36 WATER-LILIES 



vertically upward. Screw into the joint a 

 piece of pipe just long enough to reach up to 

 the desired water level. Now, when the 

 tank is full, any overflow may go down the 

 pipe and out. To empty the tank, it is 

 necessary to unscrew the upright piece from 

 the elbow. The outlet should in any case 

 be covered with a wi re net to prevent clogging 

 of the drain, to retain fish, and to keep float- 

 ing plants from beingTost. 



Should the regular outlet be over a water- 

 fall or dam, a large pipe may be laid in the 

 lower part of this wall. A wooden plug at 

 its inner end will close it on ordinary 

 occasions, and can be removed when the pond 

 is to be emptied. From small ponds the 

 water can be dipped or siphoned out. 



PREVENTING FLOODS 



Where a natural pond is subject to a sudden 

 increase in water volume, a water gate con- 

 nected with an open ditch or culvert of suffi- 

 cient size to divert the additional column of 



