es of error in the computed places of the sun and moon, have been
ascertained at Greenwich as often as those luminaries could be observed;
and Mr. Pond, the astronomer royal, having permitted access for this
purpose to the table of errors kept in the Observatory, Mr. Crosley has
calculated the corresponding effects on the longitude, and proportioned
them to the time when our observations were taken. The combined effect of
the two errors forms a correction to the longitudes obtained from the sun
and moon; but when the moon was observed with a star, then the moon's
error alone gives the correction. But it has sometimes happened, that
there were many days interval between the observations of the moon at
Greenwich, and that the errors preceding and following are so extremely
irregular, that no accuracy could be expected in reducing them by
proportion; in these unfortunate cases, that part of the error belonging
to the moon has been taken absolute, such as it was found on the day
nearest to the time of observation; but the sun's error is always from
proportion. These corrections, with the interval in the Greenwich
observations of the moon, are given under their proper heads.

8th. The longitudes thus computed, reduced to the intended point, and
corrected, are placed under each other; and the mean of the whole is
taken to be the true longitude of that point, unless in certain cases
where it is otherwise expressed. The mean is also given of the longitudes
_uncorrected_ for the errors of the sun and moon's places, that the
reader may have an opportunity of comparing them; and some sea officers
who boast of their having never been out more than 5', or at most 10',
may deduce from the column of corrections in the different tables, that
their lunar observations could not be entitled to so much confidence as
they wish to suppose; since, allowing every degree of perfection to
themselves and their instruments, they would probably be 12', and might
be more than 30' wrong.

In the nautical almanacks for 1811 and 1815, the distances are computed
from the new tables of _Burg_ for the moon, and of _Delambre_ for the
sun; and it is to be hoped that the necessity of correcting for errors in
the distances at Greenwich will have ceased, or be at least greatly
diminished. Should the computed places of the sun and moon be happily
found to agree with actual observation, and supposing that our results
may be taken as the average of what practised