[13] POND CULTURE. 479 



If ponds receive their water from springs, brooks, or lixiis which rise 

 considerably at certain seasons of the year, weirs with shiices shonkl 

 be constructed at the phiccs where the water enters ilie pond, so tliat 

 tlie supply of water can easily be regnlated. Tf, however, an entire 

 stream x^asses throngh a pond, the weirs mnst be placed in the- stream 

 itself, and the sn]iertluons water mnst be allowed to flow out through 

 side ditches. The sn])erllaous water and the water of the stream may 

 again unite below the pond. 



7. Legal right to use water. — As regards the legal right to use 

 the water coming from some distance, it will be well, before laying out 

 a pond, to examine whether one is entitled to draw the water from the 

 brooks, rivers, and. springs which it is intended to use for supplying his 

 pond. With " sky ponds " this is of course not necessary, but the con- 

 sent of the neighbors may be required for constructing ditches through 

 their property, so as to regulate the supply and outflow of rain and 

 snow water. As regards existing ponds all this has ]U'obably been sat- 

 isfactorily arranged long since ; but when new ponds are to be laid out 

 this may involve such difficulties and expenses as to prevent the whole 

 scheme. 



8. The cost. — After all the above conditions for laying out a pond 

 have been examined in the manner described, and have been found 

 favorable, the question of the cost will have to be considered, and care- 

 ful calculations should be nmde for the purpose of ascertaining whether 

 the expenses connected with the laying out and the maintenance of the 

 ponds will be so large as to be utterly disproportionate to the proflts 

 which may reasonably be expected from pond culture. The decisive 

 point will be whether the laying out of a i^ond will insure the return of 

 the capital invested within a reasonable period. 



II. — The Construction of Ponds. 



INTRODUCTION. 



In the preceding chapter we have shosni what conditions should be 



observed in the laying out of a pond; and in the present chapter we 



intend to show the manner in which ponds should be constructed in 



cases where all the above conditions are more or less favorable. 



In laying out a i^ond the conditions of the ground should, as we have 



' already mentioned, be carefully examined and the plan be made accord- 



I ingly, one of the most imi^ortant points being to secure a suitable depth 



j of water. We have likewise indicated in the preceding chapter in what 



' manner this should be done. The depth of the water is regulate<l by 



I making the level of the water in the ditch through which it flows into 



I the pond higher than the foot of the grate where the water flows out. 



J The higher the foot of the grate, so much larger an area can be evenly 



\ flooded, and the lower the foot of the grate, so much smaller an area. 



' The ;>rea of the i)0]id should l)e determined by the quantity of water 



