CHEAP FIXTURES FOR THE HATCHING OF SALMON. 957 



troughs. White pine is the favorite wood in northern sections. Arborvitse, 

 [Thuja occddentalis,) known in the north as white cedar, is unfit; water ia 

 which shavings of this wood have been soaked is deadly to grown trout. 

 Caution should also be used in employing the southern white cedar, or 

 cypress, {Qupressus tliyoides,) red cedar, or savin, {Junijperus virginiana,) 

 or any other odorous woods. 



Inch boards are heavy enough for troughs not more than six inches 

 deep, whatever their length or width. For deep distributing or filtering- 

 troughs use plank an inch and a half or two inches thick. 



All the wood-work about the troughs should be varnished with several 

 heavy coats of asphaltum varnish, thoroughly dried in before the wood is 

 wet. This makes a smooth, shining black surface, very easy to clean. 



8.— WIRE TRAYS. 



The practice of covering the bottom of the hatching- trough with gravel 

 and depositing the fish eggs directly upon that has deservedly become 

 nearly obsolete. Its principal disadvantages are, that it is impossible to 

 spread the eggs evenly on such a bed ; that there is great danger of suffo- 

 cation by sediment because of the absence of any circulation of water 

 beneath the eggs ; that the operation of cleaning them is tedious in the 

 extreme, and that the gravel seriously interferes with moving the fish 

 about in the trough or even dipping them out. 



The receptacle for the eggs which in one form or another has come into 

 general use is a shallow tray, made by attaching wire-cloth to a narrow 

 wooden frame. In its original form this was known as the " Brackett tray," 

 and that name properly applies to the sort recommended below. The promi- 

 nent advantages of this piece of apparatus are : first, the more perfect cir- 

 culation of water amongst the eggs, insuring a better supply of the air 

 demanded for their healthy development; second, almost entire safety from 

 suffocation by sediment ; third, the facility with which the eggs can be 

 cleaned and moved about in the trough or be taken out for cleaning and 

 examination. These advantages are so great and save so much labor that 

 the wire tray is almost indispensable. 



Trays of the following construction will be found most serviceable: 

 Make the frame of any easily worked wood, ("white wood," the product 

 of the tulip-tree, Liriodendron, is firstrate.) Half an inoh in width and 

 thickness are the best dimensions of material. Stouter frames would be 

 likely to float the wire, whereas it is better that they should sink. The 

 completed frame should be 12| inches wide. This precise width is chosen 

 because it is best fitted to receive wire-cloth one foot wide, — the size found 

 to be most eligible. If the cloth were cut of the full width of the frame there 

 would be many projecting rough edges, which would be an annoyance bj 



