DRUM WICKETS AND BEAR-TRAPS. 267 



before the other, and twists and strains -the leaves. Racks and pinions have been 

 tried to reduce the tendency, but without much success. The most rational method 

 of guarding against it would be to provide a culvert running the whole length of the 

 foundation, so as to admit the water simultaneously through several openings, thus 

 equalizing the pressure. It has also been suggested to use large separate pipes instead 

 of a culvert and openings, each pipe being controlled by a valve on shore. By this 

 means the pressure at any point could be regulated as desired. It has also been found 

 desirable, for similar reasons, to form the hinges of long pieces, or shafts, instead of short 

 pins, since with this construction the tendency to twist is more easily overcome. 



