HISTORY OF CIVIL ENGINEERING IN NEW SOUTH WALES. 595 



BRIDGES. 



The bridges constructed by the department up to 1865 were 

 found to be too narrow in the roadway ; from that time up to the 

 present a minimum width of eighteen feet has been adopted for 

 bridges near towns, and from fourteen feet to sixteen feet in more 

 remote localities. Spans of simple timber beams with corbels 

 have been used up to forty feet spans, and trussed timber bridges 

 with iron suspension rods up to ninety feet spans. Laminated 

 timber arched bridges, continuous, and others hinged at the 

 centre, have also been constructed. The Bathurst Bridge, designed 

 in 1868, consists of three wrought-iron spans with vertical struts 

 and diagonal ties. The upper boom and inclined end struts are 

 constructed of girder section formed of wrought-iron plates and 

 angle irons, the tension cord bemg formed of wrought iron bars 

 only. The spans are one hundred and eleven feet six inches, one 

 hundred and thirteen feet, and one hundred and eleven feet six 

 inches respectively between centres, fixed at one end and expanding 

 over the other on cast-iron rollers. The trusses, which are one 

 hundred and ten feet centres of bearing pins, eleven feet centres 

 of pannels, and twenty-four feet eight inches apart centre to centre, 

 carry wrought-iron cross girders which can be prolonged beyond 

 the main girders to form cantilever supports for the footways 

 when required. The roadway is formed of timber, twenty-one 

 feet clear, between kerbs. The substructure consists of cast-iron 

 cylinders six feet diameter, with wrought-iron bracing girders. 

 The bridge was open for traffic in 1870. 



The Parramatta Bridge, designed in 1877, consists of five wrough t 

 iron non-continuous lattice girders, one hundred and fifty and a- 

 half feet centres of piers, and a swing span revolving on a central 

 pier, and having an opening upon one side of sixty feet clear, and 

 on the other of tifty-seven feet. The main girders, which are trough- 

 shaped, braced with wrought-iron flat tie-bars, and wrought-iron 

 channel struts, stittened with ladder bracing, are one hundred and fifty 

 feet in length, thirteen feet two inches between boom plates, and 

 twenty -seven feet four inches betwen centres. Expansion is pro- 

 vided for by gun-metal plates sliding on cast iron plates. The 

 deck consists of hai'dwood, resting upon wrought-iron cross-girders. 

 The swing span consists of four wrought-iron lattice girders, seven 

 feet deep, stiffened with plates for twenty feet from centre, and 

 strongly braced together. The span revolves on a central pivot and 

 on conical wheels, rolling on a cast-iron roller-path nineteen feet 

 in diameter. The ordinary piers are constructed of cast-iron and 

 wrought-iron cylinders six feet diameter braced with wrought and 

 cast-iron. The cylinders comprising the swing-pier are of wrought 

 and cast iron six feet in diameter, five in number, braced together 

 with wrought and cast iron. The abutments at each end are of 

 sandstone masonry. This bridge was completed ready for traffic 



