Page:The American Cyclopædia (1879) Volume III.djvu/280

 274 BRIDGE either side of the roadway; its span was 449 ft. and versed sine 30 ft. The same engineer constructed the Brighton chain pier, and the bridge at Montrose. The former was built in 1823, and destroyed by a gale of wind in No- vember, 1836; its entire length was 1,136 ft., in four openings, each of 255 ft. span and 18 ft. deflection. The latter was erected in 1829, and in October, 1838, the roadway was totally destroyed by a hurricane ; Mr. Rendell recon- structed it, and materially stiffened the struc- ture by the system of trussing he adopted. The bridge over the Menai strait, by Telford, was built in 1819-'25; its span "was 580 ft., and the clear height of the roadway above the water 102 ft. ; it was seriously injured by a violent gale, which produced so great an oscillation of the main chains as to dash them against each other and break off the rivet heads of the bolts; a recurrence of the accident was pro- vided against by suitable bracing, and the iron roadway beams strengthened by an additional number constructed of timber, as it was found that the former were frequently bent and even broken by the undulations of the bridge in a gale. The Oonway bridge was also built by Telford, being completed in 1826; it crosses an estuary that divides the towns of Bangor and Chester ; its span is 327 ft., with a deflection of 22J ft. The Hammersmith bridge over the Thames was built by Tierney Clark in 1824-'7, and has a span of 422 ft. One of the most remarkable suspen- sion bridges in Europe is that of Fribourg in Switzerland; the cables are of wire, and the span is 870 ft. ; it was erected in 1831-'4 by M. Chaley ; the roadway is 174 ft. above the sur- face of the river, and although the whole is re- markably light and fragile in appearance, it has withstood several severe tests uninjured, and is still considered a safe bridge. The Pesth suspension bridge over the Danube was com- menced in 1840 by Tierney Clark, and opened in 1849, when it was crossed by a part of the Hungarian army retreating before the Aus- trians, and followed immediately by the latter, both armies with their heavy trains of artillery, ammunition, and baggage wagons; it is esti- mated that of the Austrian troops alone 30,000 crossed the bridge in two days; the clear waterway is 1,250 ft., and the centre span 670 ft., while the towers are 200 ft. in height from the foundations. In the United States, the first suspension bridges were built by Mr. Finley between 1796 and 1810, and were all of small dimensions, and constructed with chain cables. During the last 25 years, however, a large number of structures have been erected, and some of great size ; the plan of wire cables has been universally adopted in their construc- tion. The Wheeling bridge over the Ohio was built in 1848, by C. Ellet, and blown down in May, 1854; its span was 1,010 ft. The Belview bridge at Niagara, a slight structure, was built by the same engineer in 1848, and had a span of 759 ft. ; it was removed in 1854, and its ca- bles incorporated in the bridge constructed by Mr. Roebling. One of the finest structures of this kind in the country, and perhaps in the world, is Roebling's railway bridge at Niagara ; its span is 821 ft., and deflection 59 ft. ; 14,560 wires are employed in the cables, and their ul- timate strength is estimated at 12,000 tons; the elevation of the railway track above the water is 245 ft., and so great is the stiffness of the roadway that the passage of ordinary trains causes a depression of only three to four inches ; the bridge was completed in 1855, and, though continually subjected to the passage of heavy trains, has thus far proved a complete success. This able engineer has added to his fame by the construction of a suspension bridge over the Ohio river at Cincinnati. It has a total FIG. 8. Suspension Bridge over the Ohio at Cincinnati. length of 2,220 ft. and a clear span of 1,057 ft., and is 103 ft. above low water in the river. The two cables supporting the roadway are 12i inches in diameter. A still more re- markable work of this kind was designed by Roebling to connect New York city and Brooklyn, and is now (1873) in process of con- struction, under the charge of his son, Wash- ington A. Roebling. It will be 3,475 ft. long between the anchorages, with a clear span over the East river of 1,595 ft., the bottom chord of which will be 135 ft. above the water. The superstructure will consist of an iron framing 85 ft. wide, suspended from four main cables, each 16 inches in diameter, composed of gal- vanized cast-steel wire, having a strength of 160,000 Ibs. per square inch of section. The aggregate strength of the main span will be 5,000 tons. Cast-iron bridges are of recent origin. The first that was erected in England