STONE WALLS, such walls as are constructed of stone.
The modern methods of constructing stone walls, with a description of the materials employed, have already been given under the head MASONRY; we shall, therefore, confine this article to the construction of walls used by the ancient Greeks and Romans.
Vitruvius has left us an account of the construction of the walls of the ancients as follows "The sorts of walls are the reticulated, (Figure 1,) and the ancient, which is called the uncertain, (Figure 2.) Of these, the reticulated is the handsomest, but the joints are so ordered, that all the parts of the courses have an infirm position ; whereas, in the uncertain, the materials rest firmly one upon the other, and are interwoven together ; so that they are much stronger than the reticulated, though not so handsome. Both sorts are formed of very small pieces, that the walls, being satu • rated with mortar, may endure the longer ; for the stones, being of a porous and spongy nature, absorb the moisture from the mortar ; and when there is an abundance of mortar, the wall, having more.humidity, will not so soon decay, but will, on that account, be rendered more durable; for as soon as the humidity is extracted from the mortar by the suction of the stones, then the lime and sand separating, the cement is dissolved, and, the mortar, no longer uniting the materials, the walls soon become ruinous. This may be observed in some tombs near the city, which are built with marble, or hewn stone, and the internal parts rammed with rubble stones ; the mortar being by length of time drained of its humidity by the suction of the stones, and the union of the joints being dissolved, they separate and fall to ruin.
"To avoid this error, the middle space (Figure `2) must- be strengthened with abutments of the red hewn-stone, or bricks, or common flints, built in walls two feet thick, and bound to the front with cramps of iron fixed with lead ; for the work being thus built in a regular manner, and not laid in promis cuous heaps, will remain without defect ; and being, by the orderly arrangement of the courses and joints, firmly united and bound together, it will not be liable to fractures, nor will the abutments suffer it to fall to decay. For this reason, the
walls of the Greeks are not to be despised ; for though they do not use smooth or polished materials, yet where they dis continue the square stones, they lay the flints, or common hard stones, that they use, in the same manner as bricks are generally laid, bonding the courses together with alternate joints, and thus making their works strong and durable.
"These walls they build in two manners ; one is called isodomum, (Figure 3,) and the other pseudisodomwm, (Figure 4.) lsodunium is when all the courses are of an equal thickness; and pseudisodomum when they are unequal. Both these sorts are firm ; first, because the stones themselves are of a compact and solid nature, and do not absorb the mois ture from the mortar, but preserve its humidity to a great age ; and, secondly, being situated in regular and level courses, the mortar is prevented from (idling, and, the whole thickness of the wall being united, it endures perpetually.
Another sort is that which they call empleeton, (Figure 5 and 6,) which is also used by our villagers. The faces of the stones, in this kind, are smooth ; the rest is left as it grows in the quarry, being secured with alternate joints and mortar ; but our artificers, quickly raising a shell, which serves fur the faces of the wall, fill the middle with rubble and mortar ; the walls, therefore, consist of three coats, two being the faces, and one the rubble core in the middle, (Figure 5 and 6.) But the Greeks do not build in that manner ; they not only build the facing courses regularly, but also use alternate joints throughout the whole thickness, not ramming the mid dle with rubble., but building it the same as the face, and of one united coat they construct the wall ; besides this, they dispose single pieces, A, which they call diatonos, in th9 thickness of the wall, extending from one face to the other, which bind and exceedingly strengthen the walls. Those, therefore, who would build works of long duration, must attend to these rules, and make use of such methods of ; for the smooth polish, and beautiful appearance of the stones, will not prevent the wall from being ruined by age."