WATER FLOWERS 239 



in from top to bottom, outside as well as inside, 

 as a precaution against heaving by frost, this 

 slope giving the cross section of the finished 

 basin something the appearance of a huge un- 

 covered vegetable dish. 



Large pools must have thick walls and be 

 frost resistant; and even in these it is better to 

 slope the walls outward from bottom to top. 

 For in the event of water freezing in them dur- 

 ing an extreme winter, the expansion is given 

 opportunity by the greater width at the top for 

 upward play, and this insures the walls holding 

 without cracking. 



The water should flow in at the side at the top 

 and be taken out at a central vent into which a 

 standpipe is sometimes inserted to maintain the 

 overflow level. I must confess that I dislike this 

 method however as unsightly, and prefer a side 

 overflow; and as it is never supposed that either 

 intake or overflow shall be rapid, there is no 

 reasonable objection to it. The vent at the cen- 

 ter, where the floor of the pool may be slightly 

 depressed, is of course to be retained in order to 

 make complete drainage easy when necessary, 

 with a close fitting plug or cap closing it at other 

 times. For very tiny pools, however, surface 

 filling with a hose will suffice and the water may 

 be dipped out when it is advisable to clean the 



