880 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



other. To-day a piece of ground may be a field or fertile meadow ; next 

 year it will be found to be a productive pond, to serve again one or two 

 years later its first purpose. 



If the size of the principal and supplementary ponds has been de 

 cided on, the height, depth, and width must be measured, and the levels 

 of the ground and dams, if such are needed, should be caretnlly taken. 

 The leveling of the bottom is required to assist in the determination 

 of the depth of the ditches, " kettles," collector, and outlet to be dug 

 in it. 



In the erection of the required dam it is most important that it be 

 constructed of the very best material, so as to make it secure against 

 the destructive influence of the water. It ought to be three times as 

 wide at its base as it is high, and at the top the width should be the 

 same as the height. The interior or water side should be less inclined 

 than the exterior one. 



Before the foundation of the dam is laid, the ground where it is to 

 stand must be dug out to a depth of 2 and a width of from 4 to 5 feet 

 throughout the whole length of it. If the ground does not consist of 

 loam it must be filled up with it about 1 foot deep, and this must be 

 tamped down hard. A second layer follows and is disposed of in the 

 same manner. This is repeated, the clay being moistened every time 

 if required, and then beaten down solidly. This lower stratum is but 

 the foundation of the dam, which is formed from the earth dug out of 

 the pond or its vicinity. This is continued until the dam is completed. 

 Care must be taken, however, that the construction and tamping down 

 of this lower stratum be done in layers and that nothing but good clay 

 be used. In this manner the material of the foundation will become 

 a very tenacious mass, which will not allow any water to penetrate. 

 The completion of this laborious task will be a source of ultimate satis- 

 faction, as many disadvantages, which might arise after the filling of 

 the pond, will be done away with through its agency. The dam should 

 not be made entirely of clay, for in mid-summer, during the great heat, it 

 would dry out too much on that side most exposed to the sun, and con- 

 sequently it would become full of fissures, through which the water 

 would escape, and this might become disastrous for the establishment. 



On account of the required outlet-sluices, etc., the tact must be kept 

 in view, that such newly constructed dams will sink 10 per cent, after a 

 lapse of time of little more than a year, with the exception of that por- 

 tion which has been solidly made. The dam should be sodded. For 

 the draining of the pond, at the " fishing out " season, it should have an 

 outlet at the lower end, if no other advantageous arrangements can be 

 made for the purpose. The use of wood-work for the channel should be 

 avoided, its durability not being sufficient. The most desirable con- 

 struction would bo that the outlet channel consist either of masonry- 

 work or water-pipes, which maj' be made either of clay or iron. This 

 channel or pipe must be so made that it can be closed tightly or opened 



