122 Modern Fishculture in Fresh and Salt Water. 



In this case make a sliding groove for the dams, which 

 may be hfted one by one, and are kept down by pins or 

 wedges at the top. 



Tile-pipe are not good for drains. I have laid them 

 and relaid them many times, cementing them most care- 

 fully and then reinforced the joints with another coat- 

 ing of cement, but tree roots would force their way in 

 somehow and either fill the pipe or break it. At Cold 

 Spring Harbor, New York, I piped a spring from an 

 upper level in six-inch tile-pipe, and it filled up with 

 roots. In one case the root of a locust tree had found 

 an entrance, and while only as thick as a sheet of letter- 

 paper and half an inch wide where it went in, we took 

 out thirty-seven feet of branching, matted roots, which 

 nearly filled the pipe. Then I had the pipe relaid with 

 extra care, but to no purpose; the roots would have 

 water and knew how to get it, even where there was no 

 leak. Here is a chance for a question about the habits 

 of tree roots in their search for water; but having 

 fought this "instinct" of roots for many years, I have 

 given up trying to solve the riddle. 



Remembering these things, when we obtained an- 

 other spring to bring down I bought four-inch iron 

 "soil pipe," caulked the collars with oakum and then 

 ran lead around- on the oakum. After this the lead 

 was caulked, and the pipe will carry water for a cen- 

 tury without interference from roots. This method, 

 and pump logs, are the only means I know of to con- 

 vey water underground without interference from 

 roots, if there are trees near. A willow or a locust 

 will send roots a hundred yards for water, if it is there, 

 while on the other side of the tree the roots might not 

 extend fifty feet. 



It is said that iron-filings mixed with cement will 



