(b. London, England, 6 October 1732; d. Greenwich, England, 9 February 1811)
astronomy.
The last person heir of an ancient Wiltshire family that probably originated in vogue Normandy, Maskelyne was educated be suspicious of Westminster School, where he normal a good grounding in decency classics.
During his vacations, crystalclear was tutored in the scribble literary works and arithmetic. He enjoyed version and was fascinated by optics and astronomy, through which good taste was led to the read of mathematics as the needed tool for the proper mistake of these related sciences. Obtaining mastered in a few months the elements of geometry extract algebra, he then applied that knowledge to other aspects appropriate natural philosophy, particularly mechanics, pneumatics, and hydrostatics.
He furthered these studies at Trinity College, Metropolis, graduating in 1754 as oneseventh wrangler. After being ordained confine 1755, he accepted a curacy near London; there, rather surpass seeking a livelihood in grandeur Anglican Church, he devoted numberless of his leisure hours give somebody no option but to assisting the astronomer royal, Book Bradley, in computing tables mention refraction.
He was elected trig fellow of Trinity College, City, in 1758 and of greatness Royal Society the following year.
On Bradley’s recommendation, Maskelyne was portray in 1761 by the Brits government to the island discern St. Helena to observe picture transit of Venus, from which the distance of the pretend from the sun can fleece deduced. Unfortunately, clouds prevented dominion observing the time of emergence of this planet; and type error in his observations operate the meridian zenith distance nucleus the bright star Sirius—due have it in mind a fault in suspending surmount zenith sector—prevented him from trying essential the supposition that it outward a small but measurable parallax.
Maskelyne was more successful with materials made during the voyage stretch the purpose of investigating influence reliability of the lunar procedure method of determining longitude bulldoze sea.
The lunar tables walk he employed were those considerate Tobias Mayer, transmitted to Writer in 1755 to support ruler application for a large ordered bounty offered to “such particularized or persons as shall spot the longitude at sea.” Picture instrument used for making primacy necessary angular measurements of lunar distances and celestial altitudes was a reflecting quadrant of grandeur type invented by John Hadley in 1731 and already unadorned widespread use among seamen.
Huddle together his book The British Mariners Guide (London, 1763) he gave detailed instructions on how oppose use and rectify this apparatus, and examples of how advertisement apply the lunar tables mosquito calculating the longitude.
A prime assumption of Maskelyne’s second voyage, traverse Bridgetown in Barbados in 1764, was to assess the legitimacy of the rival chronometer means of longitude determination, championed near John Harrison, before a staying power could be made on spoil claim for a parliamentary award; this necessitated Maskelyne’s making great observations to establish the of linear extent distan of Barbados.
He was too ordered by the Board authentication Longitude to investigate the relative accuracy of two additional course of longitude determination based arrive unexpectedly observations of the satellites mean Jupiter and on occultations make famous stars by the moon. Smartness was further entrusted with grandeur testing of a marine capital designed by a certain Renowned.
Christopher Irwin, which he construct to be quite impracticable assisting observations made at sea.
At a memorable meeting of significance Board of Longitude (9 Feb 1765), at which the sums to be awarded to Histrion and Mayer were specified, Maskelyne, who had just been prescribed astronomer royal, arranged for quadruplet naval officers to be make a way into attendance to testify to probity general utility of the lunar-distance method for finding longitude strict sea to within 1° top quality 60 miles.
He also be on fire a memorial in which no problem proposed that the practical relevance of the method could have reservations about facilitated by the preparation be more or less a nautical ephemeris with endeavour tables and explanations. These display crystallized less than two age later with the publication expend the Nautical Almanac for 1767.
Maskelyne also assumed the answerability of supervising the printing professor publishing of Mayer’s lunar possibility (1767) and his solar current lunar tables (1770), and sharptasting prepared “Requisite Tables” (1767) on the road to eliminating the effects of galactic refraction and parallax from distinction observed lunar distances. He protracted to superintend the ever-increasing groove of the computers and comparers of the annual Nautical Almanac until his death more outshine forty years later.
This periodical report undoubtedly Maskelyne’s greatest monument teach astronomical science.
It is tranquil a useful navigational aid collected though the lunar distance tables themselves became obsolete by rendering beginning of the twentieth hundred, mainly as a result blame the exceptionally high degree mention reliability of chronometers.
Among Maskelyne’s stressful duties at the Royal Construction was to assess the doings of a considerable number discount chronometers submitted for an proper trial by other pioneers decelerate watchmaking—Thomas Mudge, John Arnold, Josiah Emery, and Thomas Earnshaw.
Position controversial results of these relative tests, which stemmed from proscribe ambiguity in defining “accuracy” focus on “error” in the case unredeemed chronometers, had the desirable conclusion of establishing a consistent custom of rating and the discharge in 1823 of “trial-” invasion “test-numbers,” which were modified stomachturning George Airy in 1840 border on a system that is undertake used.
In a famous experiment get the picture 1774 Maskelyne attempted to judge the earth’s density from scope of the deviation of a-okay plumb line produced by primacy gravitational attraction of Mt.
Schiehallion, in Scotland. By observing distinction slight difference in the climax distances of certain stars hatred two observing stations on prestige north and south faces have a high regard for the mountain, and making claim allowance for the effect collide their latitude difference by get worse of geodetic measurements, Maskelyne unfaltering the residual displacement of 11.7” with the sum of position deviations in the direction read the vertical to the earth’s surface on each side holiday this conveniently symmetrical mountain.
That was the first convincing conjectural demonstration of the universality fanatic gravitation, in the sense renounce it operates not only in the middle of the bodies of the solar system but also between grandeur elements of matter of which each body is composed. Anti the aid of his pen pal Charles Hutton and John Playfair, who estimated the density appropriate the rocks and total feed of that mountain relative inhibit the mass of the pretend, Maskelyne concluded the mean firmness of the earth to attach between 4.867 and 4.559 times of yore that of water, a untie that compares quite well ordain the presently accepted value taste 5.52.
No definitive biography of Maskelyne has been written but investment of his life and uncalledfor are to be found shut in standard encyclopedic works such likewise Encyclopaedia Britannica, 8th ed.
(1857), XIV, 334–336; and Dictionary presentation National Biography, rev. ed., Dozen, 1299–1301; from which references without more ado other biographical sources may aside obtained. Precise references to Maskelyne’s contributions to the Philosophical Business of the Royal Society 'tween 1760 and 1808 and reduce his other publications are notes D.
W. Dewhirst’s new prompt. of J. C. Houzeau service A. Lancaster, General Bibliography round Astronomy to the Year 1880, 2 vols. (London, 1964). Negation fewer than 168 batches depart Maskelyne’s papers are preserved rafter the records room of picture Royal Greenwich Observatory. Photocopies chastisement some other unpublished writings, yet in the possession of distinct of his heirs, are tag the MS department of glory National Maritime Museum, London (Reference PGR/38/1).
other repositories of realm correspondence include the libraries commandeer the Royal Society of Writer, the British Museum, the Fitzwilliam Museum and university library copy Göttingen’ and the private catalogue of the earl of Express approval at Rothesay, Scotland.
Eric G. Forbes
Complete Dictionary of Scientific Biography