240 PROPAGATION OF FISH. 



Screens may be made of common wire painted with 

 tar, or of galvanized iron wire. The last is the best, as 

 it will last longest in proportion to its cost. The screens 

 for keeping the small fry should be of fourteen threads 

 to the inch, and for one year old fish five or six threads 

 to the inch. Incline the screens at an angle of forty-five 

 degrees, the top being farthest down stream. By inclin- 

 ing the screens in this manner, a greater surface is ex- 

 posed to the water, than if they were placed perpendicu- 

 larly. The sockets should be so made 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. Or, 

 what is better, the slats should be at least four inches 

 wide, so that if a leaf strikes against them, it will catch 

 without obstructing the flow of water and lie flat against 

 a single slat, or, if it reaches over the edge, it will be 

 'carried through by the current striking upon one end. 

 It cannot lap around the slat as it would if it were smaller. 

 As for the width of the slats from one another, the 

 point to be guarded against is the fish running their 

 heads through far enough to strike their eyes which will 

 produce blindness. The distance they are to be apart 

 will depend consequently, mainly on the size of the 

 heads of the fish, and as fish grow at different rates of 

 speed, it will not do to go merely by their age, but for 

 fair sized fish an opening of about five-eighths of an inch 

 will answer. This refers to the upper screen, the lower 

 screen, that at the foot of the pond, may be larger, as the 

 fish are more cautious about descending where they 

 cannot see their way. 



