Page:Popular Science Monthly Volume 78.djvu/339

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carried Greek manuscripts westward to Europe. These stray documents gave a fresh impetus to science as they did to letters. The first one really to grasp the subject of mechanics and develop it was Galileo (1564-1642). To him we owe the true theory of falling bodies, the law of the pendulum, the theory of projectiles and two of the three great laws of motion, which were put into their final form by Newton himself.

Two stories about Galileo will serve to show what manner of man he was and also to illustrate his methods. In 1583, while worshipping in the cathedral in Pisa, he chanced to notice the swaying of the great chandelier, the lamps of which had been freshly lighted. From watching its stately vibration he fell to timing it, using as a standard his pulse-beat. Thus there dawned upon him one of the laws of the pendulum—that the time of vibration is independent of the arc of motion. How many thousands of times had that same chandelier been observed