WINDMILLS OF ANCIENT AND MODERN TYPES. 



The smaller figures show Dutch windmills of the present day, many of which are 

 identical in structure with the windmills of the middle ages. It will be seen that the 

 sails can be furled when desired to put the mill out of operation. In the mill of modern 

 type (large figure) the same effect is produced by slanting the slats of the wheel. 



