HISTORY OP CIVIL ENGINEERIXC. IN NEW SOUTH WALES. 609 



forty feet in the clear ; and three bridges, consisting of spans 

 each thirty feet in the clear ; there is one viaduct consisting of 

 five spans each forty feet in the clear, and eight spans each thirty 

 feet in the clear. The forty feet spans consist each of four Warren 

 girders under the railway, each forty-four feet long over all and 

 five feet three inches deep, resting on piers and abutments built 

 of brick in cement. The four girders are braced together, both 

 in the horizontal and vertical plane, and the deck is somewhat 

 similar to that described for the Petersham Viaduct. The thirty 

 feet spans consist each of four main plate web girders under the 

 railway, i-esting on brick piers and abutments. 



The bridge over the Nepean River at Penrith is constructed for a 

 double line of way, and carries the main Western road and a single 

 line of I'ailway. It consists of three openings, each one hundred and 

 eighty-six feet in the clear, and one opening of one hundred and 

 twenty-seven feet in the clear. The larger openings have two 

 main box girders, spaced twenty-five feet six inches apart in the 

 clear, and twenty-eight feet six inches from centre to centre, each 

 forming a continuous gii-der five hundred and ninety-four feet 

 long and thirteen feet deep, extending over two intermediate 

 piers. The roadway is carried on cross girders nineteen and a-half 

 inches deep and spaced three feet centre to centre, over which are 

 laid longitudinal timbers fourteen by nine, and three inch planking 

 throughout. The approach span of one hundred and twenty-seven 

 feet is also constructed with two main box girders, each one hundred 

 and thirty-five feet over all and ten feet deep. The piers are built 

 of masonry, and are twelve feet wide at the top, and spaced one 

 hundred and ninety-eight feet centime to centre. The main girders 

 are supported upon timber platfoims, each twelve feet long by 

 four feet eight inches in width, and the expansion rollers are 

 similar to those of the Menangle Bridge. With a live load of 1-25 

 ton per foot run on each line of w^ay, the maximum stresses in 

 the booms would be 5-82 tons per square inch in tension, and 4-64 

 tons per square inch in compression. The maximum stress in the 

 rivets over piers is 9-3 tons per square inch. With one ton per 

 foot run on the main girder, the deflection observed was -93 inches. 

 There are also tliree spans of twenty-six feet of timber framing 

 on the eastern side of the bridge, three similar spans on the 

 western side, and a timber viaduct between the Penrith Station 

 and the river Nepean, consisting of sixty-four spans of twenty 

 six feet each. 



The Knapsack Valley Viaduct is built of masonry on an 

 incline of one in thirty, and consists of five spans of fifty 

 feet each, and two of twenty feet each. Mount Clarence Tunnel, 

 eighty-eight and a-quarter miles from Sydney, is five hundred and 

 thirty-nine yards in length, and lined tliroughout in masoniy set 

 in cement. Between this point and Wallerawang Station there 

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