and the other planets were revolving round the central fire of
the system; but the sun was a reflection of this central fire,
not the fire itself. Even Pythagoras, moreover, made the heavens
a solid sphere revolving, with its stars, round the central fire;
and the truth he discovered was mingled with so much mysticism,
and confined to so small and retired a school, that it was
quickly lost again. In the next generation Anaxagoras taught that
the sun was a vast globe of white-hot iron, and that the stars
were material bodies made white-hot by friction with the ether. A
generation later the famous Democritus came nearer than any to
the truth. The universe was composed of an infinite number of
indestructible particles, called "atoms," which had gradually
settled from a state of chaotic confusion to their present
orderly arrangement in large masses. The sun was a body of
enormous size, and the points of light in the Milky Way were
similar suns at a tremendous distance from the earth. Our
universe, moreover, was only one of an infinite number of
universes, and an eternal cycle of destruction and re-formation
was running through these myriads of worlds.

By sheer speculation Greece was well on the way of discovery.
Then the mists of philosophy fell between the mind of Greece and
nature, and the notions of Democritus were rejected with disdain;
and then, very speedily, the decay of the brilliant nation put an
end to its feverish search for truth. Greek culture passed to
Alexandria, where it met the remains of the culture of Egypt,
Babylonia, and Persia, and one more remarkable effort was made to
penetrate the outlying universe before the night of the Middle
Ages fell on the old world.