Building Materials, 



27 



these causes, they undoubtedly have exercised an influence 

 more powerful than we are at first inclined to admit. 



The Sandstone procured from Irrewarra, in the parish of 

 Boroondara, singularly contrasts with other beds in the im- 

 mediate vicinity. Though, as will be shewn, it is neither so 

 durable nor so valuable in other respects as the Geelong 

 Sandstones, it is a proof that the changing character of the 

 beds needs only to be noted and followed to lead to other 

 deposits of a better description. 



The block which has been handed to me for examination 

 is composed of course quartz grains, much water worn, 

 agglutinated by an argillaceous and siliceous cement. Its 

 shades vary from pale cream color to nearly pure white, and it 

 is irregularly traversed by red and brown ferruginous streaks 

 and spots. It yields readily to the hammer in the direction 

 of its cleavage, as is usual with stones of this class. The 

 average weight is 155 lbs. per cubic foot. Its capacity of 

 absorption is so great that that alone is a sufficient reason for 

 its rejection as a material for large buildings. After im- 

 mersing a portion of the block, weighing 55*85 ozs. for 72 

 hours it absorbed 3'043 per cent, by weight, and another 

 experiment on a smaller piece gave 3"217 per cent. By 

 simple immersion, allowing it to remain till air bubbles had 

 ceased to escape, the results were as follow : — 



Experimentj No. 1, 2'542 per cent. 



2, 2-320 



3, 2-194 



Thus, it not only absorbs a large amount of water, but what 

 speaks more strongly in its disfavor, such absorption is carried 

 on very rapidly. 



This stone has been subjected to a variety of tests, some of 

 which it is necessary to particularize. A small specimen of 

 the average quality was immersed in a solution of a carbonate 

 till it had absorbed the maximum quantity ; it Avas then placed 

 in a weak solution of acid : this gave rise to brisk effervescence, 

 and frequent repetitions of this resulted in the destruction of 

 the surface of the stone. This test I have found valuable in 

 practice : it is needless to state that it can only be used when 

 the cement is not of a calcareous nature. 



Another series of tests were instituted by immersing the 

 stone in solutions of various salts, and then suspending it over 

 the vessel containing the fluid. After this process was many 

 times repeated the salt re-crystallised in the stone ; and the 



