Page:Forth Bridge (1890).djvu/64

Rh

the top members are inverted troughs of the same dimensions. Each pair of opposite struts is connected by two pairs of diagonal wind bracings carried down as low as the passage of trains will admit. All struts and ties are of box shape of varying strength and section. The joints in top booms and bottom booms were so arranged that each half-bay could be built out in succession, the length of boom just reaching beyond the junctions or beyond the vertical ties. The permanent way and the flooring in the central girders are made up much about the same as in the cantilevers, with four rail troughs and two footpaths, and a wind fence on each side. The 6-ft. way—the space between the two troughs of each line of rails and the footpaths—were made up of buckle plates supported on T bars from trough to trough.

Previous to the exact lengths of the central girders being fixed the distance between the cantilevers had been measured carefully and frequently