7i 
1830-40] ROYAL ASTRONOMICAL SOCIETY 
the Society on 1839 January 11. By the long delay in reducing 
his observations of a Centauri he lost the priority of publication, 
as Bessel had announced the discovery of the parallax of 61 Cygni 
to the Society two months earlier. 
The determinations of astronomical constants referred to in 
the foregoing, and others published abroad, were urgently required 
for the reduction of the numerous observations with improved 
instruments at that time being made. 
The Cambridge Observatory was built in 1823-24, but no work 
of any consequence was done until Airy was given charge of it 
as Plumian Professor in 1828. At first he had only a transit 
instrument and no assistant; but he fell to work at once, reducing 
the observations without delay and preparing them for the press, 
so that the printing actually commenced before the end of the year. 
The first small volume of Cambridge Observations, 1828, came out 
in the spring of 1829, soon after an assistant had been appointed. 
The observations were continued with great regularity, the planets 
being specially attended to ; but it was not till 1833 January that 
a mural circle by Troughton & Simms was ready for work. The 
observatory was in every way a model institution, and its publica 
tions exhibited the reductions to an extent hitherto unknown, 
while the principle was introduced of not attempting to correct 
the instrumental errors mechanically, but measuring their amount 
and applying numerical corrections. 
These and other contributions to practical astronomy naturally 
led to Airy’s being appointed Astronomer Royal on Pond’s retire 
ment in 1835. Pond had originally won his reputation by a paper 
published in the Philosophical Transactions, 1806, in which he 
proved that the serious errors in Maskelyne’s declinations of 
standard stars were due tp the great quadrant having become worn 
at the centre. At Greenwich, Pond on the whole followed in the 
footsteps of Maskelyne; the mural circle ordered by the latter 
shortly before his death, took the place of the quadrant, and a new 
transit instrument came into use in 1816. No improvements were 
made in the methods of reduction, so that, for instance, Bradley’s 
table of refractions continued to be used long after it had been 
abandoned as inaccurate everywhere else. But the observations 
were certainly better than Maskelyne’s, as Pond took great pains 
to find every possible cause of error. The greatly increased staff 
of assistants * also enabled him to multiply the number of single 
results of any quantity considered to be important. Towards 
the end of his life the impression gained ground in London that the 
Observatory had fallen into a state of disrepute ; and when the 
appointment was offered to Airy, it was suggested to him that 
* There was one assistant when he came and six when he left.