The North River Bridge.

The North River Bridge.

Engineering achievements, however vast, have ceased to astonish the public, which receives with perfect tranquility the details of the most gigantic undertakings; of schemes which would once have been thought as impracticable as a railroad to the moon. An enterprise like that of bridging the Hudson river does not, it is true, imply any startling defiance of the laws of nature ; for the bridging of a river is a device older than history itself. It is the tremendous dimensions of the project that chiefly distinguish it as an engineering feat and that would at an earlier day have brought upon the daring schemer who should have proposed it the imputation of lunacy. The plans submitted by Joseph W. Balet provide for an eighttrack bridge 120 feet wide and 150 feet above high water, built of solid steel and combining both the cable and the cantilever system. Neither one of the two systems would by itself, in Mr. Balet’s opinion, meet the requirements of the case ; but he claims by his method to have united “ the efficiency of the suspension cable with the rigidity of the cantilever bridge.” His plan contemplates three piers in the stream, and the four openings or spans thus created, beginning on the New York side, are respectively 900 feet, 1700 feet, 1150 feet and 900 feet long. The lightness of his bridge, proportionately to its strength ami capacity, is one of its conspicuous features, hi* estimate of its weight being 32,550 tons, or about seven-eighths of a ton per loot for each track, or seven tons per foot for the eight tracks, the length of the bridge being 4650 feet. The bridge over the Eirth of Eorth in Scotland is 750 feet longer than this, but it has only two tracks, and it is the eight-track element of the problem that gives the North river structure the primacy among the bridge-building enterprises of the century. The plan above outlined provides for the carrying of a load of 14,000 tons, which is far beyond any strain to which the bridge will actually be subjected. The financial load which will be brought upon the stockholders, or on the municipalities or States to be joined, whichever it may be, is also an interesting subject of consideration. The original estimate of the cost of the bridge was $40,000,000, but we are not sure that it has not already grown beyond that figure even in advance of the actual beginning of the work. If the mechanical difficulties ol the scheme would have been thought by the last generation to be insurmountable, still more would they, in their capacity as taxpayers, have experienced a weakness of the knees at the prospect of a pecuniary burden of such magnitude. But since their time, not only has science advanced but wealth also has grown. New York and its immediate suburbs had not then aggregate resources amounting to $3,000,000,000, and a domestic and foreign trade of corresponding extent. The gigantic commercial capital of the nation needs larger facilities .for the traffic which is poured into it from every quarter of the globe, and with the need it has acquired the means wherewith to meet the ever-expanding requirements of its imperial position.

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