Page:The American Cyclopædia (1879) Volume III.djvu/282

 276 BRIDGE road bridge across the Ohio river at Louis- ville, constructed under the supervision of Mr. Fio. 12. Lattice Girder. Albert Fink, and in accordance with the sys- tem known by his name, the essential feature of which is that the bridge carries its load Fio. 13. Lattice Girder. by the aid of suspension rods, and at the same time possesses the stiffness of a truss. The length of this bridge is 5,218| ft., divided into 25 spans, supported by 24 stone piers. Its entire cost was $2,016,819. Its height is about 96 ft. above low water. Its width is about 27 ft. The drawing (fig. 15) will show at a glance the peculiarities of this structure. The railroad bridges over the Mississippi river at Quincy, Fio. 14. Modified Fink trussed Girder. Keokuk, and Burlington, and over the Missouri river at St. Charles, are good examples of truss bridges constructed exclusively of wrought iron. Many modifications have been made in the form of the truss since the substitution of iron for wood. A very remarkable bridge, the superstructure of which is mainly composed of FIG. 15. Viaduct Bridge at Louisville. steel, is now (1873) in the process of construc- tion over the Mississippi river at St. Louis. It was designed by James B. Eads, and was begun in 1869. The piers, four in number, are corn- is 60 ft., sufficiently high to permit the pas- sage of steamboats at all stages of water. The two roadways, one for railways and one for carriages, will be carried by four arched posed of granite and limestone, and rest on trusses connected with each other by diagonal the bed rock of the river, to which they were ' braces, the top and bottom chords of which sunk through the sand, in one case as much as j are composed of steel tubes 16 inches 120 ft, by the use of wrought-iron caissons and atmospheric pressure. There will be one span of 520 and two spans of 515 ft. each over the waterway. The rise of the arches diameter. These tubes are made in sections of about 12 ft., and consist of steel staves, banded and held together by jackets or hoops of the same material ; the segments being con- Fio. 16. Truss Bridge at Rock Island.