LIGHT RAILWAYS FOR NEW SOUTH WALES. 241 
sixty pounds should be used in future. He believed that no more 
fifty pound rails were laid thereafter, and that sixty pound rails 
were now considered the minimum, 
Mr. P. Auuan had anticipated that mention would have been 
made of the danger in narrow gauge railways, of overturning due 
to wind pressure, accidents from that cause having actually 
occurred in New Zealand. He had been informed by one of the 
engineers connected with New Zealand railways that the under- 
side of the carriages had since been loaded with rails, and that a 
wind fence had been erected on either side of the line. Having 
been intimately connected with the designing of some seven 
hundred traffic bridges throughout this colony, he might perhaps — 
be permitted to offer a few remarks on this important item in 
connection with railway construction. Hitherto the use of timber 
in railway bridges had been in most cases restricted to small span 
structures, but as good sound ironbark had on the average an 
ultimate tensile strength of eight tons per square inch, or one- 
third that of wrought iron, there was no reason why full use—in 
the construction of timber bridges with fair sized spans—should 
not be made of this material, which oftentimes was in close prox- 
imity to the route of the proposed railway. If it could be shown 
that the annual cost of maintenance, plus the interest on prime 
cost, plus an amount per annum as a sinking fund to liquidate the 
cost of a timber bridge at the end of its life, was less than the 
maintenance and interest for an iron or steel bridge, then from a 
financial point of view, there could be little reason why such a 
saving in the revenue should not be taken advantage of. For 
the sake of comparison he had estimated the cost of the super- 
structure of a steel truss bridge and a timber truss bridge each of 
one hundred and twenty feet span, and to make the case favour- 
able to the steel bridge he had assumed that the proposed site was 
three hundred miles by rail from Darling Harbour, and that, there 
being no suitable timber in the locality, the whole of the timber 
had to be brought from one of the northern rivers. Omitting in 
each case the rails and fastenings, the superstructure of a steel 
P—July 5, 1893. 
