this system, which moved the mirth of Voltaire and,
according to Milton, of the Almighty, was such as to make it doubted by
some thinkers even in antiquity. Several men thought the earth
revolved on its axis, but the hypothesis was rejected by Aristotle and
Ptolemy. Heracleides, in the fourth century B. C., said that Mercury
and Venus circled around the sun, and in the third century Aristarchus
of Samos actually anticipated, though it was a mere guess, the
heliocentric theory.

Just before Copernicus various authors seemed to hint at the truth, but
in so mystical or brief a way that little can be made of their
statements. Thus, Nicholas of Cusa [Sidenote: Nicholas of Cusa,
1400-64] argued that "as the earth cannot be the center of the universe
it cannot lack all motion." Leonardo believed that the earth revolved
on its axis, and stated that it was a star and would look, to a man on
{618} the moon, as the moon does to us. In one place he wrote, "the
sun does not move,"--only that enigmatical sentence and nothing more.

[Sidenote: Copernicus, 1473-1543]

Nicholas Copernicus was a native of Thorn in Poland, himself of mixed
Polish and Teutonic blood. At the age of eighteen he went to the
university of Cracow, where he spent three years. In 1496 he was
enabled by an ecclesiastical appointment to go to Italy, where he spent
most of the next ten years in study. He worked at the universities of
Bologna, Padua and Ferrara, and lectured--though not as a member of the
university--at Rome. His studies were comprehensive, including civil
law, canon law, medicine, mathematics, and the classics. At Padua, on
May 31, 1503, he was made doctor of canon law. He also studied
astronomy in Italy, talked with the most famous professors of that
science and made observations of the heavens.

Copernicus's uncle was bishop of Ermeland, a spiritual domain and fief
of the Teutonic Order, under the supreme suzerainty, at least after
1525, of the king of Poland. Here Copernicus spent the rest of his
life; the years 1506-1512 in the bishop's palace at Heilsberg, after
1512, except for two not long stays at Allenstein, as a canon at
Frauenburg.

This little town, near but not quite on the Baltic coast, is ornamented
by a beautiful cathedral. On the wall surrounding the close is a small
tower which the astronomer made his observatory. Here, in the long
frosty nights of winter and in the few short hours of summer darkness,
he often