THE FLASH-WHEEL. 



Fig. 172. 



203 



Cylindrical Garden- engine. 



THE FLASH-WHEEL 



is employed with great advantage where the quantity 

 of water is large and is to be raised to a small height. 

 It is like an undershot- wheel with its motion reversed 

 {Fig. 173, p. 204), where the arrows show the direc- 

 tion of the current when driven upward. It must, of 

 course, be made to fit the channel closely, without 

 touching and causing friction. In its best form its 

 paddles incline backward, so as to be nearly upright at 

 the time the water is discharged from them into the 

 upper channel. It has been much used in Holland, 

 where it is driven by wind-mills, for draining the sur- 

 face-water off from embanked meadows. In Enirland 



