THE GENESIS OF TEE LAW OF GRAVITY 3 2 9 



HUTGEXS. 



carried Greek manuscripts westward to Europe. These stray documents 

 gave a fresh impetus to science as they did to letters. The one to first 

 really 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 Xewton 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 watch- 

 ing 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 pen- 

 dulum — that the time of vibration is independent of the arc of motion. 

 How many thousands of times had that same chandelier been observed 



VOL. LXXVIII 



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