constellation was a little nearer the pole in former ages than at
the present time; still its distance was always so great that its
use as a mark of the northern point of the horizon does not
inspire us with great respect for the accuracy with which the
ancient navigators sought to shape their course.

The Nautical Almanac of the present day had its origin in the
Astronomical Ephemerides called forth by the needs of predictions
of celestial motions both on the part of the astronomer and the
citizen. So long as astrology had a firm hold on the minds of men,
the positions of the planets were looked to with great interest.
The theories of Ptolemy, although founded on a radically false
system, nevertheless sufficed to predict the position of the sun,
moon, and planets, with all the accuracy necessary for the
purposes of the daily life of the ancients or the sentences of
their astrologers. Indeed, if his tables were carried down to the
present time, the positions of the heavenly bodies would be so few
degrees in error that their recognition would be very easy. The
times of most of the eclipses would be predicted within a few
hours, and the conjunctions of the planets within a few days. Thus
it was possible for the astronomers of the Middle Ages to prepare
for their own use, and that of the people, certain rude
predictions respecting the courses of the sun and moon and the
aspect of the heavens, which served the purpose of daily life and
perhaps lessened the confusion arising from their complicated
calendars. In the signs of the zodiac and the different effects
which follow from the sun and moon passing from sign to sign,
still found in our farmers' almanacs, we have the dying traces of
these ancient ephemerides.