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CHAPTER II.—UNIVERSITY PROFESSORSHIPS.

Galileo, having thus acquired some economic security, threw himself with increased ardour into the investigations that he loved, and set to work systematically to test by experiment everything in Aristotle's mechanics. The stirring in men's minds which produced the Reformation had already caused a few isolated attempts to replace dogma by proof, but no one previously had made such determined assaults on the "peripatetic" stronghold. No sooner did Galileo find any rebutting experiment than he promptly pilloried the discredited dogma, exposing it in his lectures. Once more, therefore, he drew upon himself the enmity of those professors who had objected to his sceptical attitude as a student. The best-known instance of the success of his campaign is that associated with the celebrated Leaning Tower of Pisa. According to Aristotle the velocity of falling bodies is proportional to their weight, so that a weight of a hundred pounds would fall a hundred times as fast as a weight of one pound. Galileo asserted that but for the resistance of the air, which varies with the size and shape of the body, both would fall at the same rate. The parapet of the Leaning Tower offered a very convenient opportunity of testing the point. The experiment was tried by Galileo, and in the event the heavy weight beat the light weight by about two inches. Curiously enough, many of his opponents claimed the victory for Aristotle, as the heavy weight fell more quickly than the light one, and Galileo caustically pointed out that they were trying to make his two inches cover up Aristotle's ninety-nine yards, the amount by which the heavy weight should have won the race to the ground on Aristotle's hypothesis.

It was at this period that Galileo produced one of his literary efforts in the form of a burlesque, "In Abuse of Gowns," ridiculing the University ordinance which compelled professors to wear their gowns on all outdoor occasions as well as when lecturing. Various sonnets and other effusions would also appear to have been written during his first professorship.

A combination of circumstances arose to cut short even the three years for which Galileo had received his appointment. The feeling of nearly all his colleagues was against him; he was mulcted of part of his miserable stipend for any accidental failure to lecture; moreover, he had undertaken to help in the support of his brother and sisters, the eldest of whom, Virginia, was married in 1591, Galileo pledging himself to provide her dowry. Perhaps most important of all was the animosity of Giovanni dei Medici, the Grand Duke's natural son, an engineer and architect who designed a big dredging machine to clear Leghorn harbour. Galileo reported to the Grand Duke, after examining the model at his request, that it was useless, as indeed proved to be the case. These causes combined proved sufficient to induce Galileo to resign his post and return to Florence, where he found himself, his father having died soon after Virginia's marriage, almost entirely responsible for the daily wants of his mother and the two younger sisters; his brother Michelangelo had been trained as a musician but did not yet contribute anything to the family exchequer. A more lucrative post was imperatively required, and the Padua professorship being still vacant, as it had been when Galileo applied for it in 1588, four years before, he obtained the support of his friend the Marquis del Monte, and through his aid and that of his friends succeeded in securing the post against the rivalry of the man who had defeated him for the Bologna professorship. He was appointed for four years certain at a salary three times as great as he had received at Pisa, roughly £40 a year. Besides this increase, the greater number of students at Padua meant a much larger income from pupils. For their benefit he wrote a great number of treatises (some of which have been lost, as they were for a long time only in manuscript), treating of such diverse subjects as fortifications, the geometry of the sphere, and mechanics, that is to say, the lever, the pulley, and the screw, including that of Archimedes for raising water. In this was the first development of the principle that what is gained in power is lost in speed, the foundation of equilibrium conditions. In his first summer at Padua Galileo and two friends went to sleep in a cool or perhaps poisonous draught from a cavern, with fatal effects soon afterwards, except in Galileo's case, though his previously strong constitution did not save him from acute chronic disorder.

Some three years later he invented the geometrical and military compass, known to us as the sector, for mechanically solving a great many problems, and this with other similar inventions met with such practical success that he started a workshop in his house and employed a staff of mechanics to make them under his personal supervision. Some of the ideas were plagiarised by Simon Mayer (or Marius) under cover of another man's name, but Galileo had no difficulty in proving priority.

The four years of the appointment had stretched to six years, as was contemplated by the conditions, and Galileo carried on for a seventh year without raising any question. His friends then pestered the Doge on his behalf for an increase of salary, pointing out that his Bologna rival was now receiving more than Galileo, and succeeded in having the appointment secured for a second six year period with a salary of £70 approximately. He now had a wide European reputation as a teacher, and among those who came to Padua for his lectures were the Archduke Ferdinand, afterwards Emperor of Germany, and several other princes. Harvey, the discoverer of the circulation of the blood, probably attended a course of Galileo's lectures. The next step was a move into a large house for the accommodation of resident pupils. Galileo looked after the catering himself and made practically no profit on the housekeeping. There was a large garden to which he added extra ground with vines, and in the cultivation of which he took a considerable share.

Apparently Galileo marked the occasion of his increase of salary by setting up an establishment for a Venetian lady by whom he had three children within the next few years, but at the same time he had to bear the increasing burden of the maintenance of the other members of his family, of which he had now for some years been the head. His brother was continually sponging on him, and even when Galileo succeeded in getting him established in good positions as Court Musician, first in Poland and afterwards in Bavaria, it was Galileo who had to advance the money for an expensive outfit, hardly any of which did Michelangelo ever repay. Virginia's husband caused fresh trouble by threatening to bring an action against Galileo for the unpaid balance of his wife's dowry, and another sister Livia was married in 1601, her brothers guaranteeing her dowry, which meant that the whole responsibility for this also fell upon Galileo. It may be urged in palliation of the irregular nature of Galileo's private household that no wife would have allowed so much to be spent in such ways, but that he felt bound to take his father's place, whatever the cost. It was in 1601 that he began to earn additional fees by undertaking the tuition during the holidays, which he usually spent at Florence, of the Grand Duke's son, Cosmo, both of whose parents held Galileo in high esteem, the Grand Duke regarding him as the greatest mathematician in Christendom, while the Grand Duchess Cristina believed him the greatest of astrologers. In spite of the vogue of this pseudo-science, it is difficult to suppose that Galileo had any real faith in astrology, though he did not refuse to cast horoscopes, just as he lectured on Ptolemy's system after he became a convinced Copernican.

In 1602 Galileo invented his air-thermometer which was not perfected until some years after his death. Two years later the sudden appearance of a bright new star in Ophiuchus provided him with a new interest, and he lectured on it in the great hall of the University. The ordinary lecture rooms were frequently unable to hold the large numbers of students who flocked to hear the new ideas propounded by Galileo, and it is said that sometimes even the great hall was insufficient, so that he had to lecture in the open air. Galileo's conclusions about the new star, though not now acceptable, included at any rate the fact that it was as distant as other stars and not an atmospheric phenomenon. The suggestion that it belonged to the region regarded by the Aristotelians as perfect and unchangeable led to direct conflict, and Galileo openly argued in favour of the theory of Copernicus against that of Ptolemy, who had followed Aristotle. His third term of six years began in 1604, but there was as before delay on the part of the Venetian Council. Once more, in spite of the objections urged by some, among which his irregular household was not forgotten, a fresh increase of salary was voted, partly on the very ground of his increasing family. On the whole he was very well treated by the republic, his salary, which now amounted to about £115, being higher than that of any previous mathematical professor, and his new doctrines being permitted without any protest from the Council.

The next new subject attacked was magnetism. Galileo admired the work of Gilbert of Colchester, the famous author of "De Magnete," whose habit of mind was very similar to that of Galileo in its reliance upon experiment and its bold speculations. Galileo invented an armature for increasing the lifting power of a "loadstone," finding that small magnets were more efficient than large ones, and that when shaped specially they could be made to support a mass of iron weighing some forty times their own weight.