. The roads and railroads, vehicles, and modes of travelling, of ancient and modern countries; with accounts of bridges, tunnels and canals, in various parts of the world . ined the piers of a stone bridge which pre-viously existed there, it fell down in 1754, and it wasdetermined to substitute one of timber, which, requiring asmaller number of piers was not so much exposed to simi-lar accidents. Grubenmann oflPcred a model of a bridgewithout any pier at all, but his project being consideredtoo bold, the authorities insisted that one pier of the oldbridge, which was left standing, should be us
. The roads and railroads, vehicles, and modes of travelling, of ancient and modern countries; with accounts of bridges, tunnels and canals, in various parts of the world . ined the piers of a stone bridge which pre-viously existed there, it fell down in 1754, and it wasdetermined to substitute one of timber, which, requiring asmaller number of piers was not so much exposed to simi-lar accidents. Grubenmann oflPcred a model of a bridgewithout any pier at all, but his project being consideredtoo bold, the authorities insisted that one pier of the oldbridge, which was left standing, should be used as an in-termediate support. The design was therefore modified,and the bridge was built apparently in one span fromshore to shore, but addltionalsupport was afforded by beamsspringing from the stone pier. The length of the bridgewas 364 feet, and its breadth eighteen feet. This bridge wasdestroyed by the French in 1799. John, the brother of LTIricGrubenmann, has also erected bridges with skill, equal tothat of his brother. The two brothers in conjunction TIMBER BRIDGES. 121 erected a beautiful structure over the river Limmat nearBaden, and another at Swiss Bridge. Wiebecking, Avho has been called the most skilful car-penter of modern times, has erected timber bridges of ex-traordinary dimensions. One of these structures is the seg-ment of a circle, the chord line of which measures 639 feet,its versed sine only twenty-six feet six inches, being theportion of a circle whose whole diameter is no less than3876 feet. The thickness of the framing of this extra-ordinary bridge is only four feet two inches. The Americans, having a superabundant supply oftimber, have been very successful in the construction ofwooden bridges. Timber also abounds in Norway, but,judging from the specimen represented at the head of thepresent chapter, the Norwegians are sometimes con-tented with bridges of a rude and most primitive form. Over the Schuylkill in Philadelphia is a timber bridg
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