756 THE POPULAR SCIENCE MONTHLY. 



begins, put in one of five inches and a screen above it. Just 

 above the dam put two strips each side to hold the screen, which 

 must fit tight all around, or tails will get in cracks and the fish 

 will die. This screen should be of No. 14 wire cloth, and is some- 

 times placed upright and at others with its top up stream to give 

 more surface and to release a weak fish from it by its own weight, 

 but the difficulty in keeping a screen so placed clean is an offset 

 to its advantages. If space permits, the troughs should be placed 

 by twos, but some prefer them by threes. 



Coal Tar. All troughs, screens, trays, and all wood and iron 

 that is in contact with water, should be painted with coal tar, 

 which can be had from the gas-works. Thin it with spirits of 

 turpentine, and give it two or three coats with a half-worn paint- 

 er's brush in hot weather. It must be perfectly dry before water 

 is let in, and then there will be no taste, rust, flavor of pine, nor 

 fungus. Asphaltum is used, but I have not tried it. After the 

 first season one coat each year is sufficient. 



If the hatching troughs are all exactly one width, make the 

 trays one quarter of an inch narrower and about twenty-seven 

 inches long ; use half-inch pine, cut in strips three quarters of an 

 inch wide and laid flat, so that the frame is only half an inch 

 deep ; make the corners strong. If the frames are fourteen inches 

 wide outside, have wire cloth especially woven of a length to 

 cover them all, but half an inch narrower than the frames, for 

 the selvage will be uneven ; have it made with a mesh three quar- 

 ters by an eighth of an inch, the long way of the mesh across the 

 cloth ; this holds the egg, but lets the fish drop through. Use No. 

 18 wire for the cross-wires, and finer wire for the double over 

 and under, for the warp. A double-pointed carpet tack under 

 each corner of the tray allows circulation beneath and prevents 

 crushing the fry. 



Having shown how to make the troughs, screens, and trays, 

 and how to take the eggs, we must now proceed to the care of the 

 eggs and fry. Our implements are few and simple : a wisp 

 broom, a pair of nippers, a small, flat net, and the wing-feather 

 of a goose set in a handle of light wood are all, except an out- 

 fit of pans which are to be used in stripping the fish. The little 

 hand broom is used daily ; a tray of eggs is taken from the bot- 

 tom of the trough and soused in and out of the water to remove 

 sediment, and is put over into the next trough, etc. When all 

 are out, the dam below is removed and all slime washed out and 

 both darn and eggs replaced. The nippers are cut out of wood, 

 red cedar preferred, and are about six inches long, with a spread 

 of three quarters of an inch at the points ; the latter are best 

 when finished with a loop of brass wire, but can do good service 

 without this. A dead egg turns white, and can be seen at a glance 



