Engineering Wonders of the World
Volume I

134 ENGINEERING WONDERS OF THE WORLD. the generally adopted method of railway bridge building was employed. Pier piles and arch- bent piles were first sunk, and Building coffer-dams lowered and the , , . , p . x pumped out. A seat or con- Viaducts. r r Crete was then placed at the bottom of the coffer-dam, and upon this the concrete construction of the pier rests. Twisted done, the whole was allowed twenty-eight days to set. The completion of the spandrel wall was followed by the dislodgment of the arch forms from the arch-bent piles. These were floated away on barges, and used over again as many times as the condition of their timbers war- ranted. When some ninety of the arches of the Long CONSTRUCTING A PIER “ FORM ” IN A COFFER-DAM. steel reinforcing rods were then placed in posi- tion, the upper ends protruding from the top of the concrete pier. The arch-bent piles were then ready to receive the arch forms. When the erection of the spandrel wall forms was completed on each side of the arch, the rein- forcing rods were joined by means of heavy wire to those protruding from the pier, and the reinforcing continued inside the spandrel wall in the ring of the arch. The next step was to fill the forms and spandrel walls with concrete, and tamp it into position ; which Key viaduct had been completed, a hurricane that swooped down upon the keys not only tested the work of the engineers to the utmost, but made havoc in the ranks of the men. The finished arches stood the test well, but hun- dreds of pier forms and costly wooden frame- works were washed out to sea and lost. The camps on the islands were blown down, vessel after vessel was torn from her moorings and swept out to sea, and much valuable floating equipment lost. An American writer who visited the works