Nevil Maskelyne
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Nevil Maskelyne. |
The Reverend Dr
Nevil Maskelyne (
October 6,
1732 –
February 9,
1811) was the fifth
British Astronomer Royal. He held the office from 1765 to 1811.
The
solar eclipse of 1748 made a deep impression upon him; and having graduated as seventh
wrangler from
Trinity College, Cambridge, in 1754, he determined to devote himself wholly to
astronomy.He became intimate with
James Bradley in 1755, and in 1761 was deputed by the
Royal Society to make observations of the
transit of Venus at
Saint Helena.During the voyage he experimented upon the determination of
longitude by lunar distances, and ultimately effected the introduction of the method into
navigation.In 1765 he succeeded
Nathaniel Bliss as Astronomer Royal. Having energetically discharged the duties of his office during forty-six years, he died on
February 9,
1811.
Maskelyne's first contribution to astronomical literature was
A Proposal for Discovering the Annual Parallax of Sirius, published in 1760 (
Phil. Trans. ii. 889).Subsequent volumes of the same series 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).In 1763 he published the
British Mariner's Guide,which includes the suggestion that in order 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.This important proposal, the germ of the
Nautical Almanac, was approved of by the government, and under the care of Maskelyne the Nautical Almanac for 1767 was published in 1766. He continued during the remainder of his life the superintendence of this invaluable annual.
He further induced the government to print his observations annually, thereby securing the prompt dissemination of a large mass of data inestimable from their continuity and accuracy.Maskelyne had but one assistant, yet the work of the observatory was perfectly organized and methodically executed.He introduced several practical improvements, such as the measurement of time to tenths of a second; and he 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.
In 1772 he suggested to the Royal Society the famous
Schiehallion experiment for the determination of the
Earth's density and carried out his plan in 1774 (
Phil. Trans. 1. 495), the apparent difference of
latitude between two stations on opposite sides of the mountain being 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 being 5.515). The experiment was repeated in 2005 by scientific consultants
Counting Thoughts as an educational exercise.
Maskelyne also took a great interest in various
geodetical operations, notably the measurement of the length of a degree of latitude in
Maryland and
Pennsylvania (ibid. lviii. 323), executed by
Mason and
Dixon in 1766 - 1768, and later the determination of the relative longitude of
Greenwich and
Paris (ib. 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 (1776–1811). Some of them were reprinted in S. Vince's Astronomy (vol. iii.).
Maskelyne was born in
London the third son of Edmund Maskelyne, of Purton,
Wiltshire. About 1785 he married Sophia Rose of
Cotterstock,
Northamptonshire. Their only child, Margaret (1786 - 1858), was the mother of
Mervyn Herbert Nevil Story-Maskelyne (1823 - 1911) professor of mineralogy at Oxford (1856-95).
Maskelyne was portrayed negatively in
Dava Sobel's 1995 book
Longitude : The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time about
John Harrison and the clock solution to the
Longitude Prize. While Harrison's method was indeed more accurate, Maskelyne's lunar distances method was cheaper, and was the predominate method used for the next century. Since Maskelyne's observations and calculations were based on the Greenwich meridian, it became a common base for longitude worldwide and was adopted internationally as the
Prime Meridian in 1884.
In 1989, Derek Howse published a full-length biography of Maskelyne entitled
Nevil Maskelyne: The Seaman's Astronomer. Maskelyne also appears as a supporting character in
Thomas Pynchon's novel
Mason & Dixon.
