RAILWAY CONSTRUCTION, 143 



were used, the centre one being double the strength of each of 

 the outside girders. Instead of ordinary cross-girders, transverse 

 plate-iron troughing was adopted, very similar in section to the 

 longitudinal iron troughing in Fig. 145, but stronger. The 

 troughing rested on the angle iron of bottom flange of main 

 girder, and was riveted to the vertical web-plates of main 

 girders, shallow additional vertical plates being inserted along- 

 side web-plates to prevent any drip-water or moisture coming 

 in contact with the main web-plates. The entire surface of 

 the troughing was well covered with asphalte before filling the 

 hollows with gravel ballast. An ordinary transverse wooden 

 sleeper was placed in each hollow, and on these sleepers the 

 rails were secured as shown. In this case as in others of 

 transverse troughing the rain-water had to be conveyed away 

 from the hollow of each trough by a separate outlet into 

 longitudinal gutters shown at A, B, and continued on to the 

 abutments. 



Transverse troughing is always more troublesome than 

 longitudinal troughing, as both ends of each trough must be 

 effectually closed to prevent the drainage water leaking out 

 on to the web-plates, or angles of the main girders. With 

 longitudinal troughing the water is readily carried away from 

 each hollow, to cross drains constructed at the piers, or 

 abutments. 



Fig. 147 shows cross-section of a truss-girder bridge, 120 feet 

 span, carrying a single line of railway over a river. The cross- 

 girders are placed at 10-foot centres to correspond to the vertical 

 members of the main truss-girder. Longitudinal plate-iron rail- 

 girders are riveted in between the cross-girders, and the entire 

 floor is covered with curved wrought- iron ballast plates, as 

 shown. The rails are carried on longitudinal timbers, which are 

 bolted on to the rail-girders. Angle iron brackets, riveted on 

 the top of the cross-girders, keep the rail timbers in position 

 and gauge. 



In each of the above examples, where longitudinal rail 

 timbers are adopted, flange rails are shown, as many engineers 

 prefer to have a continuous bearing for the rails on bridges, in 

 case of rail fracture. There is nothing, however, to prevent the 

 chair road being laid on longitudinal timbers, and for this 

 purpose the writer has used chairs of the ordinary pattern, 

 specially cast with side lugs to grip the timber, as shown in 



