SOME COMMON MECHANICAL MOTORS 



565 





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FIG. 351. Line for transmission of electric power from Ke.okuk to St. Louis. 



THE STEAM ENGINE 



674. Importance of the Steam Engine. No other device or 

 machine invented by man has had as great an influence upon 

 the material advancement of civilization as has the steam 

 engine. It is estimated that the steam engines of the world 

 are today doing from 150 to 209 million horse-power of work. 

 This is many times the amount of work the entire population 

 of the civilized world could do were every adult human being 

 working daily at hard manual labor. The steam engine 



