Nevil Maskelyne
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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 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 correct value being 5.515.
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 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.
| Preceded by: Nathaniel Bliss | Astronomer Royal 1765–1811 | Followed by: John Pond |