Airy, George Biddell (DNB01)

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AIRY, Sir GEORGE BIDDELL (1801–1892), astronomer royal, was born at Alnwick in Northumberland on 27 July 1801. His father, William Airy of Luddington in Lincolnshire, was then collector of excise in Northumberland, whence he was transferred to Hereford in 1802, and to Essex in 1810. Three years later he lost his appointment and lapsed into poverty. He died on 26 March 1827. His wife, Ann, a woman of strong natural abilities, was the daughter of a well-to-do Suffolk farmer; she died in 1841.

George Biddell was the eldest of four children. At ten years of age he took first place in Byatt Walker's school at Colchester, picked up stores of miscellaneous information from his father's books, and became notorious for his skill in constructing pea-shooters. From 1812 he spent his holidays at Playford, near Ipswich, with his uncle, Arthur Biddell, a farmer and valuer, whose influence upon his career proved decisive. He met at his house Thomas Clarkson [q. v.], Bernard Barton [q. v.], Sir William Cubitt [q. v.], Robert and James Ransome [q. v.], and studied optics, chemistry, and mechanics in his library. From 1814 to 1819 Airy attended the grammar school at Colchester, where he was noted for his memory, repeating at one examination 2394 lines of Latin verse. By Clarkson's advice he was sent to Cambridge, and entered as sizar of Trinity College in October 1819. In 1822 he took a scholarship, and in 1823 graduated as senior wrangler and first Smith's prizeman. His year ranked as an annus mirabilis, and he had no close competitor. On his election to a fellowship of his college in October 1824, he became assistant mathematical tutor; he delivered lectures, took pupils, and pursued original scientific investigations.

Airy's 'Mathematical Tracts on Physical Astronomy' was published in 1826, and it immediately became a text-book in the university. An essay on the undulatory theory of light was appended to the second edition in 1831. For his various optical researches, chiefly contained in papers laid before the Cambridge Philosophical Society, he received in 1831 the Copley medal from the Royal Society. He was admitted to membership of the Astronomical and Geological Societies respectively in 1828 and 1829, and was awarded in 1833 the gold medal of the former body for his detection of the 'long inequality' of Venus and the earth, communicated to the Royal Society on 24 Nov. 1831. The Lalande prize followed in 1834, and on 9 Jan. 1835 he was elected a correspondent of the French Academy of Sciences.

A trip to Scotland with his sister, Elizabeth Airy, in the summer of 1823 had 'opened,' he said, 'a completely new world to him.' In the ensuing winter he stayed in London with Sir James South [q. v.], met Sir Humphry Davy and Sir John Herschel, and had his first experience of practical astronomy. During a walking tour in Derbyshire in 1824 he proposed, after two days' acquaintance, for Richarda, eldest daughter of Richard Smith, rector of Edensor, near Chatsworth, and received a benignant refusal. Thenceforth he concentrated his efforts upon securing a position in life and an income. In 1826 and 1826 he led reading parties to Keswick and Orleans, seeing much, on the first occasion, of the poets Southey and Wordsworth, and making acquaintance in Paris, on the second, with Laplace, Arago, Pouillet, and Bouvard. On 7 Dec. 1826 he was elected Lucasian professor of mathematics at Cambridge; but the emoluments of the office—99l. per annum, with 100l. as ipso facto member of the board of longitude—very slightly exceeded those of his relinquished tutorship. Airy renewed the prestige of the Lucasian chair by his ardour for the promotion of experimental physics in the university. In his lectures on light he first drew attention to the defect of vision since called 'astigmatism,' from which he personally suffered. A trip to Dublin in 1827 in quest of the vacant post of astronomer royal in Ireland led to no result; but on 6 Feb. 1828 he succeeded Robert Woodhouse [q. v.] as Plumian professor of astronomy and director of the Cambridge observatory. His income was now augmented to 500l. a year, and thus provided for, he succeeded in inducing Richarda Smith to marry him on 24 March 1830. At the observatory he introduced an improved system of meridian observations, afterwards continued at Greenwich and partially adopted abroad, and set the example of thoroughly reducing before publishing them. He superintended besides the erection of several instruments, and devised the equatorial mount for the Cauchoix twelve-inch lens, which was presented in 1833 to the institution by the Duke of Northumberland. In February 1835 Sir Robert Peel offered Airy a civil-list pension of 300l. a year, which, by his request, was settled on his wife; and on 18 June 1835 he accepted the post of astronomer royal, for which Lord Melbourne designated him in succession to John Pond [q. v.]

Airy's tenure of the office of astronomer-royal lasted forty-six years, and was marked by extraordinary energy. He completely re-equipped the Royal Observatory with instruments designed by himself. The erection in 1847 of an altazimuth for observing the moon in every part of the sky proved of great importance for the correction of lunar tables. A new transit circle of unprecedented optical power and mechanical stability was mounted in 1851, and a reflex zenith tube replaced Troughton's zenith sector in the same year. The inauguration in 1859 of a thirteen-inch equatorial by Merz finished the transforming process. Its use the astronomer royal was resolved should never interfere with the 'staple and standard work' of the establishment; yet, while firmly adhering to the meridional system prescribed 'by both reason and tradition,' he kept well abreast of novel requirements. In 1838 he created at Greenwich a magnetic and meteorological department, Brooke's plan of photographic registration being introduced in 1848. From 1854 transits were timed by electricity; spectroscopic observations were organised in 1868, and the prismatic mapping of solar prominences in 1874; while with the Kew heliograph a daily record of sunspots was begun in 1873. Meantime Airy accomplished the colossal task of reducing all the planetary and lunar observations made at Greenwich between 1750 and 1830, for which he received the gold medal of the Royal Astronomical Society in 1846, and an equivalent testimonial in 1848. The mass of materials thus provided was indispensable to the progress of celestial mechanics.

Airy observed the total solar eclipse of July 1842 from the Superga, near Turin (Memoirs of Roy. Astr. Society, vol. xv.), and that of 28 July 1851 from Gothenburg in Sweden (ib. vol. xxi.) He subsequently visited Upsala, was received in audience by King Oscar at Stockholm, and on the return journey inspected the pumping-engines at Haarlem. For the Spanish eclipse of 18 July 1860 he organised a cosmopolitan expedition, which he conveyed to Bilbao and Santander in the troopship Himalaya, placed at his disposal by the admiralty. He fixed his own station at Herena, but was disappointed in the result. In the autumn of 1854 he superintended an elaborate series of pendulum-experiments for the purpose of measuring the increase of gravity with descent below the earth's surface. Similar attempts made by him in the Dolcoath mine, Cornwall, in 1826 and 1828, with the co-operation of William Whewell [q. v.] and Richard Sheepshanks [q. v.], had been accidentally frustrated. He now renewed them in the Harton colliery, near South Shields, at a depth of 1,260 feet. The upshot was to give 6·56 for the mean density of the earth (Phil. Trans. cxlvi. 342), a value considerably too high. Airy explained the method in a popular lecture at South Shields.

The preparations for the transit of Venus in 1874 cost him enormous labour. The entire control of the various British expeditions was in his hands; he provided twenty-three telescopes, undertook the preliminary work at the observatory, and the subsequent reduction of the vast mass of collected data. The volume embodying them was issued in 1881. Incredible industry and high business capacity alone enabled him to discharge the miscellaneous tasks imposed upon him. He acted as chairman and working secretary of the commission of weights and measures (1838-1842), sat on the tidal harbour and railway gauge commissions in 1845, on the sewers commission in 1848, on the exchequer standards and the coinage commissions in 1868. He experimented in 1838 on the correction of compasses in iron ships, devising the principle still in use; contributed energetically to the improvement of lighthouses, aided in the delimitation of the Maine and Oregon boundaries, and settled the provisions for the sale of gas. The reduction of tidal observations in Ireland and India, and the determination in 1862 of the difference of longitude between Valencia, co. Kerry, and Greenwich, engaged his strenuous attention. He was consulted about the launch of the Great Eastern, the laying of the Atlantic cable, Babbage's calculating machine, the chimes of Westminster clock, and the smoky chimneys of Westminster Palace. A paper on suspension bridges, contributed in 1867 to the Institution of Civil Engineers, was honoured with the Telford medal; and he delivered in 1869 a set of lectures on magnetism in the university of Cambridge, besides at sundry times numerous discourses to the general public. He failed in 1853 to obtain the office of superintendent of the Nautical Almanac, although 'willing to take it at a low rate for the addition to my salary.'

Airy was elected a fellow of the Royal Society on 21 Jan. 1836, frequently sat on the council, and was president 1872-73. He occupied the same post in the Royal Astronomical Society during five biennial periods, and presided over the British Association at its Ipswich meeting in 1851. He became a member of the Cambridge Philosophical Society in 1823, and later of the Institution of Civil Engineers, of the Royal Society of Edinburgh, of the Royal Irish Academy, and of several foreign scientific bodies. On 18 March 1872 he succeeded Sir John Herschel as one of eight foreign members of the French Institute ; he was presented in 1875 with the freedom of the city of London, was created D.C.L. of Oxford (20 June 1844), LL.D. of Cambridge (1862) and Edinburgh, and decided honorary fellow of Trinity College, Cambridge. The czar Nicholas sent him a gold medal specially struck; and among the orders conferred upon him were those of Pour le Mérite of Prussia, of the Legion of Honour, of the North Star of Sweden, of the Dannebrog, and of the Rose of Brazil. On 17 May 1871 he was appointed companion of the Bath, and, a year later (17 June 1872), was promoted to be knight commander. His wife died on 13 Aug. 1875, and on the ground of the lapse of her pension Airy obtained an augmentation of his salary to 1,200l. yearly.

Airy was an indefatigable traveller. In 1829 he inspected the observatories of Turin, Milan, Bologna, and Florence; in 1835 examined the Markree refractor in Ireland, and in 1848 elaborately tested the great Parsonstown reflector. In 1846 he visited Hansen at Gotha, Gauss at GÖttingen, and Caroline Lucretia Herschel [q.v.] at Hanover; in 1847 spent a month at Pulkowa with Otto Struve, and, returning by Berlin and Hamburg, saw Humboldt, Galle, Repsold, and Rtimker. He entered into correspondence with Leverrier in June 1816 about the still unseen planet Neptune, and on 9 July suggested to Professor Challis a plan of search. In the following year he escorted Leverrier to the meeting of the British Association at Oxford. His unjustifiable coldness to John Couch Adams [q.v. Suppl.] was doubtless due to the embarrassments that followed his accidental yet regrettable omission to pay due attention to the letter in which Adams communicated to him the progress of his Neptune investigation.

Airy resigned the office of astronomer royal on 15 Aug. 1881, and resided thenceforward, with his two unmarried daughters, at the White House, close to Greenwich Park, and at Playford, where he had bought a cottage in 1845. His main desire was to complete the 'Numerical Lunar Theory,' upon which he had been engaged from 1872. Printed in 1886, the colossal performance proved, however, to be undermined by unexplained errors. 'With painful alarm,' the aged author noted in the preface, 'I find that the equations are not satisfied, and that the discordance is large.' After two years of hopeless struggle, he desisted from efforts towards correction which have not been re-newed. He continued to enjoy excursions to Cumberland and Playford, but a fall on 11 Nov. 1891 produced an internal injury necessitating a surgical operation, which he survived only a few days. He died at the White House on 2 Jan. 1892, and was buried in Playford churchyard.

'He was of medium stature,' Mr. Wilfrid Airy writes, 'and not powerfully built.' 'The ruling feature of his character was order. From the time that he went up to Cambridge to the end of his life his system of order was strictly maintained.' He enforced it upon himself no less rigidly than upon his subordinates, and kept up at the Royal Observatory a cast-iron discipline, which powerfully contributed to the efficiency of his administration. He never destroyed a document, but devised an ingenious plan of easy reference to the huge bulk of his papers. In his decrepitude this methodical bent tyrannised over him, and 'he seemed more anxious to put letters into their proper place than to master their contents.' 'His nature was eminently practical, and his dislike of mere theoretical problems and investigations was proportionately great. He was continually at war with some of the resident Cambridge mathematicians on this subject. Year after year he criticised the Senate House papers and the Smith's Prize papers very severely, and conducted an interesting and acrimonious private correspondence with Professor Cayley on the same subject.' A very important feature of his investigations was their thoroughness. 'He was never satisfied with leaving a result as a barren mathematical expression. He would reduce it, if possible, to a practical and numerical form, at any cost of labour. . . . To one who had known, in some degree, of the enormous quantity of arithmetical work which he had turned out, and the unsparing manner in which he had devoted himself to it, there was something very pathetic in his discovery, towards the close of his long life, that "the figures would not add up"' (Autobiography of Sir George Biddell Airy, p. 3).

The amount of his labours almost exceeds belief. On the literary side alone they have rarely been equalled. He published eleven separate volumes, including treatises on 'Gravitation' (1834 and 1884), on 'Trigonometry' written for the Encyclopædia Metropolitana about 1825 and reprinted in 1855), on 'Partial Differential Equations' (1866), 'On Sound and Atmospheric Vibrations' (1868 and 1871). His 'Popular Astronomy,' embodying six lectures delivered at Ipswich in 1848, passed through twelve editions. And the papers contributed by him to journals and scientific collections numbered 377, besides 141 official reports and addresses. He wrote on 'The Figure of the Earth,' and on 'Tides and Waves,' in the 'Encyclopaedia Metropolitana;' his 'Report on the Progress of Astronomy,' drawn up for the British Association in 1832, is still valuable; he gave the first theory of the diffraction of object-glasses in an essay read before the Cambridge Philosophical Society on 24 Nov. 1834; for his discussion of the 'Laws of the Tides on the Coasts of Ireland' (Phil. Trans. 12 Dec. 1844) he was awarded a royal medal by the Royal Society in 1845; he communicated important researches on ancient eclipses to that body in 1853, and to the Royal Astronomical Society in 1857; and he introduced in 1859 a novel method of dealing with the problem of the sun's translation (Memoirs of the Royal Astronomical Society, xxviii. 143).

Airy left six children, his three eldest having died young. His third son, Mr. Osmund Airy, was appointed government inspector of schools in 1876; his daughter Hilda married, in 1864, Dr. Routh of Cambridge.

[Airy left a detailed autobiography, which was published at Cambridge in 1896, under the editorship of his eldest son, Mr. Wilfrid Airy, with the additions of a personal sketch and a complete bibliographical appendix. A portrait is prefixed, copied from a steel-engraving executed by C. H. Jeens in 1878 (Nature, xviii. 689). The following sources of information may also be consulted: Proceedings Royal Soc. li. 1 (E. J. Routh); Monthly Notices, lii. 212; Observatory, xv. 74 (E. Dunkin), with a photograph taken on his ninetieth birthday; Nature, 31 Oct. 1878 (Winnecke), 7 Jan. 1892; Times, 5 Jan. 1892; English Mechanic, 8 Jan. 1892; Grant's Hist. of Physical Astronomy; Graves's Life of Sir William Rowan Hamilton, passim.]

A. M. C.