George Biddell Airy
Airy, George Biddell
Airy, George Biddell
(b. Alnwick, Northumberland, England, 27 July 1801; d. Greenwich, England, 2 January 1892)
George Airy was the eldest of four children of William Airy, a farmer who through self-education acquired posts in the Excise, and of Ann Biddell, daughter of a well-to-do farmer. At the age of ten he took first place at Byatt Walker’s school at Colchester but, as he himself records, because he had very little animal vitality, he was not a favorite with his schoolmates. In the school he thoroughly learned arithmetic, double-entry bookkeeping, and the use of the slide rule. An introverted but not shy child, Airy was, even for the time and especially for his circumstances, a young snob. Nevertheless, he overcame some of the dislike of his schoolmates by his great skill and inventiveness in the construction of peashooters and other such devices.
At the age of twelve Airy came to know his uncle Arthur Biddell, a well-educated and highly respected farmer near Ipswich. He recognized in his uncle an opportunity to escape what he considered unpromising surroundings, and secretly requested that he be removed from his family. Arthur Biddell almost literally kidnapped him, without any word to his parents, but because of financial difficulties caused by William Airy’s loss of his Excise post, the escape was not blocked. From 1814 to 1819 Airy spent nearly half of his time with his uncle. In later life he put great value on this connection, especially becaue of the resulting acquaintances, including Thomas Clarkson, the abolitionist, who could help his career. It was through Clarkson and Charles Musgrave, fellow of Trinity College, Cambridge, that he was entered as sizar of Trinity College in October 1819.
Airy entered Cambridge with the determination to get on, and he was certainly equipped to do so. Although his own assessment of his abilities was immodestly high, it was nevertheless matched, albeit sometimes reluctantly, by his tutors and college friends. He graduated as a Senior Wrangler in 1823 after far outdistancing all the men of his year, although beginning in his second term he had the burden of supporting himself by taking pupils. He was elected a fellow of Trinity College in 1824.
Three incidents from this period illustrate the care and foresight with which Airy planned his life. The first concerns the habit he adopted, as an undergraduate, of always keeping by him a quire of largesized scribbling paper, sewn together, upon which everything was entered; translations into Latin and out of Greek, several lines of which he attempted every day, no matter how pressing other business might be; mathematical problems; and nearly every thought he had, complete with date. The sheets, even after the more important items were transferred to exercise books or diaries, were kept, together with nearly every communication received and a copy of those sent throughout his life, and are still extant. He seems not to have destroyed a document of any kind whatever: stubs of old checkbooks, notes for tradesmen, circulars, bills, and correspondence of all sorts were carefully preserved in chronological order from the time that he went to Cambridge. This material provides possibly the best existing documentation of a truly Victorian scientist.
The second illustrative incident involves Airy’s courtship of his future wife, Ricarda Smith, the eldest daughter of the Rev. Richard Smith, private chaplain to the duke of Devonshire. He met Miss Smith white he was on a walking tour in Derbyshire, and within two days of first seeing her he made an offer of marriage. Neither his means nor his prospects at the time permitted an immediate marriage, and the Rev. Smith would not permit an engagement. Undaunted, Airy renewed his suit from time to time, and six years after his first proposal they were married.
A similar singleness of purpose is shown in Airy’s approach to a prospective position at the Royal Greenwich Observatory. In 1824 an attempt was made to improve the educational level of assistants at the Royal Observatory by hiring one or two Cambridge graduates. Airy was proposed as one of these assistants and traveled to Greenwich to investigate the possibility. However, in his own words, “when I found that succession to the post of Astronomer Royal was not considered as distinctly a consequence of it, I took it cooly [sic] and returned to Cambridge the next night.”
Airy applied for and won the Lucasian professorship in 1826. In doing this, he exchanged an assistant tutorship worth £150 per annum, and the prospect o succeeding to a tutorship, for the £99 per annum of the professorship, supplemented by a somewhat uncertain £100 per annum as ex officio member of the Board of Longitude. Other considerations were that “my prospects in the law or other profession might have been good if I could have waited but marriage would have been out of the question and I much preferred a moderate income in no long time. I had now in some measure taken science as my line (though not irrevocably) and I thought it best to work it well for a time at least and wait for accidents.”
The Plumian professorship, which involved the care of the Cambridge Observatory, became vacant in 1828, and Airy “made known that I was a candidate and nobody thought it worthwhile to oppose me… . I told everybody that the salary (about £300) was not sufficient and drafted a manifesto to the University for an increase… . the University had never before been taken by storm in such a manner and there was some commotion about it. I believe very few people would have taken the same step… . I had no doubt of success.” He was appointed Plumian professor and director of the observatory on 6 February 1828, with a salary of £500 per annum. Although he accepted the post of astronomer royal in 1835, when he moved from Cambridge to Greenwich, Airy’s considerable influence on British astronomy stretches without break from his appointment at Cambridge in 1828 to his retirement as astronomer royal in 1881. He was knighted in 1872, after thrice refusing on the basis that he could not afford the fees.
The ruling feature of Airy’s character was undoubtedly order, and from the time he went up to Cambridge until the end of his life his system of order was strictly maintained. He wrote his autobiography up to date as soon as he had taken his degree, and made his first will as soon as he had any money to leave. His accounts were personally kept by double entry, and he regarded their keeping as one of his greatest joys. The effect of this sense of order on British observational astronomy is the only reason that Airy is included in this volume, for he was an organizer rather than a scientist. To realize his importance, it is necessary to understand the astronomy of the nineteenth century and the role played by such institutions as the Royal Greenwich Observatory.
The rise of astronomy in the seventeenth and eighteenth centuries took the form of careful observations of stellar positions made to provide a framework within which planetary motions could be measured. The first astronomer royal, John Flamsteed, provided the earliest observations of this kind that are still useful today. Although the emphasis in modern astronomy has shifted beyond the planets to the stars and external galaxies, these early observations provide us with a three-hundred-year base line for measuring the motions of the stars themselves, and knowledge of these motions is vital to the understanding of the origin and evolution of the stars. Observations of this kind are not only necessary in large numbers but they must be extremely exacting if the results are he be of general use. They are therefore best made in a routine way by those more interested in the technological problems of their procurement than in their scientific use. The Royal Greenwich Observatory, following Flamsteed’s early lead, became the primary producer of such observations, mainly because the Admiralty was interested in the more immediate need of them for navigational purposes. Partly because the utilitarian purpose was stressed, scientific supervision of the observations eventually decreased and was refocused only in the nineteenth century, when it became obvious that their lack of accuracy was adversely affecting their use in navigation. The situation was ripe for Airy with his scientific training and his sense of order. The reforms he introduced were copied by other countries that, because they were expanding their navies to protect their expanding merchant fleets, needed the navigational aids.
The secret of Airy’s long and successful official career was that he was a good servant who thoroughly understood his position. He never set himself in opposition to his masters, the Admiralty. He recognized the task for which he was appointed and transformed the Royal Greenwich Observatory into a highly efficient institution. The cost, however, was high. No independent thought could be tolerated, and as a result no scientists were trained there. The often slipshod methods that lead to scientific discovery were carried on outside, by John Herschel, John Adams, and many others. Airy himself would not understand this criticism. He wrote, in 1832,“… in those parts of astronomy which depend principally on the assistance of Governments, requiring only method and judgement, with very little science in the persons employed, we have done much; while in those which depend exclusively on individual effort we have done little… . our principal progress has been made in the lowest branches of astronomy while to the higher branches of science we have not added anything,” He needed only to add that he had done his job.
In any article on Airy mention must be made of the controversy accompanying the discovery of the planet Neptune. It is ironical that the kind of order Airy restored to the observational work at Greenwich should coincide with the greatest need for the results since Newton had put Flamsteed’s observations to such good use in the Principia—and then be unfairly blamed in nearly every subsequent article on the discovery of Neptune for withholding these observations. In fact, Airy supplied all the major participants in this discovery with the observational data they requested, and the only basis for the subsequent attacks upon him was that he was not at home when John Adams, then a young Cambridge mathematician, called unannounced to present one of his early predictions that such a planet as Neptune had to exist in order to account for the motions of the other planets. Airy’s great efficiency in the observatory was noted by other government services and he rapidly became the prototype of the modern government scientist. This kept him from the observatory a large amount of time.
Always of medium stature and not powerfully built, Airy seemed to shrink as he aged, mainly because of an increasing stoop. His constitution, even at eighty-five, was remarkably sound. He took not the least interest in athletic sports or competition, but he was always a very active walker and could endure a great deal of fatigue. His eyesight was peculiar, and he studied it thoroughly all his life, correcting the astigmatism with a cylindrical lens, a method that he invented and is still used. As his powers failed with age, he was tyrannized by his ruling passion for order, and his efforts went into correctly filing his correspondence rather than understanding its contents. He was by nature eminently practical, and his dislike of mere theoretical problems and investigations put him continually in dissent with some of the resident Cambridge mathematicians. This practical bent led him to undertake, in 1872, the preparation of a numerical lunar theory. This work consisted, essentially, of obtaining from observations numerical values of the 320 periodic terms in Delaunay’s equations for the moon’s motion. His difficulties are summed up in a note of 29 September 1890:
I had made considerable advance (under official difficulties) in calculations on my favourite Numerical Lunar Theory, when I discovered that, under the heavy pressure of unusual matters (two Transits of Venus and some eclipses)I had committed a grievous error in the first stage of giving numerical value to my Theory. My spirit in the work was broken, and I have never heartily proceeded with it since.
Airy was not a great scientist, but he made great science possible. It is true that he was indirectly responsible for guiding British observational astronomy into a cul-de-sac from which it took many years to retreat, but it was not his fault that the methods he devised to provide a particular service at a particular time were so efficiently contrived and completely implemented that weaker successors continued to apply them, unchanged, to changing conditions.
Airy’s bibliography contains over 500 printed papers and the following books: Mathematical Tracts on Physical Astronomy, the Figure of the Earth, Precession and Nutation, and the Calculus of Variations (Cambridge, 1826); 2nd ed. (London, 1831), with the Undulatory Theory of Optics added; 4th ed. (London, 1858); Undulatory Theory of Optics also published separately (London, 1877); Gravitation: An Elementary Explanation of the Principal Perturbations in the Solar System (London, 1834, 1884); Six Lectures on Astronomy (London, 1849); A Treatise in Trigonometry (London, 1855); On the Algebraical and Numerical Theory of Errors of Observations and the Combination of Observations (London, 1861; 3rd ed., 1879); Essays on the invasion of Britain by Julius Caesar, the invasion of Britain by Plautius, and by Claudius Caesar; the early military policy of the Romans in Britain; the Battle of Hastings; and correspondence were published in Essays (London, 1865); An Elementary Treatise on Partial Differential Equations (London, 1866); On Sound and Atmospheric Vibrations, With the Mathematical Elements of Music (London, 1868, 1871); A Treatise on Magnetism (London, 1870): Notes on the Earlier Hebrew Scriptures (London, 1876): and Numerical Lunar Theory (London, 1886).
The complete list of printed papers is given in Wilfred Airy’s edition of the Autobiography of Sir George Airy (London, 1896). They can be divided into four main categories: optics, both practical and theoretical; practical astronomy, including reports of progress and final publication of results obtained by the observers at Cambridge and Greenwich; government science, concerning the many tasks other than astronomy for which the government claimed his time; and contributions to the many polemics that marked nineteenth-century British science.
The extensive biographical data are housed mainly in the new Royal Greenwich Observatory at Herstmonceux Castle, Sussex. Some of those covering Airy’s pre- and post-Greenwich careers are in the hands of the writer, and the remainder are scattered between the archives of the Royal Astronomical Society, the Royal Society, and the Royal Greenwich Observatory. As already noted, Airy apparently never discarded a piece of paper. His son Wilfred (as I have been informed by Airy’s granddaughter) had no such inhibitions, and, after including a few extracts in his edition of the Autobiograophy, destroyed the voluminous correspondence between Sir George and Lady Airy.
Olin J. Eggen
Airy, George Biddell
AIRY, GEORGE BIDDELL
(b. Alnwick, Northumberland, England, 27 July 1801; d. Greenwich, England, 2 January 1892)
astronomy. For the original article on Airy see DSB, vol. 1.
The original DSB article on Airy was written by Olin J. Eggen, an astrophysicist who argued that Airy’s talents as an organizer (particularly the “sense of order” he brought to the directorship of the Royal Observatory) were the sole justification for his inclusion in the DSB. Eggen, taking a somewhat Whiggish view of the history of astronomy, concluded that Airy was “not a great scientist, but made great science possible,” and he identified that “great science” as occurring not during Airy’s tenure at the national observatory, but rather when the Greenwich stellar observations, made to provide a framework within which planetary motions could be measured, were used in the twentieth century for understanding the origin and evolution of the stars. As a result, Eggen wrote an essay that provided few details of the accomplishments that earned Airy high respect in his own lifetime.
Focusing narrowly on Airy’s formal duties as superintendent of the Royal Observatory, Greenwich, Eggen failed to comprehend why certain contemporaries considered him the astronomer par excellence of his day. Writing from the vantage point of 1903, the great American astronomer Simon Newcomb, for example, saw Airy as the most commanding figure in the astronomy of his time, and as the person who had introduced large-scale production into astronomy. Later historians have also emphasized Airy’s factory-like approach to astronomical work at Greenwich.
Early Achievements. Even while still at Cambridge as director of the University observatory, Airy demonstrated a characteristic innovativeness in his work. Perceiving that the routine reduction of positional observations could be most accurately carried out by human computers working on preprinted skeleton sheets that were easily checkable by a supervising computer, he introduced such sheets not only for the reduction of Cambridge observations, but also the solar, lunar, and planetary observations of former Astronomer Royal James Bradley (made at Greenwich) and the circumpolar star observations of English astronomer Stephen Groombridge (made at Blackheath). (Airy likewise introduced use of the skeleton sheets at Greenwich upon becoming Astronomer Royal.)
But beyond such organizational innovations, Airy made lasting scientific and technical contributions to several fields. One was optics. Although the circular “bullseye diffraction pattern around a point source of light (such as a star) as seen through a refracting telescope had earlier attracted the notice of William Herschel and Thomas Young, Airy, in an 1834 article published in the Transactions of the Cambridge Philosophical Society, was the first to analyze the pattern mathematically according to the size of the circular aperture and the wavelength of the light. The pattern still bears his name in the early twenty-first century (the Airy disk). At Cambridge, Airy designed and supervised the erection of a large equatorial refractor with an 11.75-inch Cauchoix objective whose construction was made possible with funds provided by the Duke of Northumberland. It became known as the largest and best-mounted instrument in Great Britain, and his version of the English yoke mount was later used for an even larger equatorial installed at Greenwich in 1859. After arriving at Greenwich and eventually perceiving the need for replacement instruments there, Airy designed three new positional instruments—an altitude and azimuth instrument (1847), a transit circle (1851), and a reflex zenith tube (1851)—and an associated barrel chronograph (1854).
Career and Prestige. At the Royal Observatory Airy established its magnetic, meteorological, and astrophoto-graphic and spectroscopic departments. He pioneered within England the transmission of telegraphic time signals for railway and Post Office use and arranged for the use of submarine telegraphy to determine longitude differences between Greenwich and numerous foreign observatories. He also made notable contributions to geodesy. For example, in 1854 Airy conducted an experiment of swinging a single pendulum from both the top and bottom of a deep mine, which enabled him to measure gravity and compute the density of the earth. A year later he theorized that the presence of root structures of lower density were necessary under mountains in order to maintain isostatic equilibrium.
As the senior “scientific” civil servant, Airy became the de facto government scientist to be called upon by government leaders. A significant portion of his time was devoted to so-called “extraneous government business,” that is, his participation in numerous commissions of state and other government bodies. Barely noted by Eggen,
these bodies included commissions on such wide-ranging matters as the standards of measurements, harbors, railway gauges, sewers, coinage, ordnance surveys, sale of town gas, and meteorology. Airy was also consulted concerning the Australian universities of Sydney and Melbourne, the Great Exhibition of 1851 at Hyde Park, London, and the Paris Exhibition of 1855. He provided advice regarding such topics as steam-engine propellers and ship building, compass correction in iron ships, railways, sawmills for ship’s timbers, construction of the Westminster Clock, navigation on the River Dee, the Atlantic submarine cable, and the compilation of a Gold Standard Table for the Bank of England.
The Neptune Controversies. For better or worse, Airy’s reputation, both among contemporaries and later commentators, has been highly influenced by his perceived role in the controversies surrounding the mathematical predictions and optical discovery of the planet Neptune in the mid-1840s. One has to be puzzled, however, by Eggen’s claim that commentators prior to him had almost universally blamed Airy for withholding planetary observations from John Couch Adams, one of the two mathematicians (Urbain Le Verrier was the other) engaged at this time in determining the orbit and current position of a hypothetical transuranian planet that might be causing the observed erratic motion of the planet Uranus. Quite the contrary, the controversies (too detailed to be discussed at length here) concerned whether Airy and James Challis had properly encouraged Adams’s researches (including the publication of them) in late 1845, whether these astronomers had unjustifiably delayed searching for Adams’s hypothetical planet, and whether Airy had acted properly in withholding information about Adams’s researches not only from Le Verrier (when the latter corresponded with Airy in late June 1846), but also from other British astronomers (who might have conducted planet searches independent of the one carried out by Challis, with Airy’s encouragement, in the summer of 1846). The French scientific community also questioned whether Adams and Challis deserved any share of the credit for either the mathematical or optical discovery of Neptune.
Airy himself had hoped to provide a definitive account justifying his actions through the presentation of a selection of relevant letters at the Royal Astronomical Society (RAS) meeting of 13 November 1846 and their appearance in the Monthly Notices of the RAS 7 (1846, pp. 121–144) and other publications, but these letters instead provoked interpretations unintended by and unflattering to Airy. The printed letters, however, form only a small portion of a file of Neptune-related correspondence and other documents that was maintained by Airy. For over thirty years, beginning in the late 1960s, historians were eager to consult this file, but were prevented from doing so by its removal from the Greenwich Archives by none other than Eggen himself, who secretly held onto it until his death. Fortunately it was recovered and is now available for researchers.
Airy’s Neptune file was returned in 1999 to England, where it is now a part (vol. 96a) of the Royal Greenwich Observatory Archives, Papers of George Airy, RGO 6, in the Cambridge University Library. A detailed catalogue of the entire collection, comprising 848 volumes and occupying 12 cubic meters, is available online from http://janus.lib.cam.ac.uk/db/node xsp?id=EAD%2FGBR%2F0180%2FRGO%206. The collection includes not only incoming letters, but also press copies (many unfortunately faded) of outgoing letters. Numerous letters of Airy may also be found in the papers of his contemporaries, including John Couch Adams (St. John’s College Library, Cambridge University), Charles Babbage (British Library), James Challis (Cambridge University Library), Augustus De Morgan (University College London), James Glaisher (Royal Astronomical Society Library), Sir John Herschel (Royal Society Library), Sir John Lubbock (Royal Society Library), Sir Charles Lyell (Edinburgh University Library), several Earls of Rosse (Birr Castle Archives), Sir Edward Sabine (National Archives), Richard Sheepshanks (Royal Astronomical Library), Sir George Stokes (Cambridge University Library), John Tyndall (Royal Institution of Great Britain), and William Whewell (Trinity College Library, University of Cambridge).
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———. “Airy’s Transit Circle.” Journal of Astronomical History and Heritage 4 (2001b): 115–141.
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Craig B. Waff