956 EEPOET OF COMMISSIONEE OF FISH AND FISHERIES. 



capacity of 150,000 Atlantic salmon, or say 100,000 to 125,000 Pacific 

 salmon. The troughs are about ten feet long and six inches deep, arranged 

 in pairs (except the one next the wall) with walks between. These troughs 

 are placed upon the floor, but when circumstances permit well aerated water 

 to be brought into the house high enough, it is better to place them two or 

 three feet above the floor. This is, however, entirely a question of con- 

 venience for the attendant. The water used is supposed to be unfiltered, 

 and is therefore received in a deep and wide head trough, which will serve 

 as a settling tank. From the head trough the water is delivered by 

 wooden faucets to the hatching-troughs, the fall at this point affording 

 an opportunity for aeration, which can be improved by letting the water 

 fall on a slanting board, from the edge of which it will fall in a thin sheet 

 into the trough. It is important to have the faucets all exactly on the 

 same level ; otherwise those which are lowest will, unless carefully regulated, 

 rob the others of their share of the water. The style of faucet represented 



is very convenient and safe, but a 

 plain spout of lead or wood, three 

 or four inches long, and closed by a 

 slide on the upper side, as shown 

 in Figure 6, is just as good and 

 easier made. Avoid any kind of 

 a faucet that is liable to be acci- 

 dentally closed, like a molasses 

 faucet, an occurrence that I have 

 known to be followed by very 

 serious results. The bore of the 

 faucet should not be less than one 

 inch for a trough a foot wide. 

 A very convenient outlet for a hatching-trough is formed Ijy a two-inch 

 lead pipe set into the bottom of the trough and running down through the 

 floor. The water is maintained at the proper height by a movable parti- 

 tion, or dam of thin boards sliding down between cleats nailed to the sides 

 of the trough, as shown in Figure 5. The height of the water depends 

 upon the number of pieces brought into use at any time. These boards 

 must be carefully jointed and fit nicely between the cleats, that there be no 

 waste of water. A dam of the same sort should be used to hold the water 

 at several points in an inclined trough. 



The troughs should be fitted throughout with light board covers from 

 two to four feet long, with cleats or other fittings convenient to lift them by. 

 The faucets may be covered by a box, as shown in Figure 5, on the second 

 trough. Screens fine enough to shut out all vermin should be placed at 

 both ends of the trough. 



Almost any kind of easily worked wood may be used for building the 



