41 Q Analysis of Scientific Books: 



Aid which will form the last degree on the scale, the differ* 

 ences resulting from the methods of slaking diminish, at last 

 disappear, and then increase in the opposite direction." — p. 42. 

 " Action of Water on Hydraulic Mortars. — The dissolving 

 action of water on hydraulic mortars appears to cease when it 

 has removed the excess of lime that was either in weak com- 

 bination, or entirely at liberty ; and, it was found that the 

 quantity which remained after the action ceased, was never 

 far from that which had been ascertained to be the best ; from 

 whence the following rule : " To find in all possible cases the 

 proportion of lime which is most fit for any puzzolana, a ball of 

 the hydraulic mortar, nearly an inch in diameter, must be made, 

 having rather an excess of lime ; this must be exposed for a 

 year under pure water which is to be changed frequently, and 

 then the quantity of lime which has disappeared is to be 

 ascertained either by analysis or otherwise, and subtracted 

 from the whole quantity, and the difference gives the proportion 

 required for the quantity of puzzolana taken." — p. 55. 



" Effect of Lime on Hj/draulic Mortars. — 1. Excess of lime in 

 a hydraulic mortar retards its setting: the proportions most 

 favourable to the setting are also those which give the greatest 

 strength. 



" 2. Powerful puzzolanas, combined with common lime, harden 

 much sooner than if combined with hydraulic lime ; but hy- 

 draulic lime has the advantage when combined with a less active 

 puzzolana. 



*' 3. The second and third process of slaking appears gene- 

 rally to accelerate the setting more than the first, 



" 4. Hydraulic mortars made with common lime harden more, 

 or make more progress from the second to the third year, than 

 from the first to the second, so that it may be said the rapidity 

 of their progress is accelerated. 



" 5. The resistance of hydraulic mortars, made with lime 

 slightly hydraulic, also undergoes an acceleration, but much less 

 than in the former case. 



" 6. The progress of mortars, made with lime eminently 

 hydraulic, begins to diminish at the end of the second year. 



