608 PROCEEDINGS OP SECTION J. 



wrought-iron diagonals and ties. Each lattice girder is twelve 

 feet one inch deep over all. The booms are trough-shaped, con- 

 nected with a double lattice web. A light lattice overhead 

 bracing girder, is rivetted to the top table of the main girders 

 over the piers and at mid-span. The lattice girders rest on cast- 

 iron bed plates fixed on piers. Bessemer steel rollers are provided 

 for expansion over four piers. The calculations show that, with 

 a live load of 1.4 tons per foot run on the bridge, the booms are 

 subjected to a stress of 3.82 tons per square inch in compression, 

 and 4.7 tons per square inch in tension. The stresses in lattice 

 bars in compression vary from two tons per square inch at 

 abutment to .5 tons per square inch at mid-span, while the stresses 

 in tension vary from 3.4 tons per square inch at abutments, 

 decreasing to about one ton per square inch at midspan. The 

 cross girders are to some extent relieved by the longitudinal 

 bearers ; but if these were not considered, the stresses produced 

 by the driving wheels of the heaviest engines, added to the dead 

 load, would be 5.12 tons in compression and 5.79 tons in tension. 



Just beyond Albury there is a lattice-girder bridge for a double 

 line of railway to carry the New South Wales and Victorian 

 Railways over the River Murray. Tlie bridge consists of two main 

 openings of one hundred and fifty feet in the clear, with timber 

 approaches on each side. The two main girders, which are three 

 hundred and eighteen feet over all and seventeen feet four inches 

 deep, are continuous over the central pier. There are four systems 

 of triangulation in this bridge instead of seven, as in the case of 

 the Wagga Wagga Bridge, which, with the greater depth of the 

 girder, gives it a much lighter appearance. The details of the 

 girders are also better than those of the Wagga Wagga Bridge. 

 'J'he piers consist of cast and wrought iron cylinders, braced 

 together, and sunk to an average depth of one hundi^ed and 

 twenty feet. The cross girders are three feet deep and spaced 

 five feet eight inches centre to centre, and there are longitudinal 

 rolled iron girders eight inches deep, arranged one under each 

 rail. The clear headway under the bridge is nineteen feet above 

 summer level. The unit stresses developed in this bridge, with a 

 live load of 1.4 ton per foot run on each pair of rails, are about 

 the same as those of the Wagga Wagga Bridge, and the deflec 

 tions under the test load showed that the Albury Bridge was 

 slightly stifter. 



On the Western line, from Parramatta to Penrith, all the bridges 

 are constructed to carry a double line of railway. There are four 

 heavy plate web girder bridges over streets of sixty feet and sixty- 

 six feet span, each consisting of two plate web girders, with cross 

 girders, and a longitudinal girder for distributing the loads from 

 driving wheels over two or more cross girders. There are thirteen 

 bridges or viaducts, consisting of from one to fifteen spans, each 



