190 Henry C. Richards: 



it is seen that they are nothing more than a number of grain<^ 

 cemented by secondary silica and are of secondary origin in the 

 stone. 



The average size of the grains is about .25 mm., and from 

 a microscopical examination the sandstone appears to be almost 

 the ideal one for weathering. (See Plate I.. Fig. 1.) 



Dunkeld Stone. 



This is made up almost entirely of sand grains, but differs 

 from the Stawell stone in that the grains are much smaller, and 

 of a more angular character, also they are not so much com- 

 pacted, with the result that there is a great deal more binding- 

 material. 



This cementing material is uniformly stained with iron oxide, 

 which gives it a light brown colour. It is the presence of a fair 

 amount of this fine-grained matrix and the almost total absence 

 of patches of secondary silica that renders this stone cheaper 

 than the Stawell stone to work. (See Plate I., Fig. 2.) 



Barrahool 11 ills Stone. 



It is at once seen that this stone is of an entirely different 

 nature from the Stawell and Dunkeld stones, and appears to 

 be made up of reassorted igneous materials, most of which have 

 been altered. Angular crystals of c^uartz are scattered through 

 the rock, while a good deal of both orthoclase and plagioclase is 

 present. Most of the felspars are kaolinised, and form part of 

 the cementing matrix of the stone. The quartz and felspar 

 fragments are set in a fine-grained matrix made up of chlorite, 

 haematite, mica and volcanic fragments. The minerals in the 

 rock are consideral)ly altered, and this no doubt accounts for it>i 

 low crushing strength. (See Plate II., Fig. 1.) 



A polio Bay Stone. 



The description of the Barrabool Hills stone may be taken 

 as that of this stone, with tlie exception lliat this is uiui-li 

 fresher, and small grains of magnetite occur here and there 

 through it. An examination of sections made from the fresldy 

 quarried stone, and of some which had been exposed for about 



