Fig. 144 shows the cross-section of a truss-girder bridge of 123 feet span, carrying a double line of railway over a wide thoroughfare, the load being placed on the lower flange. There are two main girders, each 12 feet 6 inches deep in the centre, and 8 feet deep at the ends. Plate cross-girders are placed at 4 feet 6 inch centres, on which is riveted longitudinal plate-iron troughing, extending across the bridge and terminating at the sides with wing-plates, as shown. The entire floor is covered with a thick layer of asphalte previous to filling in with ballast to receive the permanent way. Plate stiffeners are adopted in this bridge very similar to those in Fig. 139. Fig. 145 gives plan, elevation, and cross-section of a plate-girder bridge of 95 feet span, carrying a double line of railway over a very busy street. There are two curved-top main girders, each 10 feet 9 inches deep in the centre, and 6 feet 7½ inches deep at the ends. The arrangement of cross-girders, longitudinal plate-iron troughing, and permanent way, is very similar to that in the preceding example, but the side wing-plates are carried up higher, and are riveted up to the web-plate of main girder, forming continuous stiffeners from end to end of the main girders. A light, ornamental, close cast-iron parapet is bolted on to the top of the curved, or upper, boom of the main girder, the top line of the parapet being carried out parallel to the bottom boom of girder. This bridge crosses the street very obliquely, and, although cast-iron columns were allowed at the edge of the footpaths, the main spans are unavoidably large. When designing the above bridge, the writer had to adopt a girder that would form a screen, to provide a deck, or floor-way, which would be not only water-tight, but also deaden as much as possible the sound or vibration of passing trains, and at the same time give some ornamental appearance to the girders and parapets. This bridge carries a constant service of heavy trains; it is perfectly dry underneath, and is remarkably free from noise or vibration. [Illustration: Fig. 142]