LIME 51 



the water a thick, cohesive paste. On the other hand, 

 poor lime develops but little heat, disintegrates 

 slowly, and increases scarcely any in volume. The 

 first kind comes from nearly pure limestone and can 

 be mixed with a large proportion of sand, thus mak- 

 ing a great quantity of mortar. The second kind is 

 obtained from limestone having various foreign sub- 

 stances and will admit of but a small admixture of 

 sand, thus yielding less mortar than the other. Both 

 have the property of hardening in the air by the ab- 

 sorption of carbonic acid gas which converts them 

 into limestone. 



"There is a third variety of lime called hydraulic 

 lime, which has the peculiar merit of being able to 

 harden under water. It is made from a limestone 

 containing a certain proportion of clay. Hydraulic 

 mortar is used for the masonry of bridges, canals, 

 cisterns, foundations, vaults, in fact for all stone and 

 brick work under water or in damp soil." 



