504 KEPORT OF COMMISSIONEK OF FISH AND FISHERIES. [38] 



be sufficiently loose, and all that is necessary will be to make holes in 

 the ground for receiving the shoots In old dikes and wherever the 

 earth has settled and become hard the hoeing should never be omitted. 

 5. Wood-cocering. — This method consists in ramming in piles about 10 

 centimeters thick at intervals of 1 meter along the Avater side of the 

 dike. These piles should be square, and back of them strong boards 

 are placed, whose edges must fit closely together. They may also lap 

 over a little, but in that case more boards will be needed. The places 

 where the boards join should not be one over the other. These boards 

 are nailed to the posts, which, in order to render them more durable, 

 are generally made of oak wood. BotJi the posts and the boards should 

 be covered with tar or creosote. Such wooden dikes, as they are called, 

 sliould not rise jjerpendicularly on«the water side, but must likewise 

 slope somewhat, the base of the slope to be at least one-sixth of the 

 height of the dike. Wood-covering, however, should be employed only 

 in case of urgent necessity, *. e., when no other material for covering 

 the dike can be obtained, for it is not only very expensive, but it is also 

 the least durable kind of covering, and requiring constant repairs. 



C. — Stone dikes. 



Unless constructed of square pieces of stone fitting closely together^ 

 stone dikes are the least practical of all dikes; but if constructed in this 

 manner they will be so expensive as to ])revent the laying ont of the 

 pond altogether. Dikes composed of earth and stones mixed will have 

 the least firmness, because the water will easily work a way for itself 

 between the stones. Such dikes mnst have a covering. Dikes com- 

 posed of a large number of irregularly shaped stones, placed closely one 

 upon the other, will still let the water pass through. The walls of the 

 dike, at any rate on the water side, should therefore be well built with 

 mortar and cement. Large stones, however, may well be used for fill- 

 ing out the dike, if there is enough binding earth to cover it, especially 

 on the water side. But, wherever a firm dike is needed, and where it 

 is impossible to construct an earth dike with any of the coverings de- 

 scribed above, it will be safest to build along the water side a strong 

 wall with a slope towards the water, and supported on the back by 

 stone pillars. Back of this wall the dike is constructed of stones and 

 sand as firmly as possible. Such a dike should be very broad, so as 

 not to be pushed back by the wall (against which danger the pillars 

 afford some, but not absolute, protection), and of corresponding height^ 

 so that during freshets the water may not overflow it and carry away 

 the back part, i. e., the dike proper. To make such an occurrence abso- 

 lutely impossible, it will be necessary to build a similar wall also on the 

 land side. In cases where the ditches furnish only gravel and sand for 

 the construction of the dike it will not be advisable to lay out a pond, 

 for the bottom of such a pond would not supply sufficient and suitable 

 food to the finer kinds of fish, esi)ecially the carp, and would not hold 



