612 PROCEEDINGS OF SECTION J. 



in the world, ranging in price from £296,350 to £702,384, which 

 were submitted to a committee of eminent engineers, and to Sir 

 John Fowler, for report. Both Sir John Fowler and the com- 

 mittee were unanimous in favour of the design and tender of the 

 Union Bridge Company. The Engineer-in-Cliief, Mr. Whitton, 

 while in favour of the design, recommended certain modifications 

 and additions which increased the cost of the work £13,000, the 

 total cost being £340,000. The bridge is two thousand eight 

 hundred and ninety -six feet between abutments and is constructed 

 for a double line of way. In consists of seven spans, with a clear 

 headway of forty feet above high-water level. The super-structure 

 consists of two main trusses in each span, which are four hundred 

 and ten feet fi'om centre to centre of bearings, and fifty-eight feet 

 six inches efiective depth at the centre, spaced twenty -eight feet 

 apart centre to centre. They are constructed with eye-bar tension 

 members and pin connections on the system so largely used by 

 American engineers for long-span bridges. The ratio of span to 

 depth is about seven. There are thirteen panels in each truss, spaced 

 thirty-one feet six inches centre to centre ; the compression 

 members are of rectangular box form, composed of plates and 

 angle bars, accurately prepared at joints for butting without 

 covering plates. The trusses are braced together with complete 

 systems of lateral bracing, between both top and bottom chords, 

 and there are light sway bracings at right angles to axis of bridge, 

 in the plane of the vertical compression members, connecting the 

 top cord to the ends of the cross beams between the vertical 

 members. The end raking posts for forming the portals to each 

 span are stiffened laterally by cross frames latticed with angle 

 bars carried down as low as the traffic will allow. The floor of 

 the bridge is constructed with cross girders attached to vertical 

 compi'ession posts spaced thirty-one feet six inches centre to centre, 

 with four longitudinal girders or stringers. The ratio of depth to 

 span in the cross girders at centi'e is one to five and a-quarter. A 

 timber decking supporting the rails rests upon the longitudinal 

 stringers of the ordinary American type similar to that adopted 

 in the Petersham Viaduct. 



The six piers which suppoi't this structure in the bed of the river 

 consist of concrete from low water downwards, cased in metallic 

 caissons. The cutting edges and lower lengths for about one-thii'd 

 of the height are of steel, the remainder of wrought iron. Above 

 the concrete the pier is carried up in masonry in the foi'm of two 

 circular columns fourteen feet in diameter, and twenty-eight feet 

 centres, with a connecting wall between them six feet thick. The 

 body of the pier is forty-eight feet by twenty feet, with rounded 

 ends. The piers, as originally designed and carried out, in three 

 cases only, were splayed at the ends ; the others have been modified 

 so as to have vertical sides, which facilitates sinking in the true 



