FISH FARMING : 



the sluice boards and screens. These strips go to form two 

 grooves, one inside the other, throughout the entire length of 

 the contrivance. -Now let us stand the sluice upright and in 

 position as shown in the photograph and in Fig. 12, and firmly 

 fix the flange j to the bottom of the pond immediately over 

 the outlet N, Fig. 12, which is in communication with the 

 surplus water drain so often referred to in my plans of the 

 various ponds. The flange is preferably seated on brickwork 

 or cement concrete, to which it can be bolted by plugs let into 

 the brickwork or concrete, and fitted with screw ends and 

 nuts. What was the uncovered top of our imaginary elon- 

 gated box thus becomes the open front of the sluice. Next 

 the cap, L, is removed, and a number of sluice boards, marked 



Fig. 13. Sectional Plan of Controlling 

 Sluice. 



Fig. 14. Section of 

 Controlling Sluice. 



o in each drawing, are slipped down the inner groove until 

 the sluice is filled with them to the desired height, which in 

 Fisr. 12 is marked p. These boards govern the height of 

 water in the pond, for it is above the top edge of the top 

 board p, in Fig. 12 whatever number of boards may be in 

 place. It is equally evident that when all the boards are re- 

 moved there remains nothing to prevent the whole of the 

 water escaping into the drain N. But the apparatus is not 

 complete yet. It becomes necessary to guard against any 

 debris escaping down the sluice and so rendering the surplus 

 water drain liable to become choked; and, what is even 

 more important, the fish must be prevented from escaping in 

 the same direction. Now comes the use of the other grooves, 

 down which are slid a number of perforated zinc screens, 



