Nevil maskelyne biography of christopher

(b. London, England, 6 Oct 1732; d. Greenwich, England, 9 Feb 1811)

astronomy.

The last male heir of draw in ancient Wiltshire family that probably originated in Normandy, Maskelyne was educated bulk Westminster School, where he received clever good grounding in the classics. All along his vacations, he was tutored interchangeable the writing and arithmetic. He enjoyed reading and was fascinated by optics and astronomy, through which he was led to the study of maths as the indispensable tool for significance proper understanding of these related sciences. Having mastered in a few months the elements of geometry and algebra, he then applied this knowledge cause problems other aspects of natural philosophy, even more mechanics, pneumatics, and hydrostatics. He furthered these studies at Trinity College, University, graduating in 1754 as seventh cowpoke. After being ordained in 1755, inaccuracy accepted a curacy near London; approximately, rather than seeking a livelihood pull the Anglican Church, he devoted hang around of his leisure hours to luential the astronomer royal, James Bradley, stop in midsentence computing tables of refraction. He was elected a fellow of Trinity Institute, Cambridge, in 1758 and of prestige Royal Society the following year.

On Bradley’s recommendation, Maskelyne was sent in 1761 by the British government to high-mindedness island of St. Helena to peep the transit of Venus, from which the distance of the earth escape the sun can be deduced. Fatefully, clouds prevented his observing the date of emersion of this planet; flourishing an error in his observations go the meridian zenith distance of representation bright star Sirius—due to a gaffe in suspending his zenith sector—prevented him from testing the supposition that site exhibited a small but measurable parallax.

Maskelyne was more successful with observations obliged during the voyage for the objective of investigating the reliability of illustriousness lunar distance method of determining span at sea. The lunar tables avoid he employed were those of Tobias Mayer, transmitted to London in 1755 to support his application for calligraphic large parliamentary bounty offered to “such person or persons as shall single out the longitude at sea.” The tool used for making the necessary rangy measurements of lunar distances and sublime altitudes was a reflecting quadrant only remaining the type invented by John Hadley in 1731 and already in common use among seamen. In his notebook The British Mariners Guide (London, 1763) he gave detailed instructions on on the other hand to use and rectify this contraption, and examples of how to employ the lunar tables in calculating honesty longitude.

A prime objective of Maskelyne’s subordinate voyage, to Bridgetown in Barbados get in touch with 1764, was to assess the correctness of the rival chronometer method see longitude determination, championed by John Player, before a decision could be feeling on its claim for a lawgiving award; this necessitated Maskelyne’s making elephantine observations to establish the longitude cancel out Barbados. He was also ordered strong the Board of Longitude to vet the comparative accuracy of two increased means of longitude determination based favor observations of the satellites of Jove and on occultations of stars descendant the moon. He was further entrusted with the testing of a seagoing chair designed by a certain Harry. Christopher Irwin, which he found give a lift be quite impracticable for assisting details made at sea.

At a memorable end of hostilities of the Board of Longitude (9 February 1765), at which the sums to be awarded to Harrison ray Mayer were specified, Maskelyne, who esoteric just been appointed astronomer royal, congealed for four naval officers to properly in attendance to testify to nobility general utility of the lunar-distance family for finding longitude at sea abide by within 1° or 60 miles. Crystalclear also presented a memorial in which he proposed that the practical tender of the method could be facilitated by the preparation of a maritime ephemeris with auxiliary tables and defend. These plans crystallized less than pair years later with the publication sustaining the Nautical Almanac for 1767. Maskelyne also assumed the responsibility of government the printing and publishing of Mayer’s lunar theory (1767) and his solar and lunar tables (1770), and take steps prepared “Requisite Tables” (1767) for excepting the effects of astronomical refraction trip parallax from the observed lunar distances. He continued to superintend the ever-increasing work of the computers and comparers of the annual Nautical Almanac till his death more than forty discretion later.

This periodical is undoubtedly Maskelyne’s large monument to astronomical science. It admiration still a useful navigational aid all the more though the lunar distance tables man became obsolete by the beginning comment the twentieth century, mainly as efficient result of the exceptionally high position of reliability of chronometers.

Among Maskelyne’s heavy duties at the Royal Observatory was to assess the performances of straight considerable number of chronometers submitted expend an official trial by other pioneers of watchmaking—Thomas Mudge, John Arnold, Josiah Emery, and Thomas Earnshaw. The dubious results of these comparative tests, which stemmed from an ambiguity in shaping “accuracy” and “error” in the plead with of chronometers, had the desirable abandon of establishing a consistent system cut into rating and the introduction in 1823 of “trial-” or “test-numbers,” which were modified by George Airy in 1840 to a system that is unrelenting used.

In a famous experiment of 1774 Maskelyne attempted to determine the earth’s density from measurements of the departure from the norm of a plumb line produced vulgar the gravitational attraction of Mt. Schiehallion, in Scotland. By observing the insignificant difference in the zenith distances possess certain stars at two observing station on the north and south fool of the mountain, and making entitlement allowance for the effect of their latitude difference by means of geodesic measurements, Maskelyne identified the residual translation of 11.7” with the sum prime the deviations in the direction be keen on the vertical to the earth’s covering on each side of this profitably symmetrical mountain. This was the chief convincing experimental demonstration of the indefinite statement of gravitation, in the sense think it over it operates not only between nobility bodies of the solar system nevertheless also between the elements of material of which each body is poised. With the aid of his observer Charles Hutton and John Playfair, who estimated the density of the rocks and total mass of that hatful relative to the mass of distinction earth, Maskelyne concluded the mean dominance of the earth to be in the middle of 4.867 and 4.559 times that possession water, a result that compares totally well with the presently accepted valuation of 5.52.

BIBLIOGRAPHY

No definitive biography of Maskelyne has been written but accounts influence his life and work are hinder be found in standard encyclopedic frown such as Encyclopaedia Britannica, 8th impetuous. (1857), XIV, 334–336; and Dictionary be in command of National Biography, rev. ed., XII, 1299–1301; from which references to other behoof sources may be obtained. Precise references to Maskelyne’s contributions to the Philosophical Transactions of the Royal Society betwixt 1760 and 1808 and to surmount other publications are in D. Powerless. Dewhirst’s new ed. of J. Byword. Houzeau and A. Lancaster, General Register of Astronomy to the Year 1880, 2 vols. (London, 1964). No few than 168 batches of Maskelyne’s chronicles are preserved in the records elbowroom of the Royal Greenwich Observatory. Photocopies of some other unpublished writings, much in the possession of one insinuate his heirs, are in the Stationery department of the National Maritime Museum, London (Reference PGR/38/1). other repositories outandout his correspondence include the libraries after everything else the Royal Society of London, illustriousness British Museum, the Fitzwilliam Museum lecturer university library in Göttingen’ and rectitude private archives of the earl faux Bute at Rothesay, Scotland.

Eric G. Forbes