G;ALILE0 Grimi.m, an eminent Italian astronomer and natural philosopher, was born'at Pisa, in Italy, on the 15th February 1564, and was the son of Guilia Ammanati di Pescia, and Michelagnolo Vincenzio Galileo, a Florentine nobleman, who distinguished himself by his writings on subjects. The earlier years of Galileo were occu pied with the study of music and drawing, in both of which lie made singular progress ; hut as the limited fortune of his father did not permit hint to settle his son in a state of comfortable independence, he resolved to educate him as a physician, and after going through the usual course of in struction at Florence, he was entered in 1582, at the uni versity of Pisa, as a student of philosophy and medicine. The doctrines of Aristotle, which were then taught in the public schools of Italy, were not congenial to a mind like Galileo's, and he was equally disappointed in the pleasure which he anticipated from the study of physic. He there fore abandoned for ever the medical profession, and devoted himself with unremitting ardour and proportionate success to the study of mathematics. Without the aid of a master he studied the different books of Euclid, and made himself master of the writings of Archimedes, and the other an cient geometers. His fame as a mathematician was soon widely extended ; and in the year 1589, before he had reach ed his 26th year, the Duke of Tuscany appointed hint to the mathematical chair in the university of Pisa. In the dis charge of his duties as a professor, he incurred the resent ment of some of the more violent Aristotelians, whose doc trines he did not scruple to oppose ; and his tranquillity and his studies were frequently disturbed by the hostility of his metaphysical enemies. He resolved therefore to change the place of his residence, and he gladly accepted of an in vitation which he received to fill the mathematical chair in the university of Padua. He left Pisa in 1592, and conti nued in Itis new situation at Padua for 18 years, raising the reputation of the university by the brilliancy of his talents, and diffusing a taste for science through the whole of Tus cany. His affection for his own country, however, induced hint to accept, in 1611, the mathematical chair at Pisa, from Cosmo II. Grand Duke of Tuscany, who annexed to it a very handsome pension. The same nobleman afterwards invited him to Florence, with the title of principal mathe matician and philosopher to his highness, and continued his former pension, without any obligation to discharge the du ties of the professorship.
ln these various situations, Galileo's attention was par ticularly occupied with the subjects of optics and mecha nics. During his first residence at Pisa, he was led to the idea of measuring time by the pendulum, by observing the motion of a lamp in the cathedral of Pisa. From reading the treatise of Archimedes, De his (jute vehuntur in aqua, he was led to the invention of his Balance for determining the proportion of the ingredients in mixed metals. He con
structed a glass thermometer, which contained water or air ; and in 1597 he invented his geometrical and military com pass, of which he published a description at Padua in 1606. In April or May 1609, when he was on a visit to Venice, he was accidentally informed that a Dutchman, of the name of Jansens, had invented an instrument through which distant objects had the same appearance as if they were brought near the eye. Galileo reflected deeply on the subject of this contrivance, and, from his thorough knowledge of the properties of lenses, he was soon enabled not only to disco ver the principle of its construction, but to complete one of the instruments for his own use. He immediately applied his telescope to the heavens, and made those splendid dis coveries of which we have already given a full account in our History of ASTRONOMY.
it was during these observations that he was invited to Florence, where he enjoyed the fullest leisure to pursue them with diligence, and to carry on a correspondence with the principal philosophers of Germany, respecting the dis coveries which he had made, and the great truth of the earth's motion, which they tended to establish. Galileo had scarcely enjoyed four years of tranquillity at Florence, when the fame of his discoveries, and his sentiments re specting the stability of the sun, reached the cars of the holy inquisition. Formal complaints were laid before that vigilant body ; and Galileo was summoned to appear at Rome, in 1615, to answer for the heretical doctrines which he had taught. He was accused of maintaining the motion of the earth, and the stability of the sun ; of teaching the same doctrine to several of his disciples ; of carrying on a correspondence on the subject with several German ma thematicians ; and of having published it, and attempted to reconcile it to Scripture, in his epistles to Marc Velscr, in 1612. A meeting of the inquisition was held on the 25th of February 1616, and they decreed that Galileo should be enjoined by Cardinal Bellarmine, to renounce the doctrines -which he taught, and to promise neither to teach, nor de fend, nor publish them ; and that, if he refused to acquiesce in this sentence, lie should be thrown into prison. On the following day, the 26th of February, Galileo appeared be fore Cardinal Bellarmine ; and having declared that he would abandon the doctrine of the earth's motion, and would neither defend it nor teach it, either in his conversation or in his writings, he was dismissed from the inquisition. The mildness of this sentence was no doubt owing to the inter position of the Grand Duke of Tuscany, and other persons of great rank and influence at the papal court, who took a warm interest in the fate of Galileo. The inquisition, how ever, was not satisfied with his abjuration. They issued a decree, declaring the new opinions to he heretical and con trary to scripture, and prohibited the sale of every book in which they should be taught.