A HISTORY OF SCIENCE 



the early authorities makes it more than doubtful 

 whether any such expedient was really adopted. 



It will be observed that the chief principle involved 

 in all these mechanisms was a capacity to transmit 

 great power through levers and pulleys, and this brings 

 us to the most important field of the Syracusan phi- 

 losopher's activity. It was as a student of the lever 

 and the pulley that Archimedes was led to some of his 

 greatest mechanical discoveries. He is even credited 

 with being the discoverer of the compound pulley. 

 More likely he was its developer only, since the prin- 

 ciple of the pulley was known to the old Babylonians, 

 as their sculptures testify. But there is no reason to 

 doubt the general outlines of the story that Archi- 

 medes astounded King Hiero by proving that, with the 

 aid of multiple pulleys, the strength of one man could 

 suffice to drag the largest ship from its moorings. 



The property of the lever, from its fundamental 

 principle, was studied by him, beginning with the self- 

 evident fact that " equal bodies at the ends of the equal 

 arms of a rod, supported on its middle point, will bal- 

 ance each other" ; or, what amounts to the same thing 

 stated in another way, a regular cylinder of uniform 

 matter will balance at its middle point. From this 

 starting-point he elaborated the subject on such clear 

 and satisfactory principles that they stand to-day 

 practically unchanged and with few additions. From 

 all his studies and experiments he finally formulated 

 the principle that "bodies will be in equilibrio when 

 their distance from the fulcrum or point of support is 

 inversely as their weight." He is credited with hav- 

 ing summed up his estimate of the capabilities of the. 



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