45 



strips set on the bottom at intervals of eighteen inches. 

 The reason for this division into nests and for these cross 

 strips will be seen further on. These strips may be made 

 of half-inch stuff and cut two inches in width. There is 

 no necessity for nailing them to the bottom ; fit them in 

 accurately and set them edgeways at intervals of eighteen 

 inches. As they do not need to be removed often, it is 

 better to make them fit tightly. Other strips of the same 

 stuff must be provided, to fit upon these and made wide 

 enough to raise the \vater within an inch of the top of the 

 trough, as these need to be often moved they must be made 

 loose enough to take out, and yet fit accurately enough to 

 raise the water over them when they are put in. A groove 

 is sometimes made in which to run the strips, or shoulders 

 nailed to the sides against which to set them, but it 

 interferes with the equable flow ot the water. New wood 

 under the action of water develops a slimy sap, therefore 

 it is necessary to paint the troughs with hot coal tar mixed 

 with enough turpentine to thin it to about the consistency 

 of paint. Glass has been used to cover them, and the 

 wood has been charred to prevent the growth of lungus, 

 but nothing answers so well as gas tar, which should be 

 used to cover every thing in the troughs or ponds, and 

 where fungus can do harm. The troughs should have an 

 inclination of about one inch in eight feet just enough 

 to let the wa'er ripple gently over the cross strips. They 

 should not be longer than twenty feet, or the air in the 

 water will be exhausted before the water reaches the end 

 of the trough. There is more danger of this after the 

 eggs are hatched out and the troughs are full of young 

 fish. If possible the hatching house should be so far 

 below the level of the spring from which its supply of 

 water is derived, as to allow the troughs to be raised two 

 or three feet from the floor. Where a large number of 



