The Queensborough or Blackwell's Island Bridge crosses the East River from New York to Brooklyn at the southern end of Blackwell's Island, on which rest two of its piers. The main bridge is a continuous cantilever and the spans are 1,052, 630 and 1,182 feet respectively from west to east. The total length from Second avenue to Crescent street is 7,449 feet. Con struction was begun in 1901 and completed in 1909, the cost (excluding land) being $13,496, 500. The width is 90 feet, the roadways being 53 feet, with 16-foot sidewalks. There is 135 feet clear space under the main span for a width of 400 feet, this being practically identical with the vessel-space under the other New York and Brooklyn bridges. The total of steel and iron' employed is 73,800 tons. The carrying capacity is 89,800 tons. The towers bear obser vation balconies on Blackwell's Island which reach a height of 333 feet above high water and are reached by stairways and elevators.
The Manhattan Bridge connects the Bowery and Canal streets, New York, with Nassau street, Brooklyn. Work was begun in 1901 and completed in 1911. The structural expense was $14,104,900, and it has the greatest transporting capacity of any bridge up to its date. It is of the suspension type, having a river span of 1,470 feet, with the shore spans of 725 feet. The total length with approaches is 6,855 feet. It is 122% feet in width and is double-decked, and this tremendous roadway requires for its sup port four of the largest cables constructed to date, each inches in diameter. The total ultimate strength of these cables is 120,000 tons, or two-and-a-half times that of the Brook lyn Bridge cables. The cables run over the steel towers at a height of 322 feet above high water, and with their suspenders they weigh 7,950 tons.
There are 37 strands in each cable and 256 wires in each strand, making a total of 9,472 wires in each of the four cables. As each wire is more than half a mile in length (3,223% the total length of wire is 23,858 miles, sufficient to girdle the earth at the equator. The weight of steel in each anchorage is 1,300 tons, and of each side span 5,000 tons. The main span weighs 8,000 tons, the Manhattan approach 8,500 tons and the Brooklyn approach 8,000 tons. The excavation for each pier was about 40,000 cubic yards, and the masonry and concrete in each of the anchor piers totaled approximately 115,000 cubic yards, by far the heaviest ever laid. The towers weigh 6,300 tons each, and the three spans weigh 19,000 tons. On the lower deck are two subway tracks, driveways and footwalks. Above are four railway tracks to accommodate surface and elevated cars. The carrying capacity is
57,820 tons. The above-described four great bridges over one river, within a distance of five miles, erected at a total cost (without land and approaches) of $90,229,429, constitute the most marvelous achievement the world has recorded in Another remarkable bridge crosses the East River at Hell Gate, a few miles north of the group just described. This bridge, carrying the New York Connecting Railroad and comprising the largest steel arch in the world (1916), has a span of 977% feet, made up of 23 panels 42% feet between centres. The depth of truss at the ends is 140 feet, at the centre 40 feet and at the quarters 66 feet. The upper member of the arch truss shows a reverse curve when nearing the abutments, to afford head room for trains: it also adds much to the beauty of the struc ture. The rise of the arch is 220 feet. The lower chord is rectangular, 7 feet in width,' 10% feet deep at the abutments and 7% feet at the crown. The weight of the bridge averages 26 tons to the lineal foot. The direct thrust of the arch is upon solid walls of concrete. The clearance at the centre when the closing chord was put in place was 3% inches. This was closed by lowering the jacks on the main posts from 15 to 20 inches. This final work was con ducted through a multi-party telephone system, with stations at the centre, at each backstay jack, at each counterweight and at the office— all stations being directly connected with all the others. The foremen at the telephones ((listened and each heard all the orders given and all comments made as the work progressed. The bridge contains 18,000 tons of steel. Its de signer was Gustav Lindenthal.
The Spokane-Portland Railway finished in 1909 a drawbridge over the Willamette River below Spokane, which has a draw span of 521 feet, being one of the longest ever built. The total length of the bridge is 1,762 feet, and the piers are of reinforced concrete.
The most noteworthy bridge of the far North is that over Copper River, Alaska, com pleted in 1910 for the Alaskan Railway. No such difficult bridge engineering has been un dertaken before in such a cold climate. Owing to the nearness of large active glaciers, which at times filled the river with great masses of broken ice, the bulk of the construction work had to be completed within a few months' time. Four steel camel-back spans totaling 1,550 feet constitute the bridge proper, the two longest of these spans being 450 feet each. Three con crete piers were sunk in the river, and the en tire work completed at the remarkably low cost of less than half a million dollars.