154 DISCUSSION. 



log, however large. Before slates or iron for roofing came into 

 use it was a question of some of the Insurance Companies as to 

 whether the shingles in use were of ironbark or of oak. 



P. N. Trebeck —I take a little exception to that last remark 

 about the pastoral interest. The country ringbarked contains 

 inferior timber. Except in the Silver-leaved Ironbark country of 

 Queensland, land that grows ironbark would not grow good grass. 

 The pastoral interest did not destroy the valuable ironbark timber. 

 That country is not adapted for pasture at all. They only ring- 

 bark box timber. It is better to utilise the land for growing grass 

 than inferior timber. 



J. F. Mann — I beg to differ in opinion, having travelled 

 hundreds, perhaps thousands of miles over this country and 

 noticed with regret the reckless destruction of fine timber by 

 ringbarking. The introduction of galvanized iron has done much 

 to prevent the bark from being stripped from the straightest and 

 finest trees for roofing purposes. To such an extent was this 

 carried in the early days of gold digging, that builders and others 

 had great difficulty in obtaining sufficient timber for permanent 

 buildings. I recently visited an extensive tract of ironbark 

 country where, by the judicious process of burning off all under- 

 growth and rubbish, the large trees had been preserved and the 

 otherwise poor soil was covered with good grass. 



D. M. Maitland — I have a very few remarks to make with 

 regard to what was said by a gentleman at the last meeting in 

 connection with the reason for decking the Hawkesbury Bridge 

 with soft timber instead of hardwood. The reason given for 

 using soft wood instead of hardwood was the difference in the 

 weight, but I think it would appear to most people that the 

 difference in weight of a few tons between soft and hard wood is 

 of very little moment in a structure of the size of the Hawkesbury 

 Bridge. It would lead one to suppose if that was a consideration 

 that the margin of safety must be run very fine. I hope that in 

 his reply Prof. Warren will touch upon that subject. 



Professor Warren — I will endeavour, as far as possible, to 

 reply to the various remarks which have been made in the 

 discussion, First, with regard to the relative advantages and 

 disadvantages of pine timber and Australian timber in the decks 

 of bridges, Mr. C. 0. Burge, m. lust, c.e., Government Engineer in 

 charge of the erection of the Hawkesbury Bridge, stated "that the 

 reason ironbark timber was not used for the deck was that the 

 extra weight of the ironbark timber would necessitate a greater 

 weight of steel in the bridge, the cost of which would more than 

 compensate for any advantages due to the ironbark deck." The 

 dimensions of the present Oregon sleepers in the bridge are 24 feet 

 long by 9 inches wide by 8 inches deep, and in order that iron- 



