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Show 960-Foot, $3,500,000 Arch Is of Rare Design. NIAGARA FALLS. The 960-foot span of the new $3,500,000 bridge being built across the Niagara river gorge besides being one of the longest long-est of its type also must be literally self-supporting. Unlike bridges built over shallow water, where engineers can set up false work or pillars to support the arch, the "Rainbow" bridge will span water whose depth is undetermined, undeter-mined, but known to be at least 160 feet. Hence, when installation of the steelwork begins, the contractors will resort to the seldom-used tie-back tie-back device. The entire bridge, replacing the so-called "Honeymoon" bridge destroyed de-stroyed by ice in January, 1938, will have to be "tied back" with heavy steel cables 480 feet of steel, weighing weigh-ing approximately 3,750. tons, being anchored on each side of the river marking the boundary between the United States and Canada. The first step will be the erection at the end of each approach of a 140-foot tower. "Dead men," or anchorages, will be sunk in the ground 250 feet behind the towers. The anchorages will be 30 feet below be-low the surface and cemented in solid sol-id rock. The cables will be strong enough to carry three or four times the actual weight of the bridge. The arch girders, 12 feet high, are being made in the Bethlehem Steel corporation's Pennsylvania mills, but must be split in half to fit into a railroad car for transportation. They will be spliced at the center of the bridge, where Canadian and United States laborers, working at their respective re-spective ends of the span with materials ma-terials manufactured in their respective re-spective countries, will join forces for the final job. |