Buildivff Stones of Victoria. 183 



3. — Absorption. 



This test is one of the most important, especially with sand- 

 Btones, but the chemical and physical natures of the stone must 

 be considered as well as the absorption in ascertaining its 

 durability. 



There are several methods of determining this factor, but 

 the simplest one has been adopted — that of total immersion in 

 water till the stone is thoroughly saturated. 



TSvo-inch cubes, with faces smooth dressed, Avere used. These 

 were first thoroughly dried, weighed, and then placed in wide 

 glass beakers, covered with distilled water, and allowed to re- 

 main there for four days, which time was found sufficient for 

 the complete saturation of all the stones treated. Tlie cubes 

 were then carefully removed, the surface water absorbed by blot- 

 ting paper, and then weighed with the least possible delay. The 

 increase in weight gives the amount of water absorbed. If this 

 be multiplied by the specific gravity of the stone, it gives the 

 bulk absorption, or the weight of stone which would occupy the 

 same space as the absorbed Avater does, and so the porosity. In 

 all cases several determinations were made, and in the accom- 

 panying table are the means of these values. There is a great 

 variation in the absorption of the different stones, for the 

 Bacchus Marsh is three times as porous as the StaAvell stone. 

 The Stawell and Dunkeld stones are the least porous by a con- 

 siderable extent, while the others, with the exception of the 

 Apollo Bay stone, may be considered high, more especially that 

 from Bacchus Marsh. The freezing of absorbed Avater is a A-ery 

 large factor in the disintegration of stones, and as a rule the 

 value of a sandstone is the inverse of its absorption. 



In Melbourne, OAving to its small amount of frost, these high 

 absorptions are not of so much importance as they Avouid be 

 in less favourable climates, but it must be remembered that the 

 more porous the stone the more accessible are its alterable con- 

 stituents to the destroying elements. The Stawell value is low, 

 but this is to be expected from the physical and chemical nature 

 of the stone. The Dunkeld and Sydney percentages may be re- 

 garded as fair. Avhile the Apollo Bay stone gives a rather higli 

 value. All the others are high, more especially the Bacchus 

 Marsh value. 



