NA TURE 



689 



THURSDAY, OCTOBER 31, 1878 



SCIENTIFIC WORTHIES 

 XIII.— Sir George Biddell Airy 



SIR GEORGE BIDDELL AIRY was bom at Aln- 

 wick, Northumberland, on July 27, 1801, He was 

 first educated at private schools in Hereford and Col- 

 chester, and passed at the age of eighteen to Cambridge, 

 where he entered at Trinity College as sizar. Here he 

 developed his love for mathematics and graduated as 

 senior wrangler in the year 1823. 



In the following year, being elected a Fellow of Trinity 

 College, he was closely engaged with the introduction of 

 a new class of studies into the University, and published 

 his " Mathematical Tracts on the Lunar and Planetary 

 Theories," the "Figure of the Earth," &c., and the 

 " Undulatory Theory of Optics," a work of considerable 

 merit, which showed at once both the ingenious mathe- 

 matician and the accomplished philosopher. In the year 

 1825 he wrote for the Cambridge Transactions papers 

 "On the Forms of the Teeth of Wheels," and "On 

 Escapements." 



In the following year he was elected Lucasian Professor 

 of Mathematics, and applied himself with the utmost ardour 

 to the promotion of the knowledge of experimental philo- 

 sophy in the University, and a great many of his papers, 

 published at that time and afterwards in the Transactions 

 of the Cambridge Philosophical Society, bear on those 

 subjects, and principally on the most remarkable of them, 

 Undulatory Optics, a field of research quite new at that 

 time. The requirements of universities were never after- 

 wards lost sight of. He gave, for instance, in the year 

 1868, a course of lectures in the University of Cambridge 

 on the subject of Magnetism, with the view of introducing 

 that important department of physical science into the 

 studies of the University. His books — * ' Theory of Errors 

 of Observations," " On Magnetism," and various memoirs 

 in the Transactions of learned societies were written 

 principally for this purpose. 



In the year 1828 he was elected Plumian Professor of 

 Astronomy, and was charged with the directorship of the 

 Astronomical Observatory, where he had to superintend 

 the erection of several instruments, principally the mount- 

 ing of the great Northumberland equatorial, which was 

 constructed almost entirely under his own direction. 

 In the same year he was elected a Fellow of the Royal 

 Astronomical Society ; and now commences an activity 

 which is almost unsurpassed in the annals of astro- 

 nomy. 



Prof. Airy, after the example first given by Maskelyne, 

 and followed by Bessel and Struve, introduced into the 

 observatory a most efficient system for reducing the 

 observations, and printed them annually. The greatest 

 regularity in the routine of consecutive years was aimed 

 at and attained, in great measure, from adherence to 

 the rule of forming the plan of observations for each year 

 in the greatest detail practicable before the close of the 

 preceding year. 



These practical occupations did not divert his mind 

 from theoretical studies. In the year 1831 a most im- 

 portant paper was published in the Cambridge Transac- 



VOT,. XVIII.— No. 470 



tions, "Cn the Inequality of Long Period in the Motions 

 of the Earth and Venus." In the following year he wrote 

 for the British Association a very interesting " Report on 

 the Recent Progress of Astronomy," a little work which 

 may be read still with great profit by every student of 

 astronomy. Various lacunae of our science discovered on 

 that occasion were filled up by Prof. Airy in the next year 

 by his papers " On the Mass of Jupiter." 



When Mr. Pond, the fifth Astronomer-Royal, resigned 

 in the year 1 835, Prof. Airy was appointed his successor, 

 by Lord Auckland, first Lord of the Admiralty, and at the 

 same time he was elected President of the Royal Astro- 

 nomical Society. During the forty-three years that have 

 elapsed since his appointment as Astronomer-Royal, Sir 

 George has always been most keenly intent in promoting 

 astronomy and science in general in every way. 

 • He has equipped the Royal Observatory at Greenwich 

 with a series of new instruments of very exact construc- 

 tion, all made after his own designs, many of them in- 

 vented by himself. The first of the new instruments was 

 erected in the year 1847. It was constructed in as few 

 separate parts as possible, and no important parts were 

 connected by small screws, in order that the instrum.ent 

 might possess the greatest amount of firmness. The end 

 to be attained by its use was to make observations out 

 of the meridian as accurate as observations in the 

 meridian, and its main object of observation was the 

 moon. It must be recollected that the moon can very 

 seldom be observed with the meridian instruments before 

 her first quarter and after the last. The altazimuth was 

 designed to obtain observations of her as often as she 

 was visible in the sky and, I am sure, every astronomer 

 will agree that the erection of this instrument was a 

 most important innovation. Its great services were fully 

 acknowledged many years later, when the greatest errors 

 in Burkhardt's Tables of the Moon were shown to exist 

 in parts of her orbit never accessible to meridian obser- 

 vations. The number of days on which the moon is 

 observed by this instrument is nearly double that of the 

 observations in the meridian. 



At the end of the year 1850 the new meridian circle : 

 was erected, the object-glass of which, made by Mr. 

 Simms, has 8 inches clear aperture and 1 1 feet 6 inches 

 focal length. With this instrument there was also 

 introduced a great change in the observing routine at 

 Greenwich, the transits and the zenith distances of the 

 stars being now taken by one astronomer at the same 

 time. Nearly simultaneously the American method of 

 observing transits was adopted. 



The Troughton zenith-sector, found by Mr. Airy at the 

 Observatory, had given much trouble, and various altera- 

 tions had not improved the results obtained by it. It was 

 therefore dismantled in the year 1848, and the "reflex- 

 zenith-tube" erected, an instrument admirably calculated 

 for observing the small changes in the zenith distances of 

 y Draconis, the Greenwich zenith- star. 



When all these new instruments were well in working 

 order, Mr. Airy directed the attention of the Board of 

 Visitors, in the year 1855, to the fact that the extra-meri- 

 dional apparatus was by no means fit for the present 

 wants of astronomy. A large object-glass (12 French 

 inches in diameter) was, in consequence, procured by 

 the Astronomer-Roval from Mr. Merz, and was mounted 



