ent, while the moon
obviously followed a similar law. Philosophers thus taught that the
various heavenly bodies were in the habit of actually passing beneath
the solid earth.

By the acknowledgment that the whole contents of the heavens performed
these movements, an important step in comprehending the constitution of
the universe had been decidedly taken. It was clear that the earth could
not be a plane extending to an indefinitely great distance. It was also
obvious that there must be a finite depth to the earth below our feet.
Nay, more, it became certain that whatever the shape of the earth might
be, it was at all events something detached from all other bodies, and
poised without visible support in space. When this discovery was first
announced it must have appeared a very startling truth. It was so
difficult to realise that the solid earth on which we stand reposed on
nothing! What was to keep it from falling? How could it be sustained
without tangible support, like the legendary coffin of Mahomet? But
difficult as it may have been to receive this doctrine, yet its
necessary truth in due time commanded assent, and the science of
Astronomy began to exist. The changes of the seasons and the recurrence
of seed-time and harvest must, from the earliest times, have been
associated with certain changes in the position of the sun. In the
summer at mid-day the sun rises high in the heavens, in the winter it is
always low. Our luminary, therefore, performs an annual movement up and
down in the heavens, as well as a diurnal movement of rising and
setting. But there is a third species of change in the sun's position,
which is not quite so obvious, though it is still capable of being
detected by a few careful observations, if combined with a philosophical
habit of reflection. The very earliest observers of the stars can hardly
have failed to notice that the constellations visible at night varied
with the season of the year. For instance, the brilliant figure of
Orion, though so well seen on winter nights, is absent from the summer
skies, and the place it occupied is then taken by quite different groups
of stars. The same may be said of other constellations. Each season of
the year can thus be characterised by the sidereal objects that are
conspicuous by night. Indeed, in ancient days, the time for commencing
the cycle of agricultural occupations was sometimes indicated by the
position of the constellations in the evening.

By