OvIII. DISCUSSION, 
IRONBARK AND MURRAY RIVER RED GUM TIMBER. 
AVERAGE STRENGTH IN Pounps PER Square IncH.—Continued. 
Tensile Strength. Compressive Strength. - 
Timb ae Excess . 
imber. Speci- i: ercentage 
na es Average berate be Average * ironbark 
tested. | Strength. | over rea | tested. | Streneth- | over red 
gum. 
Ironbark ... ab oae 18,252 | 121-0 14 | 10,572 | 395 
| Red Gum ... EAS. 8,258 iss 2 7 B64 ee 
Shearing Strength. 
j | Excess 
Timber. Speci- Average "percentage 
mens Ceoneth of ironbark 
testea.| § sth. over red 
Ironbark ... veh 2 EG 2,164 43°0 
Red Gum ... 2 1518 
The experience of the Bridges Branch had been that whilst 
Murray River red gum was suitable for piles, round girders in 
short lengths and planking, that when worked into squared timber 
exposed to the sun’s rays, it warped and twisted to such a degree 
as to render its use in trusses inadvisable, even if its lack of 
strength did not preclude its use. Although it was optional with 
the contractor for the Wagga Wagga bridge, he preferred to use 
ironbark instead of Murray River red gum for piles and round 
girders, clearly showing it, in that case to be the cheaper timber 
notwithstanding the long rail carriage of three hundred and ten 
miles. 
With all the Border bridges it was customary to invite tenders 
for manufacture in either Victoria or New South Wales, Tocumwal 
bridge ironwork was manufactured in New South Wales, the 
i Swan Hill ironwork in Melbourne, had the tender for Tocumwal 
bridge, which provided for manufacture of ironwork in Melbourne — 
been accepted, it would have increased the cost of structure by 
£400. In the Swan Hill bridge alternative tenders were received 
: for colonial manufacture and importation, Messrs. J. B. and W- — 
— Farquharson’s tender being the lowest in each case, and there — 
