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GALILEO (GALILEE) GALLEO.-1564-1642.*

"Galileo, born at Pisa on the 15th February, 1564, was descended from the noble family of Bonajuti. Although he exhibited an early passion for geometry, and had studied without a master the writings of Euclid and Archimedes, yet even after he was called to the mathematical chair at Pisa, in the twenty-fifth year of his age, he was more distinguished for his hostility to the Aristotelian philosophy than for his progress in original inquiry. In 1592 he was promoted to the same chair in Padua, where he remained for eighteen years, adorning the university by his talents, and diffusing around him a taste for science. With the exception of some minor contrivances, Galileo had made no discovery till he entered his forty-fifth year.”

In 1609, the memorable year in which Kepler published his "New Astronomy," Galileo paid a visit to Venice, during which he heard of the telescope of Lippershey. The idea of so extraordinary an instrument at once filled his mind, and when he learned from Paris that it had an existence, he instantly resolved to possess it. The idea was the invention. Galileo's knowledge of optics was sufficient to satisfy him that a convex lens at one end of a tube, with a concave one at the other, must bring objects nearer to the eye. The lenses were placed in the tube, the astronomer looked into the concave lens, and saw the object before it "pretty large and pretty near him.” This little toy, which magnified only three times lineally, and nine times superficially, he carried in triumph to Venice, where the chief magistrate obtained it in barter for the life possession of his professorship, and 480 florins as an increase of salary.

*This sketch is taken, with certain slight modifications, from the "Memoir of the Life, Writings, and Discoveries of Sir Isaac Newton," by Sir David Brewster, K.H.-Hamilton, Adams & Co., 1855. Vol. 1, p. 270, et seq.

The excitement produced on this occasion at Venice was of the most extraordinary kind; and, on a subsequent occasion, when Sirturi had made one of the instruments, the populace followed him with eager curiosity, and at last took possession of the tube, till they had each witnessed its wondrous effects.

Galileo lost no time in availing himself of his new power. He made another telescope which magnified about eight or nine times, and sparing neither labour nor expense, he finally constructed an instrument so excellent as "to show things almost a thousand times larger (in surface) and above thirty times nearer to the eye.”

There, is perhaps, no invention in science so extraordinary in its nature, and so boundless in its influence, as that of the telescope. To the uneducated man the power of bringing distant objects near to the eye must seem almost miraculous; and to the philosopher who comprehends the principles upon which it acts, it must ever appear one of the most elegant applications of science.

To have been the first astronomer in whose hands such a power was placed, was a preferenee to which Galileo owed much of his reputation.

Before the telescope was directed to the heavens, it was impossible to distinguish a planet from a star. Even with his first instrument Galileo saw that Jupiter had a round appearance like the sun and moon, but on the 7th January, 1610, when he used a telescope of superior power, he saw three little bright stars very near him, two to the right and one to the left of his disc. Though ranged in a line parallel to the ecliptic, he regarded them as ordinary stars, but having on the 8th January accidently directed his telescope to Jupiter, he was surprised to see the three stars to the west of the planet, and nearer one another than before, a proof that they had a motion of their own. This fact did not excite his notice, and it was only after observing various changes in their relative position, and discovering a fourth on the 13th January, that he was

enabled to announce the discovery of the four satellites of Jupiter.

In continuing his observations with the telescope, Galileo discovered that Venus had the same crescent phases as the waxing and the waning moon; that the sun had spots on his surface, which proved that he revolved round his axis; that Saturn was not round, but had handles attached to his disc; that the surface of the moon was covered with mountains and valleys, and that parts of the margin of her disc occasionally appeared and disappeared; that the milky-way consisted of numerous stars, which the unassisted eye was unable to perceive; and that the apparent size of the stars arose from irradiation, or a spurious light, in consequence of which they were not magnified by the telescope. These various discoveries furnished new arguments in support of the hypothesis of Co pernicus; and we may now consider it as established by incontrovertible evidence, which ignorance or fanaticism only could resist, that the sun is placed in the centre of the System, in the focus of the elliptical, or in the centre of the circular orbits of the planets, and that, by some power yet to be discovered, he guides them in their course, while the Earth and Jupiter exercise a similar influence over the satellites which accompany them. But it is not merely from his astronomical discoveries, brilliant as they are, that Galileo claims a high place. His profound researches on mechanical science; his determination of the law of acceleration in falling bodies; and his researches respecting the resistance and cohesion of solid bodies, the motion of projectiles, and the centre of gravity of solids, have ranked him among the most distinguished of our mechanical philosophers. The great step, however, which he made in mechanics, was his discovery of the general laws of motion uniformly accelerated, which may be regarded as the basis of the theory of universal gravitation.

The current of Galileo's life had hitherto flowed in a smooth and undisturbed channel. His discoveries had placed him at

the head of the great men of the age, and, with an income above his wants, he possessed both the means and the leisure for prosecuting his studies. Anxious, however, to propagate the great truths which he discovered, and by force of reason to make proselytes of his enemies, he involved himself in disputes which tried his temper and disturbed his peace. When argument failed to convince his opponents, he wielded against them the powerful weapons of ridicule and sarcasm, and he had thus marshalled against himself and his opinions the Aristotelian professors, the temporizing Jesuits, the political churchmen, and that timid section of the community who trembled at innovation, whether it be in religion or in science. The party of Galileo who abetted him in his crusade against error, though weak in numbers, were strong in position and in zeal. His numerous pupils, occupying the principal chairs in the Italian universities, formed a devoted band who cherished his doctrines and idolized his genius. The enemies of religion followed the intellectual banner, and many princes and nobles who had smarted under ecclesiastic jurisdiction were willing to see it shorn of its power.

While these two parties were standing on the defensive, Galileo hoisted the first signal for war. In a letter to his friend and pupil, the Abbe Castelli, he proved that the scriptures were not intended to teach us science and philosophy, and that the expressions in the Bible were as irreconcilable with the Ptolemaic as with the Copernican system. In reply to this letter, Caccini, a Dominican friar, attacked Galileo from the pulpit, and so violent was his language, that Maraffi, the general of the Dominicans, expressed his regret that he should be implicated "in the brutal conduct of thirty or forty thousand monks."

Encouraged by this apology, Galileo launched another pamphlet addressed to the Grand Duchess of Tuscany, in which he supports his views by quotations from the Fathers, and by the conduct of the Roman pontiff himself, Paul III., in accepting

the dedication of Copernicus's work. It was in vain to meet such arguments by any other weapon than that of the civil power. It was deemed necessary either to crush the heresy or retire from the contest, and the church party determined to appeal to the Inquisition. Various circumstances concurred to excite the suspicions of Galileo, and, about the end of 1615, he set off for Rome, where he was lodged in the palace of the Tuscan ambassador. While Galileo was enjoying the hospitality of his friend, Caccini was preparing the evidence of his heresy, and in due time he was charged by the Inquisition with maintaining the motion of the earth and the stability of the sun; with teaching and publishing this heretical doctrine, and with attempting to reconcile it to scripture. On the 25th February, 1615, the Inquisition assembled to take these charges into consideration, and, having no doubt of their truth, they desired that Galileo should be enjoined by Cardinal Bellarmine to renounce the obnoxious doctrines, and to pledge himself that he would neither teach, publish, nor defend them in future. In the event of his refusing to obey this injunction, it was decreed that he should be thrown into prison. Galileo acquiesced in the sentence, and on the following day he renounced before the Cardinal his heretical opinions, abandoning the doctrine of the earth's motion, and pledging himself neither to defend nor teach it either in his writings or his conversation.

Although Galileo had made a narrow escape

from the grasp of the Inquisition, he left Rome, 1616, with a suppressed hostility against the church, and his resolution to propagate the heresy seems to have been coeval with the vow by which he renounced it. Although he affected to bow to the decisions of theology, he never scrupled, either in his writings or in his conversation, to denounce them with the severest invective. The Lyncean Academy, ever hostile to the church, encouraged him in this unwise procedure, and it was doubtless at their instigation that he took the daring step which brought him a second time to the bar of the Inquisition. Forgetting the