BuAlding Stonf'.s of Victoria. 187 



The Sydney stone, on the other hand, gained colour, due no 

 doubt to the oxidation of the ferrous iron it contains, but the 

 colouring was variable. On fracturing the cube it was seen 

 that almost the whole of the stone had undergone an alteration 

 in colour, there remaining a central core about 1 cm. in diameter 

 of unaltered appearance. From this core outwards a beautiful 

 zoning effect was produced, the colour being a deep brown, 

 about 1.5 cm. from the surface, and then fading away to the 

 surface, which in some cases was white and in others varying 

 shades of brown. 



The Darley stone was the most seriously affected of all, 

 cracks extending along the bedding planes throughout the whole 

 length of the cube. The cracks were more pronounced at the 

 corners, where some of the material fell away — in fact, the 

 stone required very careful handling to maintain the cubical 

 shape at all. Thin flakes fell away, and a good deal of dis- 

 colouration was produced by dift'erential iron-staining. 



The Bacchus Marsh stone underwent the same changes as the 

 Darley stone, but they were not so pronounced, and little or no 

 tracking was produced in it. 



In the table are shown in percentages the total loss the stones 

 (inderwent, the loss due to mechanical falling away, the loss due 

 to the chemical action of the acids, and the soluble material as 

 oxides, sulphates and chlorides. 



During the experiment the CO^ liberated by the action of 

 the acid on any carbonates present escaped of course. 



Table of Percentage Losses in Acid Test. 



Denotes ijain in Weiglit. 



