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 those made by Newton himself,—­laws which connect the mean distance of the planets from the sun with the times of their revolutions; laws which show that the orbits of planets are elliptical, not circular; and that the areas described by lines drawn from the moving planet to the sun are proportionable to the times employed in the motion.  What an infinity of calculation, in the infancy of science—­before the invention of logarithms,—­was necessary to arrive at these truths!  What fertility of invention was displayed in all his hypotheses; what patience in working them out; what magnanimity in discarding