BUILDING AND ORNAMENTAL STONES OF N.S.W. 189 



as for instance the stone of the Macquarie obelisk, which 

 has now stood all weathers for nearly 100 years and is as 

 sound as the day it was built. 



This fretting of our sandstone in certain situations has 

 received some attention from the Colonial Architect Mr. 

 Vernon and Mr. H. C. Kent, who are of opinion that it is 

 due 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. In the absence of practically any age data 

 concerning the durability of our stones, the next best 

 thing has been undertaken, viz : — crushing and fire and 

 water tests. 



Tire Tests.— As far as we have been able to ascertain, no 

 data exist as to the refractoriness of our building stones, 

 so that the data in this connection given below may be of 

 value to architects and others interested in this feature of 

 them. The samples tested were necessarily small as 

 muffles were not available to take larger samples. The 

 typical rocks were only taken and the results, few as they 

 are, are comparative. Two methods were available for 

 obtaining the temperature of muffle furnaces, viz.: Siemen's 

 pyrometer and Pitkin White's Thermo-electric pyrometer. 

 The former was found to work very satisfactorily so was 

 used for all demonstrations. The samples subjected to 

 this particular test were sandstones, marbles, trachytes, 

 and granites, and the data speak for themselves. It may, 

 however, be stated in passing, that the sandstones came 

 best through the different fire and water tests. 



Crushing Strengths.— These were carried out at the 

 Technical College by Mr. James Nangle with the 100 

 ton crushing machine, and the most interesting feature of 

 the series is the remarkable breaking resistance of some of 

 the marbles which in the case of the Caleula varieties 



