1106 EEPORT OF COMMISSIONER OF FISH AND FISHEEIES. [6] 



care should also be taken that no wood, roots, and other articles get 

 in the dike, which would gradually decay and cause the dike to shrink 

 in some places, thus diminishing its firmness, and making it possible 

 for the water to enter. Along the scarps and on the top of the dike 

 the soil must be well beaten down, or rammed down. After the dike 

 is finished it will take it some time to settle. No water should be let 

 into the pond till one-half year after the dike has been completed ; and 

 if the dike is large, one whole year should be allowed. 



While the earth of which the dike is constructed is heaped up, the 

 outflow pipe, to which I shall refer further on, must, of course, be in- 

 serted and well rammed down in a bed of clay. 



To protect the dike it is absolutely necessary to cover its scarps. The 

 simplest way to do this is to use square pieces of turf, cut regularly, 

 measuring from 30 to 40 centimeters on each side, and 10 to 15 centi- 

 meters in thickness. For this purpose thickly-grown turf should be 

 selected, with short fine grass, taken from black meadow-soil. The sod 

 had best be cut in moderately moist weather, and be laid, beginning at 

 the sole of the dike and progressing towards the crest, in such a manner 

 that the different pieces are joined closely together, the perpendicular 

 sides of the pieces of one row always standing in the middle of the 

 pieces of the contiguous row, on the same plan as bricks are laid (Plate 

 I, Fig. 3). 



The lowest row Is embedded in the ground. On the pond side of the 

 dike, which to distinguish from the other side or the back is generally 

 called the front, it is well to make the cover of the dike uij to the level 

 of the water of fibrous peat, wherever such can be obtained, as the grass 

 will generally die under the water, and the decaying of its roots will 

 tend to loosen the soil of the dike. The pieces of peat may be cut 

 larger and have a thickness of about 10 centimeters ; they will form a 

 strong and durable cover which is not liable to decay. Both sod and 

 peat are fastened to the dike with pegs. For this purpose it is advisable 

 to use live branches of the basket willow, which soon take root and cover 

 the scarp with a dense growth of willows whose branches may be cut 

 at stated times and be used for wicker work (Plate II, Fig. 4). The best 

 willows for this purpose are the Salix viminalis, and for sandy or grav- 

 elly dikes the Salix caspica. To keep the dikes in good repair, it is nec- 

 essary to examine th'em frequently, and immediately to repair any dam- 

 age, however small. Whenever the water has been let off, the scarps 

 of the front of the dike should be carefully examined, and repairs made 

 at once wherever needed. 



The bottom of the pond should slope towards its deepest place near 

 the dike, and should be as smooth as possible. Holes in which the 

 water might be retained, when the pond has been drained, should be 

 filled up as much as possible. A porous bottom can be made impervi- 

 ous by placing on it a thin, even layer of clay. In large ponds a well- 

 defined pit of even depth (the fish pit) should be dug close to the dike j 



