18 WATER SUPPLY. 



should be made so that the screens will fit tightly and yet 

 be easily taken out to clean. 



A very good screen for two and three year olds can be 

 made from strips of lath planed and nailed to a strong 

 frame, with quarter-inch openings between them. 



Water Supply. — It is immaterial what kind of water is 

 used, whether hard or soft. Neither will so-called " min- 

 eral water " hurt the Trout unless the water is very strongly 

 impregnated. Trout have been known to live and thrive 

 in a stream one-sixth of whose volume was supplied by a 

 strong sulphur spring. Still the purest water is the best. 

 The essentials are that the stream shall be reasonably pure, 

 the volume of water nearly uniform, or so arranged that 

 the supply taken from it is uniform and the temperature 

 between thirty-six and sixty-five degrees. 



The supply of water necessary for a given number of 

 Trout is yet unsettled. For a series of ponds turning out 

 one thousand large fish yearly, the water supply should fill 

 a four-inch pipe. This question will be treated more at 

 length in Chapter YI. 



