650 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



even during a dry season, and that vegetation seemed to flourish more. 

 In very damp seasons such fields may even have a hurtful excess of 

 moisture. For a light soil, neediug a good deal of moisture, ponds are 

 decidedly beneficial. 



" AVhen ponds are laid dry the consequences are similar to those 

 attending the destruction of forests. Fortunately ponds are more easily 

 restored than forests. If it seems profitable to change ponds into fields, 

 the dams should at least be left. In the district of Militsch, e. g., large 

 ponds have been laid dry and changed to fields ; on some farm-houses 

 have even been built. A few of these ponds could again be restored to 

 their original condition, but with many of them this was absolutely im- 

 possible, although they yielded very little profit as fields, while as 

 ponds they had proved a source of considerable income. Similar ex- 

 periences have been made in Bohemia, where there is an unusual number 

 of large ponds. 



" Whenever ponds are laid dry, the dams should, therefore, be pre- 

 served, and no buildings should be erected, and it will be easy to re- 

 store them whenever it should be deemed advisable. 



" It is profitable to use the ponds from time to time as fields, because 

 it proves favorable to the growth of the fish, and because the grass or 

 grain planted in the ponds needs no manure. When ponds do not re- 

 ceive sufficient food for the fish from rivers or brooks, as is the case 

 with very large ponds, it will be advantageous to introduce a regular 

 system of rotation, and use them, e. g., three years for raising fish, and 

 then three years for raising grain or grass. 



" It is of course understood that in constructing ponds it is indis- 

 pensable to have a sufficient quantity of water. In large ponds this 

 quantity is very considerable, and the entire contents of large rivers 

 are required. 



" Thus in Lorraine the Ehine-Marne Canal is used for this purpose, 

 as also the Seille and the Saar ; in the district of Militsch, the Bartsch ; 

 in the district of Bothenburg, the aSTeisse, Spree, and the Schops ; and 

 near Peitz, the Spree. 



" For small ponds, especially those used for raising carp, it is not ad- 

 visable to have them fed from rivers, because other fish — particularly 

 pike — get into them and destroy many carp. For hatching-ponds the 

 so-called sky-ponds are the best, i. e., those filled by rain and snow 

 water." 



