Nevil Maskelyne

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Nevil Maskelyne : biography

6 October 1732 – 9 February 1811

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.Sobel, Dava, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time, Walker and Company, New York, 1995 ISBN 0-8027-1312-2Landes, David S., Revolution in Time, Belknap Press of Harvard University Press, Cambridge Mass., 1983, ISBN 0-674-76800-0Gould, Rupert T. The Marine Chronometer. Its History and Development London: J. D. Potter, 1923, ISBN 0-907462-05-7 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 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 in 1884.(JR Wills The Royal Society)

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 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 1776–1811, some of them being reprinted in Samuel Vince’s Elements of Astronomy.

Schiehallion experiment

In 1772 Maskelyne proposed to the Royal Society what was to become known as the Schiehallion experiment (named after the 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.

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).

Other work

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.

Honours

  • 1775 – Awarded the Royal Society’s Copley medal
  • The lunar crater Maskelyne is named for him.
  • Captain Cook named the Maskelynes Islands in southern Malekule, Vanuatu after him on his voyage in Resolution.