MECHANICS OF LIQUIDS 



75 



factories and mills are located on the borders of rivers in the 



valleys of hilly communities. The water 



draining the hills rushes with considerable 



force down the rivers. The energy of 



this water is utilized by allowing it to run 



ovef an overshot water wheel (Fig. 44). 



The weight and force of the moving water 



are such as to cause the wheel to move, 



which in turn moves the machinery by 



means of belts or gears. 



The most effective method of utilizing 



water power is by means of a wheel called 



a turbine. The river is dammed, and the 



water is conducted through a canal which 



runs alongside the" mills. The water is al- 

 lowed to pass through a 

 cylindrical tube to a pen- 

 stock which surrounds an 

 ironcasecontainingthe tur- FIG. 45. ;Use of Tur- 

 bine or rotating wheel (Figs. 

 45 and 46). By means of a connecting shaft 

 the wheel may be made to operate a dynamo. 

 Where there is current and little elevation, 



the energy of the water may be 



utilized by means of an undershot 



wheel (Fig. 47) . The force of the 



current strikes against the lower 



part of the wheel. 



Where the water is delivered 



under considerable pressure its 



power may be utilized to run 



lathes, sewing machines, and FIG. 47. Undershot Wheel. 



FIG. 46. Tur- 

 bine Wheel. 



