to have pronounced on _Columbus_. But let us return to _Galileo_.(6) _Galileo Galilei_, the great Italian physicist, was born in 1564, at Pisa. At first he was professor in his native town, then at Padua, where he taught the doctrine of _Ptolemy_, although at that time there was no obstacle to accepting the Copernican system. In 1611 he became mathematician at the court of _Cosimo II._ at Florence. His talents and happy discoveries soon won fame. In general he was more of a physicist than an astronomer; his astronomical discoveries were, almost without exception, of a kind that did not presuppose a thorough astronomical training. As is known, he was not the original inventor of the telescope, though with its aid he achieved some of the most important of his discoveries; for instance, that of the satellites of Jupiter. The telescope was invented in Holland. When he went to Rome, in 1611, he was received with great honour. In one of his letters from there he wrote: “I have received marked favours from many Cardinals and prelates here, and from several princes. They wanted to hear of my inventions, and were all well pleased.” The Jesuits gave a special reception in his honour at the Roman College. This shows in what esteem science was then held at Rome. But five years later _Galileo_ returned to the Eternal City under quite different circumstances. What had happened? In 1612 he had issued a treatise on “The History and Explanation of the Sun-spots,” in which he declared unreservedly for the Copernican system. And this caused the change. True, _Copernicus_ himself was a Catholic Priest, and had dedicated his principal work to Pope _Paul III._ But it was generally supposed that he had brought forward the doctrine only as an hypothesis, only to illustrate and facilitate calculations, not claiming for it absolute certainty. This assumption was based on the preface of the first edition of his book, containing assurance to that effect. That preface, however, was not the work of _Copernicus_, but had been smuggled into the book by the Protestant publisher _Osiander_, without the author’s knowledge, because _Osiander_ feared _his own_ church authorities. _Galileo_ spoke in quite another tone. He defended the doctrine as true. He soon aroused opposition. Men standing for the geocentric theory were opposed by others, siding with _Galileo_ for the solar system, such as the learned Benedictine, _Castelli_. _Galileo’s_ great bitterness and sarcasm in dealing with his opponents aggravated the quarrel with the “partisans of _Aristotle_.” Extreme irritability and love of praise were prominent traits of _Galileo’s_ character.