THE GREAT RAILWAY BRIDGE OVER THE FIRTH OF FORTH. The co struction of the great railway bridge to cross the irth of Forth at Queensferry just beyond south shore the water shoals rapidly with a bed of bowlder clay and a very deep stratum of mud but the Fife shore is an almost perpendicular cliff and the intervening islet is a rock ill the center of the deep channel with 200 feet depth of water on each overhanging extended part being balanced by its weight at the other end. This engineering device is the most novel feature of the Forth Bridge. The main spans of the bridge are to be upheld over
THE GREAT RAILWAY BRIDGE OVER THE FIRTH OF FORTH. The co struction of the great railway bridge to cross the irth of Forth at Queensferry just beyond south shore the water shoals rapidly with a bed of bowlder clay and a very deep stratum of mud but the Fife shore is an almost perpendicular cliff and the intervening islet is a rock ill the center of the deep channel with 200 feet depth of water on each overhanging extended part being balanced by its weight at the other end. This engineering device is the most novel feature of the Forth Bridge. The main spans of the bridge are to be upheld over the deep water channels by the projecting ends of cantilever and Linlithgowshire nearly approach each other with the rocky islet of Inchgarvie between them is one of the grandest works of modern engineering. It was de signed for the North British Railway Company by Sir John Fowler and Mr. Benjamin Baker has been four or five years in actual progress and will be com pleted in the autumn of this year. The width of the estuary in this part is reduced by the peninsula of side and with a strong tide current sweeping up and down on each side. It was impossible to erect piers anywhere but on this islet ; hence the bridge must rest on three main piers one at South Queensferry one at Inchgarvie and one on the Fife shore besides two supplementary piers which serve to relieve the balance arms of the cantilever girders and to connect the bridge with a long approach viaduct. A cantilever is a girder supported at one point its one-sixth of the span. Each cantilever girder is a com plex structure framed of four vertical columns stand ing not parallel but from a wide base narrowing t the top ; two bottom members formed of horizontal tubes arranged in an upward curve of 680 feet span ; two top members consisting of box lattice girders ar ranged horizontally on vertical columns ; twenty-eight struts holding the top and the bottom together ; and FIFE MAIN PIER. PROGRESS OF THE FORTH BRIDGE GLITEEN
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