264

HISTORY OF ENGINEERING.

Book I.

Aqueduct of Montpellier , is one of the finest works of the kind in France , and conductswater from the sources of St. Clement and Boulidou to the town of Montpellier . It wasbuilt in 13 years by Pitou.

There are two tiers of arches, the lower is 70 in number, their span is 27 feet S inches,the thickness of the piers 12 feet 3 inches. Those of the upper tier are only 9 feet. Thegreatest height of the aqueduct is 92 feet. It is entirely constructed of squared stone ; oneof its terminations is in the Place de Peyrou, which it traverses on three arches, wherethere is a reservoir. The total length is 3215 feet.

Aqueduct of Carpentras , on the Auzon, has 33 semicircular arches, 38 feet 4 inches span,and 12 lesser arches of 25 feet 7 inches, without comprising a segmental arch of 76 feet9 inches, on which it crosses the Auson. The thickness of the piers is 12 feet 9 inches.Its width is 7 feet 3 inches above and 17 feet below ; the greatest height is 82 feet, andthe total length 2560 feet.

Bridge of Dole , on the Daubs, begun in 1760, and finished in 1764 by Gu6ret, consists of11 elliptical arches rising a third, from 52 to 62 feet in span. The piers are from 10 feet8 inches to 11 feet 6 inches in thickness. Their foundations, 7 feet 6 inches below th«water, are supported by little piles about 13 feet long. The facings are of squared stone,and the bridge appears to have been carefully built.

A sort of false framework was constructed below bridge, and some jetties made roundthe piers; two, however, sunk, which has occasioned the fall of the corresponding arches.The piles which supported them had been entirely deprived of the materials which re-tained them, and it had been thought sufficient to place jetties round the piers, withoutfilling up the void formed in the interior of the foundation.

Bridge of Mantes, on the Seine , where the river is divided into two principal brancheseach about 360 feet wide, and one lesser branch : the old bridge, called that of Limay, was

Hi,

constructed on the first of these; the second, called l'ayol, from the name of the engineer,is composed of thirteen arches, comprising one for the towage ; there is also a third, withthe same number of arches, below which a new bridge was commenced.

Fig.273.

PLAN OF MANTES UKIDGK.

The stone employed was brought from the quarries of Saillancourt, Cherance andVetciul, all of which were of excellent quality. In Perronet’s work is shown the con-struction of the centres, and the methods adopted to supply the various material to theworkmen, which arc novel and interesting.

The cofferdam was formed in a similar manner to that constructed at Neuilly ; thepiles were shod with iron and driven with heavy rams, some with a force of half aton; and after the whole were placed, the dragging commenced, and was continueduntil all the mud and sand were removed; the machine used being that contrived