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MURUS, MOE´NIA (τεῖχος), a wall surrounding an unroofed enclosure, in contradistinction to PARIES (τοῖχος), the wall of a roofed building, such as a temple or a house. This distinction appears to be the true differentia of the words: the fact that the murus usually was a wall of more massive construction is rather an accidental than an essential difference. As far as concerns construction, there is no difference between them, and so the following remarks on this point may be taken to refer equally to Murus and Paries.

A third word, macerìa, is often used by Latin authors to denote a fence wall of a less massive kind than the murus (see Cato, Cat. Agr. 15; and Caes. Gal. 7.69); and hence it is also used, like the Greek μáκελον or μáελος, to denote the space enclosed.

Pre-Roman Methods of Construction.

I. Bricks.--It is only within recent years that archaeologists have realised how very important and extensive the use of sun-dried bricks was, not only in Egypt and the plains of the Euphrates, but also in Greece and Rome, even as late as the Christian era. The fact is that, as long as a wall of unburnt bricks is protected from the weather, either by a facing of stone or even by a coating of fine stucco, it is almost as durable as stone or kiln-fired bricks. When, however, it once begins to fall into ruin, the process of decay is very rapid and complete, and it is only in exceptional circumstances that remains of this kind of wall have lasted to the present day.

In Egypt, although carefully dressed blocks of stone were used for the main walls of the principal temples, yet unburnt brick was by far the most common method of construction, not only for ordinary domestic buildings, but also very largely for the outer precinct walls of the temples, and for such magnificent royal palaces as that of Rameses the Great, which was discovered a few years ago at Tel-el-Yahoudeh in the Delta. In the Greek city of Naucratis, also in the Egyptian Delta, unburnt clay was not only used for all the houses of the colony [DOMUS Vol. I. p. 659 a], but was also employed for the walls of the various temples, and for the great Pan-hellenicon or commercial Guildhall of the associated Greek states. In the account of the pre-historic palace at Tiryns [DOMUS Vol. I. p. 655], a common early method of construction is described; the lower part of the wall being of stone to a height of about 3 feet, and the upper part of sun-dried bricks covered with painted stucco.

The most remarkable examples of the use of sun-dried bricks for the most massively built and lofty structures of every kind were to be found in ancient Assyria and Chaldaea, where stone was scarce, and large quantities of the finest clay had been deposited by the Tigris and Euphrates. Great care was taken in the preparation of these bricks: the clay was tempered by long beating and turning over for complete exposure to the weather, then mixed with straw or rushes, and firmly pressed by hand into wooden moulds; lastly, the bricks were thoroughly dried in the summer sun. The outer faces of the more important walls, those of the temples, palaces, and circuit walls of the cities, were defended by casings of stone or of burnt brick, built “battering” with offsets, so as to be much thicker at the base than at the top. An excellent natural cement was supplied by the numerous springs of hot bitumen, applicable both to fired and sun-dried bricks (see Hdt. 1.179). Bond-courses, consisting of layers of reeds, were built in at regular intervals: this is mentioned by Herodotus (loo. cit.), and examples of the practice have been found by recent excavators. Great care was taken to keep the masses of crude brick from suffering from damp: ventilating pipes were arranged so as to expose the inner parts of the walls to the drying power of the wind, and also to allow the escape of any enclosed moisture. This was specially necessary, as in some cases no bitumen or other mortar was used; instead of which the [p. 2.183]bricks were set while still moist, so that each adhered to the next course, and thus the whole wall became one homogeneous mass of clay. Kiln-fired bricks were also used from very early times, not only as facings, but for vaults, domes, arches, and other important constructional purposes. The Tower of Babel, mentioned in Gen. 11.3, was of burnt bricks set in bitumen; and the most magnificent kind of mural decoration was produced by the use of bricks coated with brilliant coloured enamels. (See Vitr. 1.5. For further information, see Layard, Nineveh; Loftus, Travels in Assyria; Place, Ninive; and Perrot and Chipiez, Chaldaea and Assyria, vol. i.; and, by the same authors, Egypt.) [LATER]

Among early examples of skilfully constructed walls for purposes of defence, some of those erected by people of the Phoenician race, in various parts of the world, are perhaps the most striking. Recent excavations at Thapsus, near Carthage, have brought to light the elaborate and massive character of the city wall, which was about 21 feet thick, with square towers projecting outwards at regular intervals, so as

Section of Wall of Thapsus.

to command the flank of an attacking army. The lower part of this wall, above the groundlevel, was built of solid stone, roughly dressed, so as to resist battering-rams. The upper part was of sun-dried bricks coated with stucco, and contained two tiers or stories of guard-chambers, sufficient to give accommodation for a large garrison of both men and horses. Access was given to the lower story of chambers by inclined planes for the use of the horses. Cisterns for the storage of rain-water in case of siege were constructed below the ground-level in the thickness of the wall--a common arrangement in early systems of fortification. (See Perrot and Chipiez, Phoenicia, i. p. 354.)

In other places the Phoenicians appear to have built wholly of stone. According to Appian (Anabasis, 2.21, 3), the walls of Tyre were built of large stones set in lime (mortar). Only scanty traces now exist of this once almost impregnable city; but another Phoenician wall near Banias (Syria) still exists in places to a height of 35 feet, varying from 16 to 30 feet in thickness. It is built of roughly-dressed blocks of limestone, set on horizontal beds, but with irregular butt joints filled up by the insertion of small stones. The remains of the Punic citadel at Eryx in N. Sicily are of similar character, with massive stones roughly shaped and coursed in an irregular manner.

It is interesting to compare with these Phoenician walls the famous citadel of Tiryns, rounded with a most massive wall, constructed of blocks of such immense size that the Greeks

Tiryns. Section of outer Wall.

of the historic period attributed their erection to the fabled Cyclops, working for god-like [p. 2.184]heroes (see Paus. 2.25). The above cut shows a probable restoration of the Tirynthian wall, as discovered by Dr. Dörpfeld (see Schliemann and Dörpfeld, Tiryns, p. 318 seq.). The base of the wall rests on a levelled surface cut for it in the rock: its lower part is built of those immense blocks which aroused the wonder of Herodotus and other Greeks down to Pausanias. Some are as much as 10 feet long, roughly shaped, with smaller stones to fill up the interstices,

Pre-historic Wall in Greece.

and the whole bedded carefully in clay, used instead of mortar: another common early method of construction. As in the walls of the Punic Thapsus and Byrsa, the lower part is solid, but above that rows of chambers are formed, together with a covered passage into which each room opens. The roofing is formed by large blocks, set like corbels, each projecting over the course below, a very usual primitive method of obtaining the arch shape without the principle of the arch. Above this, along part of the circuit, was a second story of chambers, built of sun-dried bricks; and above the passage was an open colonnade, with wooden pillars resting on stone blocks, and supporting (probably) a flat wooden roof covered with clay.

A very interesting inscription (Cor. Insc. Att. 2.167), relating to a restoration in the 4th century of the walls of Athens, shows that a very similar arrangement existed there. It mentions the upper portion of the Athenian wall as being of brick, with, at the top, a covered gallery supported on columns, and rows of windows closed by wooden flap-shutters. The roofing consisted of wooden beams or joists, on which were burnt clay tiles bedded in moist clay. This wall was destroyed by Sulla, and a large number of fine tomb-reliefs were discovered a few years ago safely buried in the decomposed crude clay bricks of which the upper part of the walls of Athens had been constructed. As appears to have been the general custom, the walls of Tiryns, and those of Athens nearly a thousand years later in date, were strengthened by square towers set at intervals along the circuit.

Another interesting example of this use of crude brick and stone is still to be traced Mantineia, where almost the whole circuit of the city wall still exists up to where the brick began. The stone base, which is nearly 4 feet high, is formed with a level bed at the top to receive the upper clay part. Its thickness is 10 feet, made up thus--first an outer facing of dressed stone 4 feet thick, a similar inner facing 2 feet thick, and an intermediate filling in 4 feet thick. The facing is of closely-jointed blocks, set without mortar: the inner portion is a sort of concrete made of small stones, lime and gravel. The wall had ten gates and closely-set towers, with a moat on the outside.

The use of crude brick for city walls led to a curious system of attack being sometimes adopted. Thus, when Agesipolis, king of Sparta, besieged Mantineia, he directed the stream Ophis along its walls, and so washed away the brick at one place sufficiently to make a breach. The same method of attack was employed by Cimon, the son of Miltiades, against the walls of Eion on the Strymon.

Though kiln-fired bricks were largely used in ancient Egypt and still more in Assyria, the Greeks appear to have employed them very sparingly, and no Roman examples are known of earlier date than the 1st century B.C. According to Pausanias (5.20), the circular Philippeion at Olympia was built of baked brick, but the existing remains were found to be of stone ashlar.

II. Stone Construction.--The most primitive type of stone masonry is that in which large blocks are used, very roughly dressed with an axe or hammer; small stones being used to fill up the open joints, and, as a rule, a bedding of clay instead of a lime mortar. The above-mentioned walls of Tiryns, dating probably not less than 11 or 12 centuries before Christ, are the most remarkable existing examples. This method of building was not, however, employed, even at so early a date as the construction of the Tirynthian Acropolis, on account of want of sufficient skill to work stone neatly; but simply because such rough and massive masonry was practically as good as the finest ashlar for the outer walls of a fortification. Within the palace Dr. Dörpfeld found ample evidence to show that. the Tirynthian builders possessed tools of the most varied kinds, fit for the most elaborately finished stone-work. Not only chisels were used, but even jewel-tipped drills, both solid and tubular, and saws set with corundum, or other hard crystals, such as were used as early as 4000 B.C. in Egypt to work the refractory granites and basalts of the ancient dynasties.

Any chronological arrangement of the various kinds of masonry would be misleading. One of the oldest existing buildings in the world, the so-called “Temple of the Sphinx,” near the Great Pyramid in Egypt, is built of the most perfectly regular and neatly-fitted blocks of stone; its inner walls being lined with great. slabs of beautiful translucent alabaster, 5 or 6 inches thick, so perfectly fitted that the joints at are hardly visible: this beautiful lining is now rapidly being stolen. The walls of Mycenae, certainly earlier than 1000 B.C., consist in most. places of large blocks very accurately squared, with perfectly fitting beds and joints: enormous monoliths are used for the jambs, lintel, and threshold of the principal gate, over which still exists the well-known relief of the pillar between the guardian lions. This is shown in the annexed cut. The slab itself fills up the “relieving” opening, which was of triangular shape, as was usual at that date. The missing heads [p. 2.185]of the lions appear to have been of bronze: holes for their attachment still exist, with blue stains of copper oxide.

Lion Gate of Mycenae.

The name Cyclopean or Pelasgic has been popularly given to masonry constructed of polygonal blocks, which in many cases are fitted

Polygonal Masonry.

together with great care and skill. Examples of this exist at Signia (Segni), Norba, and many other ancient sites in Etruria, Central Italy, and in Greece itself. This style of building appears really to belong to no special race or date. (See Bunbury, Cyclopean Remains, in Museum of Class. Arch. ii. p. 147; and Dodwell, Tour in Greece.) The latest dated example of this polygonal masonry is the cella of the small Temple of Themis in antis at Rhamnus, not earlier than the 5th century B.C.: in this case the blocks are smaller than those used in the primitive fortifications of Central Italy. Though more economical of material, the polygonal method of construction would not require less, but rather more skill on the part of its masons; it being no easy matter to fit together such irregular forms with the perfect accuracy that in many cases had been attained: and it should not therefore be taken as a proof of very early date.

During the historic period of Greece, the more important buildings, such as the temples, were usually built of quadrangular blocks of stone, each course having a level bed running from end to end of the wall. The beds and joints were worked to a much more accurately smooth surface than the visible faces of the wall, because whenever stone was used by the Greeks it appears to have been the custom to cover it with a thin skin of very fine white stucco, made of lime and powdered marble or limestone, mixed with some kind of size. (See Vitr. 7.6.) This mixture set to the hardness and durability of the best quality of stone; it received, by working over while soft, a pleasant ivory-like texture, and its slightly absorbent surface formed an excellent ground for the application of the coloured ornament which seems to have been always used on Greek buildings. The modern word “stucco” gives a very erroneous notion of this beautiful material. The chief existing examples of this fine stone masonry are those at Selinus and Agrigentum in Sicily, and Paestum in Magna Graecia. (See Serradifalco, Antichità di Sicilia, and Wilkins, Magna Graecia.

After the Persian war, in the first half of the 5th century B.C., the Athenians began to use marble for their finest buildings. The walls, for example, of the Athenian Propylaea and the Parthenon are marvels of perfect masonry. The blocks of marble are cut in courses of regular depth; and, no cement being used, each block was made to fit with absolute precision to the adjacent blocks by being moved backwards and forwards over its bed, till its surfaces were rubbed perfectly smooth. So absolutely air--tight were these surfaces that in many cases age and pressure have made adjacent surfaces actually, as it were, grow together: this is, shown in a very striking way by the fact, that in certain places, where the wall is broken, the fracture has gone through the solid block rather than cause a separation of two blocks at the joint or bed. Great labour was also spent in clamping horizontally with iron or bronze each block to the next one on the same course; and vertical dowels were used to fix each block to the next courses above and below. In most cases the metal clamps were fixed by pouring in fluid lead, the cavity in the marble being cut a little larger than the actual clamp required at its turned down ends. Even during the 5th century the use of marble was as a rule limited to places which, like Athens, had marble quarries at hand; and such important buildings as the Temple of Zeus at Olympia, and that of Apollo at Bassae, had their walls constructed of local stone. It was not till the 4th century, when many of the great temples of Western Asia, Minor were reconstructed on so magnificent a scale--as e. g. those at Didyme, Ephesus, Teos,. Magnesia, and the Smintheum in the Troad--that the use of marble was considered necessary for the construction of a magnificent building. The fact is that, as long as they were not ruined, the general effect of the stone temples coated [p. 2.186]with their fine skin of marble dust gesso, enriched by brilliant coloured decoration, must have been as beautiful as that of a building of solid marble, and not distinguishable from it except by the closest examination.

During the 5th to the 3rd century B.C. stone masonry of almost equal beauty to that of the temples was often used for the fortification walls of Greek cities. The usual scheme of defence was to have, on the outside, a deep foss, either filled with water or, where that was not possible, merely an empty trench. The wall was from 10 to 15 feet in thickness, with, on the top, a walk for sentinels and a parapet with battlements all along. At regular intervals were towers, usually square, but sometimes rounded in plan, projecting on the outside like those of the Phoenicians, two being placed to lank each gateway. This general scheme was

Wall and Gateway of Posidonia.

adopted in the walls of the Greek city of Posidonia (Paestum) in Magna Graecia, which, like Tiryns, had chambers for the garrison: they are well illustrated in the Museum of Classical Antiquities, vol. i. p. 35. The walls of Messene, on the slopes of Mt. Ithome, are among the most perfect remains of Greek building in the Peloponnese, and are a beautiful example of Hellenic masonry during the best period. They are wholly built of neatly-dressed blocks, regularly bedded without mortar in horizontal courses. Along the top of the wall is a levelled walk defended by a battlemented parapet: in each of the many projecting square towers is a chamber with its floor at the level of the top of the curtain wall, on to which access as given from the towers by doorways with fat lintels, so that the towers do not interrupt the passage round the wall. Square battlements crowned the summit of each tower, as a defence to the soldiers posted on the roof of the lower chamber.

In the finest sorts of masonry, both among the Greeks and Romans, metal clamps instead of cement were used, each block fitting with absolute closeness to the next; but in the rougher sort of walling the blocks were less carefully dressed, and a fine lime mortar was used to bed each course. The famous “Long Walls” from Athens to Peiraeus were of this latter sort, as Plutarch describes (Cim. 13), χάλικι πολλῇ καὶ λίθοις βαρέσι τῶν ἑλῶν πιεσθέντων. Other parts, perhaps the facing, of this wall described by Thucydides (1.93) appear to have been of the finer kind of masonry, with blocks so large that each was a cart-load (ἁμαξιαῖοι), closely fitted (ἐν τομῇ ἐγγώνιοι) and secured by metal clamps run with lead, like those used in the Parthenon.

Though as a rule the joints in fine masonry must have been practically invisible, owing either to the coating of stucco or to the perfect grinding together of the surfaces, yet we read of one case (Plin. Nat. 36.98) in which the joints were treated in a conspicuously decorative way. This was a temple at Cyzicus, in which the interior walls of the cella had a fine thread of gold inserted in the joints of every course. That this statement is probably true is borne witness to by the discovery, among the ruins of the Artemision at Ephesus, of certain bases of the great Ionic columns, in which the quirks between the astragals still contained bits of a strip of pure gold fixed with lead into its place: thus forming two or more rings of gold ornament all round each of the main bases of the order.

Pre-Roman Methods of Mural Decoration.

The earliest example of a decorated wall-surface is the Temple of the Sphinx, c. 4000 B.C., mentioned above as being lined with slabs of alabaster. Sculpture, in low relief, was used in the most lavish way, during a space of between three and four thousand years, to decorate the tombs and temples of Egypt. This sculpture is, as a rule, not cut on slabs affixed to the wall, but on the coursed blocks of which the wall consists: the joints, which, in the present ruined state of the building, cut through and disfigure the reliefs, were originally concealed by a thin skin of fine stucco, like that used by the Greeks, on which the colouring was applied. In ancient Assyria and Chaldaea wall reliefs were used in no less lavish a way; but, as a rule, with this difference, that the sculpture was carved on thin slabs, which were fixed to the surface of the wall, not, as in Egypt, cut on the solid wall itself.

Painting on stucco is perhaps the most widely used method of wall decoration among all classical races and at all periods [see PICTURA]. Another very costly and magnificent method of wall decoration, largely used in early times, was to cover the surface with plates of bronze, beaten into relief, and usually gilt. Traces of this method of enriching wall-surfaces have. been found in the palaces of Persepolis, the socalled treasuries of Mycenae and Orchomenos, and in the palace of the Tirynthian Acropolis. The splendour of these delicately enriched metal surfaces, gleaming with gold and broken into points of light, varied with the half-shadows of the reliefs, must have been of the most dazzling kind. We know now that such descriptions as Homer's golden house of Alcinous need not be considered wholly the offspring of a poet's fancy. The Treasury of Myron and the Shrine of Athene Chalcioecus, mentioned by Pausanias (6.19 and 3.17), were probably examples of the same method of decoration by bronze repousse plates.

Reliefs moulded in clay, and then coloured with brilliant enamel pigments, were used [p. 2.187]for wall-decoration in Egypt, Assyria, and Persia. Friezes, with lines of kings, soldiers, and processions of captives, in enamelled relief, formed on tiles or plaques, were found in Rameses the Great's palace at Tel-el-Yahoudeh. Their execution is a marvel of technical skill, in the minute use of the most delicate relief, and the most varied enamels of jewel-like brilliancy. Recent excavations at Susa have brought to light examples of this kind of decoration on the most magnificent scale. The walls of one room were lined with life-sized figures, moulded, not on slabs but on the ordinary coursed brickwork, so that each figure is built up of about 20 courses of bricks, all fitting together with great accuracy. The whole of this magnificent procession is covered with enamels of various colours--a combination of the plastic and pictorial arts which gives an effect of unrivalled splendour, and from its vitreous surface has the advantage of being almost imperishable. Some of these wonderful reliefs were brought in 1887 to the Museum of the Louvre, and give one a most vivid notion of the skill and decorative taste of the Persian craftsmen.

The decoration of wall-surfaces by thin marble linings does not appear to have been much used by the Greeks. According to Pliny (Plin. Nat. 36.47), thin slabs (crustae) of Proconnesian marble were used to decorate the Palace of Maussolus at Halicarnassus, c. 360 B.C.; and when the remains of Queen Artemisia's mausoleum leum were used by the Knights of St. John, in the 15th and 16th centuries, to build the castle of St. Peter at Halicarnassus (Budrum), they are said to have found the interior of the Heroon lined with slabs of various coloured marbles. (See Newton, quoting Guichard, Travels in the Levant, vol. ii. p. 126.) As a rule, however, the use of coloured marbles for wall-linings was not introduced till later times, and would have been rather displeasing to the severe taste of the best period of Hellenic art, though it was the favourite method of mural decoration in the artistically inferior period of the Roman empire. [See DOMUS]

The Roman Period.

A great deal that is wholly misleading has been written about the methods of building used in the walls of ancient Rome, partly because the real methods of construction are frequently hidden behind very deceptive modes of surface decoration. The systems of wall-building in Rome may be classified thus:--I. Sun-dried bricks (lateres orudi), of which no example now exists. II. Opus quadratum, solid walls of squared stone. III. Concrete, opus coementitium. (a) unfaced concrete; (b) faced with opus incertum; (c) faced with opus reticulatum; (d) faced with burnt brick (lateres cocti); (e) faced with the so-called opus mixtum. The usual error has been to class opus incertum, opus reticulatum, &c., as separate constructional categories; whereas, in reality, they are merely different methods of facing concrete walls.

I. Sun-dried bricks in Rome, as in Greece, appear to have been largely used for all except the more important public buildings, till about the 1st century B.C. The remarks of Vitruvius (2.3) about the names and the sizes of bricks appear to refer wholly to crude bricks; the kiln-baked bricks used for wall-facing in Rome being always triangular in shape, not rectangular, like those described by Vitruvius. Care was taken to dig out the clay at the right season, and also to keep the bricks for a long time before being used--a precaution that would have been useless in the case of kiln-fired bricks. Careful directions are given in the same chapter (Vitr. 2.3) as to the formation of good “bond,” by alternate courses of “headers” and “stretchers.” This, again, does not apply to the burnt bricks of Rome, which are never used, to build a wall, but merely as facing.

II. Opus quadratum, masonry of solid ashlar. The earliest existing example of this in Rome is the pre-historic fortification wall of Roma Quadrata on the Palatine, popularly called the “wall of Romulus.” This consists of blocks of the local tufa, with very even beds, but less careful vertical joints. The blocks run in fairly even courses of nearly 2 Roman feet in depth, but vary in length. The bond is imperfect: joints are often allowed to come one over another; and no mortar is used. The cut shows a piece of the best preserved part at the west angle of the Palatine. The Servian wall shows the next stage; harder stone is used, the courses

Existing plece of the “Wall of Romulus.”

are more regular, the surfaces more truly dressed, and the bond more workmanlike. Under the later republic the harder peperino was usually employed for external work, the soft tufa being reserved in many cases for internal walls. The most perfectly developed opus quadratum is to be seen in the walls of the Capitoline Tabularium, which, on the exterior, are built of perfectly regular blocks of lapis Albanus (peperino), each exactly 2 Roman feet [multi] 2 ft. [multi] 4 ft. long, arranged in alternating courses of “headers” and “stretchers,” such as in modern language is called technically “English bond.” So accurately are the blocks worked and set, that each series of joints comes exactly over those [p. 2.188]below, up the whole height of the wall. These blocks are bedded in a very thin layer of pure lime, used, not as a binding cement, but as a method of obtaining absolutely perfect contact in all the adjacent surfaces--a very early practice in Rome, which is to be seen even in the primitive Tullianum or lower chamber of the “Mamertine prison.”

In the 1st century B.C. the hard, creamcoloured limestone, lapis Tiburtinus (Travertino), came into use for the more costly buildings, but the principal examples of its use date from the 1st and 2nd centuries A.D., as in the lower part of the cella walls of the temples of Concord, Vespasian, and Faustina. In these the blocks are worked with courses of varying thickness, and the beds and joints are rubbed to such a perfect surface that absolutely close contact is obtained without the use of the thin skin of lime mortar. As among the Greeks, the blocks of the finest masonry are fixed by iron clamps run with lead ( “ansis ferreis et plumbo,” Vitr. 2.7), or, in some cases, by wooden “dovetail dowels.” In the same chapter Vitruvius describes the methods of bonding derived, as he says, from the Greeks. The best class of masonry (ἔμπλεκτον) was formed by alternating “headers” and “stretchers,” i. e. blocks laid cross-wise or lengthways; and, in some cases, “through stones” (διατόνοι) were introduced, i. e. blocks set as “headers,” of sufficient length to reach through the whole thickness of a wall--a needless precaution, unless the wall were rather thin.

Existing specimens of domestic architecture in Rome, built with opus quadratum, are very rare. One of the chief examples is the older part of the Regia, or official house of the Pontifex Maximus, in which remains still exist of early tufa masonry, with accurately squared blocks. Similar tufa blocks are also used for the walls of the oldest houses in Pompeii,--those, that is, which survived the earthquake by which the town was mostly destroyed, a few years before its final destruction in 79 A.D. Some of these probably date from the 1st century B.C., or even earlier.

In all cases in ancient Roman buildings, whether tufa or peperino were used, it appears to have been the custom to coat the stone with the fine marble or limestone stucco (opus marmoreum), such as was used in Greece, and is described in great detail by Vitruvius (7.2, 3 and 6). Thin coatings of this beautiful hard substance were used in some cases to cover travertine, and even marble walls. With tufa, as with unburnt brick, it was a constructional necessity, the soft tufa being the worst possible “weather stone;” but in other cases it appears to have been applied for decorative purposes.

III. Concrete.--The use of concrete, both among the Greeks and Romans, is really much older than has usually been supposed. It was largely used in the palace of Tiryns, especially for floors; and in Rome still exists as backing to part of the Servian wall on the Aventine. Concrete in Rome was made of broken stones, together with lime and pulvis Puteolanus (pozzolana); or else, during the Imperial period, broken pieces of burnt brick frequently replaced the stone. The pozzolana, great beds of which, showered down from long extinct volcanoes, exist over most of the Roman Campagna, forms, when mixed with lime, a very strong hydraulic cement, applicable to a great variety of purposes, such as concrete walls, mortar, and stucco. In the older concrete tufa is the stone usually employed, but under the Empire other harder stones were used, especially for foundations of walls which had to carry a heavy weight. The best and most durable kind of concrete was made with pieces of lava, the silex of Pliny and Vitruvius, with which the Roman roads were generally paved.

The method of forming concrete walls is shown in the annexed cut. Upright posts,

Method of casting concrete Walls.

about 6 [multi] 5 inches thick and 10 to 15 feet high, were stuck at intervals of about 3 feet in the ground along the line of both faces of the future wall; and against these posts wooden planks, 10 to 12 inches wide, were nailed horizontally, overlapping one another. Into the intermediate space the semi-fluid concrete was poured, receiving on its surface the imprint of the posts and boards. When the first layer of concrete had set hard, the wooden framing was removed and refixed on the top of the concrete wall. The process was then repeated till the wall was raised to the required height. Walls thus formed, especially if the hard lava or travertine were used, were stronger and more durable than even the most solid masonry. Blocks of stone could be removed, one by one, by the same force that set them in place; but a concrete wall was one perfectly solid and coherent mass, which could only be destroyed by a laborious process, like that of quarrying hard stone from its native bed.

As a rule, except when used for foundations, the Roman concrete was not left without some facing. During the Republican period, the method of facing was opus incertum, but it was nearly obsolete in the reign of Augustus, as Vitruvius (2.8) writes: “reticulatum, quo nunc omnes utuntur, et antiquum quod incertum dicitur.” In this method irregularly shaped bits of tufa, 3 to 5 inches across, were cut smooth on one face, and roughly pointed behind. The whole [p. 2.189]face of the concrete wall was studded with these stones, like a magnified mosaic, the points sticking into the wall, and the smooth ends appearing on the surface.

Opus reticulatum, universally used (as Vitruvius says) in his time, is very like opus incertum, except that each little block of tufa is cut to a true square at one end, and all are arranged to run in regular diagonal lines, like a piece of network, whence came its name. Though of no

Concrete Wall faced with (A) Opus incertum and (B) Opus reticulatum. C shows the section, similar in both.

real constructional importance, it is very neat in appearance, and it is rather strange to find that, like the incertum, it was usually, if not always, covered with stucco. It appears to have come into use about the beginning of the 1st century B.C., and continued in use, though becoming less common, till the reign of Hadrian. Facing with kiln-fired brick appears not to have been used in Rome before the 1st century B.C. In fact, no examples are known to exist earlier than the wall of J. Caesar's Rostra, rebuilt on a new site in 44 B.C.

It is an important thing to observe that in ancient Rome burnt brick was never used to build walls, but merely as a thin facing. In the true sense of the word, there is no such thing as a brick wall among all the ruins of

Concrete Arch: half with its brick facing removed.

Rome; the actual wall being of concrete, with merely a thin facing of triangular bricks, arranged as is shown in the woodcut. Even party-walls of small houses, sometimes only 7 inches thick, are not built of solid brick, but

Concrete Wall faced with brick.

have an inner core of concrete faced with small brick triangles. Thus, for example, such a building as the Pantheon of Agrippa, which appears to be built of brick, is found on examination to consist of walls with about 18 feet in thickness of concrete, and a facing of brick averaging only 3 or 4 inches in depth.

The advantages of this concrete construction, both for walls and vaults, were very great: each wall was like one solid slab of stone, any part of which might be cut away without destroying stroying the est. A striking example of this is to be seen in the Thermae of Caracalla: in one place the concrete wall originally rested on two marble columns. The columns were stolen some centuries ago, and the wall above still remains hanging like a curtain from the concrete vault.

It is not easy to explain why the Romans were so fond of using this brick facing over their concrete. It was not a constructional necessity, as the many walls of unfaced concrete which still exist clearly show. It was not for the sake of its appearance, as, except in a very few cases. such as the great aqueducts, the brick facing was concealed by stucco or by marble linings. The very smoothness of the brick was practically a disadvantage, being unsuited to the reception of stucco; and great cost and labour were expended in studding the brick facing with metal nails or plugs of marble in [p. 2.190]order to form a “key” for the coating of stucco, which adhered firmly, without any such help, to the bare concrete of unfaced walls.

The character of brick facing, the thickness of the bricks and the mortar joints, is often a very valuable indication of the date of a building; the general tendency being for the bricks to get thinner and the mortar joints thicker. Thus the Pantheon, dated 27 B.C., has bricks 1 1/2 inches thick, with joints averaging 3/8 inch. In the palace of Sept. Severus, 200 A.D., the bricks are 1 inch and the joints 3/4 inch in thickness. In the Aurelian walls of Rome, c. 270 A.D., bricks and joints average the same thickness, both measuring about 1 1/4 inches.

The term opus mixtum, though not a classical one, is now used to denote wall-facings of a late period, with alternating courses of brick and small rectangular blocks of tufa. The earliest dated example is the Circus of Maxentius, c. 310 A.D.; it continued in use till the time of Theodoric, c. 500 A.D.; after which destruction, not construction, went on in the unhappy city of Rome.

The above methods of Roman construction are those which were employed in the greater part of Italy; but in their distant provinces, such as Britain or Gaul, the systems of building were often modified to suit the nature of the materials which the country supplied. Thus, outside of Italy, owing to the lack of pozzolana to make a strong hydraulic cement, concrete was less extensively used for walls. In Britain one of the favourite Roman methods was to build the wall with more or less carefully dressed stone for the facing, and an internal filling in of rubble. At regular intervals “lacing courses” of brick were built, extending through the whole thickness of the wall; large rectangular bricks (tegulae) being used instead of the triangles of Rome itself. The Roman fortification walls of London, Richborough, and many other places are examples of this mixed construction.

In all cases the mortar used in Roman walls is of a very hard and durable character, owing to the great care taken in preparing and mixing the materials. Much of the Roman mortar owes its strength to the lime being mixed with finely-pounded brick or pottery, the opus e testis tunsis of Vitruvius; a much better substance for the purpose than such sand as is now commonly used. Vitruvius' chapters on sand (arena, 2.4), on lime (calx, 2.5), and the preparation of concrete, mortar, cements, and stucco of all kinds, are of the highest practical value; and modern builders would produce much better work if they would follow Vitruvius' injunctions. It is, however, useless to hope for that: the chief secret of the immense superiority of the Roman work to that of the 19th century is due to the fact that in the old days the builder's first object was to produce a strong and lasting piece of work, not to erect his building at the lowest possible cost, as is the case now.

Fortification Walls of the Romans.

Many different systems of fortification were adopted, according to the varying natures of the sites. The pre-historic defence of Roma Quadrata, on the summit of the Palatine hill, was arranged thus. The base of the circuit was set neither at the foot of the cliff nor at its summit, but on an artificially cut shelf, at an average distance (along the Velabrum side) of

Section of the Wall of Roma Quadrata. Section of the Wall of Roma Quadrata., A. Original height of wall.

B. Upper part of cliff, now crumbled away.

C. Cistern cut in tufa rock.

D. Levelled platform to receive base of wall.

E E. Cliff made steeper by cutting.

about 40 feet from the top. The face of the cliff above this shelf was cut back into an almost perpendicular precipice, slightly sloping back or “battering” inwards, as is shown in the cut. Against this the wall was built, rising to the top of the hill, and probably a little above it, to shelter the garrison. The native tufa at this point is very soft, and so it was thought advisable to line the cliff with a wall of harder tufa, which would not give foothold to an enemy. In other places, as on the Capitoline hill, the native rock is harder; and so the place was made secure simply by scarping the rock to a perpendicular surface, and then only a low wall of defence was required at its summit. The above cut shows also one of the cisterns for storing rain-water, which were cut in the rock for use in time of siege.

Along one space of about 1400 yards, in the circuit of the early or “Servian city,” the wall had to cross a level piece of ground, and so the defence got no help from the natural contour of the rock, as it did in most other parts of the circuit (see Dionys. A. R. 9.68). For this reason a more elaborate system of fortification was adopted: a great fossa, 30 feet deep and 100 wide, was dug, and its earth heaped up on the inside to form an agger, which was kept up by a massive stone retaining wall, 9 feet thick and about 30 feet or more in height. This wall, in some places, is strengthened by great square buttresses. A lava-paved road ran along the outer edge of the fossa. (See Middleton, Ancient Rome, pp. 69-74.)

The later fortification wall of Rome, which encloses a very much larger area than the Regiones of Servius, was planned and in great [p. 2.191]part built by Aurelianus, in 270-5 A.D. It is built of concrete faced with brick, and extends along a circuit of about 12 miles. Like the

Section of Wall and Agger of Servius. The plan is double the scale of the section. AA. Undisturbed earth of fossa.

B. Earth excavated from fossa.

C. Road at brink of fossa.

D. Wall and buttress.

E. Back retaining wall of agger.

F. Level to which the fossa was filled up and built upon under the Empire.

early Greek walls, its lower part is solid, to resist battering-rams, and the upper part contains in its thickness a passage for the garrison, extending all along its circuit. This passage

Aurelian's Wall. Plan showing one of the towers and the passage in the thickness of the wall.

opens on the interior with a series of tall arches, something like those of an aqueduct, and is vaulted overhead, forming a wide platform at the top, guarded by battlements, for the soldiers. At close intervals, only 45 feet apart, tall and massive square towers were set, 383 in all, with a guard-room below, and a sleeping-room for the garrison above. The plan of one of these towers and a bit of the sentinels' passage is shown in the woodcut. The passage, which continued through the towers, formed a covered walk along the whole 12 miles of the circuit. The height of the wall varied according to the contour of the ground: it probably averaged nearly 50 feet; the towers rising about 20 feet above the top of the intermediate wall. Except where the wall skirted the river along the Campus Martius, its circuit still exists, more or less perfectly preserved. In some places, as e. g. in the now destroyed Ludovisi gardens, it is still in a very perfect state, with the exception of its battlements, almost all of which have perished.

The walls--of Pompeii, which are in parts very perfect, are an interesting example of the defences of a smaller city. They, too, have towers, square in plan, set at close intervals, and near the top a broad platform for the defenders of the town.

In other cases--as, for example, in the Roman fort at Old Cairo (the mediaeval Babylon)--towers of circular plan are used. (See A. J. Butler, Coptic Churches, i. p. 155.) This system is recommended by Vitruvius, on the very reasonable ground that the angles of square towers form weak points when attacked by the batteringram. (See the whole of Vitr. 1.5.)

Respecting the gates, see PORTA

Literature.--Perrot and Chipiez's various works on Egypt, Assyria, Phoenicia; Schliemann's works on Troy, Mycenae, and Tiryns; Blümner, Technologie bei Griechen und Römern; Winckler, Die Wohnhäuser der Hellenen; Helbig, Das Homerische Epos; Adamy, Architectonik der Hellenen; Middleton, Ancient Rome in 1885, and an article on “Roman Construction” in Archaeologia, vol. 51, for 1888; Nissen, Pompeianische Studien; Overbeck, Pompej, re-edited by Mau. See Also DOMUS


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