128 



FISH FARMING : 



are placed in position, slanting away at the top in the direc- 

 tion of the current, for reasons already explained in slanting 

 screens for ponds, etc. They are kept in position by means of 

 slats screwed on the sides of the boxes, two of which go to 

 form a groove down which the screen is slidden. These screens 

 and the method of keeping them in the proper position are 

 better explained in the next drawings. In Figs. 27 and 28 

 I show five screens, but the aiotual number necessary is deter- 

 mined by the quantity of sediment in the water when it 

 reaches the hatchery. The flannel o<n the screens may, advi- 

 sably, vary in coarseness, those nearest the outlet being, of 

 course, the finest. If very much sediment comes into the box 



Fig 29. Cross Section of Filtering: Box. 

 Fig. 30. Section of Screen. 



in the first place it is advisable to let the screens terminate 

 some two or three inches from the top of the box. In this 

 way, should one of the screens clog during the absence of the 

 attendant, the water will flow over the top of it, and so 1 on to 

 the next. If this precaution be no taken, the result may be 

 of a disastrous nature, for the water, instead of flowing 

 through the screens 1 and sc* into the distributing box, may 

 overflow in the first section between the first screen and ths 

 inlet end of the box, and leave the cutlet section so low that 

 not a sufficient supply will flew through the outlet and so 

 into the distributing boxes. This ir.eans no flow of water 

 through the hatching boxes, which in its turn spe^s death to 

 your trout in embryo if it continues any appreciable length 



