556 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



through the dam at its lowest point. It usually consists of heavy 

 hollowed logs, imbedded in soft moss. These will last much longer if the 

 bark is uninjured. It may also be constructed of bricks, or of earthen- 

 ware pipes, with cement. On the water-side it passes through sheet- 

 piling, or a cemented wall, and is closed by a plug, or better, by means 

 of a drop- valve, which can be opened by ay rod with a screw attached. 

 A stand-pipe is also often placed vertically upon the horizontal discharge- 

 pipe. It is closed on the front, from the bottom to the water-level, with 

 sluice-boards placed on top of each other. These may be placed in posi- 

 tion or removed at will, according as it may be desired to raise or lower 

 the water in the pond. Where small streams flow through the pond, 

 this arrangement affords the additional advantage of keeping the depth 

 of water uniform, since it flows out over the top board through the 

 drain-pipe. A wooden grate is placed at the entrance of the drain- 

 pipe, to prevent the fish from passing into it. It is entirely sub- 

 merged to preserve it from decay. Iron grates are altogether unsuit- 

 able, ou account of their rapid destruction by rust. The fish-pit is an 

 excavation in which the fish collect when the pond is emptied. It must 

 be capable of being completely drained, and in loose, soft soil it is well 

 to line it with wooden or stone walls, and give it a firm bottom of sand, 

 stone, or boards. The greatest attention should be given to the fish- 

 pit, and it should be carefully freed from all mud whenever fish are 

 caught. It is also advisable to form a pit, called in Bohemia the sluice- 

 pit, at the outlet of the drain-pipe, in order to catch any fish that may 

 escape through a defective grate; and for this reason it should also be 

 supplied with a grate at its outlet. When the ponds are large, this is 

 lined with wood or stone. It should be kept full of water that the dis- 

 charge-pipe may be preserved from decay. After some time the flow of 

 water renders the interior of the drain-pipe so rough that the fish are so 

 injured in their passage through it, that it is very undesirable that they 

 should be found in the sluice-pit. The bottom of the pond is traversed 

 with ditches, so that the water may flow off freely and rapidly from all 

 sides, and the fish find their way easily into the fish-pit, and also that 

 the rich, muddy soil may dry off rapidly, and soon permit the passage 

 of draught-animals over it, if the pond is to be put in order. Depres- 

 sions in the pond, from which the water cannot be completely drained, 

 are very objectionable, since a great number of fish are lost in them, 

 and the removal of the predaceous fish is prevented. No trouble should 

 therefore be spared to drain such depressions. If the supply of water 

 is such that the pond can be filled with certainty in the spring, it is 

 well to allow it to become dry after the fall fishing, in order that the 

 soil may be freshened, and a portion of the enemies of the fish may be 

 destroyed. Ponds which are supplied exclusively by rain or snow water 

 must be filled again in the fall immediately after they have been emptied. 

 The water from villages and cultivated land is very advantageous, on 

 account of the nutriment contained in it, and in Wittiugau ponds are, 



