This was the avowed object of the foundation of the observatory at
Greenwich;[A] and no one subject has received more of the attention of
astronomers, than those investigations of the lunar theory on which
the requisite tables of the navigator are founded. The pathways of the
ocean are marked out in the sky above. The eternal lights of the heavens
are the only Pharos whose beams never fail, which no tempest can shake
from its foundation. Within my recollection, it was deemed a necessary
qualification for the master and the mate of a merchant-ship, and even
for a prime hand, to be able to "work a lunar," as it was called. The
improvements in the chronometer have in practice, to a great extent,
superseded this laborious operation; but observation remains,
and unquestionably will for ever remain, the only dependence for
ascertaining the ship's time and deducting the longitude from the
comparison of that time with the chronometer.

[Footnote A: Grant's _Physical Astronomy_, p. 460.]

It may, perhaps, be thought that astronomical science is brought already
to such a state of perfection that nothing more is to be desired, or at
least that nothing more is attainable, in reference to such practicable
applications as I have described. This, however, is an idea which
generous minds will reject, in this, as in every other department of
human knowledge. In astronomy, as in every thing else, the discoveries
already made, theoretical or practical, instead of exhausting the
science, or putting a limit to its advancement, do but furnish the means
and instruments of further progress. I have no doubt we live on the
verge of discoveries and inventions, in every department, as brilliant
as any that have ever been made; that there are new truths, new facts,
ready to start into recognition on every side; and it seems to me there
never was an age, since the dawn of time, when men ought to be less