REARING 155 



A similar breakwater is inserted midway between this 

 and the lower end of the box. Whatever the dimen- 

 sions of your box are, the height of the breakwaters 

 will always be the same. 



A sheet of perforated zinc (No. 7 size), called a 

 screen, is fixed in front of each breakwater in a 

 slanting position, with its lower end up-stream, at an 

 angle of 45 degrees with the bottom of the box. A 

 similar screen is inserted in front of the lower end of 

 the box. In fixing these screens care must be taken 

 to leave sufficient space between them and the 

 breakwater to admit your hand for cleaning purposes. 



Unlike the breakwaters, the screens reach to the 

 top of the box. They are very carefully fitted to the 

 sides and bottom of it. The lower or outlet end of 

 the box rises only four inches high (the same height 

 as the breakwaters) and attached to the top of it is a 

 zinc shoot to carry off the water. The illustration 

 shows only two compartments. But the number is 

 increased if the box is made larger. I need hardly 

 say that a large hatching-box, requiring as it does 

 more water than a small one, needs also a wider 

 inlet. 



Before beginning operations, raise the upper end 

 of the box until the water stands in each compartment 

 at a level two inches below the top of the upper 



