ILLUSTRATIONS. 
PLATE VII. 
Fic. 1. The effect of sun and rain on a cement which remained sound in 
water and in air. 
2. The same cement more finely ground and subjected to the same 
conditions. 
TEXT FIGURES. 
Fic. 23. Typical curve of the tensile strength of Portland cement. 
24. A diagram showing the evil effects of overburning a Roman 
cement. 
25. Expansion curves showing the effect of free lime in indurated 
Portland cements made by Campbell and White. 
26. Expansion curves showing the effect of free lime in indurated, 
hard-burned commercial Portland cements submerged in water. 
27. Diagram showing the effect of permeability on the expansion due 
to free lime. 
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