enters the trough that would clog the screen at the lower end of the hatching trough and cause it to overflow and the fry to escape.
These hatching troughs are best made of soft wood, preferably sound, clear white pine, and if possible have them up so that the tops are three feet six inches above the floor, for convenience in working over them. If the bottoms are an inch and a half thick, three carpenter's horses will sustain them. A trough thirteen feet long, fourteen inches and a quarter wide, and seven inches deep, inside measure, will be sufficient for twenty-five thousand trout fry after they are hatched and feeding, but will be capable of developing four times that number of eggs. The troughs should be made of regular width, to a hair's breadth, in order to have any hatching tray fit every trough in any part of it, and the edges of the bottoms should be carefully dressed and the
Lower Ends of Troughs with Outlet Pipes.
sides nailed to them after being touched with thin white lead. The ends should be let in (see cut), in order to be nailed both ways and be tight. An inch-and-a-half hole in the bottom of the lower end will take the waste water where required; a sink outlet with the cross-pieces cut out is good to attach a waste-pipe to; above this hole nail an upright strip to each side to hold the dam. During the egg stage use one of two inches or less; after hatching
