reflecting on these facts the early astronomers were enabled to
demonstrate the apparent annual movement of the sun. There could be no
rational explanation of the changes in the constellations with the
seasons, except by supposing that the place of the sun was altering, so
as to make a complete circuit of the heavens in the course of the year.
This movement of the sun is otherwise confirmed by looking at the west
after sunset, and watching the stars. As the season progresses, it may
be noticed each evening that the constellations seem to sink lower and
lower towards the west, until at length they become invisible from the
brightness of the sky. The disappearance is explained by the supposition
that the sun appears to be continually ascending from the west to meet
the stars. This motion is, of course, not to be confounded with the
ordinary diurnal rising and setting, in which all the heavenly bodies
participate. It is to be understood that besides being affected by the
common motion our luminary has a slow independent movement in the
opposite direction; so that though the sun and a star may set at the
same time to-day, yet since by to-morrow the sun will have moved a
little towards the east, it follows that the star must then set a few
minutes before the sun.[1]

The patient observations of the early astronomers enabled the sun's
track through the heavens to be ascertained, and it was found that in
its circuit amid the stars and constellations our luminary invariably
followed the same path. This is called the _ecliptic_, and the
constellations through which it passes form a belt around the heavens
known as the _zodiac_. It was anciently divided into twelve equal
portions or "signs," so that the stages on the sun's great journey could
be conveniently indicated. The duration of the year, or the period
required by the sun to run its course around the heavens, seems to have
been first ascertained by astronomers whose names are unknown. The skill
of the early Oriental geometers was further evidenced by their
determination of the position of the ecliptic with regard to the
celestial equator, and by their success in the measurement of the angle
between these two important circles on the heavens.

The principal features of the motion of the moon have also been noticed
with intelligence at an antiquity more remote than history. The
attentive observer perceives the important truth that the moon does not
occupy a fixed position i