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 being comparatively indistructible. 



Uniformity of colour is a tolerably correct 



criterion of uniformity of structure, and this constitutes, 

 other circumstances being equal, one of the practical excellen- 

 cies of building stones. 



BlUCKS. 



The great expense 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 following 

 experiments will shew. 



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, shewing the presence 

 of embedded quartz pebbles, with occasionally pieces of 

 unmixed talcose clay of a pure white color. 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 foUoAvs : — 



llamsay's Fire Brick, Newcastle-on-Tyne, 2*204 

 White Brickj Launceston, ... ... 2*153 



