WALLS OF ARTIFICIAL PONDS. 233 



order that they may have the benefit of sharply 

 running water. The lower part of the inclined 

 plane, or the deepest part of the pond, suits best 

 the fry after incubation. 



The walls that are to secure the ponds must 

 be strongly built of rough stone. No lime must 

 be used in the construction of the walls, or of any 

 thing connected with the ponds. Every one ought 

 to know the destructive effects of lime upon fish. 

 To secure the ponds from the entrance of the 

 smallest fish, besides the iron grating already men- 

 tioned, there must be another fixed inside it of 

 copper wire closely interlaced, so closely as to 

 prevent the possibility of the smallest trout passing 

 through the interstices. If a diminutive trout 

 should enter, it would devour the fry as soon as 

 they were hatched. Each end of the pond should 

 be secured in the same way. At the end where 

 the pond- water runs out there should be if pos- 

 sible a fall into the river, which would effectually 

 prevent the ascension to the ponds of any pre- 

 datory fish. 



Some persons have tried artificial breeding in 

 ponds supplied with water from springs and hill- 

 burns, but in such trials no sensible person ought 

 to expect satifactory results, or at any rate results 

 similar to those that would be derived by the use 



