WINDMILLS 311 



tages of this mill over the former are that it is always 

 in the wind and is much less liable to be injured by 

 storms. 



By a comparison of tables from different manufacturers 

 of windmills the following table has been compiled of the 

 size of steel windmills required for various lifts and size 

 of cylinder. Although it cannot be said that the table is 

 accurate, it conforms very closely to the general practice. 



The above table is for mills back-geared about 10 to 3. 

 Since wood-wheel mills are generally direct-stroke, they 

 require a much larger wheel to accomplish the same work 

 as the steel wheels. 



432. Towers. The Hollanders built their towers in 

 the form of a building which either had a revolving roof 

 or the tower itself revolved. Within the tower they kept 

 mills and grain. Often to-day we see the towers of 

 American mills housed in a similar way, with the excep- 

 tion that they do not revolve. This is not an economical 

 way of providing room, for it requires much more ma- 

 terial in the construction than a low building does to 

 withstand the excessive wind pressure which it receives. 



Since the top of the tower vibrates greatly, the tower 

 needs to be very stiff. Probably a wood tower is stiffer 



