Meuse, and other French rivers. The details of all the methods in use in France are given in full in the report of the Board of Engineers on movable dams and hydraulic gates, which is printed as Ex. Doc. No. 127, H. of R., 43d Cong., 1st sess.* The system that meets with most favor in France is that known from its inventor as the Chanoine. A drawing of the more important features of this system accompanies this report. The Brunot gate will probably be a useful auxiliary to this or any other system that may be adopted, and I had expected to have an opportunity of testing its practicability on a working scale before the meeting of Congress. As it has been decided that money appropriated for the Ohio cannot be expended on a dam in the Monongahela, this trial has necessarily been abandoned. While I regret this, I do not consider that its lack will have any influence on the method of movable dam that may be selected for use.

It

There is nothing to prevent the subsequent trial and adoption of the Brunot gate on one of the movable dams should it seem desirable. is merely a useful adjunct at best, and not an indispensable necessity. A Chanoine wicket, when in position, is a solid frame of timber about 3 feet wide and 13 feet high, sloping down stream and supported behind by a heavy iron prop. The horse is hinged to the wicket and to the floor. The prop turns on the upper axle of the horse, as does also the wicket. The latter is not fastened to the floor except by the horse, and can swing around the upper axle of the latter when not held down by the pressure of water. A series of such frames or panels makes the dam. The intervals between the frames are about 2 inches, and if it is necessary to make the dam tight these intervals can be covered. Usually the waste through them will be less than the discharge of the river, and therefore the level of the pool will not fall below the tops of the wickets.

The dam is thrown down by means of a long iron bar laid on top of the masonry-base, extending from one shore to the other, and armed with projections or shoulders. By moving this rod a few feet, which is done from the abutment by proper gearing, the feet of the props are tripped successively, and the wickets fall into a shallow recess where they are below the reach of passing boats. The river is then in its natural condition, offering no obstacle to boats nor to the passage of floods. In the navigable pass nothing projects higher than 2 feet below low-water line. On the weir the height of masonry is usually about 20 inches above low water.

The wickets are raised in succession by the use of a boat which works across the stream. It has a sheave in its bow, and a geared drum near the stern. The first wicket is raised by the boat being so placed that its bow projects beyond the abutment half the width of a wicket. The hoisting rope has a boat-hook fastened to its outer end. The man at the bow hooks the boat-hook over a handle at the lower end of the wicket, and the other man then winds up the rope. The wicket is thus raised, pulling up with it the horse and the prop. When the horse is at its proper elevation the prop drops into position. The wicket is still nearly horizontal, and if it is let go it will retain an inclined position with the water rushing under it. A slight push on its lower end brings it against the sill, and the water pressure holds it in place. After one wicket is raised the boat is pushed out the width of a wicket, supporting itself partly against the abutment and partly against the wicket first raised. This operation is continued until all the wickets are in place.

* See Appendix N 3.