a6> 



THE IMPROVEMENT OF RIVERS. 



feet high above the sill. It was so badly projxtrtioned that it proved a failure, after 

 having cost $488 per lineal foot to construct, ami as a result the type was gener- 

 ally condemned. In the last few years, however, other examples have been built in 



America <>f lengths from 14 feet to 120 feet 

 and t>f heights from 7 fei-t t'> i t feet, and have 

 shown that with pn>]>er designing the bear-trap 

 is a valuable device. 



Description. The bear-trap, as usually 

 built, consists of three varieties, the original 

 or "old" type, the Parker, and the Lang. 

 The first consists of two straight leaves, hinged at the liottom, the up-stream leaf over- 

 lapping the down-stream one when lowered, and when the water is introduced underneath 

 it pushes up both, the end of the latter sliding along and helping t'> push up the former. 



In the Parker type the up-stream leaf is divided into two parts, hinged together, 

 so as to save width in the foundation, and the tops of both leaves are hinged together, 

 thus avoiding the sliding friction of the old type. Sometimes the down-stream leaf 



SECTION OF OLD BEAR-TRAP DAM. 



SECTION OP PARKER BEAR-TRAP DAM WITH 

 IDLER LEAF. 



SECTION OF LANG BEAR-TRAP DAM. 



is divided instead of the up-stream one. in which case the structure is known as the 

 reversed Parker. 



The Lang gate is the same as the Parker, except that the upper part of the 

 up-stream leaf is replaced by a chain, and the opening covered by a sliding ' ' idler " leaf. 



Many other varieties have been proposed, but, with the exception of one built for 

 a regulating-weir on the Chicago Drainage Canal, none has come into use. 



The following gates have been constructed by the United States and are still in 

 operation. One or two others were also built, but were subsequently removed. 



Parker Gates. One on the Muscle Shoals Canal, Tennessee, built in 1892. Length, 

 40 feet; height, 8.5 feet. 



One on the Louisville and Portland Canal, Kentucky, built in 1897. Length, 40 

 feet; height, 15 feet 3$ inches; made of steel. 



