THE RIVER SEINE.

Between Montereau and Moret, for 12 kilometers, the Seine has a breadth of 100m to 110m. Between Moret and Paris the breadth is

from 140 to 170m.

The navigable condition of the Seine between Montereau and Paris, previous to the month of September, 1871, was powerfully influenced by the system of "éclusées" on the Yonne, so that for nearly threequarters of the year navigation was intermittent. This precarious and inconvenient state of things on a river of such importance as the Seine has ceased to exist since the month of September, 1871, owing to the construction of 12 barrages during the last few years, between Montereau and Paris. These 12 barrages are constructed on the Chanoine's system. The barrages at Melun have alone retained for the river the trestle and needle system in use on the right branch of the Seine.

Experience has led to the detection of some faults in the working of the original shutters, and a movable foot-bridge on trestles, with a plank flooring, has been constructed on the upper or head side of the shutter-weir.

MOVABLE SHUTTER-WEIRS ON THE UPPER SEINE ABOVE PARIS.

(Drawings and models.)

The barrages of the Upper Seine consist of two parts. A navigable passage from 40 to 50m and a weir of from 60m to 70m in breadth, provided with movable shutters. The two parts are separated by a pier, and a lock is generally joined to the barrage.

The sill of the navigable passage is placed 0.60 below low-water mark. The shutters are 3m in height and are level with the water, which gives 2.40 for the depth of the upper or head water above the low water mark.

A shutter consists of a wooden frame and of a wrought-iron trestle and prop; the trestle is a trapezium, strengthened by a cross-bar; the prop is a wrought-iron bar, and is intended to support the shutter and the weight of the head water. It is joined to the top of the trestle by a bolt, and the lower end abuts against a cast-iron shoe or catch, strongly imbedded in the flooring. This shoe, in the form of an inclined. plane, is inserted into two widened ears, and has a guide-bar, much bent, terminated by an ear. When it is desired to lower the shutter, the end of the prop is removed, and as soon as it leaves the front of the shoe it slides along the guide bar, while the tres le, turning on its base, falls with the shutter on the flooring. To raise it the base is furnished with a broad iron handle, with which the keeper connects a hook attached to a rope. Then, by means of a small winch fixed in a boat for this purpose, the various parts are successively raised, the breech, the trestle, and lastly the prop, the foot of which moves up the inclined

plane, and resumes its place against the shoe. The fall of water assists this operation to a considerable extent, since it tends to raise the frame of the shutter, of which the axis of rotation is placed at a certain height above the sill.

The operation of opening a passage is performed from the bank, and by the aid of the winch, in 3 seconds per meter run, the closing is ef. fected with a boat at the rate of 11 minutes.

The weirs of the Upper Seine are from 60m to 70m in length. They are leveled to 0.50 above low-water mark.

The self-acting shutters of the weirs are 2m in height by 1m.30 in breadth and are formed like those of the passages, according to the original system conceived by M. Chanoine, engineer-in-chief, i. e., to rise and fall of themselves.

Owing to the position of the axis of rotation, these shutters raise and lower themselves, this axis being only raised 0.05 above the third of their height; there is also a movable counterpoise.

The striking simplicity of this ingenious system of shutters, called selfacting, led to some isolated experiments being made in a single barrage. But the working of the system being more completely tested by its application to twelve weirs on the Seine, between Montereau and Paris, some grave miscalculations were made apparent. The self-acting shutters lowered themselves too quickly, and did not rise till after a lowering of one meter of the upper or head water.

A foot-bridge, composed of iron trestles on the Poirée system, was constructed above each weir to work the shutters. The counterpoises, being no longer useful, have been removed.

The new system has been a complete success. At night every keeper is warned of any variations in the upper water of the barrage, by the ringing of a bell put in motion by a float. In addition, all the barrages communicate with each other by telegraph, and the excellence of the arrangements precludes the possibility of surprise.

NEW NAVIGABLE PASSAGE OF THE PORT-À-L'ANGLAIS BARRAGE.

In consequence of fresh arrangements for establishing an uninterrupted passage by the Seine to Paris, it became necessary to lower by 1th the tail sill of the lock at Port-à-l'Anglais; this required, to sustain the increased pressure of water, a corresponding increase in the height and strength of the shutters.

The new shutters are 3m.70 by 1m (instead of 3m by 1m.20); the framework is simplified, the inclination increased from 80 to 20°, and the axis of rotation placed only 15cm below the axis of figure. Small butterfly valves have been contrived to prevent the shutters from turning spontaneously.

The shutters are worked from trestle bridge (Poirée's system), on which travels a winch.

(See page 688, Chief of Engineers' Report, Part 1, 1875, for more detailed description.)