BY HENRY C. RICHARDS, M.SC. 20B 



situations, this being due in the opinion of Messrs. Vernon 

 and Kent to a perishing of the cementing medium of the 

 quartz particles, a kind of dry rot, and which only appears 

 to occur when the stone is not exposed to the moisture 

 of the atmosphere.* 



The variety used here is grey- coloured, though occa- 

 sional blocks of the brown variety have been employed, 

 and these arranged somewhat haphazardly produce an 

 effect which serves to break what would otherwise be a 

 somewhat monotonous dull-grey colour. An examina- 

 tion of the stone work around the beautiful window on the 

 N.E. side of the building shows the manner in which this 

 material lends itself to carving. 



Views have been expressed to the effect that the 

 Helidon stone might, with more advantage, have been used 

 for the external purposes to which the Sydney freestone 

 has been put. 



The former, from a colour effect, may have been more 

 pleasing, but its w^eathering qualities for this type of work 

 have yet to be fully demonstrated. The brown variety of 

 Sydney stone, such as has been recently used in the New 

 Zealand Life Assurance building, in Queen Street, is 

 peculiar, owing to its taking on the familiar soft brown 

 colour after being exposed for some time. This is due 

 to the fact that the stone when f res lily quarried contains 

 a small amount of ferrous iron, sometimes in the form of 

 carbonate, which becomes oxidised to the ferric state on 

 exposure. 



Owing to the somewhat uneven distribution of the 

 ferrous iron contents, the stone does not become a uniform 

 brown, which is rather fortunate from an architectural 

 point of view. 



The following tests of the Sydney stone will be of 

 interest. Those with an asterisk are taken from the paper 

 published by Nangle and Baker, in Proc. Roy. Soc, X.S.W.,. 

 Vol. XLIII., while the others were carried out by the 

 author, and published in " The Building Stones of Victoria,'^ 

 in Proc. Roy. Soc, Vic, Vol. XXII. 



*K,. T. Baker and J. Wangle, Proc. R.8. of N.S.W., Vol. XLIII., p. 189- 



