1869.] Mortar. 759 MORTAR. WHAT a simple word, consisting of but six letters, yet what a mighty work it does ! " The cloud capp'd towers, the gorgeous palaces," are all dependent on its adhesion to their cause, and without it they could not assume the proud position they hold, no more than the ambitious little creature man could live without breath. Mortar is the life of masonry, as masonry is the minion of man. It binds the slave to his master's will, and is, in fine, the good genius of Building. That this friend of our species, this best ally of our enterprises in raising en- during monuments to fame, should be well treated, would seem natural enough, and yet the exception is too often the rule. Here, for thousands of years, has man's intimacy with Mortar been great, and yet our knowledge of it to-day is actually more theoretic than prac- tical. The ancients had more sense in this respect than we, and studied well the nature and properties of this great ma- terial, and they were repaid in the en- durance of their structures; which, after centuries upon centuries of exist- ence, are to-day more stable and more likely to remain than nine-tenths of the buildings we, in our generation, attempt to make lasting. Yitruvius has given instructions on this subject which it would be well if our modern builders would study and practice. After descanting on the na- ture and quality of the various sorts of sand, he says : — " We proceed to an ex- planation of the nature of lime, which is burnt either from white stone or flint. That which is of a close and hard tex- ture is better for building walls, as that which is more porous is better for plas- terings. When slaked for making mor- tar, if pit sand be used, three parts of sand are mixed with one of lime. If river or sea sand be made use of, two parts of sand are given to one of lime, which will be found a proper proportion. If to river or sea sand, potsherds ground and passed through a sieve, in the pro- portion of one-third part be added, the mortar will be better for use. The cause of the mass becoming solid when sand and water are added to the lime, appears to be that stones, like other bodies, are a compound of elements ; those which contain large quantities of air being soft, those which have a great proportion of water being tough, of earth, hard, of fire, brittle. For, stones which, when burnt, would make excel- lent lime, if pounded and mixed with sand, without burning, would neither bind the work together, nor set hard ; but having passed through the kiln, and having lost the property of their former tenacity through the action of intense heat, their adhesiveness being exhausted the pores are left open and inactive. The moisture and air which were in the body of the stone, having therefore been extracted and exhausted, the heat being partially retained, when the substance is immersed in water before the heat can be dissipated, it acquires strength by the water rushing into all its pores, effervesces, and at last the heat is ex- cluded. Hence, limestone, previous to its burning, is much heavier than it is after having passed through the kiln, for, though equal in bulk, it is known, by the abstraction of the moisture it previously contained, to lose one-third of its weight by the process. The pores of limestone being thus opened, it more easily takes up the sand mixed with it, and adheres thereto ; and hence, in dry- ing, binds the stones together, by which sound work is obtained." In the admixture of the lime with the sand, for the production of mortar, the greatest care must be taken that the in-
