CHAPTER LIII 

 WINDMILLS 



Utility. The windmill is adapted to work which may per- 

 mit of a discontinuance during a period of calm. It is 

 adapted to regions where wind of a velocity sufficient for its 

 operation prevails generally throughout the year. One line 

 of work which will permit of a discontinuance during calm is 

 pumping, and for this reason the use of the windmill is con- 

 fined largely to this work. 



When properly installed and working under proper condi- 

 tions, the windmill is perhaps one of the most economical of 

 all motors. As a source of energy it costs nothing; the cost 

 of the power is due solely to the interest on the investment 

 and to depreciation and repairs. 



Development. The use of windmills dates back to a 

 very early time. Wind and water wheels were used as the 

 first source of power long before heat engines were thought 

 of. The windmill years ago reached a rather high stage of 

 development in Europe, those of Holland being especially 

 famous. The Holland or Dutch mills represent a distinct 

 type, in that there were usually four canvas sails mounted on 

 a wooden frame. The speed was regulated by varying the 

 amount of sail surface exposed to the wind. In most cases 

 the mill was turned toward the wind by hand. The steel 

 windmill was developed in the United Stated about 1883. 



The Wind. Wind is simply air in motion. It represents 

 kinetic energy, and the windmill obtains power from it by 

 reducing its velocity, causing a certain amount of energy to 



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