gravitation. In recognition of this work the medal of
the Royal Astronomical Society was awarded to him in 1833.
In June 1835 Airy was appointed Astronomer Royal in succession
to John Pond, and thus commenced that long career of wisely
directed and vigorously sustained industry at the national
observatory which, even more perhaps than his investigations
in abstract science or theoretical astronomy, constitutes
his chief title to fame. The condition of the observatory
at the time of his appointment was such that Lord Auckland,
the first lord of the Admiralty, considered that ``it ought
to be cleared out,'' while Airy admitted that ``it was in
a queer state.'' With his usual energy he set to work at
once to reorganize the whole management. He remodelled the
volumes of observations, put the library on a proper footing,
mounted the new (Sheepshanks) equatorial and organized a new
magnetic observatory. In 1847 an altazimuth was erected,
designed by Airy to enable observations of the moon to be
made not only on the meridian, but whenever she might be
visible. In 1848 Airy invented the reflex zenith tube to
replace the zenith sector previously employed. At the end
of 1850 the great transit circle of 8 in. aperture and 11 ft.
6 in. focal length was erected, and is still the principal
instrument of its class at the observatory. The mounting in
1859 of an equatorial of 13 in. aperture evoked the comment
in his journal for that year, ``There is not now a single
person employed or instrument used in the observatory which
was there in Mr Pond's time''; and the transformation was
completed by the inauguration of spectroscopic work in 1868
and of the photographic registration of sun-spots in 1873.
The formidable undertaking of reducing the accumulated planetary
observations made at Greenwich from 1750 to 1830 was already
in progress under Airy's supervision when he became Astronomer
Royal. Shortly afterwards he undertook the further laborious
task of reducing the enormous mass of observations of the moon
made at Greenwich during the same period under the direction,
successively, of J. Bradley, N. Bliss, N. Maskelyne and John
Pond, to defray the expense of which a large sum of money was
allotted by the Treasury. As the result, no less than 8000
lunar observations were rescued from oblivion, and were, in
1846, placed at the disposal of astronomers in such a form
that they could be used directly for comparison with the
theory and for the improvement of the tables of the moon's
motion. For this work Airy received in 1848 a testimonial
from the Royal Astronomical Society, and it at once led to
the discovery by P. A. Hansen of two new inequalities in the
moon's motion. After completing these reductions, Airy made
inquiries, before engaging in any theoretical investigation
in connexion with them, whether any other mathematician was
pursuing the subject, and learning that Hansen had taken
it in hand under the patronage of the king of Denmark, but
that, owing to the death of the king and the consequent lack
of funds, there was danger of his being compelled to abandon
it, he applied to the admiralty on Hansen's behalf for the
necessary sum. His request was immediately granted, and
thus it came about that Hansen's famous Tables de la Lune
were dedicated to La Haute Amiraute de sa Majeste la
Reine de la Grande Bretagne et d'Irlande. One of the most
remarkable of Airy's researches was his determination of the
mean density of the earth. In 1826 the idea occurred to him
of attacking this problem by means of pendulum experiments at
the top and bottom of a deep mine. His first attempt, made
in the same year at the Dolcoath mine in Cornwall, failed in
consequence of an accident to one of the pendulums; a second
attempt in 1828 was defeated by a flooding of the mine,
and many years elapsed before another opportunity presented
itself. The experiments eventually took place at the Harton
pit near South Shields in 1854. Their immediate result was
to show that gravity at the bottom of the mine exceeded that
at the top by 1/19286th of its amount, the depth being 1256
ft. From this he was led to the final value of 6.566 for
the mean density of the earth as compared with that of water
(Phil. Trans. cxlvi. 342). This value, although considerably
in excess of that previously found by different methods, was
held by Airy, from the care and completeness with which the
observations were carried out and discussed, to be ``entitled
to compete with the others on, at least, equal terms.''
In 1872 Airy conceived the idea of treating the lunar theory
in a new way, and at the age of seventy-one he embarked on
the prodigious toil which this scheme entailed. A general
description of his method will be found in the Monthly
Notices of the Royal Astronomical Society, vol. xxxiv. No.
3. It consisted essentially in the adoption of Delauny's final
numerical expressions for longitude, latitude and parallax,
with a symbolic term attached to each number, the value of
which was to be determined by substitution in the equations of
motion. In this mode of treating the question the order of the
terms is numerical, and though the amount of labour is such as
might well have deterred a younger man, yet the details were
easy, and a great part of it might be entrusted to a mere
computer. The work was published in 1886, when its author was
eighty-five years of age. For some little time previously he
had been harassed by a suspicion that certain errors had crept
into the computations, and accordingly he addressed himself
to the task of revision. But his powers were no longer what
they had been, and he was never able to examine sufficiently
into the matter. In 1890 he tells us how a grievous error
had been committed in one of the first steps, and pathetically
adds, ``My spirit in the work was broken, and I have never
heartily proceeded with it since.'' In 1881 Sir George Airy
resigned the office of Astronomer Royal and resided at the
White House, Greenwich, not far from the Royal Observatory,
until his death, which took place on the 2nd of January 1892.
A complete list of Airy's printed papers, numbering no less
than 518, will be found in his Autobiography, edited in
1890 by his son, Wilfrid Airy, B. A., M. Inst. C.E. Amongst
the most important of his works not already mentioned may be
named the following:--Mathematical Tracts (1826) on the Lunar
Theory, Figure of the Earth, Precession and Nutation, and
Calculus of Variations, to which, in the second edition
of 1828, were added tracts on the Planetary Theory and
the Undulatory Theory of Light; Experiments on Iron-built
Ships. instituted for the purpose of discovering a correction
for the deviation of the compass produced by the Iron of
the Ships (1839); On the Theoretical Explanation of an
apparent new Polarity in Light (1840); Tides And Waves
(1842). He was elected a fellow of the Royal Society in
1836, its president in 1871, and received both the Cooley
and Royal medals. He was five times president of the
Royal Astronomical Society, was correspondent of the French
Academy and belonged to many other foreign and American
societies. He was D.C.L. of Oxford and LL.D. of Cambridge and
Edinburgh. In 1872 he was made K.C.B. In the same year
he was nominated a Grand Cross in the Imperial Order of the
Rose of Brazil; he also held the Prussian Order ``Pour le
Merite,'' and belonged to the Legion of Honour of France
and to the Order of the North Star of Sweden and Norway.
See also Proc. Roy. Society, li. 1 (E. J. Routh); Month. Notices
Roy. Astr. Society, lii. 212; Observatory, xv. 74 (E. Dunkin);
Nature, 31st of Oct. 1878 (A. Winnecke), 7th of Jan. 1892; The
Times, 5th of Jan. 1892; R. Grant's Hist. of Phys. Astronomy;
R. P. Graves's life of Sir W. Rowan Hamilton. (A. A. R.*)
AISLABIR, JOHN (1670-1742), English politician, was born at
Goodramgate, York, on the 7th of December 1670. He was the
fourth son of George Aislabie, principal registrar of the
archiepiscopal court of York. In 1695 he was elected member
of parliament for Ripon. In 1712 he was appointed one of the
commissioners for executing the office of lord high admiral,
and in 1714 became treasurer of the navy, being sworn in two
years later as a member of the privy council. In March 1718
he became chancellor of the exchequer. The proposal of the
South Sea Company to pay off the national debt was strenuously
supported by Aislabie, and finally accepted in an amended form
by the House of Commons. After the collapse of that company a
secret committee of inquiry was appointed by the Commons, and
Aislabie, who had in the meantime resigned the seals of his
office, was declared guilty of having encouraged and promoted
the South Sea scheme with a view to his own exorbitant profit,
and was expelled the House. Though committed to the Tower he
was soon released, and was allowed to retain the property he
possessed before 1718, including his country estate, to which
he retired to pass the rest of his days. He died in 1742.
AISLE (from Lat. ALA, a wing), a term which in its primary
sense means the wing of a house, but is generally applied in
architecture to the lateral divisions of a church or large
building. The earliest example is that found in the basilica
of Trajan, which had double aisles on either side of the
central area; the same number existed in the original church
of St Peter's at Rome, in the basilica at Bethlehem, and
according to Eusebius in the church of the Holy Sepulchre at
Jerusalem. The aisles are divided from the nave or central area
by colonnades or arcades, and may flank also the transept or
choir, being distinguished as nave-aisles, transept-aisles or
choir-aisles. If the choir is semi-circular, and the
aisles, carried round, give access to a series of chapels,
the whole arrangement is known as the chevet. As a rule
in Great Britain there is only one aisle on each side of
the nave, the only exceptions being Chichester and Elgin
cathedrals, where there are two. Many European cathedrals
have two aisles on each side, as those of Paris, Bourges,
Amiens, Troyes, St Sernin, Toulouse, Cologne, Milan, Seville,
Toledo; and in those of Paris, Chartres, Amiens and Bourges,
Seville and Toledo, double aisles flank the choir on each
side. The cathedral at Antwerp has three aisles on each
side. In some of the churches in Germany the aisles are of
the same height as the nave. These churches are known as
HALLENKIRCHEN, the principal examples being St Stephen's,
Vienna, the Weissekirche at Soest. St Martin's, Landshut,
Munich cathedral, and the Marienkirche at Danzig. (R. P. S.)
AISNE, a frontier department in the north-east of France,
formed in 1790 from portions of the old provinces of
Ile-de-France and Picardy. Area 2866 sq. m. Pop. (1906)
534,495. It is bounded N. by the department of Nord and
the kingdom of Belgium, E. by the department of Ardennes,
S.E. by that of Marne, S. by that of Seine-et-Marne, and W.
by those of Oise and Somme. The surface of the department
consists of undulating and well-wooded plains, intersected
by numerous valleys, and diversified in the north-east by
hilly ground which forms a part of the mountain system of the
Ardennes. Its general slope is from north-east, where the
culminating point (930 ft.) is found, to south-west, though
altitudes exceeding 750 ft. are also found in the south.
The chief rivers are the Somme, the Escaut and the Sambre,
which have their sources in the north of the department; the
Oise, traversing the north-west, with its tributaries the
