924 PROCEEDINGS OF SECTION J. 



said, such bricks are most difficult to get here. In many- 

 parts of Europe and America the demand for brick fronts is 

 so great that the country has been prospected for brick-earths 

 of a desirable kind, and these are now worked and sometimes 

 forwarded to great distances by rail. 



Such is not generally the case in Australia, not because 

 the proper brick-earths do not exist, but because the demand 

 for high-class work is so very restricted. The various 

 colonies are rapidly becoming netted with railways, so 

 accessibility to the best deposits will be easier when the time 

 arrives for their utihsation, but that time will not arrive until 

 the public are in deeper sympathy with artistic brickwork. 



Mortar. 



Besides bricks, another very important factor is needed in 

 order to make brickwork — that is, mortar. Lime, of course, is 

 the most important feature in all mortars, not excluding 

 cements, and its strength depends on the class to which it 

 belongs, the proportion of its combination with other substances, 

 and the mode of its manufacture. 



Everybody is aware of the importance of cement in making 

 a reliable and non-skrinking mortar, but as it is used princi- 

 pally for piers under great pressure, additions to existing 

 structures, and other important works, rather than as an 

 ordinary building mortar, I do not propose to follow uj) this 

 subject. 



Building limes may be divided into four classes : — 



1 . Fat limes. 



2. Feebly hydraulic limes. 



3. Moderately hydraulic limes, and 



4. Eminently hydraulic limes. 



Fat limes are calcined from such materials as chalk, pure 

 marble, oolitic limestones, and shells. They throw off much 

 heat in slaking, and set badly. Although they may be of 

 service for sanitary purposes and plastering, they make poor 

 mortar, and ought not to be used in any important work, as 

 unfortunately is frequently the case. 



Hydraulic limes owe their property to some other material 

 contained in the stone. Many different substances tend to 

 produce hydrauUcity, but the principal constituent is clay, and 

 upon the proportion of the combination depends the quality 

 of the building lime. 



Some hydraulic limes slake slowly, others with difficulty, 

 whilst a few require to be ground. Feebly hydrauhc Hmes 



