Page:Popular Science Monthly Volume 47.djvu/774

756 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 sometimes 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.

—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 painter'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 quarters 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 outfit 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 bottom 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