Engineering Wonders of the World
Volume I

270 ENGINEERING WONDERS OF THE WORLD. having been drawn forward to the distant strand-shoe, the adjusted wire was ready to be bunched with others to form a strand. When all the wire of a strand had been strung, making two hundred and fifty-six separate spans of wire all looped in a con- tinuous length round the two strand-shoes, its ends were joined, and the strand was bound with wire at inter- vals. Then the strand, still resting on temporary sup- ports above its final position, was lowered to its permanent place in the saddles, and at the same time pulled up to its pre- cise adjustment by a strong hydraulic jack. Work then pro- ceeded on another strand, with another set of strand-shoes. When all strands were complete, the whole mass of wire of each cable was squeezed into com- pact circular shape by a hydraulic squeezing ring, which could be shifted along the cable from end to end. The unpre- cedented size of the Manhattan Bridge cables made it necessary to do the work in two stages to get a solid core, squeezing first the seven inside strands, and later the entire thirty-seven strands of the cable. The bridge is now ready for bolting the heavy cast-steel cable bands round the cables and attaching the suspender ropes (Fig. 21). These comparatively slender, but immensely Fig. 20.—ANCHORAGE END OF A CABLE OF THE MAN- HATTAN BRIDGE. This view shows how each strand of the cable is attached independently to an anchor chain. strong, steel ropes are to carry the whole weight of floor and load. In due course the wrapping wire will be added by an ingenious winding machine. From this point onward the erection work again becomes simple and familiar. Floor- beams and truss members are hung to the suspender ropes by great derricks, start- ing from firm footing at towers and anchor- ages, and working outward over the several spans until the steel members meet at the centre. Then the floor must be laid, tracks and railing put in place, a couple of coats of paint applied, and the great structure is ready to enter into service. BLACKWELL’S ISLAND OR QUEENSBORO< BRIDGE. The new Black- well’s Island Bridge —r echristened Queensboro Bridge— crosses over the pris- ons and hospitals of Blackwell’s Island, and rests on two intermediate piers built on the island. Because this shortened its span as compared with the three suspension bridges four and five miles south, it was thought proper to adopt the cantilever principle of construction. However, after seeing the im- posing aspect which the finished structure presents, one is justified in giving it equal rank with the other East River bridges.