Company
The Hamilton Watch Company was originally formed to produce high quality pocket watches and wristwatches mid-range and luxury. Hamilton would become a corporate conglomerate diversified in other operations...
in the US perfected the process of mass production
Mass production
Mass production is the production of large amounts of standardized products, including and especially on assembly lines...
, which enabled them to produce thousands of their superb Hamilton Model 21 & Hamilton Model 22 chronometers of World War Two for the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Navy & Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
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. Mercer of St. Albans in Britain, for instance, continued to produce high-quality chronometers by traditional production methods well into the 1970s.
Without their accuracy and the accuracy of the feats of navigation that marine chronometers enabled, it is quite likely the ascendancy of the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
, and by extension that of the British Empire
British Empire
The British Empire comprised the dominions, colonies, protectorates, mandates and other territories ruled or administered by the United Kingdom. It originated with the overseas colonies and trading posts established by England in the late 16th and early 17th centuries. At its height, it was the...
, would not have occurred; 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. For example: the French were well established in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and other places before Britain, but were defeated by naval forces in the Seven Years' War
Seven Years' War
The Seven Years' War was a global military war between 1756 and 1763, involving most of the great powers of the time and affecting Europe, North America, Central America, the West African coast, India, and the Philippines...
.
The most complete international collection of marine chronometers, including Harrison's H1 to H4, is at the National Maritime Museum, Greenwich, Britain.
Mechanical chronometers
Balance wheel
The balance wheel 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 spring, the balance spring or hairspring...
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
Elinvar
Elinvar is a nickel steel alloy with a modulus of elasticity which does not change much with temperature changes. The name is a contraction of the French elasticité invariable. It was invented in the late 1890s by Charles Édouard Guillaume, a Swiss physicist who also invented Invar, another...
for its invariable elasticity at normal temperatures. The inventor was Charles Edouard Guillaume
Charles Edouard Guillaume
Charles Édouard Guillaume was a Swiss physicist who received the Nobel Prize in Physics in 1920 in recognition of the service he had rendered to precision measurements in physics by his discovery of anomalies in nickel steel alloys.Guillaume is known for his discovery of nickel-steel alloys he...
, who won the 1920 Nobel Prize for physics in recognition for his metallurgical work (the only Nobel that has been granted for work related to horology
Horology
Horology is the art or science of measuring time. Clocks, watches, clockwork, sundials, clepsydras, timers, time recorders and marine chronometers are all examples of instruments used to measure time.People interested in horology are called horologists...
).
The escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
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.
Chronometers often included other innovations to increase their efficiency and precision. Hard stones such as ruby and sapphire were often used as jewel bearing
Jewel bearing
A jewel bearing is a plain bearing in which a metal spindle turns in a jewel-lined pivot hole. The hole is typically shaped like a torus and is slightly larger than the shaft diameter. The jewel material is usually synthetic sapphire...
s to decrease friction and wear of the pivots and escapement. 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
Maintaining power
In horology, a maintaining power is a mechanism for keeping a clock or watch going while it is being wound.-Huygens:The weight drive used by Christiaan Huygens in his early clocks acts as a maintaining power...
which keeps the chronometer going while it is being wound, and a power reserve
Power reserve
Power Reserve Indicator is a complication of the watch, which is designed to show the amount of remaining stored energy. The power reserve indicator indicates the tension on the mainspring at any particular moment.-Overview:...
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 tenth of a second per day. This is accurate enough to locate a ship's position within 4600 feet (1,402.1 m) after a month's sea voyage.
Today
Ships and boats commonly utilize electronic aids to navigation, mostly the Global Navigation Satellite SystemGlobal Navigation Satellite System
A satellite navigation or SAT NAV system is a system of satellites that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location to within a few metres using time signals transmitted along a line-of-sight by radio from...
s. However celestial navigation
Celestial navigation
Celestial navigation, also known as astronavigation, is a position fixing technique that has evolved over several thousand years to help sailors cross oceans without having to rely on estimated calculations, or dead reckoning, to know their position...
, which requires the use of a precise chronometer, is still a requirement for certain international mariner certifications
Licensed mariner
A licensed mariner is a person who holds a license issued by one or more countries to hold senior positions aboard ships, boats, and similar vessels. The United States Coast Guard grants licenses to members of the United States Merchant Marine in five categories: deck officers, engineers, staff...
such as Officer in Charge of Navigational Watch, and Master and Chief Mate deck officers,
and supplements offshore yachtmasters on long-distance private cruising yachts.
Modern marine chronometers can be based on quartz clock
Quartz clock
A quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency, so that quartz clocks are at least an order of magnitude more accurate than good mechanical clocks...
s that are corrected periodically by GPS
Global Positioning System
The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...
signals or radio time signal
Time signal
A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible time signals:...
s (see radio clock
Radio clock
A radio clock or radio-controlled clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic 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, that are accurate to within 10 or 20 seconds per year.
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.
See also
- ClockmakerClockmakerA clockmaker is an artisan who makes and repairs clocks. Since almost all clocks are now factory-made, most modern clockmakers only repair clocks. Modern clockmakers may be employed by jewellers, antique shops, and places devoted strictly to repairing clocks and watches...
- Larcum KendallLarcum KendallLarcum Kendall was a British watchmaker.-Commission:The Board of Longitude asked Kendall to copy and develop John Harrison's ingenious fourth model of a clock useful for navigation at sea...
- Noon GunNoon GunThe Noon Gun has been an historic time signal in Cape Town, South Africa since 1806. The gun is situated on Signal Hill, close to the centre of the city.- History :...
- Timeball
- Time signalTime signalA time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible time signals:...
- Railroad chronometerRailroad chronometerRailroad chronometers, or Railroad Standard Watches, are specialized timepieces that once were crucial for safe and correct operation of trains in many countries...
- Rupert GouldRupert GouldRupert Thomas Gould , was a Lieutenant Commander in the British Royal Navy noted for his contributions to horology .-Life:...
, author of the definitive history of the marine chronometer - Radio-controlled watch
- WatchmakerWatchmakerA watchmaker is an artisan who makes and repairs watches. Since virtually all watches are now factory made, most modern watchmakers solely repair watches. However, originally they were master craftsmen who built watches, including all their parts, by hand...
- Timeline of invention
External links
- National Maritime Museum, Greenwich
- Henri MOTEL n°258 Chronomètre de Marine 40 heures
- GUB Marine-Chronometer caliber 100 - Presentation of marine chronometers of "Glashütter Uhrenbetriebe VEB" with picture and explanation (German)
- A working chronometer, National Museum of Australia. Short MPEG film showing an 1825 Barraud chronometer in action.