252 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Ill Fig. 1' the upper portion presents a longitudinal section of the 

 pond. The lower part shows a portion of the same section enlarged, so 

 that the arrangement of the pond is clearly illustrated. The fish arc 

 readily drawn into the collector C. A hook for removing the planks 

 y g g is shown at h. 



The "overflow" indicated at O is very important, and especial attention 

 is directed to its construction. This outlet is located in the solid ground 

 at the side of the pond rather than in any part of the embankment, 

 which might be weakened by its presence; and is protected by three 

 wire-cloth screens of varying texture, the coarser mesh being placed 

 farthest in the pond in order to collect all drift, and thus prevent the 

 clogging of the second and third screens, the meshes of which should be 

 fine enough to preclude the escape of the smallest fish. The screens 

 are so placed as to present a considerable surface below the water-level, 

 to insure them against being clogged by drift. This arrangement will 

 always afford a free exit to the water beneath the mass of rubbilh. 



The general details of the outlet A are indicated in the views given. 

 The screens s s s, as well as those of the "overflow," are disposed in a 

 frame- work, and should slide easily in their grooves, so that they may be 

 removed and cleaned. An additional set of such grooves are provided at 

 this outlet, and these which are the inuermost are furnished, instead of 

 screens, with solid planks g g g the edges of which are neatly fitted 

 to each other so as to render their joints water tight. The upper 

 edge of each plank is provided with staples or eyes / //, through 

 which the hook h may be passed to lift the plank from the frame. When 

 the planks are in position these eyes are received into slots n n in the 

 lower edge of the planks above them, so as to allow them to fit closely 

 together. 



The purpose of this fourth, and solid, screen is to lower the water in 

 the pond by drawing it from either the surface or the bottom, as may be 

 deemed most advisable. To draw it from the surface only, it will simply 

 be necessary to open the valve c; .and to remove the planks in succes- 

 sion as the water subsides, while to draw from the bottom will require 

 all the planks to be first removed ; and the valve to be opened when this 

 has been done. 



In addition to the valve c, the drain-pipe P may be provided at m 

 with a clog or strainer, to guard it against the accumulation of rubbish. 

 The collector should be placed at the lowest point in the pond, and, 

 unless excavated in hard clay, should be floored and faced with plank, 

 cement, or other hard material. Carp have a strong tendency to bury 

 themselves in the mud, not only during hibernation, but whenever 

 alarmed or pursued; If the collector has been constructed as suggested, 

 and the fish gradually drawn into it, danger of loss on this account will 

 be obviated. 



The details of the "overflow," "outlet," "collector," &c, may be 

 varied, according to the circumstances; but the general requirements 



