60 DOMESTICATED TROUT. 



all the fish that come through the screen, but will al- 

 ways tell you whether any are escaping, and also 

 whether the screens are tight. If you do not provide 

 this safeguard, thousands of fish may escape before 

 you know it. It is a good plan also to have a larger 

 box or reservoir, still farther down, on a similar plan, 

 collecting the water from all the troughs, and arranged 

 so as to detain everything that may have escaped, from 

 any cause, from above ; and I think I may safely say 

 that you will be astonished to find how often the 

 young fry slip past places that you have considered 

 perfectly tight. Having so far prepared the hatching 

 troughs for action, and having tried them by running a 

 stream of water through them, the next thing is 



Laying the Gravel. 



Gravel is used to hatch the eggs upon. This 

 hatching gravel should be the size of half a pea, 

 or less. Coarser gravel will not do, because the 

 eggs will get into the chinks between the stones, and, 

 being out of sight, will die without your knowledge ; 

 and when they die, the dead eggs will certainly grow 

 the fatal byssus, which will stretch its long arms out 

 over other eggs above or near it, and destroy them. 

 Coarse gravel is very vexatious on this account. Any 

 clean gravel of the right size, free from rust, rotten 

 stone, and the like, will do, and you will frequently 

 find such gravel nearer than you suppose. It is 

 therefore a good plan to try any high banks near by, 

 before sending a great way for it. You may often 

 find just what you want in a bank right over your 



