Maskelyne, Nevil

(1732-1811), astronomer and mathematician

by Derek Howse

© Oxford University Press 2004 All rights reserved

Maskelyne, Nevil (1732-1811), astronomer and mathematician, was born on 5 October 1732 in Kensington Gore, London, the third of the four children of Edmund Maskelyne (1698-1744), one of the clerks of the duke of Newcastle, secretary of state, and his wife, Elizabeth (d. 1748), the only child of John Booth of Chester, a distant cousin. In his own words, written about 1800, Nevil was 'the last male heir of an antient family long settled at Purton in the County of Wilts, which from the name probably came from Normandy, where there is or was 50 years ago a family of that name Masqueline' (autobiographical notes, CUL, RGO MS.4/320:8). All Nevil's siblings were born in Kensington: William in 1725, Edmund in 1728, and Margaret in 1735. The following year the family moved to Tothill Street, Westminster, saving a walk of more than 2 miles each way to Edmund senior's office in Lincoln's Inn Fields, and to Westminster School, where the two eldest boys were king's scholars. In January 1741 Nevil followed his brothers to Westminster, becoming a town boy.

In March 1744 their father died, leaving a somewhat meagre inheritance in trust for the three younger children. Then, in the winter of 1748-9, their mother died also. William and Edmund were already provided for. Nevil became a boarder in Vincent Bourne's house in Westminster, and Margaret went to live with her aunts in Wiltshire until 1752, when she sailed to India to join her brother Edmund, whose friend and colleague Robert Clive she married in Madras in 1753.

Preparations for astronomy
It was while Nevil was still at Westminster School that he decided that astronomy was the career for him. For this, the study of mathematics was essential, and he decided he must follow his eldest brother to the University of Cambridge. After leaving Westminster in July 1749 he entered St Catharine's College as a sizar in November, and migrated in July 1750 to Pembroke College, where he matriculated. In 1752 he moved again, to Trinity, the college of his brother William, where he took the mathematical tripos for the BA degree in 1754 and graduated as seventh wrangler.

Maskelyne wanted to be an astronomer--and an important one. The first hurdle was the mathematical tripos. Then, fellowship of Trinity would be an enormous advantage, not only for its academic distinction but also because it would pay a small stipend and give free board and lodging in college until marriage. While waiting for the appropriate moment to apply, he decided to anticipate one of the fellowship requirements, the taking of holy orders. At Michaelmas 1755 he was ordained to the curacy of Chipping Barnet in Hertfordshire, where he came under the rector of East Barnet. In 1756 he was elected a fellow of Trinity, and, after proceeding to the MA degree, in July 1757 was elected to his major fellowship.

It was about this time that Maskelyne was introduced to the astronomer royal, James Bradley, who, in January 1758, was one of those signing a certificate recommending Maskelyne, 'well versed in Mathematical Learning and Natural Philosophy', for fellowship of the Royal Society, to which he was duly elected on 27 April 1758, at the age of twenty-five.

Expedition to St Helena
Of Maskelyne's activities in Chipping Barnet, pastoral or scientific, little is known, but he began to see his way ahead in an astronomical career on 14 July 1760, when he was appointed by the Royal Society to go to St Helena to observe the transit of Venus, a phenomenon which was to occur on 6 June 1761. This was part of an international programme of observers all over the world (in the event somewhat frustrated by the Seven Years' War) to measure the sun's parallax and thereby derive the mean distance between the earth and sun, a fundamental quantity known today as the astronomical unit.

With Robert Waddington as second observer, Maskelyne sailed for St Helena in the East Indiaman Prince Henry on 18 January 1761. While on passage he became involved for the first time in practical navigation at sea, in the development of which he was later to play such an important role. He had with him a 20 inch Hadley quadrant by Bird and, thanks to Bradley, a copy of Mayer's solar and lunar tables, so was able to try out the lunar-distance method of measuring longitude, effectively continuing the 1757-9 trials of Captain John Campbell.

Maskelyne's first task on arrival at St Helena on 6 April 1761 was to find a site and to set up the instruments for observing the transit of Venus on 6 June. Sadly, clouds covered the sun at the critical moment. Waddington left the island immediately, but Maskelyne remained to continue scientific observations, principally to measure the annual parallax of the star Sirius, which passes nearly overhead there. However, after many months of inconsistent results he decided there was a defect in his zenith sector, so he sailed for home in the East Indiaman Warwick in February 1762, taking further lunar-distance observations for longitude while on passage. He reached Plymouth on 15 May.

Maskelyne resumed his pastoral duties at Chipping Barnet. At the same time he assiduously attended Royal Society meetings and wrote The British Mariner's Guide, published in April 1763, containing an English edition of Mayer's tables and giving simple instructions for finding longitude at sea by lunar distance, with worked examples from his observations in the Warwick.

Finding longitude
Meanwhile, the board of longitude was giving much attention to the rival method of finding longitude--by chronometer. The longitude watch (H4) of John Harrison had been tried out on a voyage to Jamaica in 1761-2, but the results did not satisfy the board, which decided that, if Harrison was to qualify for the full reward offered by the Longitude Act of 1714, there must be another sea trial to the West Indies. In August 1763 Maskelyne agreed to sail on the board's behalf (with Charles Green, assistant at the Royal Greenwich Observatory) to establish the longitude of Barbados by observations of the eclipses of Jupiter's satellites, so that the accuracy of H4 could be assessed. Maskelyne and Green left from St Helens Roads off the Isle of Wight in HMS Princess Louisa on 23 September, and on 7 November reached Bridgetown, Barbados, where they set up an observatory and began observations. John Harrison's son William arrived with H4 on 13 May 1764, when he objected to Maskelyne being involved because, he said, the latter was a candidate for a reward on behalf of the lunar-distance method. Maskelyne was greatly upset by this slur on his character. Why this objection was not raised before Harrison left England is not clear, but a compromise was reached so that Maskelyne and Green made observations on alternate days. Harrison, Green, and H4 sailed for home on 4 June; Maskelyne remained until 30 August to complete his longitude observations and continue some lunar observations started in St Helena.

Maskelyne reached London on 12 October 1764 to be greeted with the news that Bradley's successor as astronomer royal, Nathaniel Bliss, had died on 2 September and that he, Maskelyne, was a strong candidate for the vacant post. The royal warrant appointing him director of the Greenwich observatory was dated 8 February 1765. The very next day he was at the Admiralty in London attending his first meeting as an ex officio member of the board of longitude. At what was probably the most important meeting of that body in the 114 years of its existence, the board recommended awards to Harrison for his watch--only half the major award--and to Mayer and Euler for the lunar tables. They also approved a proposal by Maskelyne that the board should publish annually a nautical almanac containing tables for facilitating the lunar-distance method of finding longitude at sea, to be edited by Maskelyne himself. With minor amendments, these proposals were ratified by parliament in May.

Astronomer royal
Maskelyne took up residence at the Greenwich observatory on 16 March 1765. According to the king's instructions:

forthwith to apply yourself with the most exact Care and Diligence to the rectifying the Tables of the Motions of the Heavens, and the Places of the fixed Stars, in order to find out the so much desired Longitude at Sea, for perfecting the Art of Navigation (royal warrant, 8 Feb 1765)
Maskelyne's primary task was astronomical observation. Top priority was given to the moon: the astronomer royal and his assistant took observations on every possible occasion it crossed the meridian, the former noting the time of crossing with the transit instrument, the latter measuring the zenith distance with the mural quadrant. The sun and planets were observed likewise, though at lower priority. As for star positions, Maskelyne decided that enough such data existed on some 3000 stars for the time being, so, except in special circumstances, limited his observations to thirty-six stars, lying near the celestial equator and bright enough to be visible through a telescope in daylight, needed to ascertain the going of the clocks. With one assistant only, Maskelyne followed this policy for more than forty-five years, and some 90,000 observations were made. Through the Royal Society, the results were published every ten years or so, something his predecessors had failed to do.

Many occasional observations had to be taken at Greenwich in addition to the routine meridian observations--the timing of predictable phenomena used for finding longitude, such as the eclipses of Jupiter's satellites; the occultation of stars and planets by the moon; solar and lunar eclipses; and measuring the places of newly discovered bodies, such as Uranus in 1781, Ceres and two other minor planets in 1801-4, and fairly frequent comets. Then there was the transit of Venus of 1769, when Maskelyne was not clouded out as he had been in St Helena in 1761.

The annual Nautical Almanac and Astronomical Ephemeris and its companion Tables Requisite were undoubtedly Maskelyne's greatest contribution to the improvement of navigation and astronomy and to science as a whole. It was almost entirely through his efforts and persistence that they came to be published in the first place--for the year 1767--and he was the first editor. As such he superintended the complex calculations, the precision of which was improved year by year as a result of work by mathematicians and astronomers throughout Europe with whom, despite the bellicose state of that period, Maskelyne kept in touch. He was entirely responsible for the first forty-nine issues of the almanac, from 1767 to that for the year 1815, published in 1811, the year of his death; and for three editions of the Tables Requisite, published in 1766, 1781, and 1801. He also had to oversee the production of some eighteen other works published by the board of longitude.

Other work for the board of longitude kept Maskelyne extremely busy, particularly arranging for and assessing the performance of timekeepers submitted for trial at Greenwich, which led to acrimonious disputes with Harrison (in 1765-7), Thomas Mudge (in 1774-93), and John Arnold and Thomas Earnshaw (in 1798-1807). He was also responsible for the planning of the scientific sides of voyages of exploration to which the Royal Society or board of longitude appointed observers--for the 1769 transit of Venus, for the first fleet to New South Wales, and the voyages of Cook, Phipps, Vancouver, and Flinders.

Density of the earth
Maskelyne's other responsibility was to the Royal Society, to whose council he was elected in December 1766, and on which he remained, except for two short breaks, until his death. In the summer of 1774, having obtained the king's leave of absence, he went on the Royal Society's behalf to conduct an experiment which he had himself proposed, to determine the earth's density--to 'weigh the world'--by measuring the deviation of a plumb line produced by the gravitational attraction of the mountain Schiehallion in Perthshire, and by observing stars near the zenith on both the north and south sides of the mountain. From the results he postulated that the density of the whole earth was 4.5 times that of water; the current accepted value is 5.52. For this work he was given the society's highest award, the Copley medal, in November 1774. In the society's dissensions in 1784 he strongly supported Dr Charles Hutton (who had carried out the analysis of the Schiehallion results) against the president, Sir Joseph Banks.

In 1768 Maskelyne took the degree of bachelor of divinity at Cambridge, followed in 1777 with that of doctor of divinity. In 1775 he was presented by his nephew Lord Clive with the living of Shrawardine in Shropshire, and in 1782 by Trinity College to the rectory of North Runcton, Norfolk. On 21 August 1784, in St Andrew's, Holborn, he married Sophia Rose (1752-1821), the second daughter and coheir of John Pate Rose of Cotterstock, Northampton, and Jamaica; she was twenty years his junior. Their only child, Margaret, was born in Greenwich on 27 June 1785. Nevil's eldest brother, William, had died in 1772, leaving him Pond's Farm, Purton Stoke, Wiltshire, which became his 'country cottage' after he married, and where the family used to go for five weeks or so each autumn.

Maskelyne was elected fellow of the American Academy of Arts and Sciences at Cambridge, Massachusetts, in 1788, and received honours from Hanover, Russia, and Poland, but the honour he appreciated most was his election in 1802 as one of only eight foreign members of the Institut de France, established in 1795.

Final years
Maskelyne's final years were as busy as ever, and he had a large amount of paperwork to deal with, particularly on Nautical Almanac business and during the Earnshaw affair of 1806. He took what proved to be his last recorded astronomical observation on 1 September 1810. The same year he attended all three meetings of the board of longitude, and on 6 December took the chair--his 150th attendance (he missed only one, when on Schiehallion); he was also at the Royal Society council meeting on 13 December. Then, in mid-January, he fell ill, and he died at the Greenwich observatory on 9 February 1811 in his seventy-ninth year, having completed forty-six years as astronomer royal. He was buried on 20 February at the church of St Mary, Purton, Wiltshire. He was survived by his widow, Sophia, and his daughter, Margaret, who in 1819 married Anthony Mervyn Story (who subsequently took the additional name of Maskelyne); their eldest son, Nevil Story Maskelyne, became a distinguished mineralogist.

The evidence from the large body of correspondence that has survived proves that, pompous and a bit of a bore as he might have seemed to some, Maskelyne was almost universally liked and admired by his contemporaries--except perhaps by some chronometer makers and their families. The reputation that survives in some popular twentieth-century books of Maskelyne as the evil genius who tried to deprive the poor illiterate carpenter of his just rewards--out of personal spite and because of his own involvement in the rival lunar-distance method of finding longitude--was certainly not one that was held generally in his own day, nor is it in any way justified by modern research: he was a member of the board of longitude, appointed by parliament to advise on the award of large sums of public money; there is no evidence whatsoever that he at any time abused his position as a public servant, still less lined his own pocket.

Although he promoted the cause of astronomical science through his routine work at Greenwich--and, most important, made it available to mathematicians and astronomers the world over by ensuring the prompt publication of results--Maskelyne never lost sight of the principal object of the observatory's existence, the improvement of navigation. But undoubtedly his greatest achievement was to set in motion the annual publication of Britain's Nautical Almanac, the model for similar ephemerides now published worldwide, and the reason why the international system of time and longitude measurement are today based upon the Greenwich meridian.

DEREK HOWSE

Sources  
D. Howse, Nevil Maskelyne: the seaman's astronomer (1989)
parish register, St Andrew's, Holborn [marriages]

Archives  
CUL, Board of Longitude MSS, RGO MS 14
CUL, corresp. and papers
NMM, account books (microfilm)
priv. coll., letters and three account books
RS, MS vols. 371, 372 (class Gh)
RS, corresp.; observations
St John Cam., papers
Wilts. & Swindon RO, corresp. and papers, 1390 |  Armagh Observatory, corresp. with J. A. Hamilton
MHS Oxf., corresp. with Lewis Evans
NL Wales, letters to John Walsh
NRA, corresp. with Sir Joseph Banks
RAS, corresp. with Sir William Herschel; letters to Nathaniel Pigott
W. Yorks. AS, Leeds, Yorkshire Archaeological Society, remarks by him on memoranda of John Edwards relating to telescopes

Likenesses  
attrib. J. Russell, black and red chalk, c.1776, repro. in Howse, Nevil Maskelyne; priv. coll.
J. Downman, oils, 1779, NMM
L. F. G. van der Puyl, oils, 1785, RS [see illus.]
M. Byrne, miniature, 1801, priv. coll.
Threed junior, miniature, 1801, priv. coll.
J. Russell, pastel, 1804, priv. coll.
stipple, pubd 1804, BM
J. F. Skill, J. Gilbert, W. and E. Walker, group portrait, pencil and wash (Men of science living in 1807-8), NPG
portraits, repro. in Howse, Nevil Maskelyne


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