Engineering Wonders of the World
Volume I

THE BRIDGES OF NEW YORK CITY. 273 Fig. 25.—WORK OVER MID-STREAM, BLACKWELL’S (and in our bridge also the island span) are built up on falsework by the usual bridge- erection methods. The novelty in the Queens- boro operations was the use of costly steel falsework in place of timber, owing to the enormous weight of the bridge members. For the rest, the Queensboro Bridge had the advantage of good rock foundations for its piers, all of which were built on land. The steelwork was the weighty element, so to speak. It amounted to 50,000 tons ; and some parts of it were made of a new material, nickel-steel—that is, steel containing about three per cent, of nickel. This compound is nearly twice as strong for its weight as ordin- ary bridge steel, and therefore seems to have a brilliant future before it. After this review of the four great East River bridges, we may glance at the other (1,408) •, ISLAND BRIDGE. (Photo, Topical Press.) 9 notable bridges of New York. The many smaller structures must be passed over here and left for the study of the bridge specialist. OTHER LARGE BRIDGES OF NEW YORK CITY. Twelve miles north of New York’s business centre, the Harlem River is crossed by two handsome structures which afford a striking contrast. High Bridge, carrying the first Croton Aqueduct over the Harlem to New York city, recalls the famous Roman aqueducts. It was completed in 1848. Some of its stately semicircular arches span 80 feet, others 50 feet, and the top of the structure, crossed by a footpath, is 114 feet above the water. Washington Bridge, with its modern steel arches (Fig. 27), is forty years younger ; it S VOL. II.