ion by actual
experiment, he repaired to the leaning tower of Pisa, and demonstrated
that he was right and Aristotle was wrong. The Aristotelians would not
believe the evidence of their own senses, and ascribed the effect to
some unknown cause. To such a degree were men enslaved by authority.
This provoked Galileo, and led him to attack authority with still
greater vehemence, adding mockery to sarcasm; which again exasperated
his opponents, and doubtless laid the foundation of that personal
hostility which afterwards pursued him to the prison of the Inquisition.
This blended arrogance and asperity in a young man was offensive to the
whole university, yet natural to one who had overturned one of the
favorite axioms of the greatest master of thought the world had seen for
nearly two thousand years; and the scorn and opposition with which his
discovery was received increased his rancor, so that he, in his turn,
did not render justice to the learned men arrayed against him, who were
not necessarily dull or obstinate because they would not at once give up
the opinions in which they were educated, and which the learned world
still accepted. Nor did they oppose and hate him for his new opinions,
so much as from dislike of his personal arrogance and bitter sarcasms.

At last his enemies made it too hot for him at Pisa. He resigned his
chair (1591), but only to accept a higher position at Padua, on a salary
of one hundred and eighty florins,--not, however, adequate to his
support, so that he was obliged to take pupils in mathematics. To show
the comparative estimate of that age of science, the fact may be
mentioned that the professor of scholastic philosophy in the same
university was paid fourteen hundred florins. This was in 1592; and the
next year Galileo invented the thermometer, still an imperfect
instrument, since air was not perfectly excluded. At this period his
reputation seems to have been established as a brilliant lecturer rather
than as a great discoverer, or even as a great mathematician; for he was
immeasurably behind Kepler, his contemporary, in the power of making
abstruse calculations and numerical combinations. In this respect Kepler
was inferior only to Copernicus, Newton, and Laplace in our times, or
Hipparchus and Ptolemy among the ancients; and it is to him that we owe
the discovery of those great laws of planetary motion from which there
is no appeal, and which have never been rivalled in importance except