Mortar

—A cementing material consisting of a mixture of lime and sand with water, used to bind together bricks or stones into structures. It “sets” or hardens in the air, and not under water, its setting consisting in the changing of the hydrate of lime into the carbonate by the absorption of carbonic acid from the atmosphere. This naturally is a slow proce . Hardening also depends upon the crystallization ot the mortar, and is greatly facilitated by using uniform sand of sharp and angular nature, as lake or river sand. The best known and most reliable mortar used in building construction is composed of three parts of clean sharp sand, free from earthy matter, and one part of freshly slaked lime.