180 FISH CULTURE 



there is a greater latitude of choice. The best 

 water is that taken from a natural lake having 

 no floating sediment; but that from a stream 

 will answer admirably, provided it is unpol- 

 luted by industrial establishments, or is not 

 muddied by storms for too long at a time. 

 Some eggs are quickly harmed by mud, while 

 others will survive in turbid waters almost 

 throughout the period of incubation. When 

 the hatchery is for general work, it is not ad- 

 visable to use water directly from a spring or 

 which is piped directly from one. It is pos- 

 sible that fresh spring water may not be harm- 

 ful to the eggs of some species of fish but for 

 others it is often sure death. 



When the water is introduced by gravity, 

 there should be enough at all times in the year 

 to fill a six-inch pipe, unless only one battery 

 is operated. Under pressure, however, a four- 

 inch pipe will supply two batteries with seven 

 troughs, each 30 feet long and containing 350 

 jars. A six-inch pipe, under pressure, will 

 supply with a safe surplus three such batteries. 

 To bring the water into the hatching-house by 

 gravity is naturally very desirable, because it 



