2 6o POPULAR SCIENCE MONTHLY. 



seconds, 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 Owing to his father's poverty, Galileo was withdrawn from 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 Eome 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 mechan- 

 ics. Archimedes discovered the theory of the lever : ' Give me where 

 I may stand and (with the lever) I will move the world.' His knowl- 

 edge 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 basil- 

 icas 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 compre- 

 hended its fundamentals is abundantly shown by his note-books re- 

 cently 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 dy- 

 namics — and nothing was done in this science till the time of Galileo. 



