CHAPTER IX. 



The Developing of Power. 



"PHYSICAL power Is the moving force of the world and 

 It represents the work done by a machine or any agency 

 In accomplishing any change which requires work. Until 

 man began to use the force of the muscular strength of ani- 

 mals and the forces of nature to aid In accomplishing his 

 work, all the utilized power was that of human muscular 

 force. Primitive man had lived through many thousands of 

 years before he began to utilize the muscular force of ani- 

 mals to aid him, and even then, he passed through many 

 more thousands of years before he began to utilize the 

 forces of nature. We have seen that he utilized the force 

 of the Instantly released tension of his bow to furnish the 

 propelling power that drove his arrow and that he used a 

 stone propelled by the muscles of his arm with which to 

 crack nuts or crush the bones of some animal he had killed. 

 These were, doubtless, the first agencies used by primitive 

 man aside from his own muscular forces. 



Early In the history of our civilization primitive man 

 made use of the force of gravity In floating down the 

 streams on a raft or In a crude canoe and he also made use 

 of the force of the wind by attaching sails to his rafts or 

 boats. Aside from satisfying his hunger and protecting him- 

 self against the cold and his enemies, his wants were few, 

 but even before written history began he had discovered 



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