512 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [46] 



might be damaged, the pipes sliould extend 2 or 3 meters into the pond, 

 and project about 1 meter on the land side. When laid, the pipes should 

 be well enveloped in clay on all sides, so that the water may not force 

 a passage by the side of them ; for this will always be the place where 

 there is danger that the water may escape from the pond. These pipes 

 are made of the trunks of trees which are split in half and hollowed 

 out ; another half trunk, likewise hollowed out, is used for the upper 

 portion, or lid ; as soon as the lower one has been laid, the upper one is 

 placed on the top of it. They should, of course, fit accurately. For 

 this purpose a layer of fine moss is made, carefully cleaned of roots, 

 branches, stones, &c. Such pipes can hold a good deal of water, and 

 are, especially in large ponds, the safest means of supplying an exit for 

 the water. If made of sound pines felled during winter, they will last 

 for centuries, provided that they are constantly kept under water. As 

 the laying of the pipes always necessitates the digging up of the dike, 

 durability should of course be the first consideration ; for this labor in- 

 volves many inconveniences and considerable expense. The width of 

 bore of these pipes should be regulated by the size of the pond, so as 

 to allow the water to flow off in a suitable period of time. As a rule, 

 however, the bore should not be wider than 30 centimeters, particularly 

 as the water is apt to widen it in course of time. In large ponds there 

 should be two, three, or more of these pii)es, which should be laid at 

 such distances from each other that for the purposes of repairs one of 

 them can be dug up without interfering with the others. 



In small, remote ponds, which are apt to be visited by fish-thieves, 

 the openings of the pipes should be narrow, so that the water cannot 

 flow off quickly, and requires more time than fish-thieves generally have 

 at their disposal ; for it will of course be easier to steal fish from a pond 

 which can be drained in four to six hours, therefore in one night, than 

 from one which takes from twelve to twenty-four hours. 



C. — The staxd-pipe. 



This consists of a second pipe placed vertically on the exit-pipe. This 

 pipe is likewise made of a hollow trunk which is open on one side,where 

 grooves run along its edges in which small boards can be inserted, and 

 easily removed. The vertical pipe should project somewhat over the 

 dike, so that the pond may be filled to any desired height. According to 

 Jokisch, vertical pipes are also employed which are only as high as the 

 average height of water in the pond (especially in ponds which have a 

 constant supply of water). Such pipes are left open at the top, so that 

 the small boards reach as far as the other sides of the pipe. The upper 

 square opening is covered with a grate, so that the water when it rises 

 above its normal height may flow off without carrying any fish with 

 it. The same author says that a better contrivance of a similar char- 

 acter may also be connected with the common vertical pipes. They are 

 allowed to rise as complete pipes (not halved), and only a little above 



