The Great International Railway Suspension Bridge Over the Niagara RiverThe Illustrated London News, vol. 40, no. 1127, p. 67-68.
January 18, 1862
BRIDGE OVER THE NIAGARA RIVER.
This magnificent work was erected for the purpose of connecting the New York Central and the Great Western of Canada Railways, and the cost was contributed by both companies in equal portions. It is by means of this bridge only that an unbroken journey can be made from New York, or Boston, to the western part of Canada, without changing carriages; the consequence of which is, that the best and cheapest route to the west, not only of Canada, but also of the United States, is still by the New York Central and the Great Western of Canada Railways, although many other western routes have sprung into existence since this was completed. Chicago and the western prairie country generally are reached by this route more easily than by any other, as is also Detroit and all parts of Michigan.
The great bridge the subject of our present notice was not the first of the kind which spanned the gorge of the Niagara River, an ingenious suspension-bridge having been constructed across it many years ago by Mr. C. Ellett, but of very fragile and temporary character when compared with the present work.
The Niagara Railway Suspension-bridge was erected from the designs, and under the personal superintendence, of Mr. John A. Roebling, at a cost of 400,000 dols. The first engine crossed over it on the 8th of March, 1855. It carries a double line of rails on the upper part, and an ample roadway for carriages below.
The plan adopted in the construction of this suspension-bridge differs materially from those usually built in England. Instead of flat wrought-iron plate-links, connected together by pins passing through their extremities, Mr. Roebling uses a simple wire-cable, or rather four wire cables, each 10in. in diameter, and composed of 3640 separate wires, the whole of the cables being capable of bearing a weight of 12,000 tons; the actual load they carry never exceeds 1000 tons. The wire ropes are securely anchored in the solid rock, 30ft. below the surface; they pass over the summits of four solid stone towers, 80ft. in height. Beside the wire cables there are 624 suspending-rods, whose ultimate strength is equal to 18,720 tons; these support the roadway at different parts, and are connected with the cables above. There are also sixty-four over-floor stays, whose ultimate strength is 1920 tons, and fifty-six river-stays, whose ultimate strength is 1680 tons; these latter stays extend from the bridge to the rocks on either side of the ravine. The total length of span between the towers is 800ft., and the "railway track," as it is always called in America, is 250ft. above the surface of the water in the river.
The great object sought to be obtained in this remarkable bridge, after strength to carry its load, was rigidity; for in all suspension-bridges, as ordinarily constructed, the deflection and oscillation would be such as to entirely prevent their being used for the purposes of carrying railway traffic. The Niagara Suspension Railway-bridge, although not perfectly rigid, is sufficiently so to allow of heavily-laden trains passing over it at a maximum speed of five miles per hour; even then a very considerable deflection takes place, but not such as to in any way betray weakness; on the contrary, it is rather an indication
Page 68of strength, as showing the correct action of all its parts, by which means a true bearing is obtained over every part of it.
A wonderful amount of ingenuity and mechanical skill is displayed in the construction of the roadway, which forms a species of lattice or tubular girder, the railway track being on the top outside, and the carriage roadway on the bottom inside. The frequent admixture of wood and iron, and the numberless small bolts and screws passing through the former material, will require constant care and supervision to prevent decay occurring, and may probably cause the cost of maintenance of the bridge to be excessive. Portions are now being constantly renewed, and always with an increased strengthening of the parts. The bridge, however, taken as a whole, must be looked upon as a decided success and a triumph of American engineering skill; while the advantages of a perfect communication between the United States and the most valuable portions of the British possessions in North America cannot be overrated. The general effect of the Niagara Suspension-bridge is that of extreme lightness and beauty; the situation in which it is placed is exceedingly fine, being in view of the Great Falls, while below it the Niagara River rushes through its confined channel, a foaming, noisy rapid 150ft. deep, almost as terrible in its roar and force as the mighty cataract itself.
A bridge similar to the Niagara Suspension-bridge, and of even greater span, but only carrying an ordinary roadway, ha[s] been built over the River St. John, in the city of St. John, in New Brunswick. This bridge, some time after it was erected, gave way during a terrific gale of wind. The suspension cables remained sound and fully equal to their duty; but the roadway had been insecurely connected with the abutments, and it broke adrift at that point. The whole length of roadway oscillated many feet clear of the abutment altogether, yet only a portion of it gave way, the bridge proving itself in all other respects equal to withstanding strains that it never was expected to be subjected to.