All the lime necessary for any required quantity or batch of mortar should be slaked at least one day before it is mixed with the sand.

All the water required to slake the lime should be poured on at one time, the lime should be submerged, and the mass should then be covered with a tarpaulin or canvas, and allowed to remain undisturbed for a period of 24 hours.

The ingredients should be thoroughly mixed, and then heaped for use as required.

Recent experiments have developed that most American cements will sustain, without any great loss of strength, a dose of lime paste equal to that of the cement paste, while a dose equal to ½ to ¾ the volume of cement paste may be safely added to any Rosen-ale cement without producing any essential deterioration of the quality of the mortar. Neither is the hydraulic activity of the mortars so far impaired by this limited addition of lime paste as to render them unsuited for concrete under water, or other submarine masonry. By the use of lime is secured the double advantages of slow setting and economy.

Pointing Mortar is composed of a paste of finely-ground cement and clean sharp silicious sand, in such proportions that the volume of cement paste is slightly in excess of the volume of voids or spaces in the sand. The volume of sand varies from 2½ to 2¾ that of the cement paste, or by weight. 1 of cement powder to 3 to 3 1/3 of sand. The mixture should be made under shelter, and in quantities not exceeding from 2 to 8 pints at a time.

Before pointing, the joints should be reamed, and in close masonry they must be open to 1/5 of an inch, then thoroughly saturated with water, and maintained in a condition that they will neither absorb water from the mortar or impart any to it. Masonry should not bo allowed to dry rapidly after pointing, but it should be well driven in by the aid of a caulking iron and hammer.

In the pointing of rubble masonry the same general directions are to be observed.