(224.) 
Results. 
(225.) 
Bessel’s 
own obser- 
vations, 
(226.) 
iis numer- 
ous works 
on astrono- 
my: 
Cuar. III., § 3.] 
refer the places of wandering bodies to standard 
points, 
Bessel’s work includes a methodical reduction of 
the places of above 3000 stars observed by Bradley, 
and an investigation of the sun’s apparent path, to- 
gether with a full discussion of the principles and 
application of every correction, instrumental and 
uranographical, which such observations require, and 
which are applicable to all others of the same kind. 
It includes, therefore, dissertations on some of the 
most delicate points of Astronomy, and “ Constants” 
for the different corrections, which, with slight varia- 
tion, have been since employed in every observatory. 
Bessel devised also a remarkably simple mode of find- 
ing for each star the varying corrections of its place. 
The proper motions of the stars were also determined 
for the first time with approximate exactness, by 
comparing Bradley’s places with more modern ob- 
servations. 
In subsequent years (the Fundamenta were pub- 
lished in 1818) Bessel contributed to the science of 
astronomy numerous and regular observations of the 
heavenly bodies; the Annals of the Kénigsberg 
Observatory were regularly published from 1814, 
being (I believe) the first foreign establishment 
which followed the example set by Maskelyne at 
Greenwich, with the important addition of systematic 
reduction. 
Of the subsequent labours of Bessel we must speak 
very shortly. The determination of the parallax of 
the star called 61 Cygni, perhaps the most original 
and important of these, we shall refer to another sec- 
tion, where we shall compare it with the results ob- 
tained by other astronomers. He made interesting 
physical observations on Halley’s comet at its return 
in 1835; he prepared the materials for a very ex- 
tended catalogue of fixed stars, arranged in zones, 
more recently published by Professor Weisse. In 
connection with the theory of the pendulum as a 
measure of gravity, he repeated and extended Newton's 
important experiments on the uniformity of the gra- 
vitating force on all kinds of matter; he applied a 
new correction to the vibrations of the pendulum, and 
improved the method of observing them correctly ; 
and he discussed with his habitual mathematical skill 
and elaborate perseverance the figure of the Earth, 
from the whole of the then existing observations ; 
whilst he also directed an operation for connecting 
the Russian triangulations with those of western 
Europe,—a delicate task, which he performed with 
consummate skill. It will thus be seen that (without 
mentioning a host of minor works and memoirs) there 
was hardly a great department of Astronomy in which 
Bessel did not take a distinguished part. Even the 
discovery of Neptune, by calculation from the irregu- 
larities of Uranus, was contemplated as a practicable 
problem by the veteran astronomer in his later years. 
He died on the 17th March 1846; therefore only a 
few months previous to the publication of MM, Le- 
VOL. I. 
ASTRONOMY.—BESSEL—MR AIRY. 
849 
verrier and Adams’ discoveries, and their triumphant 
consummation by M. Galle. 
Even before Bessel’s career as an astronomer had  (227.) 
properly commenced, Pond, in England, had antici- Fond, the 
pated, in a good measure, the improvements in prac- soy te 
? 
tical astronomy to which we have referred in the an excel- 
beginning of this section, Already, in the earliest !ent ob- 
server. 
years of this century, he had made observations at his 
private residence with a comparatively small circular 
instrument by Troughton, which led him to detect the 
gradually increasing errors of Bradley's quadrant still 
in use at Greenwich, and to recommend the adoption 
of complete circles (disused since the time of Rémer) 
and the specific examination of errors of division. 
These principles he carried out at Greenwich, to which 
establishment he was afterwards appointed. His very 
indifferent health prevented that incessant activity 
which the management of a first-rate observatory re- 
quires; nevertheless, he is justly regarded as one of the 
ps reformers oi the practical astronomy of those 
ays, 
His successor, Mr Airy, has distinguished himself 228.) 
by a more active career. Endowed with very un- Succeeded 
common abilities, and with great physical powers of He 
endurance, he has, from his youth, been ever foremost x 
not only in promoting, in every one of its departments, 
his favourite science of Astronomy, but also many 
other allied subjects, particularly Optics, to which we 
shall have occasion to refer in another section. 
Born in the county of Northumberland in 1801, 229.) 
Mr Georce Brppext Airy acquired great distinction is numer- 
at Cambridge, where he graduated in 1823, and was °"* salionas 
“alee 
appointed to the charge of the Observatory there in oh aa 
1828, after the death of Professor Woodhouse, a per- cal astro- 
son sincerely attached to astronomy and well skilled in 2°™Y 
it, yet one who did not succeed in imparting much in« 
terest either to its theoretical or practical departments. 
Mr Airy engaged in the important investigation of a 
new irregularity in the motion of the Harth and 
Venus, to which I have referred in the chapter on 
Physical Astronomy (114), and at the same time he 
undertook to publish his own Observations in regular 
annual volumes, including a complete comparison 
of the results with the best tables, thus presenting 
ata glance the existing errors of theory, This prac- 
tice he introduced at Greenwich on succeeding Pond 
there in 1835; and he has pursued it ever since. 
But not contented with rendering the annals of the 
National Observatory a correct reflection of the state 
of the heavens in his own day, and also of the con- 
dition of Astronomical Theories, he did not rest until 
he had performed for the observations of his prede- 
cessors the same service, and thus produced a series 
of comparisons of the observed and calculated places 
of the moon and planets, unexampled for extent and 
accuracy. Beginning with Bradley’s Observations 
in 1750, he investigated and applied all the instru- 
mental and uranographical corrections to each, as 
Bessel had done for the observations of the sun and 
5 P 
