88 



SALMONID.E. 



trough, and about six inches or more wide, Avhich, when 

 nailed upon the edges of the side pieces, will keep them more 

 steady and firm. 



" 4. Let the lower end board, where the water is to run 

 off again, be at least three inches thick, as the greatest pres- 

 sure is against it, have an opening cut at the top six inches 

 wide and four inches deep ; have a ravet made on the outside 

 and another on the inside, deep enough to leave at least an 

 inch thick of the solid board in the middle, and wide enough 

 to admit a frame with a brass-wired grate, like No. 2, on the 

 outside, which can be pushed in from the top ; the wires 

 should not be above a line and a half asunder, no more than 

 those at the top, for the same reason as mentioned before. 

 In the inside, opposite this opening, push a bit of board 

 downwards into the groove to stem the water either entirely 

 or to regulate its running off, according as you find it neces- 

 sary, or to pull it entirely out when the whole of the water is 

 to run off. 



"5. There must be two strong covers, one between the 

 two cross pieces described in 2, 3, and the other below the 

 middle cross quite to the lower end, 4 ; both covers must be 

 fastened behind with strong hinges, and before with handles, 

 to lift them conveniently up by ; and as these boards are apt 

 to warp, on account of the water within and the air without, 

 it is requisite to have each clamped with two or three cross 

 pieces. 



