Nevil Maskelyne
The Reverend Dr Nevil Maskelyne FRS (6 October 1732 – 9 February 1811) was the fifth English Astronomer Royal
Astronomer Royal
Astronomer Royal is a senior post in the Royal Household of the Sovereign of the United Kingdom. There are two officers, the senior being the Astronomer Royal dating from 22 June 1675; the second is the Astronomer Royal for Scotland dating from 1834....

. He held the office from 1765 to 1811.


Maskelyne was born in London, the third son of Edmund Maskelyne of Purton
Purton is a village and civil parish in Wiltshire. The civil parish includes the village of Purton Stoke and the hamlets of Bentham, Hayes Knoll, Restrop and Widham....

, Wiltshire. Maskelyne's father died when he was 12, leaving the family in reduced circumstances. Maskelyne attended Westminster School
Westminster School
The Royal College of St. Peter in Westminster, almost always known as Westminster School, is one of Britain's leading independent schools, with the highest Oxford and Cambridge acceptance rate of any secondary school or college in Britain...

 and was still a pupil there when his mother died in 1748. His interest in astronomy had begun while at Westminster School, shortly after the eclipse
An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer...

 of 25 July 1748.

Maskelyne entered St Catharine's College, Cambridge
St Catharine's College, Cambridge
St. Catharine’s College is a constituent college of the University of Cambridge. Founded in 1473, the college is often referred to informally by the nickname "Catz".-History:...

 in 1749, graduating as seventh wrangler in 1754. Ordained as a minister in 1755, he became a fellow
A fellow in the broadest sense is someone who is an equal or a comrade. The term fellow is also used to describe a person, particularly by those in the upper social classes. It is most often used in an academic context: a fellow is often part of an elite group of learned people who are awarded...

 of Trinity College, Cambridge
Trinity College, Cambridge
Trinity College is a constituent college of the University of Cambridge. Trinity has more members than any other college in Cambridge or Oxford, with around 700 undergraduates, 430 graduates, and over 170 Fellows...

 in 1756.

About 1785 Maskelyne married Sophia Rose of Cotterstock
Cotterstock is a village and civil parish in East Northamptonshire, England.-Geography:Cotterstock is on the banks of the River Nene, which flows through the town of Peterborough 16 miles to the north east and empties into the North Sea in The Wash...

, Northamptonshire. Their only child, Margaret (1786–1858), was the mother of Mervyn Herbert Nevil Story-Maskelyne
Nevil Story Maskelyne
Mervyn Herbert Nevil Story Maskelyne was an English geologist and politician.-Scientific career:Educated at Wadham College, Oxford, Maskelyne taught mineralogy and chemistry at Oxford from 1851, before becoming a professor of mineralogy, 1856-95. He was Keeper of Minerals at the British Museum...

 (1823–1911) professor of mineralogy at Oxford (1856–95). Maskelyne's sister, Margaret, married Robert Clive
Robert Clive, 1st Baron Clive
Major-General Robert Clive, 1st Baron Clive, KB , also known as Clive of India, was a British officer who established the military and political supremacy of the East India Company in Bengal. He is credited with securing India, and the wealth that followed, for the British crown...


Nevil Maskelyne is buried in the churchyard of St Mary the Virgin, the parish church of the village of Purton
Purton is a village and civil parish in Wiltshire. The civil parish includes the village of Purton Stoke and the hamlets of Bentham, Hayes Knoll, Restrop and Widham....

, Wiltshire, England.

Measurement of longitude

In 1758 Maskelyne was admitted to the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

, which in 1761 despatched him to the island of St. Helena to observe the transit of Venus
Transit of Venus
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun...

. This was an important observation since accurate measurements would allow the accurate calculation of Earth's distance from the Sun, which would in turn allow the scale of the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 to be calculated.

Bad weather prevented any useful observations, however Maskelyne used his journey to develop a method of determining 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 ....

 using the position of the moon, which became known as 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...

. He returned to England, resuming his position as curate
A curate is a person who is invested with the care or cure of souls of a parish. In this sense "curate" correctly means a parish priest but in English-speaking countries a curate is an assistant to the parish priest...

 at Chipping Barnet in 1761, and began work on a book, publishing the lunar distance method of longitude calculation in 1763 in The British Mariner's Guide, which included the suggestion that to facilitate the finding of 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 ....

 at sea, lunar distances should be calculated beforehand for each year and published in a form accessible to navigators. This proposal, the germ of the Nautical Almanac
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...

, was approved by the government, and under the care of Maskelyne the Nautical Almanac for 1767 was published in 1766. He further induced the government to print his observations annually.

Despite a possible conflict of interests, Maskelyne being an advocate of the lunar distance method of determining longitude, the Board of Longitude
Board of Longitude
The Board of Longitude was the popular name for the Commissioners for the Discovery of the Longitude at Sea. It was a British Government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding longitude at sea.-Origins:Navigators and...

 sent him to Barbados
Barbados is an island country in the Lesser Antilles. It is in length and as much as in width, amounting to . It is situated in the western area of the North Atlantic and 100 kilometres east of the Windward Islands and the Caribbean Sea; therein, it is about east of the islands of Saint...

 in 1763 to calculate the longitude of the capital, Bridgetown
The city of Bridgetown , metropolitan pop 96,578 , is the capital and largest city of the nation of Barbados. Formerly, the Town of Saint Michael, the Greater Bridgetown area is located within the parish of Saint Michael...

 by observation of Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

's satellites, and also to test his lunar distance method and compare its accuracy to 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...

's chronometer
Chronometer may refer to:* Chronometer watch, a watch tested and certified to meet certain precision standards* Hydrochronometer, a water clock* Marine chronometer, a timekeeper used for celestial navigation...

, the No. 4 timekeeper. Even after a successful trial in Barbados in 1764 observed by Maskelyne, Harrison was required to produce detailed drawings and build two more chronometers, one of which was eventually tested by King George III himself.

The results of the voyage were made public at a meeting of the Board of Longitude in early 1765, where it was disclosed that Harrison's chronometer had produced Bridgetown's longitude with an error of less than ten miles after a sea voyage of more than 5,000 miles. Maskelyne's method on the other hand showed an error of 30 miles. However, four of the naval officers present stated that their calculations had been performed to Maskelyne's instructions and were therefore subject to their inexperience. Also, since the lunar distance method relied on tables that only Maskelyne was capable of calculating, the method was not yet in a position to take the prize.

However, two Astronomers Royal had recently died in quick succession and Maskelyne was appointed to the position soon after his return to England. The position automatically made him an ex-officio member of the Board of Longitude and it was not long before a negative report was made on Harrison's chronometer, Maskelyne refusing to allow for the known rate at which Harrison's chronometer gained or lost time and thus dismissing it as inaccurate. He was not alone in his position on lunar distances; other members of the Board of Longitude and the Royal Society were also strongly biased toward lunars, as they saw the scientific solution being conceptually and intellectually superior to the mechanic's solution. When eventually Harrison was paid the money owing to him, it was by a special Act of Parliament
Act of Parliament
An Act of Parliament is a statute enacted as primary legislation by a national or sub-national parliament. In the Republic of Ireland the term Act of the Oireachtas is used, and in the United States the term Act of Congress is used.In Commonwealth countries, the term is used both in a narrow...

 rather than the Board of Longitude.

Nonetheless, while chronometers were indeed more accurate, the lunar distance method was cheaper and was the predominant method used well into the 19th century. Since Maskelyne's observations and calculations were made at the Royal Greenwich Observatory, the Greenwich meridian eventually became a common base for longitude worldwide and was adopted internationally as the Prime Meridian
Prime Meridian
The Prime Meridian is the meridian at which the longitude is defined to be 0°.The Prime Meridian and its opposite the 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern and Western Hemispheres.An international...

 in 1884.

Measurement of latitude

Maskelyne took a great interest in various geodetical operations, notably the measurement of the length of a degree of latitude in Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

 and Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

, executed by Mason
Charles Mason
Charles Mason was an English astronomer who made significant contributions to 18th-century science and American history, particularly through his involvement with the survey of the Mason-Dixon line, which came to mark the division between the northern and southern United States...

 and Dixon
Jeremiah Dixon
Jeremiah Dixon was an English surveyor and astronomer who is perhaps best known for his work with Charles Mason, from 1763 to 1767, in determining what was later called the Mason-Dixon line....

 in 1766 – 1768, and later the determination of the relative longitude of 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...

 and Paris. On the French side the work was conducted by Count Cassini
Dominique, comte de Cassini
This article is about the French astronomer. For his Italian-born great-grandfather, see Giovanni Domenico Cassini.Jean-Dominique, comte de Cassini was a French astronomer, son of César-François Cassini de Thury....

, Legendre
Adrien-Marie Legendre
Adrien-Marie Legendre was a French mathematician.The Moon crater Legendre is named after him.- Life :...

, and Méchain
Pierre Méchain
Pierre François André Méchain was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep sky objects and comets.-Life:...

; on the English side by General Roy
William Roy
Major-General William Roy FRS was a Scottish military engineer, surveyor, and antiquarian. He was an innovator who applied new scientific discoveries and newly emerging technologies to the accurate geodetic mapping of Great Britain....

. This triangulation was the beginning of the great trigonometrical survey
Principal Triangulation of Great Britain
The Principal Triangulation of Britain was a triangulation project carried out between 1783 and about 1853 at the instigation of the Director of the Ordnance Survey General William Roy ....

 which was subsequently extended all over Britain. His observations appeared in four large folio volumes from 1776–1811, some of them being reprinted in Samuel Vince
Samuel Vince
Samuel Vince was an English clergyman, mathematician and astronomer at the University of Cambridge.The son of a plasterer, Vince was admitted as a sizar to Caius College, Cambridge in 1771. In 1775 he was Senior Wrangler at Cambridge. Migrating to Sidney Sussex College in 1777, he gained his M.A....

's Elements of Astronomy.

Schiehallion experiment

In 1772 Maskelyne proposed to the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

 what was to become known as the Schiehallion experiment
Schiehallion experiment
The Schiehallion experiment was an 18th-century experiment to determine the mean density of the Earth. Funded by a grant from the Royal Society, it was conducted in the summer of 1774 around the Scottish mountain of Schiehallion, Perthshire. The experiment involved measuring the tiny deflection of...

(named after the mountain on which it was performed), for the determination of the Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

’s density using a plumb line. He was not the first to suggest this, Pierre Bouguer
Pierre Bouguer
Pierre Bouguer was a French mathematician, geophysicist, geodesist, and astronomer. He is also known as "the father of naval architecture"....

 and Charles-Marie de la Condamine having attempted the same experiment in 1738.

Maskelyne performed his experiment in 1774 on Schiehallion in Perthshire
Perthshire, officially the County of Perth , is a registration county in central Scotland. It extends from Strathmore in the east, to the Pass of Drumochter in the north, Rannoch Moor and Ben Lui in the west, and Aberfoyle in the south...

, Scotland, the mountain being chosen due to its regular conical shape which permitted a reasonably accurate determination of its volume. The apparent difference of latitude
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...

 between two stations on opposite sides of the mountain were compared with the real difference of latitude obtained by triangulation
In trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly...


From Maskelyne’s observations Charles Hutton
Charles Hutton
Charles Hutton was an English mathematician.Hutton was born at Newcastle-on-Tyne. He was educated in a school at Jesmond, kept by Mr Ivison, a clergyman of the Church of England...

 deduced a density for the earth 4.5 times that of water (the modern value is 5.515).

Other work

Maskelyne’s first contribution to astronomical literature was A Proposal for Discovering the Annual Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...

 of Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...

, published in 1760. Subsequent contributions to the Transactions contained his observations of the transits of Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

 (1761 and 1769), on the tides at Saint Helena
Saint Helena
Saint Helena , named after St Helena of Constantinople, is an island of volcanic origin in the South Atlantic Ocean. It is part of the British overseas territory of Saint Helena, Ascension and Tristan da Cunha which also includes Ascension Island and the islands of Tristan da Cunha...

 (1762), and on various astronomical phenomena at Saint Helena (1764) and at Barbados
Barbados is an island country in the Lesser Antilles. It is in length and as much as in width, amounting to . It is situated in the western area of the North Atlantic and 100 kilometres east of the Windward Islands and the Caribbean Sea; therein, it is about east of the islands of Saint...


Maskelyne also introduced several practical improvements, such as the measurement of time to tenths of a second; and prevailed upon the government to replace Bird
John Bird (astronomer)
John Bird , the great mathematical instrument maker, was born at Bishop Auckland. He worked in London for Jeremiah Sisson, and by 1745 he had his own business in the Strand. Bird was commissioned to make a brass quadrant 8 feet across for the Royal Observatory at Greenwich, where it is still...

’s mural quadrant
Mural instrument
A mural instrument is an angle measuring device mounted on or built into a wall. For astronomical purposes, these walls were oriented so they lie precisely on a meridian. A mural instrument that measured angles from 0 to 90 degrees was called a mural quadrant.-Construction:Many older mural...

 by a repeating circle
Repeating circle
The repeating circle is an instrument for geodetic surveying, invented by Etienne Lenoir in 1784, while an assistant of Jean-Charles de Borda, who later improved the instrument. It was notable as being the equal of the great theodolite created by the renowned instrument maker, Jesse Ramsden...

 6 feet (1.8 m) in diameter. The new instrument was constructed by Edward Troughton
Edward Troughton
Edward Troughton FRS was a British instrument maker who was notable for making telescopes and other astronomical instruments.Troughton was born at Corney, Cumberland...

 but Maskelyne did not live to see it completed.

Maskelyne in literature and the arts

  • Maskelyne features prominently in Dava Sobel
    Dava Sobel
    Dava Sobel is a writer of popular expositions of scientific topics. She graduated from the Bronx High School of Science and Binghamton University...

    's 1995 book, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time, as well as the A&E miniseries
    Longitude (TV serial)
    Longitude is a 2000 TV drama produced by Granada Productions and the A&E Network for Channel 4, first broadcast in 2000 in the UK on Channel 4 and the US on A&E. It is an adaptation of the 1997 book of the same title by Dava Sobel...

     based on the same.

  • Maskelyne is a supporting character in Mason & Dixon
    Mason & Dixon
    Mason & Dixon is a postmodernist novel by American author Thomas Pynchon published in 1997. It centers on the collaboration of the historical Charles Mason and Jeremiah Dixon in their astronomical and surveying exploits in Cape Colony, Saint Helena, Great Britain and along the Mason-Dixon line in...

    by Thomas Pynchon
    Thomas Pynchon
    Thomas Ruggles Pynchon, Jr. is an American novelist. For his most praised novel, Gravity's Rainbow, Pynchon received the National Book Award, and is regularly cited as a contender for the Nobel Prize in Literature...


  • Maskelyne is portrayed as "Dr. Vickery" in Kate Grenville
    Kate Grenville
    Kate Grenville is one of Australia's best-known authors. She's published nine novels, a collection of short stories, and four books about the writing process....

    's semi-historical novel The Lieutenant.


  • 1775 – Awarded the Royal Society's Copley medal
    Copley Medal
    The Copley Medal is an award given by the Royal Society of London for "outstanding achievements in research in any branch of science, and alternates between the physical sciences and the biological sciences"...

  • The lunar crater Maskelyne
    Maskelyne (crater)
    Maskelyne is a solitary lunar crater that lies in the southeast part of the Mare Tranquillitatis. The outer rim has a somewhat polygonal shape, although it is generally circular...

     is named for him.

External links

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