HATCHING APPARATUS. 



51 



the tank at a very considerable angle, say 45°, with 

 the lower end up stream. 



a Flannel filters. 



b Hatching-room aqueduct or inlet. 



c Outlet. 



The tank should be built very solid, of two-inch 

 plank, charred, and should be bound with iron bands, 

 to prevent spreading. Its size will be governed, of 

 course, by the amount of filtering required, a small or 

 very clean stream needing less than a large or com- 

 paratively turbid one. But be sure of one thing, that 

 the tank is large enough, no matter how large tliat 

 may be, to arrest all the sediment, beyond all possi- 

 bility of risk. Thousands of eggs have been lost by 

 the filtering tank being inadequate. Better have it 

 twice as large as is necessary, than to incur any risk 

 of not stopping the sediment. 



At the Cold Spring Trout Ponds there are two 

 tanks for filtering, one containing eighty-one gallons 

 and six filters, the other one hundred and sixty-eight 

 gallons and seven filters. 



I should say that it was better to have two medi- 



