Nevil Maskelyne

Maskelyne was born in London, the third son of Edmund Maskelyne of Purton in Wiltshire, and his wife, Elizabeth Booth. Maskelyne's father died when he was 12, leaving the family in reduced circumstances. Maskelyne attended Westminster School 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 of 14 July 1748.{{cite book | author=Howse, Derek | title = Nevil Maskelyne: The Seaman's Astronomer | year = 1989 | publisher=Cambridge University Press | isbn = 052136261X}}

Maskelyne entered St Catharine's College, Cambridge in 1749, graduating as seventh wrangler in 1754.{{acad|MSKN749N|name=Nevil Maskelyne}} Ordained as a minister in 1755, he became a fellow of Trinity College, Cambridge in 1756 and a Fellow of the Royal Society in 1758.{{cite web|title=Election Certificate|url=https://collections.royalsociety.org/DServe.exe?dsqIni=Dserve.ini&dsqApp=Archive&dsqDb=Catalog&dsqSearch=RefNo==%27EC%2F1758%2F04%27&dsqCmd=Show.tcl|website=Royal Society Library|access-date=16 April 2015|ref=EC/1758/04}} Maskelyne became a member of the American Philosophical Society, elected in 1771.{{Cite web|url=https://search.amphilsoc.org/memhist/search?creator=Nevil+&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced|title = APS Member History}}

Originally pursuing his career as a Church of England minister, he was Rector of Shrawardine in Shropshire from 1775 to 1782 and then Rector of North Runcton in Norfolk from 1782. In 1784 he was elected a Fellow of the Royal Society of Edinburgh. His proposers were John Playfair, John Robison and Dugald Stewart.{{cite book|title=Biographical Index of Former Fellows of the Royal Society of Edinburgh 1783–2002|date=July 2006|publisher=The Royal Society of Edinburgh|isbn=0-902-198-84-X|url=https://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp2.pdf|access-date=30 August 2017|archive-url=https://web.archive.org/web/20160304074135/https://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp2.pdf|archive-date=4 March 2016|url-status=dead}}

On 21 August 1784 Maskelyne married Sophia Rose, then of St Andrew Holborn, Middlesex.{{Cite web|url=https://www.ancestry.com/interactive/1623/31281_a100986-00037?pid=215083&backurl=https://search.ancestry.com/cgi-bin/sse.dll?dbid%3D1623%26h%3D215083%26indiv%3Dtry%26o_vc%3DRecord:OtherRecord%26rhSource%3D1981&treeid=&personid=&hintid=&usePUB=true&usePUBJs=true|title=London, England, Church of England Marriages and Banns, 1754-1932 for Nevil Maskelyne|date=21 August 1784|website=Ancestry.com|access-date=19 December 2018}} Their only child, Margaret (25 June 1785{{Cite web|url=https://search.ancestry.com/cgi-bin/sse.dll?dbid=1624&h=152721897&indiv=try&o_vc=Record:OtherRecord&rhSource=1623|title=London, England, Church of England Baptisms, Marriages and Burials, 1538-1812 for Nevil Maskelyne|date=26 July 1785|website=Ancestry.com|access-date=19 December 2018}}–1858), was the mother of Mervyn Herbert Nevil Story-Maskelyne (1823–1911) professor of mineralogy at Oxford (1856–95). Maskelyne's younger sister, Margaret, married Robert Clive.

Maskelyne is buried in the churchyard of St Mary the Virgin, the parish church of the village of Purton, Wiltshire, England.Maskelyne's grave can be seen by going through the church gates and veering to the right, against the right outside wall of the church.

In 1760 the Royal Society appointed Maskelyne as an astronomer on one of their expeditions to observe the 1761 transit of Venus. He and Robert Waddington were sent to the island of Saint Helena in the South Atlantic. 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 actual rather than the relative scale of the Solar System to be calculated. This would allow, it was argued, the production of more accurate astronomical tables, in particular those predicting the motion of the Moon.{{cite book|last1=Woolf|first1=Harry|title=The Transits of Venus. A study of eighteenth-century science|date=1959|publisher=Princeton University Press|location=Princeton, NJ}}

Bad weather prevented observation of the transit, but Maskelyne used his journey to trial a method of determining longitude using the position of the moon, which became known as the lunar distance method.Nevil Maskelyne [http://cudl.lib.cam.ac.uk/view/MS-RGO-00004-00150/1 Journal of a Voyage to St Helena], RGO 4/150, Cambridge Digital Library He returned to England, resuming his position as curate at Chipping Barnet in 1761, and began work on a book, publishing the lunar-distance method of longitude calculation and providing tables to facilitate its use in 1763 in The British Mariner's Guide, which included the suggestion that to facilitate the finding of longitude at sea, lunar distances should be calculated beforehand for each year and published in a form accessible to navigators.

In 1763 the Board of Longitude sent Maskelyne to Barbados in order to carry out an official trial of three contenders for a Longitude reward. He was to carry out observations on board ship and to calculate the longitude of the capital, Bridgetown by observation of Jupiter's satellites. The three methods on trial were John Harrison's sea watch (now known as H4), Tobias Mayer's lunar tables and a marine chair made by Christopher Irwin, intended to help observations of Jupiter's satellites on board ship. Both Harrison's watch and lunar-distance observations based on Mayer's lunar tables produced results within the terms of the Longitude Act, although the former appeared to be more accurate. Harrison's watch had produced Bridgetown's longitude with an error of less than ten miles, while the lunar-distance observations were accurate to within 30 nautical miles.

Maskelyne reported the results of the trial to the Board of Longitude on 9 February 1765.{{cite web|title=Confirmed Minutes of the Board of Longitude|url=http://cudl.lib.cam.ac.uk/view/MS-RGO-00014-00005/79|website=Cambridge Digital Library}} On 26 February 1765 he had been appointed Astronomer Royal following the unexpected death of Nathaniel Bliss in 1764; making him ex officio a Commissioner of Longitude. The Commissioners understood that the timekeeping and astronomical methods of finding longitude were complementary. The lunar-distance method could more quickly be rolled out, with Maskelyne's proposal that tables like those in his "The British Mariner's Guide" be published for each year. This proposal led to the establishment of The Nautical Almanac, the production of which, as Astronomer Royal, Maskelyne oversaw. Taking even occasional astronomical observations was also the only way to check that a timekeeper was keeping good time over the course of a long voyage. The Commissioners also needed to know that more than one sea watch could be made, and that Harrison's methods could be communicated to other watchmakers.{{cite book|last1=Dunn|first1=Richard|last2=Higgitt|first2=Rebekah|title=Finding Longitude: How Ships, Clocks and Stars Helped Solve the Longitude Problem|date=2014|publisher=Collins|location=Glasgow|isbn=978-0007525867}}

The Board of Longitude therefore decided that rewards should be given to Harrison (£10,000), Mayer (£3000, posthumously) and others involved in helping to develop the lunar-distance method.{{cite web|last1=Higgitt|first1=Rebekah|title=Barbados or bust: longitude on trial|website=TheGuardian.com|date=9 September 2013|url=https://www.theguardian.com/science/the-h-word/2013/sep/09/history-science-longitude-maskelyne-barbados|access-date=15 April 2015}}{{cite journal|last1=Howse|first1=Derek|title=Britain's Board of Longitude: The Finances, 1714-1828|journal=The Mariner's Mirror|date=1998|volume=84|issue=4|pages=400–417|url=http://blogs.rmg.co.uk/wp-content/uploads/sites/5/2013/03/howse.pdf|access-date=16 April 2015|doi=10.1080/00253359.1998.10656713|archive-date=23 May 2014|archive-url=https://web.archive.org/web/20140523173104/http://blogs.rmg.co.uk/wp-content/uploads/sites/5/2013/03/howse.pdf|url-status=dead}} Harrison was told that a further reward of £10,000 would be forthcoming if he could demonstrate the replicability of his watch. Although Harrison and his son later accused Maskelyne of bias against the timekeeping method, charges repeated by authors such as Dava Sobel and Rupert Gould, Maskelyne never submitted a method or an idea of his own for consideration by the Board of Longitude. He was to play a significant role in having marine timekeepers, as well as the lunar-distance method, developed, tested and used on board voyages of exploration.

Since the observations that fed into the Nautical Almanac were made at the Royal Observatory, Greenwich, the Greenwich meridian became the reference for measurements of longitude in the Royal Navy, and on British Admiralty charts. It was subsequently chosen for adoption as the international Prime Meridian in 1884.(JR Wills The Royal Society){{cite book|last1=Dunn|first1=Richard|last2=Higgitt|first2=Rebekah|title=Finding Longitude: How Ships, Clocks and Stars Helped Solve the Longitude Problem|date=2014|publisher=Collins|location=Glasgow|isbn=978-0007525867|page=221}}

Maskelyne took a great interest in various geodetical operations, including the measurement of the length of a degree of latitude in Maryland and Pennsylvania,Philosophical Transactions of the Royal Society. lviii. 323 executed by Mason and Dixon in 1766 – 1768, and later the determination of the relative longitude of Greenwich and Paris.Philosophical Transactions of the Royal Society. lxxvii. 151 On the French side the work was conducted by Count Cassini, Legendre, and Méchain; on the English side by General Roy. This triangulation was the beginning of the great trigonometrical survey which was subsequently extended all over Britain. His observations appeared in four large folio volumes from 1776 to 1811, some of them being reprinted in Samuel Vince's Elements of Astronomy.{{cite book | last = Vince | first = Samuel | author-link = Samuel Vince | title = The Elements of Astronomy: Designed for the Use of Students in the University | publisher=J. Smith | year = 1811 | url =https://archive.org/details/elementsofastron00vincrich}}

In 1772 Maskelyne proposed to the Royal Society what was to become known as the Schiehallion experiment (named after the Scottish mountain on which it was performed), for the determination of the Earth's density using a plumb line. He was not the first to suggest this, Pierre Bouguer and Charles-Marie de la Condamine having attempted the same experiment in 1738 in the Andes.

Maskelyne performed his experiment in 1774 on Schiehallion in Perthshire, Scotland,Philosophical Transactions of the Royal Society. 1. 495 the mountain being chosen due to its regular conical shape which permitted a reasonably accurate determination of its volume. The apparent difference of latitude between two stations on opposite sides of the mountain were compared with the real difference of latitude obtained by triangulation.

From Maskelyne's observations Charles Hutton deduced a density for the earth 4.5 times that of water (the modern value is 5.515).

Maskelyne's first contribution to astronomical literature was A Proposal for Discovering the Annual Parallax of Sirius, published in 1760.Philosophical Transactions of the Royal Society. ii. 889 Subsequent contributions to the Transactions contained his observations of the transits of Venus (1761 and 1769), on the tides at Saint Helena (1762), and on various astronomical phenomena at Saint Helena (1764) and at Barbados (1764).

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's mural quadrant by a repeating circle 6 feet (1.8 m) in diameter. The new instrument was constructed by Edward Troughton but Maskelyne did not live to see it completed.{{EB1911|wstitle=Maskelyne, Nevil|volume=17|last1= Clerke |first1= Agnes Mary |author1-link= Agnes Mary Clerke |page=837|inline=1}}

File:Grave of Nevil Maskelyne.JPG, Wiltshire]]

• Maskelyne features prominently in Dava Sobel's 1995 book, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time, as well as the television serial based on the book, where he is portrayed by Samuel West.{{cite web |title=Longitude © (1999) |url=http://movie-dude.com/[Film]%20Longitude%20(1999).htm |access-date=22 June 2021}}
• Maskelyne is a supporting character in the novel Mason & Dixon by Thomas Pynchon. He and Charles Mason (and briefly, Jeremiah Dixon before he returns to Cape Town) meet on Saint Helena - with the characters of the two clashing while they spend time which each other.
• Maskelyne is portrayed as "Dr. Vickery" in Kate Grenville's semi-historical novel The Lieutenant.

• 1775 – Awarded the Royal Society's Copley Medal{{Cite web |title=Copley Medal {{!}} Royal Museums Greenwich |url=https://www.rmg.co.uk/collections/objects/rmgc-object-249548 |access-date=2024-08-25 |website=www.rmg.co.uk}}
• 1776 – Elected a Member of the Saint Petersburg Academy of Sciences.{{cite web|title=Papers of Nevil Maskelyne: Certificate and seal from Catherine the Great, Russia|url=http://cudl.lib.cam.ac.uk/view/MS-REG-00009-00037/1|publisher=Cambridge Digital Library|access-date=19 January 2015}}
• 1778 – Elected a Foreign Honorary Member of the American Academy of Arts and Sciences.{{cite web|title=Book of Members, 1780–2010: Chapter M|url=http://www.amacad.org/publications/BookofMembers/ChapterM.pdf |archive-url=https://web.archive.org/web/20060618085944/http://amacad.org/publications/BookofMembers/ChapterM.pdf |archive-date=2006-06-18 |url-status=live|publisher=American Academy of Arts and Sciences|access-date=28 July 2014}}
• The lunar crater Maskelyne in the Sea of Tranquility is named after him.
• William Wales named the Maskelyne Islands in southern Malekule, Vanuatu after him while on James Cook's second voyage on HMS Resolution.{{cite book|last1=Wales|first1=William|title=The Original Astronomical Observations, Made in the Course of a Voyage towards the South Pole, and Around the World|date=1777|location=London|page=lv}}
• Also during Cook's second voyage, the colony at Botany Bay had a small area next to the newly established observatory named Point Maskelyne.Map of Port Jackson (now known as Sydney) 1788

File:Maskelyne, Nevil – Tables requisite to be used with the astronomical and nautical ephemeris for finding the latitude and longitude at sea, 1781 – BEIC 782957.jpg

• {{Cite book|title=Tables requisite to be used with the astronomical and nautical ephemeris for finding the latitude and longitude at sea|volume=|publisher=William Richardson|location=London|year=1781|language=en|url=https://gutenberg.beic.it/webclient/DeliveryManager?pid=782957}}

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• {{cite journal |last=Delambre |first=Jean-Baptiste-Joseph |author-link=Jean Baptiste Joseph Delambre |title=Biographical Account of the Rev. Nevil Maskelyne, D. D. Astronomer Royal |journal=Annals of Philosophy |year=1813 |volume=1 |number=6 |pages=401–414 |url=https://books.google.com/books?id=2xsAAAAAMAAJ&pg=PA401 }}

{{commons category|Nevil Maskelyne (astronomer)}}

• [http://janus.lib.cam.ac.uk/db/node.xsp?id=EAD%2FGBR%2F0180%2FRGO%204 Online catalogue of Maskelyne's working papers (part of the Royal Greenwich Observatory Archives held at Cambridge University Library)]
• [http://cudl.lib.cam.ac.uk/view/ES-LON-00027/1 Essay on Nevil Maskelyne, Cambridge Digital Library]

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Nevil