Public Works. Hudson River Tunnel.

Public Works. – There are but few public buildings of much architectural pretension. The principal are the city-hall, the general post-office, the custom-house, the barge office at the Battery for the accommodation of passengers landing from steamships the new produce exchange, and the Roman Catholic cathedral in Fifth Avenue. The two great public works of the city are the Croton aqueduct and the suspension bridge, spanning the East River, connecting New York with Brooklyn. The former, which carries the water supply of the city over 40 miles from the Croton Lake in Westchester county, has a capacity of 115,000,000 gallons daily, and is now delivering 90,000,000 gallons daily. It has for forty years supplied the inhabitants with water with a profusion never seen elsewhere in the modern world, and with little or no restriction on its use. of late the supply has begun to be inadequate, and provision has (1883) been made by the legislature for the construction of an additional reservoir and aqueduct.

The Brooklyn Bridge connecting New York with Brooklyn across the east River is much the largest suspension bridge yet constructed, measuring 5989 feet in length, while that at Kieff, the next largest, only measures 2562. The work on it began in 1870, and it was opened for traffic on May 24, 1883. The bridge consists of a central span 1595 _ feet in length from tower to tower, tow spans of 930 feet each from the towers to the anchorage on either side, and the approaches of ironwork and masonry, the one on the New York side being 1562 _ feet, and that on the Brooklyn side 971 feet in length . The towers, between which the central span extends, are 276 _ feet above high water, and rest upon a rock foundation 80 feet below the surface of the river and 40 feet below its bed. The cables, four in number, supporting the spans, are 15 _ inches kin diameter, and 3757 _ feet in length. They rest on movable "saddles" where they pass over the towers, exerting here a vertical pressure only, the stress 9or lengthwise pull) being sustained wholly at the anchorages, masses of solid stone masonry weighing 60,000 tons each, and rising 90 feet above the river’s edge. Each cable contains 5282 galvanized steel wires in nineteen separate strands, consisting of 278 lengths, each strand having over 200 miles of continuous wire. The wires are laid parallel (not twisted), and packed as closely as possible, he greatest care being necessary to secure perfect evenness of length, and re covered with an outside spiral wrapping of wire. The deflection of the cables between the towers is 128 feet; the clear height of the bridge above high water is 135 feet in the center and 118 feet at the towers, giving a free passage to shipping. The width of the bridge is 85 feet, divided between five passage ways. In the center is a footway 15 _ feet wide and raised 12 feet above the other passages, giving an open view on both sides; next this on each side are tracks for cars, worked by cables from a stationary engine at the Brooklyn terminus; and outside of these are wagon ways 19 feetwide. The entire cost of the bridge, $15,500,000, was borne by the cities of New York and Brooklyn, the latter paying two-thirds.

Hudson River Tunnel. – The width of the Hudson River along the city’s front is so great that no engineer has yet proposed to bridge it there; but an engineering feat almost as difficult is now in progress. This is the excavation of a tunnel beneath the bed of the river large enough to permit the running of steam trains in it. The work is in the hands of private capitalists. The entrance of the tunnel in New York is at the foot of Morton Street; in Jersey City it is at the foot of Fifteenth Street, near the Hoboken line. Work was begun at the New Jersey entrance in 1874, and at New York entrance several years later. There are in fact to be two tunnels, about 25 feet apart, with connection every 1000 feet. This mode of construction is easier than to make one tunnel of double width. The river from bulkhead to bulkhead at this point measures 5400 feet in width, and each entrance is about 60 feet back from the bulkhead. The tunnel will measure, inside, 17 feet in width and 17 feet in height. From Jersey City one tunnel had been, in August 1882, completed a distance of 1600 feet, and the other a distance of 640 feet; from New York 170 feet of one tunnel only is completed. Unfinished work has been pushed a considerable distance farther on each side. The material through which the tunnel is cut has made its construction very difficult – on the New Jersey side silt, and on the New York side a light sandy soil, through both of which the overlying water percolates freely, and it was necessary to keep this water out of the excavated sections as the work proceeded. The plan adopted consisted of the sinking, at each mouth, of a heavy caisson of timber to the required depth. In the river side of this, when it was completed, a hole was cut corresponding with the mouth of the tunnel. The caisson was air-tight, and into it the air was pumped until it reached a density sufficient to prevent the entrance of the water. as soon as a short section is excavated it is lined with iron plates firmly braced. The interior of the tunnel will therefore consist of an outer lining of iron, and an inner lining of bricks laid in mortar. Whenever one section is completed an iron bulkhead is moved to its further end, and a new air-tight chamber is formed beyond the bulkhead. The company has met with financial embarrassments, and the work has meanwhile been suspended.





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