BY H. C. RICHARDS. 155 



average of a number of specimens crushed under the same 

 conditions should be obtained if a reliable indication is 

 required. 



The values for specific gravit}^ in the case of porous 

 stones like sandstones, require to be carefully accepted, 

 as considerable difficulty is attached to the correct determin- 

 ation of the specific gravity of a porous stone. 



In several places in Brisbane the practice of cementing 

 the bar posts of iron fencing on top of stone by means of 

 pouring in molten sulphur and letting it solidify has been 

 adopted. This is fraught with much risk and very frequently 

 results in the splitting open of the stone just as is done by 

 the " plug and feathers " method of splitting. This 

 is well seen on the fence wall along the river side of William 

 ^Street opposite the Treasur}- building. 



Sulphur is used on account of its cheapness and great 

 chemical stabilit}^ but the use of lead is preferable. The 

 splitting of stone resulting from the use of sulphur instead of 

 lead is a common feature in Melbourne in the basalt fence 

 bases so that it is not restricted to Brisbane or to sand- 

 stones. Sulphur changes its ci'ystalline form and becomes 

 more dense after its initial cooling in the hole, but it is 

 difficult to see. how this could cause the pressure — it should 

 have the reverse effect. Differences in the rates of expan- 

 sion and contraction of the iron, sulphur and stone may bring 

 about the cracking. 



Summary and Conclusions. 



The great advisability of closely considering the 

 available supplies of suitable building stones in Queensland 

 has been pointed out and the necessity of insisting on only 

 sound Aveathering material being used has been urged. A 

 systematic treatment of the physical, chemical and miner- 

 alogical characters of the stones which have been used 

 and those likely to be used has been given. Queensland is 

 well off for suitable granites in many places, and as far as 

 Brisbane is concerned, a good dark "" granite '" from the Mt. 

 Crosby district is worthy of further development. The 

 defects of the Enoggera granite have been show^i, but 

 further prospecting of the granite mass in search of material 

 free from pyrites is suggested. At present the grej' granite 



