252

HISTORY OF ENGINEERING.

Rook I.

eight new arches, built on the island which separated them, in a curved line, so as to unitethe two parts already existing ; these latter have many sinuosities, although no reason canhe assigned for such a deviation from the straight line ; the whole number of arches wasthen twenty-one, of about 180 feet span, and the total length was about 2953 feet.

In 1385, Eonifaee IX., who resided at Avignon , demolished some arches to ensure hisown safety : in 1410, the inhabitants of the town, to rid themselves of a Catalan garrisonwhich Benedict XIII . maintained, blew up the tower which defended the bridge; care-lessness in repairing a fallen arch, in 1002, caused the fall of three others, and in 1670 theRhone having been frozen, the melting of the ice threw down some more, leaving onlyfour entire on the side of Avignon , where the bridge is 21 feet above the soil, no othermeans of ascent remaining than that afforded by the natural inclination of the ground.The bridge is terminated at each end by two towers; on the Villeneuve side the ascent ismore than one in three. Its breadth is only 13 feet between the parapets, the thickness ofwhich is a foot. These circumstances render it doubtful whether carriages ever passedthe bridge, mules being formerly the only means for conveying burdens from one place tothe other.

On the second pier is a chapel formerly dedicated to St. Nicholas , patron of navigators,one part of which is supported on corbels. The piers are constructed of squared stone ashigh as the level of the river, and the rest of small rubble work; their upper part and thehaunches of the arches are pierced by round apertures. The remaining arches are wellpreserved; they consist of fine squared stones, 2 feet 10 inches high, and so disposed as toform four separate arcs, which in the first arch present no apparent connection ; there isonly one in the second, and seven or eight in the third. The heads are a little distancefrom the centre in the first; some iron cramps remain which united the arcs to each other.

Bridge of La Guillotiere over the Rhone, at Lyons, consists of eighteen arches from26 feet to 105 feet span; its total length is 1870 feet; its water-way 1204 feet. It washu’dt by Pope Innocent IV . during his sojourn at. Lyons, partly at his own cost, and partlyby granting indulgences to those who concurred in this useful enterprise. An inscriptionon a tower, since destroyed, preserved the memory of the fact; but on one of the squaredstones of the bridge, the following inscription has since been discovered: —

FOXTIFEX AN1MARUM FECIT FOXTEM PETRAXUM.

Pope Innocent having resided at Lyons about 12-15, the foundation of the bridge maybe assigned to that epoch. But the disparity which exists in the construction of the piersand arches appears to prove that they were built at different, and perhaps very distant,periods ; they are all semicircular.

Bridge of St. Esprit. — Its foundation dates from the year 1285, one hundred years afterthat of Avignon . The first stone was laid by the prior of the monastery of St. Saturninedu Port, and the original documents are found in the archives of the hospital; its con-struction was effected by the alms which the “Brothers of the Bridge” solicited through-out Christendom. It was completed in 1305; its plan is bent in three directions, andconsists of nineteen great arches and six small, which were afterwards constructed underthe ascent. The span varies from 80 to 109 feet. The total water-way is 2021 feet; thelength 2690 feet.

The piers are more than one-third the span of the arches which they support, and arecarried by a foundation of '•onsiderable breadth, presumed to be of rubble work. Theyare surrounded with starlings projecting 9 feet 9 inches, and rising about 6 feet 6 inchesabove low water ; they are formed by double courses of blocks, 6 feet 6 inches long, and2 feet 3 inches thick, and are further strengthened by jetties, which are maintained withthe greatest care. A tax was formerly imposed on salt ascending the Rhone, to defraythis expense as well as that of the banks above; in 1790 it yielded 28,000 francs, but ithas since been suppressed.

The slope of the jetties being one in one and a half, the surface of the water-way isrendered exceedingly narrow, notwithstanding the great length of the bridge, a seriousinconvenience, considering the rapidity of the current in Hoods, and even at ordinary times.The starlings do not overtop altogether the very high levels; there arc holes in the upperpart through which, however, the water but seldom passes.

The arches are constructed of squared stone, the voussoirs are disposed so as to form fourseparate arches, united at every four courses by an intermediary one of only three stones,and their thickness is 5 feet 11 inches. The bridge is very strongly constructed,and the only injury that has hitherto occurred to it are some slight settlements inthe first arch on the town side; its breadth is 17 feet 6 inches, but that of the roadwayis reduced by the parapets, to 14 feet 11 inches: this is not wide enough to allow of twocarriages passing easily, on account of the great length of their axles. From this cause, orfrom fear of other injury being sustained, the passage was not freely opened to the public ;the waggons were unloaded before they were permitted to pass, and the goods transported