78 Modem Fireproof and Watertight Building Materials.,. 



is their being free from any rafters and purlins ; only tierods 

 are required if the walls be not strong enough to resist the 

 horizontal thrust. The vertical iron you see in the plan is 

 mere thin hoop iron to keep the tierod in a horizontal position. 

 Such roofs have been carried out up to a span of one hundred 

 and twenty feet. They have a parabolic form ; the rise is 

 generally one-fifth of the span, and they are provided with 

 louvres in intervals of three or five feet. For small spans 

 up to twenty-five feet our light Colonial corrugated-iron 

 roofs are cheaper than these Traegerwellblech roofs ; but for 

 roofs over factories, or railway stations with large span, 

 they are highly to be recommended. 



As far as I am aware, the Dutch Government has ordered 

 gatekeeper cottages of Traegerwellblech for their colonies. 

 Considering that such cottages would stand a bush fire, 

 especially if covered with stone-paper outside, which would 

 also make a good ventilated cool wall, it should be worth 

 while trying such cottages for our country stations. 



All Traegerwellblech plates are either varnished or zinc- 

 coated, not galvanised. 



Messrs. Palmer, Scott and Co., who are the agents of the 

 manufacturers, Hein, Lehmann and Co., and Mr. Mephan 

 Ferguson, who has acquired the right to carry out all con- 

 structions of Traegerwellblech in Victoria, have kindly sent 

 specimens of this material for your inspection. 



I shall now proceed to the second part of my paper, to 



Watertight Building Materials. 



I use this term advisedly, since I am aware that it is apt 

 to sound somewhat strangely to English ears. It has been 

 adopted, however, after mature deliberation, by the profession, 

 and signifies absolute imperviousness to moisture. 



I shall not, on this occasion, refer to the pernicious 

 influences of damp dwellings, nor shall I enlarge on the 

 waste of capital in the multiplication of ill-considered and 

 defective structures. Suffice it for me to enumerate the 

 several quarters from which buildings are exposed to the 

 attacks of moisture : — 



1. Rain, and consequent percolation from above ; 



2. Absorption from the atmosphere, consequent on the 

 hygroscopic innate qualities of the material employed ; 



3. Absorption from below the surface of the ground. 



