LIFT BRIDGE OVER THE MURRAY AT SWAN HILL. XCIII. 
raised and lowered by means of one winch driving the two 
sprocket wheels, working two chains attached to the bottom of 
the two weights (over one pier) and is then secured (after passing 
under sprocket wheels) to bottom corners of lift span. 
In 1889 Mr. J. A. McDonald, mM. Inst. c.E., Engineer for Bridges 
for New South Wales, introduced a new design for the Mulwala 
Bridge over the Murray River, the author working out under 
Mr. McDonald the details in connection with the structure, this 
design being repeated for the Wentworth Bridge over the 
Darling River, the clear fairway provided is 46’ 3” and the 
clear headway above highest flood being 23’ 4”. The leading 
features of this design were—the stiffening of superstructure by 
the better disposition of the materials, the substitution of wire 
ropes for the cumbersome chains previously used, the placing 
of the operating winch overhead at the centre of the lift span, 
and the arranging of the winch so that the one main longi- 
tudinal shaft geared directly with the two transverse shafts 
carrying the rope wheels. The design was far in advance of 
previous lift bridges but difficulties were met with owing to the . 
untwisting of ropes causing the weights working in the towers to 
brush, inducing considerable friction, which it was thought 
advisable to avoid when the Wilcannia and Tocumwal Bridges, 
designed by Mr. J. A. McDonald, under Mr, Hickson, were 
being considered. 
In the design for these two bridges the driving shaft was 
placed transversely and geared into two longitudinal shafts 
carrying the rope wheels placed directly over the centre of the 
towers, the balance boxes being placed on the outside of towers 
working on V guides. The clear fairway provided is 50’ 5” and 
clear headway above when span is raised full height being 25’. 
The Swan Hill bridge designed by the author in 1894, was the 
next and latest type of lift bridge to be erected. The bridge 
consists of one steel lift span 58’ 4” between centres of bearings 
Over piers, two 91’ 6” timber truss spans, and four 35’ timber 
approach spans, (Plates 1 and 2.) The bridge is designed for a 
