Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/379

EXAMPLE] P> R I D G E S 333 ill the four towers of the bridge. Tlic bridge lias 29 j on each face. The roadway is 11 feet wide over the centre FIG. 115. Old Bridge at York. arches of 50 feet span, and the pillars are 25 feet thick. In the illustration the arches are Moorish, and the covered sideways lofty, with 3 arches of small span over each main arch of the bridge. The design is remarkably fine. Heck calls it the bridge of Barbaruh, and states that it is named from its builder, but it is of unknown antiquity. All the bridges of Ispahan are said, in the 7th edition of the present work, to have been built under Shah Abbas I. (1585 to 1G28). Heck mentions a bridge at Loyang in China, said to have a length of 2G,80U feet, and another at Focheu 22,000 feet long, both from GO to 70 feet wide. 7G. 1700 to 1817. Old Westminster Bridge (Labelye) and Old Blackfriars Bridge (Mylne), both of which have now been removed, were built in the middle of the 18th century. Their failure after so short a period was due to a defective system of foundation and to the increased scour caused by the removal of old London Bridge. The Pont-y-tu-Prydd over the River Taff near Newbridge is shown in fig. 117. The arch measures 140 feet between the abutments, and has a rise or versed sine of 35 feet. The width of the soffit is 15 feet 10 inches at the springing, diminishing to 14 feet 5 inches at the crown by six offsets FIG. 116. Llannvst Bridge, Wales, of the arch. The arch stones on the face are 2 feet G inches FIG. 1 1 7. Pont-y-tu-Prydd. deep, the rest of the ring being rubble masonry. This FIG. 118. Half Truss of Wittingcn Bridge. bridge was built by William Edwards, a self-educated country mason. It was completed in 1750 after the failure FIG. 119. First Arch of Schaffhanson Bridge, of a similar structure, in which the weight of the haunches was excessive and forced up the crown, the depth of which I was very small. This failure led to the adoption of the I pierced spandrils. Fig. 118 shows half of the truss for the bridge of Wit- tingen, built in 1758 by the brothers Grubenmann, prob ably the finest specimen of a wooden bridge that has ever been constructed ; the design might be analyzed as con sisting of a series of superposed trusses, as in fig. 87, which represents the bridge at Schaffhauscn built by the &amc engineers or village carpenters. The Schaffhausen bridge (fig. 119), destroyed by French troops in 1799, had two openings, one of 172 feet and the other 193 feet. The Wittingen bridge, burnt shortly afterwards, had a span Wilti Rrli.iff-

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