[5] UTILIZING WATER BY FISH-CULTURE. 1105 



it is being constructed. A gravel or sand-dike of course resists the 

 pressure of the water as much as one constructed of clay, and all that is 

 necessary is to prevent the water from oozing through by providing a 

 strong layer of clay. The first work is to stake off the sole, or foundation, 

 of the dike, and clear away all grass, shrubs, &c. The same of course 

 applies also to the edges of the valley on which the dike is to rest. If 

 by this work an impenetrable foundation has been laid bare, the con- 

 struction of the dike may be commenced at once, but if marshy soil or 

 gravel has been brought to light, it will have to be removed along the 

 entire extent of the ground which the dike is to cover, until firm, im- 

 penetrable soil is reached, because otherwise the water would ooze 

 through below the dike, thereby occasioning not only a gradual decrease 

 of water in the pond, but also the slow but sure destruction of the dike. 

 As soon as suitable soil has been reached along the entire extent of the 

 dike, it is well, especially in dikes which are not very broad, to dovetail 

 the dike with the foundation. For, this purpose two or more ditches 

 are dug along the entire length of the proposed dike and parallel with 

 its edges, measuring about 50 centimeters in breadth and depth; the 

 bottom of these ditches is made broader that the top. Only after these 

 ditches have been filled with the same material of which the dike is to 

 be constructed, which is well pammed down, the construction of the dike 

 is commenced. If the main body of the dike can only be constructed 

 of gravel or other porous material, the ditch nearest to the waterside 

 should be filled with clay, and, as the building of the dike progresses, 

 the layer of clay, referred to above, should be begun on this tlitch and 

 continue through the entire dike. 



It is of the utmost importance for the durability of the dike to giveit 

 the proper degree of consistency and shape. The sole of the dike must 

 be twice as broad as the proposed height of the dike, and the top of the 

 dike should be half as broad as it is high. The slope and sole should, 

 ^therefore, form an angle of about 50 degrees. Steeper slopes are not 

 to be recommended, and there may be circumstances which make it ad- 

 visable to have an angle of only 45 degrees. The height of the dike 

 will, of course, be regulated by the proposed depth of water. To avoid 

 any damage to the top of the dike it may be well to make it a meter 

 higher than the normal height of the water. 



It is important to select a suitable season and favorable weather for 

 constructing the dike. If the material is to gain some consistency, the 

 work must not be done in frosty weather, nor when the weather is very 

 damp. If it is unavoidable to work during wet weather, the material 

 of which the dike is constructed must be thoroughly rammed down, 

 which, of course, is hardly necessary when the soil that is heaped up 

 is dry and loose. To guide the workmen the outlines of the dike must 

 be staked out at distances of 2 meters by poles and laths. (Plate 1, 

 Fig. 2.) 



It is absolutely necessary to have the work properly superintended ; 

 H. Mis. 67 70 



