1902 Encyclopedia > Rome > Ancient Rome - Architecture and Construction

Rome
(Part 21)




UNIT II: ROMAN TOPOGRAPHY AND ARCHAEOLOGY

SECTION II: ANCIENT ROME

Architecture and Construction


Building Materials

The chief building materials used in ancient Rome were those materials, enumerated below. (1) Tufa, the "ruber et niger tophus" of Vitruvius (ii. 7), the formation of which has been described above, is usually a warm brown or yellow colour. The Aventine, Palatine, and Capitoline Hills contained quarries of the tufa, much worked at an early period (see Liv., xxvi. 27, xxxix. 44, and Varro, L.L., iv. 151). It is a very bad "weather-stone," but stands well if pro-tected with stucco (Plin., H.N., xxxvi. 48). (2) Lapis Albanus, from Alba Longa, is also of volcanic origin, a conglomerate of ashes, gravel, and fragments of stone ; its quarries are still worked at Albano and Marino. (3) Lapis Gabinus, from Gabii, is very similar to the last, but harder and a better weather - stone ; it contains large lumps of broken lava, products of an earlier eruption, and small pieces of limestone. According to Tacitus (Ann., xv. 43), it is fireproof, and this is also the case with the Alban stone. Both are now called peperino, from the black scoriae, like pepper-corns, with which the brown conglomerate mass is studded. (4) Silex (mod. selce), a lava from the now extinct volcanoes in the Alban Hills, was used for paving roads, and when broken into small pieces and mixed with lime and pozzolana formed an immensely durable concrete. It is dark grey, very hard, and breaks with a slightly conchoidal fracture (Plin., H.N., xxxvi. 29 ; Vitr., ii. 7), but does not resemble what is now called silex or flint. (5) Lapis Tiburtinus (travertine), the chief quarries of which are at Tibur (Tivoli) and other places along the river Anio, is a hard pure carbonate of lime, of a creamy white colour, deposited from running or dripping water in a highly stratified form, with frequent cavities and fissures lined with crystals. As Vitruvius (ii. 5) says, it is a good weather-stone, but is soon calcined by fire. If laid horizontally it is very strong, but if set on end its crystalline structure is a great source of weakness, and it splits from end to end. Neglect on the part of Roman builders of this important precaution in many cases caused a complete failure in the structure. This was notably the case in the rostra (see below). (6) Pulvis Puteo-lanus (pozzolana), so called from extensive beds of it at Puteoli, is a volcanic product, which looks like red sandy earth, and lies in enormous beds under and round the city of Rome. When mixed with lime it forms a very strong hydraulic cement, of equal use in concrete, mortar, or undercoats of stucco. It is to this material that the concrete walls of Rome owe their enormous strength and durability, in many cases far exceeding those of the most massive stone masonry. Vitruvius devotes a chapter (bk. ii. ch. 6) to this very important material.

Bricks were either sun-dried or kiln-baked (lateres crudi aut cocti). The remarks of Vitruvius (ii. 3) seem to refer wholly to sun-dried bricks, of which no examples now exist in Rome. It is very important to recognize the fact that among the existing ancient buildings of Rome there is no such thing as a brick wall or a brick arch in the true sense of the word; bricks were merely used as a facing to concrete walls and arches and have no constructional importance. Concrete (fartura, caementum, or opus structurae caementitiae, Vitr., ii. 4, 6, 8), the most important of all the materials used, is made of rough pieces of stone or of fragments of brick, averaging from about the size of a man's fist and embedded in cement made of lime and pozzolana,—forming one solid mass of enormous strength and coherence. Stucco, cement, and mortar (tectorium, opus albarium, structura testacea, and other names) are of many kinds ; the ancient Romans especially excelled in their manufacture. The cement used for lining the channels of aqueducts (opus signinum) was made of lime mixed with pounded brick or potsherds and pozzolana; the same mixture was used for floors under the "nucleus " or finer cement on which the mosaic or marble paving-slabs were bedded, and was called caementum ex testis tunsis. For walls, three or four coats of stucco were used, often as much as 5 inches thick altogether ; the lower coats were of lime and pozzolana, the finishing coats of powdered white marble (opus albarium) suitable to receive painting. Even marble buildings were usually coated with a thin layer of this fine white stucco, nearly as hard and durable as the marble itself—a practice also employed in the finest buildings of the Greeks—probably because it formed a more absorbent ground for coloured decoration ; stone columns coated in this way were called "columnae dealbatae " (Cic, In Verr., ii. 1, 52 sq.). For the kinds of sand used in mortar and stucco Vitruvius (ii. 4) mentions sea, pit, and river sand, saying that pit sand is to be preferred.

Decorative Materials

Marble appears to have come into use about the beginning of the 1st century B.C. Its introduction was at first viewed with great jealousy, as savouring of Greek luxury. The orator Crassus was the first to use it in his house on the Palatine, built about 92 B.C. ; and, though he had only six small columns of Hymettian marble, he was for this luxury nicknamed the "Palatine Venus" by the stern republican M. Brutus (Plin., H.N., xxxvi. 3). The temporary wooden theatre of the redile M. Aemilius Scaurus, built in 58 B.C., appears to have been the first building in which marble was more largely used ; its 360 columns and the lower order of its scena were of Greek marble (see Plin., H.N., xxxvi. 3, 24). In a very few years, under the rule of Augustus, marble became very common.

Of white statuary marble four principal varieties were used. (1) Marmor Lunense, from Luna, near the modern Carrara (Strabo, v.), is of many qualities, from the purest creamy white and the finest grain to the coarser sorts disfigured with bluish grey streaks. (Ex., the eleven Corinthian columns in the Dogana di Terra.) (2) Marmor Hymettium, from Mount Hymettus, near Athens, is coarser in grain than the best Luna marble and is usually marked with grey or blue striations (Strabo, x.). (Ex., the forty-two columns in the nave of S Maria Maggiore and the columns in S. Pietro in Vincoli.) (3) Marmor Pentelicum, from Mount Pentelicus, also near Athens, is very fine in grain and of a pure white ; it was more used for architectural purposes than for statues, though some sculptors preferred it above all others, especially Scopas and Praxiteles (Paus., Arcad., viii.). (Ex., the bust of the young Augustus in the Vatican.) (4) Marmor Parium, from the Isle of Paros, is very beautiful, though coarse in texture, having a very crystalline structure.

Coloured Marbles

Nine chief varieties of coloured marbles were used in Rome. (1) Marmor Numidicum (mod. giallo antico; Plin., H.N., v. 3), from Numidia and Libya, hence also called Libycum, is of a rich yellow, deepening to orange and even pink. Enormous quantities of it were used, especially for columns, wall-linings, and pavements. (Ex., six large columns in the Pantheon and seven on the arch of Constantine, taken from the arch of Trajan ; the eighth column is in the Lateran basilica.) (2) Marmor Carystium (mod. cipollino), from Carystus in Euboea (Strabo, x.), has alternate wavy strata of white and pale green—the "undosa Carystos" of Statius (Silv., i. 5, 36). From its well-defined layers like an onion (cipolla) is derived its modern name. (Ex., columns of temple of Faustina.) (3) Marmor Phrygium or Synnadicum (mod. pavonazetto), from Synnada in Phrygia (Strabo, xii. ; Juv., xiv. 307 ; Tibull., iii. 3, 13), is a slightly translucent marble, with rich purple markings, violet verging on red. It was fabled to be stained with the blood of Atys (Stat., Silv., i. 5, 36). (Ex., twelve fluted columns in S. Lorenzo fuori le Mura, and large columns in the apse of S. Paolo fuori, saved from the ancient nave of the basilica, burnt in 1823.) (4) Marmor lasium (probably the modern porta santa), from Iasus, is mottled with large patches of dull red, olive green, and white. The "holy door" of St Peter's is framed with it, hence its modern name. (Ex., the slabs in front of the Graecostasis and four columns in S. Agnese fuori le Mura.) (5) Marmor Chium (probably the modern Africano), from Chios, is similar in colour and marking to the porta santa, but more brilliant in tint. (Ex., a great part of the paving of the Basilica Julia and two large columns in the centre of the facade of St Peter's.) (6) Rosso antico (the ancient name is unknown) is a very close-grained marble of a rich deep red, like blood. As a rule it does not occur in large pieces, but was much used, for small cornices and other mouldings in interiors of buildings. Its quarries in Greece are still worked. (The largest pieces known are the fourteen steps to the high altar of S. Prassede and two columns nearly 12 feet high in the Rospigliosi Casino dell' Aurora.) (7) Nero antico is probably the ancient marmor Taenarium, from Cape Taenarus in Sparta. It is mentioned by Tibullus (iii. 3, 14) in conjunction with Phrygian and Carystian marbles ; see also Prop., iii. 2, and Plin., H.N., xxxvi. 43. (Ex., two columns in the choir of the church of Ara Coeli.) (8) Lapis Atracius (verde antico), found at Atrax in Thessaly (Liv., xxxii. 15), was one of the favourite materials for decorative architecture ; it is not strictly a marble (i.e., a calcareous stone) but a variety of "precious serpentine," with patches of white and brown on a brilliant green ground, it seldom occurs in large masses. (The finest known specimens are the twenty-four columns beside the niches in the nave of the Lateran basilica.) (9) The hard Oriental alabaster, the "onyx" or " alabastrites" of Pliny (H. N., xxxvi. 12, xxxvii. 32); its chief quarries were on the Nile near Thebes, in Arabia, and near Damascus. In Pliny's age it was a great rarity ; but in later times it was introduced in large quantities, and fragments of a great many columns have been found on the Palatine, in the baths of Caracalla, and elsewhere. It is semi-transparent, and beautifully marked with concentric nodules and wavy strata. An immense number of other less common marbles have been found, including many varieties of breccia, but their ancient names are unknown.

Granites and Basalts

From the latter part of the 1st century B.C. hard stones—granites and basalts—were introduced in great quantities. The basalts— " basanites "of Pliny (xxxvi. 11)—are very refractory, and can only be worked by the help of emery or diamond dust. The former was obtained largely at Naxos ; diamond-dust drills are mentioned by Pliny (H.N., xxxvii. 76). The basalts are black, green, and brown, and are usually free from spots or markings ; examples of all three exist, but are comparatively rare. The red variety called "porphyry " was used in enormous quantities. It is the " porphyrites " of Pliny (H.N., xxxvi. 11), and was brought from Egypt. It has a rich red ground, covered with small specks of white felspar; hence it was also called "leptopsephos." A large number of columns of it exist, and it was much used for pavements of opus Alexandrinum. A rich green porphyry or basalt was also largely used, but not in such great masses as the red porphyry. It has a brilliant green ground covered with rectangular light green crystals of felspar. This is the lapis Lacedaemonius (wrongly called by the modern Romans "serpentino"), so named from its quarries in Mount Taygetus in Lacedaemonia (Paus., Lac., iii. and viii. ; Plin., H.N., xxxvi. 11; Juv., xi. 173). It appears to have been mostly used for pavements and panels of wall linings. The granites used in Rome came mostly from near Philse on the Nile (Plin., H.N., xxxvi. 13). The red sort was called lapis pyrrhopoecilus and the grey lapis psaronius. The columns in the Basilica Ulpia are a fine example of the latter ; both sorts are used for the columns of the Pantheon and those of the temple of Saturn in the Forum. Gigantic ships were specially made to carry the obelisks and other great monoliths (Plin., H.N., xxxvi. 1, 14).





Architectural Styles

The style of architecture employed in ancient Rome may be said to have passed through three stages,—the Etruscan, the Greek, and the Roman. During the first few centuries of the existence of the city, both the methods of construction and the designs employed appear to have been purely Etruscan. The earliest temples were either simple cellae without columns, as we see on the Palatine by the Scalae Caci, or else, in the case of the grander temples, such as that of Capitoline Jupiter, the columns were very widely spaced (araeostyle), and consequently had entablatures of wooden beams. The architectural decorations were more generally in gilt bronze or painted terra-cotta than in stone, and the paintings or statues which decorated the buildings were usually the work of Etruscan artists. The Greek influence is more obvious ; almost all the temples of the earlier imperial age are Greek, with certain modifications, not only in general design but in details and ornaments. Greek architects were largely employed ; and Roman architects such as Vitruvius and C. Mutius in the 1st century B.C., Severus and Celer under Nero, and Rabirius under Domitian were Greek by education, and probably studied at Athens (see Vitr., vii., Praef.; Hirt, Gesch. d. Baukunst, ii. p. 257 ; Burn, Rome, p. 76). The Romans, however, though quite devoid of artistic originality, were very able engineers, and this led to the development of a new and more purely Roman style, in which the restrictions imposed by the use of the stone lintel were put aside and large spaces were covered with vaults and domes cast in semifluid concrete, a method which had the enormous advantage of giving the arched form without the constant thrust at the springing which makes true arches or vaults of wide span so difficult to deal with. The enormous vaults of the great thermae, the basilica of Constantine, and the like cover their spaces with one solid mass like a metal lid, giving the form but not the principle of the arch, and thus allowing the vault to be set on walls which would at once have been thrust apart had they been subjected to the immense leverage which a true arched vault constantly exerts on its imposts. This is a very important point, and one which is usually overlooked, mainly owing to the Roman practice of facing their concrete with bricks, which (from an examination of the surface only) appear to be a principal item in the construction. The walls of the Pantheon, for example, are covered with tiers of brick arches, and many theories have been invented as to their use in distributing the weight of the walls. But a recognition of the fact that these walls are of concrete about 20 feet thick, while the brick facing averages scarcely 6 inches in thickness, clearly shows that these "relieving arches" have no more constructional use as far as concerns the pressure than if they were painted on the surface of the walls. Exactly the same reasons apply to the superficial use of brick in all arches and vaults.

Opus Quadratum

At first tufa only was used in opus quadratum, as we see in the Opus so-called wall of Romulus. Next the harder peperino began to be quadworked : it is used, though sparingly, in the great Servian wall, ratum. and during the later republic appears to have been largely employed for exterior walls or points where there was heavy pressure, while other parts were built of tufa. Thirdly, travertine appears to have been introduced about the 2d century B. C., but was used at first for merely ornamental purposes, very much as marble was under the empire ; after about the middle of the 1st century A.D. travertine began to be largely used for the solid mass of walls, as in the temple of Vespasian and the Colosseum. The tufa or peperino blocks were roughly 2 (Roman) feet thick in regular courses, iso-domum, by 2 feet across the end, and under the republic often exactly 4 feet long, so that two blocks set endways ranged with one set lengthways. They were then arranged in alternate courses of headers and stretchers, so as to make a good bond ; this is the "emplecton" of Vitruvius (ii. 8). The so-called Tabularium of the Capitol is a good example of this (see fig. 1). The harder and more valuable travertine was not cut in this regular way, but pieces of all sizes were used just as they happened to come from the quarry, in order to avoid waste : blocks as much as 15 by 8 feet were used, and the courses varied in thickness—the pseudisodomum " of Vitruvius. "When tufa or peperino was mixed with the travertine, it was cut so as to range with the irregular courses of the latter.

It is an interesting point to note the manner in which the Roman builders mixed their different materials according to the weight they had to carry. While tufa was frequently used for the main walls, peperino (e.g., in the Servian wall on the Aventine) or travertine [e.g., in the forum of Augustus and the temple of Fortuna Virilis, so called) was inserted at points of special pressure, such as piers or arches (see fig. 21 below). The Colosseum is a particularly elaborate example of this mixed construction with three degrees of pressure supported by three different materials (see fig. 2).

The Use of Mortar

The use of mortar with opus quadratum is a sign of an early rather than a late date. It occurs in the Servian wall on the Aventine, in the Tabularium, and, most striking of all, in the Tullianum under the "Mamertine prison" — certainly one of the oldest buildings in Rome (see fig. 11). Under the empire massive blocks, whether of tufa, travertine, or marble, are set without any mortar. It must, however, be observed that in these early instances the "mortar " is but a thin stratum of lime, little thicker than stout paper, used not as a cement to bind the blocks together, but simply to give the joints a smoothly fitting surface.

Clamps

The actual binding together was done by clamps and dowels, as well as by the mass and weight of the great blocks used. Except in the earliest masonry, each block was very carefully fastened, not only to the next blocks on the same course, which was done with double dove-tailed dowels of wood, but also to those above and below with stout iron clamps, run with lead (Vitr., ii. 8). In more ornamental marble work bronze clamps were often used.

When concrete was employed it was faced either with blocks of opus quadratum (e.g., the Servian wall along the Aventine) or with opus incertum—small irregularly shaped blocks of tufa 3 to 6 inches across, with pointed ends driven into the concrete while it was soft, and worked smooth on the face only (see fig. 3).

Opus Reticulatum

Thirdly, in the 1st century B.C. opus reticulatum, also of tufa, was largely used alone; after that it began to be mixed with brickwork. It is very neat in appearance, and is often fitted with great care, though it was generally covered with stucco. The so-called "house of Livia" on the Palatine is a good example of the earlier sort, when the quoins were made of small rectangular blocks of tufa. The palace of Caligula has it with quoins of brick facing. Though in Rome opus reticulatum was always made of tufa, in the neighbourhood of the city it was sometimes of peperino or even lava, where these materials were found on the spot.

Brick Facing

Of concrete walls faced with burnt bricks no dated example Brick earlier than the middle of the 1st century B.C. is known. The facing. Pantheon (27 B.C.) is the most important early specimen of certain date. The bricks used are always triangular in. shape, so as to present a large surface on the face with little expenditure of brick, and also to improve the bond with the concrete behind (see fig. 4). Even party walls of small rooms, only 7 inches thick, are not built solid, but have a concrete core faced with brick triangles about 3 inches long. Owing to this method of forming the walls it was necessary to support the facing until the concrete was set, which appears to have been done with a wooden framing covered with planks on the inside. In some cases the planks were nailed outside the wooden uprights, as was done with the unfaced concrete walls (see below), and then a series of perpendicular grooves appear in the face of the brickwork. Walls faced with opus reticulatum must have been supported temporarily in the same way.

The character of the brick facing is a great help towards determining the date of Roman buildings ; it has been stated that this can be done simply by measuring the number of brick courses that go to a foot,—the more the bricks the earlier the work. This, however, is not the case. In early work the bricks are thick and the joints thin, while in later times the reverse is the case. Thus brickwork of the time of Severus and later usually has more bricks to the foot than that of the Flavian period. The following list gives a few characteristic specimens of different dates.

== TABLE ==

The length of the bricks as it appears on the lace is no guide to the date, owing to the fact that one or more of the sharp points of the brick triangles were very frequently broken off before they were used. Moreover, varieties both in quality of workmanship and size of the bricks often occur in work of the same date ; a new gang of workmen or a batch of bricks from a fresh ftglina might easily occasion this. In the remains of Nero's Golden House great varieties appear, and some of the walls in the inferior rooms are faced with very irregular and careless brickwork. Special care and neatness were always employed in the rare cases when the wall was not to be covered with stucco, which in the absence of marble was usually spread over both inside and outside walls. All these circumstances make great caution necessary in judging of dates; fortunately after the 1st century A.P., and in some cases even earlier, stamps impressed on bricks, and especially on the large tiles used for arches, give clearer indications. The reason of the almost universal use of smooth facings either of opus reticulatum or of brick over concrete walls is a very puzzling question ; for concrete itself forms an excellent ground for the stucco coating or backing to the marble slabs, while the stucco adheres with difficulty to a smooth facing, and is very liable to fall away. The modern practice of raking out the joints to form a key was not employed by the Romans, but before the mortar was hard they studded the face of the wall with marble plugs and iron or bronze nails driven into the joints, so as to give a hold for the stucco—a great waste both of labour and material. The quality of the mortar varies according to its date : during the 1st and 2d centuries it is of most remarkable hardness, —made of lime with a mixture of coarse pozzolana of a bright red colour ; in the 3d century it began to be inferior in quality ; and the pozzolana used under the later empire is brown instead of red.





Concrete Walls and Vaults

Concrete was at first always made of lumps of tufa ; then travertine, lava, broken bricks, and even marble were used, in fact the chips and fragments of the mason's yard. Under the empire the concrete used was of travertine or lava mostly for foundations, of tufa or broken bricks for walls, and of tufa or pumice-stone (for the sake of lightness) for vaults. Massive walls were cast in a mould ; upright timbers, about 6 by 7 inches thick and 10 to 14 feet long, were set in rows on each face of the future wall; planks 9 to 10 inches wide were nailed to them, so as to form two sides of a sort of box, into which the semi-fluid mass of stones, lime, and pozzolana was poured. When this was set the timbers were removed and refixed on the top of the concrete wall; then fresh concrete was poured in ; and this process was repeated till the wall was raised to the required height. Usually such castwork was only used for foundations and cellar walls, the upper parts being faced with brick ; but in some cases the whole wall to the top was cast in this way and the brick facing omitted. In strength and durability no masonry, however hard the stone or large the blocks, could ever equal these walls of concrete when made with hard lava or travertine, for each wall was one perfectly coherent mass, and could only be destroyed by a laborious process like that of quarrying hard stone from its native bed. Owing to this method of forming the Roman buildings the progress of the work from day to day can often be traced by a change in the look of the concrete. About 3 feet high appears to have been the average amount of wall raised in a day.

FIG. 5 -Example of marble lining, from the cella of the temple of Concord. A. Slabs of Phrygian marble. B. Plinth moulding of Numidian " giallo." C. Slab of cipollino (Carystian marble). D. Paving of porta santa. E and P. " nucleus " and " rudus " of concrete bedding. G, G. Iron clamps run with lead to fix marble lining. H. Bronze clamp. J. Cement backing.


Marble Buildings, etc.

Marble linings were fixed very firmly to the walls with long clamps of metal, hooked at the end so as to hold in a hole made in the marble slab. Fig. 5 gives an example, of the time of Augustus, fixed against a stone wall. The quantity of rich marbles which, for at least three centuries, were being dug out in countless quarries in the East, by whole armies of workmen, and constantly poured into Rome is almost beyond calculation. Scarcely a church is without columns and wall-linings stolen from ancient buildings, and the more magnificent chapels, such as those of the Borghese, Corsini, and Cibo families, with the whole church of S. Maria della Vittoria, owe their splendour entirely to their wall-linings of ancient marbles, porphyry, and alabaster.1 The blocks were usually marked in the quarry with a number, and often with the names of the reigning emperor and the overseer of the quarry. These quarry-marks are often of great value as indications of the date of a building or statue.2 Metropolitan building Acts, not unlike those of modern London, were enacted by several of the emperors. These fixed the materials to be used, the thickness of walls, the minimum width of streets, the maximum height allowed for houses, and the like. After the great fire in Nero's reign, 64 A.D., an Act was passed requiring external walls to be faced with fire-proof materials, such as peperino or burnt brick ; this Act was being prepared long before the fire,—strong evidence as to this being a wilful act on Nero's part, as is asserted by Suetonius (Nero, 38).

Ancient Works of Art

Enormous accumulations of statues and pictures enriched Rome during its period of greatest splendour. In the first place, the numerous statues of the republican and even of the regal period were religiously preserved at a time when, from their archaic character, they must have been regarded rather as objects of sacred or archaeological interest than as works of art (Plin., H. N., xxxiv. 9-16, xxxv. 7). Secondly came the large Graeco-Roman class, mostly copies of earlier Greek works, executed in Rome by Greek artists. To this class belongs most of the finest existing sculpture preserved in the Vatican and other museums. Thirdly, countless statues and pictures were stolen from almost every important city in Greece, Magna Graecia, Sicily, and western Asia Minor. These robberies began early, and were carried on for many centuries. The importations included works of art by all the chief artists from the 5th century downwards. Long lists are given by Pliny (H. N., xxxiii. -xxxvi.), and pedestals even now exist with the names of Praxiteles, Timarchus, Polycletus, Bryaxis, and others (see Bull. Comm. Arch. Rom., ii. p. 176). These accumulated works of sculpture were of all materials—gold and ivory (Suet., 'fit., 2), of which seventy-four are mentioned in the catalogue of the Breviarium (see Preller, Regionen, p. 231), many hundreds or even thousands of silver3 (Plin., H.N., xxxiii. 54), while those of gilt bronze and marble must have existed in almost untold numbers (Paus., viii. 46). Nor were the accumulated stores of Greek paintings much inferior in number; not only were easel pictures by Zeuxis, Apelles, Timanthes, and other Greek artists taken, but even mural paintings were carefully cut off their walls and brought to Rome secured in wooden frames (Plin., H.N., xxxv. 49, and compare ibid., 45).

Roads

The basalt (silex) roads were made of polygonal blocks of lava neatly fitted together and laid on a carefully prepared bed, similar to that used for mosaic paving (see MOSAIC and ROADS). Roads thus made were called "viae stratae." One portion only exists in Rome of early date, when the blocks were fitted together with the utmost accuracy viz., a piece of the Clivus Capitolinus in front of the temple of Saturn (see fig. 6, which also shows the massive travertine curb which bordered the road ; in some cases the curb was of lava). The other best preserved viae stratae in Rome are those leading up to the Palatine from the Summa Sacra Via and that which follows the curved line of shops in Trajan's forum. Many others exist, but have all been relaid in later times, with badly fitting joints.

The following is a list of the chief roads which radiated from Rome (see Plate VII.):—(1) Via Appia and (2) Via Latina, both issued from the Servian Porta Capena, and both met at Bencventum ; (3) Via Labicana, from the P. Esquilina, passing Labicum, joined the Via Latina 30 miles from Rome ; (4) Via Gabina (later called Praenestina), also issued from the P. Esquilina and joined the Via Latina,—these two roads pass through the Claudian aqueduct gate (mod. Porta Maggiore); (5) Via Tiburtina, from the gate of that name to Tibur ; (6) Via Nomentana, from the P. Collina, passing Nomentum, joined the Via Salaria ; (7) Via Salaria, also from the P. Collina, joined the Via Flaminia at Ancona ; (8) Via Flaminia, its first half-mile or so after leaving the Servian Porta Ratumena was known as the Via Lata ; it afterwards passed out of the Aurelian P. Flaminia, and with many branches led to the chief towns of Northern Italy, and so into Cisalpine Gaul; (9) Via Amelia, issued from the trans-Tiberine P. Aurelia and passed through Pisa to Gaul; (10) Via Portuensis, from the gate of that name, also on the right bank of the Tiber, to Portus Augusti near its mouth ; (11) Via Ostiensis, from the Servian P. Trigemina and the Aurelian P. Ostiensis to Ostia ; (12) Via Ardeatina, probably a branch from the Via Appia, led to Ardea.


Footnotes

3 The oft-quoted boast of Augustus (Suet., Aug., 29) that he "found Rome of brick and left it of marble" has probably much truth in it, if for "brick" we read " peperino and tufa." In the time of Augustus burnt brick was very little used, the usual wall-facings being opus guadratum of tufa or peperino, and opus reticulatum of tufa only. The confessiones or crypts in front of the high altars of St Peter's, S. Maria Maggiore, S. Pietro in Vincoli, and other churches in Rome are museums of the rarer and more splendid marbles used by the ancient Romans, as their walls and pavements are covered with the richest specimens found during excavations. All the fine marbles in Roman churches have been taken from ancient buildings ; an excellent account of these is given by Corsi, Pietre antiche, 1845.

4 In the beautiful drawings of Choisy (L'Art de bâtir chez les Romains, Paris, 1873) the structural importance of the brick used in vaults and arches is very much exaggerated.

1 Choisy (L'Art de bâtir chez les Romains, Paris, 1873) is mistaken in his denial of the early use of mortar by the Romans.
2 The expansion of the iron through rust, which caused the stone to split, has frequently been a great source of injury to Roman walls, as well as the practice, common in the Middle Ages, of breaking into the stones in order to extract the metal.
3 These two kinds of stone facings are mentioned thus by Vitruvius (ii. 8), ' ' reticidatum, quo nunc [reign of Augustus] omnes utuntur, et antiquum, quod incertum dicitur."
4 Some of the bricks are as much as 2 1/2 inches thick, while 1 1/2 inches is the usual maximum for Roman bricks.
5 The Roman method of applying stucco to walls with a wooden "float," exactly as is done now, is shown in a painting from Pompeii (see Ana. Inst., 1881).

1 Yet for many centuries during the Middle Ages the richest sites of ancient Rome were riddled with lime-kilns, in which the greater part of the marble was destroyed ; see Raphael's letter to Leo X. on this subject published by Visconti (Rome, 1834).
2 See Bruzza, in Ann. Inst., 1870, p. 106.
3 Eighty silver statues of Augustus, some equestrian and some in quadrigaa, mentioned in the Mon. Ancyr. See p. 822 below.
4 See NIbby, Vie degli Antichi, in Nardini, vol. iv. 1820 ; also Livy, x. 23, 51, xli. 27.

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e.g.j in the lion-tomb at Cnidus and the temple of Zeus at Agrigentum. Sur-face enrichments over the mouldings were used far more largely by the Romans th an by the Greeks.


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