XCIy. PERCY ALLAN. 
live load of 84 Ibs. per square foot of floor space, and a concentrated 
load of 164 tons on a 10’ 4” wheel base, with 94 tons on a pair of 
wheels, 5’ centres. The wire ropes carrying counterweights are 
21” circumference composed of six strands round a core of hemp, 
each strand containing seven wires of mild crucible steel, having 
after galvanising, an ultimate strength of 87 tons per square 
inch, and a twisting strength of 34 turns in a length of 8”. 
Prof. Warren, M.Inst.C.£., has carried out at the University of 
Sydney for the Bridges Branch of the Public Works Department, - 
a number of tests on rope of the same section, the results (given 
in appendix A.) showing the ultimate strength of a full size “laid” 
_ rope to be 90% of the strength of the forty-two wires tested indi- 
vidually, and the strength of a turned and spliced end to be 837, 
of the ultimate strength of the rope. As the ultimate strength 
of the sixteen ropes in Swan Hill bridge is 266 tons, and the 
weight of lift span only 34} tons the ropes have a “factor” of 73, 
an ample margin in view of the slow speed and large diameter of 
the rope wheels, the wheels being seventy-seven times the 
diameter of the ropes. 
The steel used in the superstructure is of a mild quality, having 
an ultimate strength of 26 to 29 tons per square inch, with an 
elongation of from 20% to 26% in a length of 10”. The main 
girders of steel lift span stand 16’ 4” apart and have sliding bear- 
ings at each end, whilst the timber trusses are 21’ 7” apart centre 
to centre. The 4” sawn tallow wood planking on the lift spam 
rests on longitudinal ironbark girders secured to steel web plate 
“fish-bellied” cross girders pitched 8’ 4” apart. 
The planking on truss spans and approach spans rests on iron- 
bark longitudinal girders. The carriage way is 14’ between the 
sawn ironbark kerbs on lift span, and 18’ 3” and 21’ 11” between 
kerbs on truss and approach spans respectively, one 4’ 6” foot way 
being provided on the upstream side of truss and approach spans: 
The two river piers each consist of a pair of cast-iron cylinders 
18' 4” centre to centre, founded on rock and extending to a height 
