22 TEOUGHS WATER SUPPLY. 



shoulders nailed to the sides against which to set them. 

 We do not recommend either of these, as it interferes with 

 the equable flow of the water. New wood under the action 

 of water develops a slimy sap, therefore it would be well 

 to line the bottom and sides of the trough with glass. The 

 troughs should have an inclination of about one inch in 

 eight feet — just enough to let the water ripple gently over 

 the cross strips. They should not be longer than twenty 

 feet, or the air on the water will be exhausted before the 

 water reaches the end of the trough. There is more dan- 

 ger of this after the eggs are hatched out and the troughs 

 are full of young fish. This method is that which we pur- 

 sue and have found most successful in practice. There are 

 many other methods, all of course depending upon the same 

 general principles, but we give only that one which we 

 consider best. If possible the hatching house should be so 

 far below the level of the spring from which its supply of 

 water is derived, as to allow the troughs to be raised two 

 or three feet from the floor. Where a large number of 

 eggs are to be hatched, the inconvenience of stooping to 

 care for them is very great. 



Water Supply. — From the filter the water runs into 

 the distributing trough or pipe, which runs along the head 

 of all the hatching troughs. The water may be let into 

 the hatching troughs by faucets, or through holes cut into 

 the trough. These holes should be covered with netting, 

 or the young fish will run up out of the troughs into the 

 filter, or coarse gravel may be heaped up at the head of the 

 trough through which the water will run, but through 

 which the young fish cannot work their way. The supply 

 of water for one trough should be equal to that coming 

 through a half-inch hole with three inches head ; just 

 enough to make a gentle ripple over the cross-pieces. Be 

 careful to get the troughs level cross ways, and the strips 



