JOURNAL OF THE FRANKLIN INSTITUTE OF THE STATE OF PENNSYLVANIA FOR THE PROMOTION OF THE MECHANIC ARTS. FEBRUARY, 1851. CIVIL ENGINEERING. Improvements of the River Seine. By GEO. R. BURNELL.* Some very important works are in progress at present upon the river Seine, for the improvement of the navigation of that river, a succinct account of which is appended. The Seine has a very long devious course, principally through a valley in the tertiary limestones of the Paris basin, and through the chalk between Mantes and the sea. It is very subject to floods in the winter and spring, which come down from the hills of Burgundy with considerable violence; whilst in the summer it is often so low that, as in 1842, the navigation by barges drawing 4 feet water is suspended. The tide runs to a little beyond Pont de l'Arche, a distance of perhaps 60 miles. Owing to the configuration of the embouchure a bar is formed at Quillebœuf and Tancarville, at a point where the river-which had previously spread out on both sides over a flat alluvial plain, sometimes bare at high tides-is contracted between two advancing spurs of the chalk formation. Formerly the regime thus superinduced was such as to give rise to a "bore" of about 3 to 4 feet high occasionally; but at neap tides there was never enough water on the bar to allow a 400 tons' burden ship to mount the river, although directly the stream became narrowed above Villequier, sufficient depth to float even a 1000 ton ship existed at high tides. The objects proposed then were to deepen the river so as to allow large vessels to reach Rouen, and to establish such a system of locks, &c., in the upper portion, as to ensure a constant depth of 6 ft. 6 in. in the driest From the London Architect, September, 1850. VOL. XXI.-THIRD SERIES.-No. 2.-FEBRUARY, 1851. 7 seasons as far as Paris. The works already executed have succeeded most remarkably in the attainment of these objects as far as they bore upon them. They are as follows: Tidal Portion.-Up to August, 1850, they had been confined to the embankment of the river between Candebec to Villequier and Quillebœuf, by means of rubble-stone embankments of length of 18,000 metres on the right bank, and of 9600 on the left bank. At the point where the works commenced the channel was made 300 metres (1000 feet) wide; and it was augmented 10 metres in a kilometre, or in the ratio 1 100 to the embouchure. The concave embankment was found to require twice as much stone as that upon the convex side, the former taking 100 metres cube, the latter 50 metres cube, per metre forward. The result has been to deepen the river 2·80 metres (a little more than 9 feet). The "bore" has disappeared in the parts regularised; the length of the duration of the flood tide increased one hour; the still water, or dead tide, has also gained a quarter of an hour. The flood would be sent much further up the country did not the stone thrown to protect the feet of the piers of the Manoir Bridge, on the Rouen and Paris Railway, act as a dam to keep it back. It is probable that the result of the works in the river upon this bridge will be to throw it down. The total cost of the embankments has been hitherto 2,310,000 francs, or 92,4007. sterling, being at the rate of 3 francs the metre cube of stone in place. To complete the project, it would be necessary to execute above Candebec and la Meilleraie 5122 metres of embankment on the right, and 8700 upon the left shore. Below Quillebœuf it is proposed to continue the channel through the sandbanks of the embouchure, by the execution of 12,540 metres on the right bank, and 9600 upon the left. Natural Water Course above Tides.-The system adopted for the attainment of the depth required in this portion, has been to erect a series of barrages or weirs upon the river, so as to divert the water into the arm rendered navigable, and to leave an overflow under the control of the locksman at the head of the pond or reach. The weirs are formed according to the plan so successfully applied by M. Poirée at Bezons, consisting of a series of wrought iron frames with wooden blades to close the openings, fixed by hand; the wing walls are in stone, and dressed off at a level to allow any flood-water to overflow at 6 inches above the depth required in the lock, should any sudden flood come down by night. The locks are made 120 metres long by 12 metres wide (400 feet by 40 feet), and a fall of 2 metres, or 6 ft. 7 in. nearly. Originally it was proposed to form at least ten of these barrages. The first is formed in Paris itself, and is actually in course of execution; the river is being inclosed to a width of 32 metres in the narrowest part, beginning from the extremity of the Isle de la Cité, and terminating at the extremity of "terre Plein" of the Pont Neuf. The wing walls of the dam are dressed off at a height to secure 2.16 metres water; the barrage is meant to heap them up to 2.26 metres; but of course before arriving at this height, some of the blades would be drawn. Quay walls and roads, with inclined approaches from the upper level, are being formed; a large culvert, 2.50 metres wide by 2.50 metres from invert to key, is also constructed to take off the lateral sewers to a level below the locks. These works are estimated to cost 200,000l. sterling. Connected with these works may be cited the lowering of the roadway of the Pont Neuf, to cost 72,000l. The old arches are cut away where necessary, and replaced by new arches of an elliptical form, the space between the new and old work, where any exists, being filled-in with hydraulic lime concrete. The scaffolding employed is very remarkable, being in fact a suspension scaffolding, hanging from the turrets on the piers of the bridge. Indeed, it would be impossible to imagine how works could be so carefully, so perfectly, and so elaborately executed, as all these are, unless by French engineers, working with government money. Other barrages have been executed at Bezons, Andresy, and Vernon; one at les Poses, near Pont de l'Arche, is in course of execution. Barrages are to be formed immediately at St. Ouen Meulan; others are proposed at Suresnes, Maisons, Triel, and perhaps others below Meulan. The barrage executed at Bezons, at a cost of 70,000l., gave a surelevation of 120 metres (4 feet) at a distance of 7 miles from the locks, the fall of the river being on the average 0.10 per kilometre, or 1 in 10.000. The heaping-up of the waters by the barrage of Andrésy is felt in the Seine and Oise, at a distance of 20 kilometres, or 12 miles. At some future day I will send you drawings of the barrage of Bezons, which will illustrate the very simple, but efficient means employed on this river, to canalise it completely. Southampton, Oct. 23, 1850. Ventilation.* Sir John Walsham has devised a very simple plan for ventilating workhouses, and which has been most effectual in the several unions where it has been introduced, and would, no doubt, be equally available for hospitals, factories, or workhouses. It consists of zinc tubes, three inches in diameter, perforated at the sides, towards the bottom, with holes of th of an inch diameter, which are carried across the ceiling of the room, sus pended by hooks, and taken through the walls to the open air, where they terminate in perforated convex ends, provided with caps, hung by a small chain, to cover the end most exposed to the wind in extremely cold weather. Three tubes will suffice for a room 23 feet by 16, or in that proportion for large apartments, intervals of about 10 feet in the length of the room being ordinarily the just medium. They can be fixed at 5d. per foot run. Mr. Bridgham, master of the Loddon union-house, describes them as most beneficial, particularly in the sleeping rooms. "The inmates are much pleased with them-many were fearful they would take cold from them; they are now satisfied that there is not any draft occasioned in the room by them." In the Bishop Stortford union, "in a sick ward, with cases of a loathsome and offensive kind, tainting the air to such an almost incredible extent that few gentlemen of the committee would go into it, the effect was so good, that the guardians gave an order to ventilate the whole house." From the London Architect, for November, 1850. |