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The Niagara Falls Suspension Bridge, which stood from 1855 to 1897 across the Niagara River, was the world's first working railway suspension bridge. It spanned and stood downstream of Niagara Falls, where it connected Niagara Falls, Ontario, to Niagara Falls, New York. Trains used the upper of its two decks, pedestrians and carriages the lower. The brainchild of Canadian politicians, the bridge was built by one American and one Canadian company. It was most commonly called the Suspension Bridge; other names included Niagara Railway Suspension Bridge, Niagara Suspension Bridge, and its official American name, the International Suspension Bridge. The bridge was part of Canadian politician William Hamilton Merritt's vision to promote trade within his country and with its neighbor the United States. Many, including bridge builders, argued that a suspension bridge could not allow the safe passage of trains. Nonetheless, the bridge companies hired Charles Ellet, Jr., who laid a line by a kite across the chasm and built a temporary suspension bridge in 1848. Ellet left the project after a financial dispute with the bridge companies, who hired John Augustus Roebling to complete the project. By 1854, his bridge was nearly complete, and the lower deck was opened for pedestrian and carriage travel. On March 18, 1855, a fully laden passenger train officially opened the completed bridge. A border crossing between Canada and the United States, the Suspension Bridge played significant roles in the histories of the Niagara region and the two countries. Three railway lines crossed over the bridge, connecting cities on both sides of the border. The Great Western Railway, New York Central Railroad, and New York and Erie Rail Road differed in the track gauge; the bridge used a triple gauge system to conserve space, overlapping two tracks on top of each other and using a rail of each to form the third track. The railroads brought a large influx of trade and tourists into the region around the Niagara Falls. In the time leading to the American Civil War, the Underground Railroad helped slaves in the United States escape across the Suspension Bridge to freedom in Canada. After the war, the bridge became a symbol of inspiration to Americans, encouraging them to rebuild their country and pushing them to quickly industrialize their nation. The bridge's success proved that a railway suspension bridge could be safe and operational. Slowly decaying, the bridge's wooden structures were replaced with stronger steel and iron versions by 1886. Heavier trains required its replacement by the Steel Arch Bridge, later renamed the Whirlpool Rapids Bridge, on August 27, 1897. == Conception and construction == In the mid-19th century, the hinterlands of the North American East Coast opened up rapidly. In Canada, entrepreneur and politician William Hamilton Merritt helped establish several trade routes, especially in dredged waterways between the lake cities. He also envisioned a U.S. and Canadian rail network to connect the Atlantic coast with new territories in the West, and this led to a railway suspension bridge across the Niagara River below the falls. Merritt's vision for the Niagara Suspension Bridge was conceived at the Niagara River itself. In summer 1844 while taking a picnic on the river shores, near what was then the town of Clifton, Merritt read a letter from his sons to his wife. The younger Merritts were touring Europe and visited the town of Fribourg, Switzerland. Amazed by the Freiburg Suspension Bridge, they wrote to their parents, describing the wonders of the bridge in eloquent terms. Their writing had a profound effect on their parents, and the elder Merritts wondered if such a suspension bridge could be built across the Niagara. Merritt was driven to realize that vision, and he approached the relevant authorities, including the Queen of England, for permission to start the construction of the suspension bridge. His efforts were rewarded in 1846; the state of New York and the government of Canada approved the charters to form the Niagara Falls International Bridge Company and the Niagara Falls Suspension Bridge Company, respectively. In the years before the first bridge was built over the Niagara River, the river was crossed entirely by boats. Powered by steam engines, vessels ferried people and carriages across the raging river at calmer points of the water. One of these vessels was the ''Maid of the Mist'', the first tourist boat to ply the waters of the Niagara River. Named after a local legend, the steamer began service in 1846. Launching from a point below the Horseshoe Falls, it chugged up to the base of the falls, offering a close-up view of the natural wonder to its passengers, before moving to the opposite shore. The site for the Suspension Bridge was half a mile (0.8 km) from the ''Maid of the Mist''s landings. The selection of the bridge site was based more on aesthetics than technical ease; it was the narrowest point of the gorge— across and deep—that allowed a full view of the falls from the American side. After the bridge companies were founded, they invited engineers to submit plans and cost estimates for a suspension bridge that carried a railway. The invitation was met with skepticism among the engineering community. At that time, there was not a suspension bridge that could allow a train to pass over it safely. While the Europeans were erecting suspension bridges by the hundreds, the Americans mostly ignored them out of safety concerns; in 1831 Sir Samuel Brown's Broughton Suspension Bridge in Britain had collapsed under the marching feet of a troop of soldiers, sending those on its deck into the River Irwell. Furthermore, many American bridges had collapsed without experiencing weight and pressure equivalent to railroad traffic, and American engineers feared that any railway bridge would likely fail—especially a suspension bridge. Four engineers responded: Edward Serrell, Samuel Keefer, Charles Ellet, Jr., and John Augustus Roebling. All submitted designs for a suspension bridge. At the time of the bidding, Ellet and Roebling were acknowledged as masters of suspension bridge building in America. Roebling submitted two designs, a conservative single-deck suspension bridge and a double-decked version, both with meticulous calculations and drawings. Instead of relying solely on submissions, Charles Ellet, Jr. took a proactive approach. When he got wind of the project in 1845, he wrote to Charles B. Stuart, chief engineer of the Great Western Railway, boldly proclaiming that he could build a bridge for any likely purpose across the Niagara. After the charters had been obtained, Ellet helped Stuart to sell the bridge companies' stock and offered to buy US$30,000 worth of stock himself. His efforts earned him the $190,000 bridge contract on November 9, 1847. 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「Niagara Falls Suspension Bridge」の詳細全文を読む スポンサード リンク
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