Bailding Stonei^ of Victoria. 179 



pale green patches of shaley material in lenticular masses, bound 

 to^^ether by a whitish cementing material uniformly speckled 

 Avith iron oxide. The stone is friable, and works very easily, 

 but needs care in dressing. From samples the stone seems uni- 

 form in hardness and colouring, but the author has not visited 

 the quarry, which is a few miles from Ballan. and nothing is 

 known of its weathering properties in buildings. 



It should be mentioned that all these stones, after being quar- 

 ried or dressed, get a thin skin or coating of harder material all 

 over them. This is more pronounced in the Bacchus Marsh, 

 Darley, Egerton and Green dale stones than in the others, and 

 is ])roduced by the percolation of the "■ sap " water to the sur- 

 face, and there evaporating, leaves the dissolved material in 

 the form of a thin hard skin. 



METHODS OF TESTIXCx. 



The determination of the actual qualities of a stone, good or 

 l)ad, by laboratory tests, is exceedingly difficult. As the object 

 of many of the tests conducted in the laboratory is to produce 

 the same effects in a few davs as are produced in as many or 

 more years under normal weathering conditions, a great deal 

 depends on the methods adopted. However, if all the stones 

 are uniformly treated by these methods, which must necessarily 

 be arbitrary, one obtains at least comparative results, and the 

 relation which one stone bears to another is derived. Stones 

 of known weathering properties, either good or bad, may form 

 part of the series imiformly treated, and the relations which 

 the unknown stones bear to the known ones will give a fairly 

 accurate idea of the durability of the former. Unfortunately, 

 the methods adopted in the laboratory are not the same in all 

 countries, although steps are being taken by an International 

 Congress to fix standard tests. 



In the main the tests aj)plied ])y the author are those followed 

 by r;. P. Merrill,! of Washington, U.S.A. 



1 Merrill. ''Stones for Building- and Decoration." 



