OF THE SALMON. 39 



ticular form. Yet it will be necessary to give a 

 description bow tbose tbat I use are made. 



Section L 



" 1st. I had boxes made of various woods, but I 

 found oak to be tbe best, about twelve feet long, 

 one foot and a balf wide, and six inches deep. 



" 2d. At the head of the trough, where the water 

 is to run in, is laid a thick board, about two and a half 

 or three inches thick, about a foot wide, and as long as 

 the trough is wide. In the middle of this board is 

 made a hole, six inches long, and about four inches 

 wide in the clear, with a ravet on all the four sides 

 of this hole, about an inch and a half wide and deep, 

 so as to admit of a square frame with an aperture of 

 six inches by four inches, or of the same size as the 

 hole, which frame must be covered with a brass grating 

 of a moderate strength, and close enough to prevent 

 the smallest water-shrew from passing through, other- 

 wise all the spawn and young fry will be in danger 

 of being devoured by them. 



"3d. Near the middle of the box or trough lay 

 another piece of thick board across, as long as the 

 width of the trough, and about six inches or more 

 wide, which, when nailed upon the edges of the side- 

 pieces, will keep them more steady and firm. 



"4th. Let the lower end board, where the water 

 is to run off again, be at least three inches thick, as 

 the greatest pressure 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. 

 D 4 



