MORTAR-MAKING. 903 



allowance must be made for the gradual settlement of the 

 building; especially must this be considered in arch work. 



The success attending a lengthened trial of mortar made 

 from some Victorian lime has been very marked ; it was 

 used in building a weir in this colony some years back, M'hich, 

 after standing the strain of several floods, is still intact ; 

 indeed, so strong have the joints become that when a httle 

 while back some alterations were being made, the sprawls of 

 stone had to be broken in some cases before the mortar 

 allowed them to be removed. The builder was so pleased 

 with the results of his trial of the lime that he has decided to 

 use it in the construction of another weir. This gentleman 

 writes as follows regarding his weir : — " It is built with 

 mortar made from Victorian hydraulic lime, no ' cement ' 

 whatever being used, and its resistance to water is so effective 

 that when the water does not cascade over it the bed-rock on 

 the lower side is as dry as a bone. So convinced am 1 of its 

 superior hydraulic character that I am now using it in the 

 construction of another weir lower down on the same 

 creek." 



Professor Rankine, in his treatise on " Civil Engineering," 

 tabulates the results of experiments as follows : — 



A year and a half after mixture — 



Crushing force in lbs. 

 on the square inch. 



Ordinary lime mortar 580 



Hydraulic lime mortar 680 



Ordinary lime mortar beaten 800 



Hydraulic lime mortar beaten 930 



Sixteen years after mixture the increase of strength is in 

 the following proportions — 



For common mortar... 

 For hydraulic mortar 



One year after mixture — 



Tenacity in lbs. on 

 the square Inch. 



Good hydraulic lime 170 



Ordinary hydraulic lime J J^^^ ,qq 



Rich lime 40 



Good hydraulic mortar 140 



Ordinary hydraulic mortar 85 



Good common mortar 50 



Bad common mortar 20 



