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CHAPTER II.

THE TELESCOPE AND ITS REVELATIONS.

Term of Professorship at Padua renewed.—Astronomy.—A New Star.— The Telescope.—Galileo not the Inventor.— Visit to Venice to exhibit it.—Telescopic Discoveries.—Jupiter's Moons.—Request of Henry IV.—"Sidereus Nuncius."—The Storm it raised.—Magini's attack on Galileo.—The Ring of Saturn.—An Anagram.—Opposition of the Aristotelian School.—Letter to Kepler.

The first six years of Galileo's professorship at Padua had passed away, but the senate were eager to retain so bright a light for their University, and prolonged the appointment of the professor, whose renown was now great, for another six years, with a considerable increase of salary.^[1]

As we have seen, he had for a long time renounced the prevailing views about the universe; but up to this time he had discussed only physical mathematical questions with the Peripatetic school, the subject of astronomy had not been mooted. But the sudden appearance of a new star in the constellation of Serpentarius, in October, 1604, which, after exhibiting various colours for a year and a half, as suddenly disappeared, induced him openly to attack one of the Aristotelian doctrines hitherto held most sacred, that of the unchangeableness of the heavens. Galileo demonstrated, in three lectures to a numerous audience, that this star was neither a mere meteor, nor yet a heavenly body which had before existed but had only now been observed, but a body which had recently appeared and had again vanished.^[2] The subject,

1. Op. xv. p. 390. His salary at first was 72 Florentine zecchini=£18, and rose by degrees to 400 zecchini=£100. (Op. viii. p. 18, note 3.)
2. Some fragments of these lectures are extant, and are included by Albèri in the Op. v. part ii.