Trout Breeding. 119 



The raceway should be covered with gravel at all 

 times; for if the fish are not well, or are troubled with 

 parasites, they resort to swift water and gravel bot- 

 toms to rub their sides and clean themselves. This 

 gravel should be from half an inch to an inch or more 

 in diameter. 



In facing the pond with boards the pressure of the 

 earth must be provided for, or the sides will soon fall 

 in, or at least become badly bulged. To prevent this, 

 lay timbers on the bottom and frame the uprights into 

 them; nail the boards on the outside of the uprights, 

 which should extend above the ground and be braced 

 apart by joists running across the pond a foot or more 

 above water. Even these will spring in time if not 

 quite stiff. Ponds well built require but little work to 

 keep them in order an occasional stopping of muskrat 

 or of crawfish holes, and in the spring to repair dam- 

 age from frost, if any, or to patch up a bank or wall. 

 There are hard soils where neither wood nor stone are 

 needed (except on the spawning races, whose sides 

 should be vertical), but may be made at a slope more or 

 less inclined. Willows planted near the pond are valu- 

 able as shade trees, or floats of boards may be of use in 

 keeping the water cool, besides being a sort of protec- 

 tion from the little kingfisher. 



Perhaps an account of the way I made the ponds for 

 the New York State hatchery at Cold Spring Harbor, 

 Long Island, will be of interest, for they involved great 

 labor. I took charge on January I, 1883, and started 

 work. An old building was used to hatch eggs .ob- 

 tained elsewhere, and there was a spring reservoir some 

 300 feet long by 20 wide, which had been made to turn 

 a turbine wheel in the old building. This reservoir 

 was high enough to bring water into troughs on the 



