ON SMALLER PONDS. 161 



be permitted to accumulate in them than is just 

 sufficient for shelter, and the production of food for 

 the fish. In HoUand, where, as I have stated, this 

 subject is properly studied and understood, the ponds 

 are usually made in series or chains of two, three, or 

 more, communicating by hatches with one another; 

 so that when one is drained the others may remain 

 full, and each or all of them can be raised or let down 

 at pleasure. One or the other of them is usually 

 drained down and left dry yearly, or every year or 

 two, for some months, in^ order to allow the soU to 

 exhale and the weeds to die down. Some weeds 

 are indispensable, as they harbour food, and are more 

 particularly needed for the fish to spawn amongst. 

 Indeed, the fish cannot spawn without them; and, 

 added to this, the spawn is said to require the aera- 

 tion afforded by the weeds for its proper vivification. 

 The little gold fish often die off in great numbers, 

 from no other cause than that of being placed in 

 tanks or reservoirs where there are no weeds for it 

 to rub itself against, in order to free itself from the 

 spawn. The Water Crowsfoot is one of the most 

 useful weeds for ponds, but the Alsinastrum should 

 be avoided, or it wOl soon choke up the pond. 



Ponds should be fished once in every three or four 

 years ; they do not pay if left for longer intervals^ 



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