Reports on the Philadelphia International Exhibition of 1876.

Date:
1877-1878
Catalogue details

Licence: Public Domain Mark

Credit: Reports on the Philadelphia International Exhibition of 1876. Source: Wellcome Collection.

    377/446 page 279
    The Iron Lighthouse on Coffins Patch, Sambroro Shoal, Florida Reef, lens of Coffins Patch. 1 st 01* dci* The Iron Screw-pile Lighthouse on Brandywine Shoal, Delaware Bay, lens of Brandywine 3rd order, furnished with fog-signal bell. ' The Lighthouse, an Iron Tower 83 feet high, on the north pier of Chicago Chicago Harbour, visible 16 miles, lens 3rd order. > N h * f The vast extent of coast required to be lighted m the United States, which, Lighthouses including Ocean, Bay, Lake, and River, without including the Pacific Coast, and Light-ships, amounts to more than 5,000 miles, requires numerous lights, and the number of Lighthouses under the charge of the Lighthouse Board of the United States, including 36 on the Pacific Coast, amounted in 1875 to 639. The number of Light-ships was 23. Bridges. The magnitude of the Rivers and the skill and boldness of the engineers have led to some remarkable specimens of Bridge building in the United States. The well-known Suspension Bridge, 800 feet in span, erected over the River River St. St. Lawrence some years ago, is being far surpassed by a suspension bridge now ^a™ce. building over the East River, to connect New York and Brooklyn. Over a East Rlver- whole length of 3,455 feet a Bridge will be suspended in three main openings. The central span will be 1,595 feet from centre to centre of Tower, and the side spans, measuring from the centre of Tower to the face of the anchor walls, will each be 930 feet. The Roadway which the Bridge is designed to carry will pass the Towers at an Roadway, elevation of 119 feet, and in the centre of the main span the elevation in the clear will be 140 feet above low water. The suspended superstructure will consist of an iron framing, 85 feet in Construction width, suspended from four main cables by wire ropes attached to iron floor beams placed 7 feet 6 inches apart. The flooring is further to be divided into five spaces by six lines of iron trusses, of which the two centre trusses have a depth of 12 feet, and the others of 8 feet. The outer spaces have a width in the clear between the trusses of 18 feet, and each will accommodate two lines of iron tramways for ordinary street traffic. The next two spans, 13 feet 2 inches wide, will be provided with iron rails for running two passenger trains to be worked by a wire rope. The Bridge is to be supported by four main cables, two outer ones and two Supports, near the middle of the flooring. The Cables, of which a specimem was in the Exhibition, will be 16 inches in diameter, composed of galvanized tempered cast-steel wire, No. 6 gauge, having a strength of 160,000 pounds per square inch of section. The Cables are to be aided by a system of 104 stays in each quarter, which are together assumed to be capable of upholding the super- structure of the main span, the aggregate weight of which, inclusive of cables, will be 5,000 tons. Another illustration of Bridge building on a grand scale is the Illinois and |t. Louis Steel St. Louis Steel Arched Bridge, spanning the Mississippi at St. Louis—a ge< work remarkable for boldness of design and for originality in the mode of ' construction. This Bridge has three main arches of large size. The central arch has a span of 52Q feet, with a versed sine of 47 feet, and two arches, one on each side the central arch, have spans of 515 feet. Each of the three arches consists of four ribs about 12 feet deep, the top and bottom of each rib being steel cylinders, 18 inches in diameter, 2 inches thick at the skew- back, and |ths of an inch thick at the soffit. These are connected and braced together also by cylindrical tubes. The bridge carries a Roadway on the top and a double line of Railway beneath. The segments of the ribs as the erection advanced were supported by overhead guys passing over temporary towers erected on each pier and abutment, so that all scaffolding, centering, or supports from below were dispensed with. The Raritan Bay Swing or Pivot Raritan Bay Bridge, of which a model was exhibited, is a good illustration of a large Swing Brid^e- bridge of another class. The moveable part of the bridge is 472 feet in length, 220 f^t When tllC bridge is swunS °Fen> clear waterways on each side of The largest Iron Truss Bridge at present in use in the United States seems Newport and to be the Newport and Cincinnati Bridge, the channel span of which is 420 feet Cincinnati r ' Bridge.
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