Mr. Pond on the Declinations, See , 421 
tlieir declinations ; and for a considerable period I constantly 
observed them on the meridian, whenever they passed at a 
convenient hour ; usually reversing the instrument in azimuth 
at the end of every day’s observation ; never considering any 
observation as complete that had not its corresponding one in 
a short interval of time. When this circumstance is not at- 
tended to, I think, a great part of the advantage arising from 
the circular construction is lost. 
The observations themselves will show, if they have been 
made with the requisite care and attention to merit the notice 
of astronomers ; for it is one of the many advantages of 
circular instruments, that from the observations made with 
them, we may infer with great precision not only the mean 
probable error, but likewise the greatest possible error to 
which they are liable. From a careful comparison of the 
errors of collimation, as deduced from different stars, I con- 
cluded that the greatest possible error was 2", 5, and the mean 
error about 1"; and by a comparison with other observations 
with similar instruments, it will be seen that this supposition 
was well founded, since nearly the same quantities are de- 
duced by another method to be considered hereafter. 
The polar distances are annexed to each observation : a 
method which I borrowed from Mr. Wollaston, and which 
is rendered very easy by employing his useful tables calcu- 
lated for that purpose. This practice of reducing every day’s 
observations cannot be too much recommended, as the labour 
of calculating accumulated observations is thus rendered un- 
necessary. 
When.I had deduced the decimations of these stars from 
my own observations, continued long enough to divest them 
