Building Materials. 17 



a 4 inch cube of the Cape Nelson stone, weighing when dry 

 SSoz. lOdwts. 12grs., absorbed 4ozs. 7dwts. of water after six 

 hours' immersion. 



A very important discovery has recently been made which 

 unless counterbalanced by chemical or other scientific agency 

 is likely to affect the use of nearly all the colonial building 

 stones. 



Symptoms of exfoliation have lately been exhibited in the 

 stone of which some of the most important of our public 

 buildings are constructed, and wherein the Bacchus Marsh, 

 Darley, Western Port, and Geelong stones have been used. 



A chemical examination of the decayed particles shows all 

 the stone to be impregnated more or less with a large quantity 

 of salts, the principal and worst ingredient being sulphate of 

 soda. A survey of the quarries has also been made, and salts 

 have been found in very large quantities ; these are not dis- 

 tributed equally over the rocks, but in veins and patches, so 

 that without the constant application of chemical tests it would 

 be impossible to distinguish the good from the bad stone. In 

 one case a small block containing only five cubic feet of appa- 

 rently equally good stone was found to contain in one part of it 

 salts equal to 351bs. to the ton, and in the other part only 18ozs. 

 to the ton. Further examination proved that the stone near 

 the surface of the quarry was free from salts, while the deeper 

 the bed was worked the more salts were obtained. The quar- 

 ries at Bacchus Marsh are about 500 feet above the level of 

 the sea, The stone impregnated with salts does not appear to 

 be in any way injured so long as the blocks remain in a moist 

 or wet state, or are kept perfectly dry. It is when the sul- 

 phates are drawn out to the surface of the stone by solar heat 

 or evaporation that they become crystalized and thrown 

 off the particles which previously enclosed them, that the 

 crumbling away or exfoliation takes place. The stone from 

 the quarries referred to was analysed before being used for 

 the public buildings in which it is now employed, but being 

 opened expressly for these works the samples experimented 

 upon were necessarily from near the surface and hence 

 exhibited no indication of salts. It is usual to find better 

 stone below the surface of the rock, and in the present 

 instances the quality of the material appears to improve in 

 all other respects excepting the presence of saline matters. 

 A portion of these consist of the chlorides of calcium and 

 magnesium, so that in the event of Ransom's process for pre- 

 serving stone being proved efficacious, the application of 



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