[15] POND -CULTURE. 481 



As a general rule small ponds are preferable to laroe ones, and the 

 increased cost, occasioned by a larger number of <likes, will bo ani])ly 

 repaid ; for the water in small ponds can be rai)idly heated by the sun, 

 and in proportion to their size they aUbrd more food for the fish than 

 large ponds, and the fishing will be less expensive. This should be 

 specially borne in mind in constructing a large pond, involving the ne- 

 cessity of including within its limits high ground having gravelly soil, 

 which is of no value for fish-cnlture, and which would onlj' produce a 

 depth of water in the lower portions which would prove unfavorable to 

 vegetation. The above, of course, applies only to the construction of 

 new ponds ; while in existing ponds inquiry will have to be made 

 whether, and in how far, they answer the above conditions, and what 

 improvements may be introduced either at the present or at some futui-e 

 time. 



The work of constructing a pond may be subdivided as follows : (1) 

 Building the dikes ; (2) Constructing the principal ditches ; (3) Con- 

 structing the side ditches ; (4) Preparing the deep place where the fish 

 go when the pond is drained — the fish-pit; (5) Preparing the deep place 

 on the other side of the dike — the outer fish-pit ; (G) Constructing the 

 ditches for the superfluous water; (7) Making the proper arrangements 

 for letting the water in and out ; and (8) Placing the grates in position. 



1. THE DIKE. 



The building of the dike is the first work which should be done when 

 a pond is to be constructed, for it serves to prevent the water in certain 

 places from flowing any farther. It gathers the water, and thus forces 

 it to spread in both directions above the dike. In large ponds, which 

 frequently slope also toward the sides, it will sometimes be necessary 

 to construct dikes along the side ; but the pressure of the water against 

 them will not be nearly so strong as against the main dike, and they 

 therefore need not be built so solidly. 



As a general rule, dikes should be constructed only on that side of 

 the pond where the water is to be stojjped in its flow. They have there- 

 fore to resist the pressure of the entire mass of water which rushes 

 against them with full force. In order, therefore, for the dike to answer 

 its purpose, i. e., to resist the rushing waters, it must be built solidly. 

 The larger the pond, the stronger the fall of the water, and the deeper 

 the water, the more powerful will be the pressure against the dike, and 

 the strength of the dike should be proportionate to the force of the 

 water rushing against it. 



In order to possess the necessary strength a dike should be solid, 

 should have the requisite height and breadth, and its sides should slope 

 in such a manner that the water cannot easily break through or overflow 

 it. The solidity of a dike does not only dejjend on the manner in wliich 

 it is constructed, but alsq on tlje material employed, Pikes axq coU* 

 H. Mis. 08 31 



