30 Building Materials. 
ness, strength, and impermeability, with a peculiar richness 
of effect. 
As an example of the waste of labour and capital which 
sometimes results from using an untried sandstone, I may 
cite the case of an enterprising citizen of Melbourne, who 
some ten years ago built an hotel of a material quarried from 
the extensive formation to which the Boroondara stone 
belongs. Within three years after its completion the stone 
was found to be so far decayed that it became necessary to pro- 
tect the walls with a facing of another material. This is suffi- 
cient to illustrate the practical utility of inquiries such as these. 
Major-General Sir John Burgoyne, in speaking of this 
class. of stones, has thus expressed himself:—“From the 
nature of the composition of sandstones, it results that their 
resistance against or yielding to, the decomposing effects to 
which they are subjected, depends to a great extent, if not 
wholly, upon the cementing substance by which the grains 
are united; these latter bemg comparatively indistructible. 
. Uniformity of colour is a tolerably correct 
ériterion of uniformity of structure, one of the practical ex- 
cellences of “ building stones.” 
BRICKS. 
The great effects attending the working and procuring of 
building stone in this City, has led to the adoption of Bricks 
as a convenient and ready substitute. Very little attention 
has been paid to their manufacture, as a detail of the follow- 
ing experiments will show. 
I have procured my specimens from large buildings which 
are at present in course of erection, with the hope of drawing 
attention to a matter of such importance. 
These Bricks are composed of clay which has resulted from 
the decomposition of clay slate and Basaltic rocks, and that 
again is mixed with a large per centage of siliceous earth, 
washed down from the more recent formations which form 
the capping of the adjacent hills. 
The fracture is rugged and uneven, showing the presence 
of embedded quartz pebbles, with occasionally pieces of 
unmixed talcose clay of a pure white colour. They are light 
and porous, and readily yield in any direction to a slight blow. 
The specific gravity is 2°078, and compared with other 
Bricks is as follows :— 
Ramsay’s Fire Brick, Newcastle-on-Tyne, 2°204 
White Brick, Launceston, ae .. 29153 
