198 THE WORLD MACHINE 



verger had just lighted and thereby set in motion. In that 

 day there is a dearth of clocks, and the young student of medicine 

 wants a machine that he may count pulses by. He observes 

 that the time of the lamp's swing remains, so far as he can 

 decide, the same, though its path of motion grows less and 

 less. He reflects upon his observation, tests the matter when 

 he has a chance ; the isochronism of the pendulum is discovered 

 anew. Not that the pendulum had not been known before. 

 We may trace it back to the Arabs. It was even known in 

 Europe a century before Galileo's time. But discoveries made 

 headway slowly then ; it had not come into general use. Galileo 

 gave it a practical turn, made of it a pulsilogy, a pulse-counter. 



His mechanical instincts were now wide awake. One day, 

 soon after, he overhears a lesson in Euclid. It is good-bye to 

 medicine. A few years later, at twenty-six, all the apprehensions 

 of his practical father are realised ; Galileo is appointed pro- 

 fessor of mathematics, with the princely income of sixty scudi 

 a year, something like 13. No matter ; destiny, in Emersonian 

 phrase, is working through him and in him ; already he has 

 made a discovery great enough to bear his fame through all 

 the coming years. 



One day a treatise of Archimedes falls into his hands ; he 

 gets to thinking over the laws of falling bodies. For the first 

 time in history, so far as we know, he measures the rate of the 

 fall. His earlier discovery with the pendulum here stands him 

 in good stead, and he lays the foundations of a new science, 

 the science of bodies in motion, what we call to-day dynamics. 



He is young, ardent ; this restless, inquiring habit of mind 

 gets him into difficulties. One of the foolish, unverified dogmas 

 that had come down from Aristotle is that heavy bodies fall 

 faster than light ones that a twenty-pound weight will fall 

 twice as fast as a ten-pound weight. There are plenty of 

 people in the world who believe this still. Galileo questions 

 it, stirs up a hot controversy about it, and to prove his ideas 

 he mounts Pisa's celebrated Leaning Tower, and lets fall a 

 hundred-pound and a one-pound shot. The whole university 

 is there to watch the weights fall ; there is no question that 

 they strike the ground together. Any one who has eyes to 

 see may see. But the philosophers of the books will not believe. 

 They simply intensify their dislike of the young man who had 

 shown them they were wrong. In a little while he gets an offer 



