CHAPTER IX. 



DRUM WICKETS AND BEAR-TRAPS. 

 DRUM WICKETS. 



THE drum wicket was invented by M. Desfontaines, and applied first in 1857 at 

 Damery, on the Marne, a tributary of the Seine. After its success was assured, others 

 were built on the same river, the best known being that of j uinville, finished n 1867. Other 

 examples are to be found in Germany, generally as sluices, their lengths varying from 

 17 feet to 39^ feet, with depths of water on the sills from 5.6 feet to 9.2 feet. Only 

 one example is to be found in America, of modified design, that upon the Osage River, 

 in Missouri, where a total opening of 750 feet is closed by 10 wickets, each 75 feet long, 

 in one piece, the sections being separated by masonry piers. The depth on the sill is 

 7 feet. There has also been built a lock-gate of similar design, for lock No. 2 of the 

 Mississippi River, near St. Paul. 



Description. The Desfontaines wicket consists of two diaphragms in approx- 

 imately the same plane, one above and one below, joined together and turning on a 

 horizontal axis. The upper one is exposed; the lower one works in a closed chamber 

 which is filled or emptied by culverts closed with valves. To raise the dam the water 

 from the upper pool, which must have more or less head, is admitted to the chamber, 

 and by pressing on the lower diaphragm, causes the whole wicket to revolve, thus 

 raising the upper diaphragm. To lower the dam, the water in the chamber is allowed 

 to escape, and the water of the upper pool pushes over the upper diaphragm and 

 forces it down behind its sill. The operating valves are always placed on shore, so 

 that the pool can be regulated from the bank. The lower arm is usually made of the 

 same length as the upper one, or a little longer. 



Owing to the existence of the chamber, which requires a certain depth of founda- 

 tion, and to the necessity of a head of water for operation, these wickets have only 

 been used for weirs. 



Joinville Dam. -The pass of this dam is 39.4 feet long, and is closed by needles. 

 The weir, which has a length of 206.7 feet, is closed by 42 drum wickets 3.3 feet high 

 above the sill, placed side by side, each wicket being a little less than 5 feet long. They 

 are separated in the recess by cast-iron diaphragm plates, built in the masonry and 

 pierced for the openings required for the admission and exit of the operating water. 



The entire weir can be raised or lowered in a few minutes, and against a full head 



of water, one wicket rising or falling after another until all are maneuvered. 



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