40 THE NATURAL HISTORY AND HABITS 



The wires should not be above a line and a half 

 asunder, no more than those at the top, for the same 

 reason as mentioned before. In the inside, opposite 

 this opening, push a bit of board downward into the 

 groove to stem the water, either entirely, or to regu- 

 late its running off, according as you find it necessary, 

 or to pull it entirely out when the whole of the water 

 is to run off. 



"5th. There must be two strong covers, one be- 

 tween the two cross-pieces described in 2 and 3, and 

 the other below the middle cross, quite to the lower 

 end. Both covers must be fastened behind with strong 

 hinges, and before with handles, to lift them con- 

 veniently up by ; and as these boards are apt to warp, 

 on account of the water within and the air without, 

 it is requisite to have each clamped with two or three 

 cross-pieces. 



" 6th. If you think fit to give the young fish more 

 air than what enters at the two brass grates, you may 

 have in each cover a hole made of the same size, and 

 guarded with a brass-wire grate, as in No. 3, and for 

 the same reasons. I have done this out of precaution, 

 but have found it in the end to be unnecessary. 



Section II. 



" 1st. Spring-water, out of rocks or stony ground, 

 is the properest for breeding of trout or salmon ; but 

 where it is not to be had, other spring-water may do, 

 provided the current is strong enough not to freeze in 

 hard frosty weather. 



" 2d. If the spring has not fall enough, you must 

 raise a dam around it one or two feet higher than the 

 top of your trough ; convey the water from thence, 

 through a pipe or gutter, to the first grate in the open- 

 ing on the head-part of the trough, of one square inch 



