n the heavens. During the course of a single
night the fact that the moon has moved from west to east across the
heavens can be perceived by noting its position relatively to adjacent
stars. It is indeed probable that the motion of the moon was a discovery
prior to that of the annual motion of the sun, inasmuch as it is the
immediate consequence of a simple observation, and involves but little
exercise of any intellectual power. In prehistoric times also, the time
of revolution of the moon had been ascertained, and the phases of our
satellite had been correctly attributed to the varying aspect under
which the sun-illuminated side is turned towards the earth.

But we are far from having exhausted the list of great discoveries which
have come down from unknown antiquity. Correct explanations had been
given of the striking phenomenon of a lunar eclipse, in which the
brilliant surface is plunged temporarily into darkness, and also of the
still more imposing spectacle of a solar eclipse, in which the sun
itself undergoes a partial or even a total obscuration. Then, too, the
acuteness of the early astronomers had detected the five wandering stars
or planets: they had traced the movements of Mercury and Venus, Mars,
Jupiter, and Saturn. They had observed with awe the various
configurations of these planets: and just as the sun, and in a lesser
degree the moon, were intimately associated with the affairs of daily
life, so in the imagination of these early investigators the movements
of the planets were thought to be pregnant with human weal or human woe.
At length a certain order was perceived to govern the apparently
capricious movements of the planets. It was found that they obeyed
certain laws. The cultivation of the science of geometry went hand in
hand with the study of astronomy: and as we emerge from the dim
prehistoric ages into the historical period, we find that the theory of
the phenomena of the heavens possessed already some degree of coherence.

Ptolemy, following Pythagoras, Plato, and Aristotle, acknowledged that
the earth's figure was globular, and he demonstrated it by the same
arguments that we employ at the present day. He also discerned how this
mighty globe was isolated in space. He admitted that the diurnal
movement of the heavens could be accounted for by the revolution of the
earth upon its axis, but unfortunately he assigned reasons for the
deliberate rejection of this view. The earth, according to him,