510 REPOET OF COMMISSIONER OF FISH AND FISHERIES. [44] 



and c d, are rammed in, and connected by a cross-beam of equal strength, 

 If. The opening should be tolerably wide, esi^ecially where much water 

 flows into the pond. The bottom should be covered with strong pieces 

 of wood, or with masonry, up to a level with the average height of the 

 water. On this foundation rest strong movable boards, g, h, i, which 

 should tit so exactly in grooves in the posts that no water can pass 

 through. The two posts a b and c d must be so firmly connected 

 with the dike, or with the banks of the stream, that the water cannot 

 possibly force a passage between the posts and the sides of the dike. 

 Instead of making grooves in the two posts a h and c d two posts 

 may be j^laced on each side so close together that the spaces between 

 them form grooves for the boards. In that case the posts should be so 

 close together that no water can pass between them and the boards. 

 The lowest board shouki fit exactly in a groove in the strong beam on 

 which it rests. It will, of course, depend on the accuracy with which 

 all this work is done whether the flow of the wjiter can be properly reg- 

 ulated. The foundation beam, with its groove, should always be secured 

 by iron clami)S, so as to resist any pressure of the water. If one board 

 is not sufficient, another one, or several, one above tlie other, should be 

 used. Suitable contrivances should be connected with the cross-beam 

 Z/for raising and lowering the boards. The easiest way to do this is to 

 make the cross-beam iu the shape of a roller, as shown in the figure, or 

 to place a roller immediately below the cross-beam. The roller and 

 the boards are connected by a chain, A-, so that by turning the roller by 

 means of the lever j the boards can be raised or lowered. When the 

 boards have been raised to the desired height, the lever is fastened to 

 the post c d by the chain m, and secured in its position by a padlock, w, 

 so that the arrangement cannot be tami)ered with. If the weir is very 

 broad, it may be well to ram down in the center one or two posts of equal 

 strength with the side posts, and use only short boards, which run in the 

 grooves formed ])y these center posts. These short boards are easily 

 raised and lowered and may be recommended because the water can 

 be more easily regulated by them, as it will not be necessary to open 

 the entire weir. In order to give firmness to the whole, strong jiosts 

 should be laid close together at the bottom of the weir, and reach up to 

 the first board. In order to prevent the water from washing out the 

 holes underneath the weir, and thereby forcing a passage (which might 

 easily happen if the weir was placed directly upon the ground), the ground 

 below the weir should be covered for a length of 2 to 2.5 meters, or more, 

 with strong posts and boards forming a firm floor, so that the superflu- 

 ous water may easily flow ofl" along this floor. Such weirs are, especially 

 in large ponds, the safest and simi)lest means of regulating the water. 

 If it is impossible to carry off the superfluous water of a brook or stream 

 passing through a pond by means of outside ditches, it should be allowed 

 to flow in over a weir, so as to direct it towards the exit by the shortest 

 road, so that the fish may not be disturbed or carried away by it. It 



