Page:Popular Science Monthly Volume 66.djvu/264

 therefore. These laws are the basis of horology. They were first fully utilized in the construction of clocks by Huyghens.

A lesson in geometry overheard by Galileo while a pupil excited his deepest interest. Euclid soon became his master and, from this day, his attention to medicine slackened, much to his father's regret. The salaries of mathematical professors were extremely small in those days, while the rewards of successful physicians were very much greater. Owing to his father's poverty, Galileo was withdrawn from the university in 1586, and returned to Florence. It is recorded that at the university he was known as a brilliant, though disputatious, pupil, and was nicknamed 'The Wrangler.' At Florence he lectured before the academy on the situation and dimensions of the Inferno of Dante—a question partly philosophical, partly scientific. It was at this time that he studied the works of Archimedes and wrote a little treatise on the hydrostatic balance. In 1587 he went to Rome and made the acquaintance of Clavius and other scientific men.

In 1588 he had the great good fortune to meet a generous patron, the Marchese Guidobaldo del Monte, and, in the same year, wrote at his request a treatise on the center of gravity of solid bodies. By his influence Galileo was appointed to be lecturer on mathematics in the University of Pisa (1589). His salary was only sixty scudi annually (about $65), and he was obliged to eke it out by giving private lessons. The salary of the professor of medicine was 2,000 scudi. During the years 1589 to 1591 he made those experiments on falling bodies which are the basis of the science of mechanics.

From the time of Archimedes (287-212 B. C.) till that of Leonardo da Vinci and Galileo there had been no progress in theoretical mechanics. Archimedes discovered the theory of the lever: 'Give me where I may stand and (with the lever) I will move the world.' His knowledge of practical mechanics was, no doubt, derived from his famous works of military engineering. All the great buildings of antiquity had been built by processes not unfamiliar to him. All the great basilicas of Europe and all the Gothic cathedrals with their nice system of balanced thrusts had also been erected before the time of Leonardo. The practical processes of engineering were highly developed, therefore, but as yet no one had formulated a theory. That Leonardo comprehended its fundamentals is abundantly shown by his note-books recently published. Every military engineer who had watched the flight of a projectile was aware that the received notions of mechanics would not explain its motions. No theory of the impact of such projectiles had even been proposed. A whole science was to be created. The doctrine of mechanical equilibrium is statics—and this science was founded by Archimedes. The doctrine of mechanical motion is dynamics—and nothing was done in this science till the time of Galileo.