Chap. VI.

FRANCE.

277

M. Becquey de Beaupre, and executed by M. Vigourcux; it was finished inconsists of nine principal semicircular arches, 59 feet in span, and twolesser 16 feet 4 inches in span for the towing path. The thickness ofthe piers is 11 feet 5 inches; the width of the bridge 42 feet 7 inches.

It occupies the situation of an old wooden bridge, and the axis is inthe direction of the dome of the Invalides. The piers were foundedby means of caissoons. The arches were constructed on trussedcentres, which did not change their form during the placing of thevoussoirs.

All the arches were keyed in July, 1815, except the first on theright bank, where there still remained fourteen courses of voussoirs toplace, when orders were given to break dow’n the bridge, and thecentre of this arch was first set on fire, and the fourth blown up bytwo discharges, which caused the rupture of some of the innervoussoirs of the arches, and it was afterwards discovered that settle-ments had taken place in the third, fourth, fifth, and sixth piers, thegreatest of which was 2^ inches. In 1818, the sixth pier was loadedwith 112 tons, without any movement resulting; it was thought fit,however, to discharge the weight by means of arches in the piers.

The foundation piles were 3 feet 11 inches apart, and each carried aweight of fifty-two tons; the voidings, however, diminished this weightby about five tons and a half. A general foundation was also con-structed by throwing in rubble. The settlements are attributed tothe effect of the explosions; but they would not, perhaps, have takenplace had the piles been less loaded, or the intervals between thembeen filled in with hydraulic masonry to a height of 6 or 8 feetbetween the ground and the tops of the piles, instead of with ma-sonry laid in common mortar, which does not harden under water.

In this beautiful example, the roadway is kept perfectly levelthroughout, and the arches are all of the same span; this was ren-dered necessary, as the banks on each side of the river were low, andit was not deemed advisable to raise the crown of the roadway, whichmight have been done on the Paris side, but towards the town ofSevres , it would have been more difficult to accomplish, as thehouses on each side of the street, and the entrance to the royal park,would have been equally inconvenienced. The piers, all of the samedimensions, are of great strength, their width being nearly equal toa fifth of the span of the arch.

The faces of the voussoirs, which are rusticated and rounded,increase in depth towards the springing; the effect is improved by thisarrangement, and we have an additional strength given where it ismost required.

For the piers, abutments, and arch stones, the best stone whichcould be obtained was made use of, and apparently the atmosphere hasproduced little change upon it: as the stones laid in the quarry, soare they bedded, and their dimensions and proportions are well definedfor their respective situations. In the spandrills and wing-walls,there does not appear to have been sufficient attention paid to thebacking, and inferior material is said to have been used.

This bridge, which has a decidedly Roman character, is one of thebest where semicircular arches have been preferred to the elliptical;the same centre would serve for all the arches, and there is someeconomy in such an arrangement ; but the piers occupy togetherupwards of 90 feet, while the breadth between the abutments orwater-way does not exceed 622 feet: by the adoption of a flatterarch, fewer piers would have been required, and consequently morewater-w'ay would have been obtained: but the whole is deservedlymuch admired, and its design seems in harmony with the sceneryaround, and with the character of the river: over a stream where rthe tide rose considerably, or the navigation was more important, ]

bolder design might have been introduced.

The elevation and section through the piers show its solid con-struction, and the form also of its starlings: over the arch are wellcontrived drains, which lead off the waters that fall upon the road-way, and conduct them behind the spandrills into the stream below:the blocking course, which forms the parapet, is supported upon abold block cornice, and the absence of all balustrade and railing

t 3

1820, and

i

Fig. 285. BRIDGE AT SEVBES.