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Roebling's Delaware Aqueduct, also known as the Roebling Bridge, is the oldest existing wire suspension bridge in the United States. It runs 535 feet (175 meters) over the Delaware River, from Minisink Ford, New York, to Lackawaxen, Pennsylvania. Opened in 1849 as an aqueduct connecting two parts of the Delaware & Hudson Canal (D&H), it has since been converted to carry automotive traffic and pedestrians. ==Construction== The bridge was begun in 1847 as one of four suspension aqueducts on the D&H Canal, a system of transportation connecting the coal fields of northeastern Pennsylvania with markets on the Hudson River. The canal opened in 1828, was enlarged after the 1840s, and closed in 1898. Russell F. Lord and John A. Roebling designed the bridge and supervised its construction. Roebling would design the Brooklyn Bridge 20 years later. Two important local industries with conflicting needs brought about construction of Roebling's Delaware and Lackawaxen Aqueducts: canal traffic and timber rafting. Since the mid-18th century, timber from the Delaware valley had been floated down the river to shipyards and industries in Trenton and Philadelphia. The D&H Canal's rope ferry crossing of the Delaware at Lackawaxen created a bottleneck, and there were numerous collisions with timber rafts headed downstream. In 1846, to alleviate both problems, the D&H Canal Company approved Russell F. Lord's plan to substitute two new aqueducts in place of the rope ferry.〔(Vogel 1971, p. 9)〕 After evaluating several options, Lord recommended designs submitted by John A. Roebling, who had already built a wire suspension aqueduct at Pittsburgh in 1845.〔(Vogel 1971, p. 4)〕 To raise the canal enough to allow the passage of ice floes and river traffic, Lord's plan called for three locks to be built on the eastern side.〔National Park Service. Interpretive sign at the bridge site. Accessed: August 22, 2011〕 An immediate success, the Delaware Aqueduct — which cost $41,750 – and the Lackawaxen Aqueduct — which cost $18,650, and of which only the abutments remain – reduced canal travel time by one full day, saving thousands of dollars annually.〔(Vogel 1971, p. 10)〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Roebling's Delaware Aqueduct」の詳細全文を読む スポンサード リンク
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