THE CONQUEST OF NATURE 



efforts of men whose power, if directly expended, would 

 be altogether inefficient to stir the weight. 



The pulley was doubtless invented at a much later 

 stage of human progress than the simple lever. It 

 was, however, well known to the ancients. It was 

 probably brought to its highest state of practical per- 

 fection by Archimedes, whose experiments are famous 

 through the narrative of Plutarch. It will be recalled 

 that Archimedes amazed the Syracusan general by con- 

 structing an apparatus that enabled him, sitting on 

 shore, to drag a ponderous galley from the water. 

 Plutarch does not describe in detail the apparatus with 

 which this was accomplished, but it is obvious from his 

 description of what took place, that it must have been 

 a system of pulleys. 



It will be observed that the pulley is a mechanism 

 that enables the user to transmit power to a distance. 

 But this indeed is true in a certain sense of every form 

 of lever. Numberless other contrivances are in use 

 by which power is transmitted, through utilization of 

 the same principle of the lever, either through a short 

 or through a relatively long distance. A familiar illus- 

 tration is the windlass, which consists of a cylinder 

 rotating on an axis propelled by a long handle, a rope 

 being wound about the cylinder. This is a lever of 

 the second class, the axis acting as fulcrum, and the 

 rope operating about the circumference of the cylinder 

 typifying the weight, which may be actually at a con- 

 siderable distance, as in the case of the old-fashioned 

 well with its windlass and bucket, or of the simple form 

 of derrick sometimes called a sheerlegs. 



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