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Originally appearing in Volume V23, Page 587 of the 1911 Encyclopedia Britannica.
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THE ANCIENT CITY The chief building materials used in ancient Rome may be enumerated as follows: (1) Tufa, the "rubes et niger tophus " of Vitruvius (ii. 7), varying in colour from Building warm brown to yellow or greyish green (called materlcapellaccio). The Aventine, Palatine and Capitoline dis• Hills contained quarries of the tuf a, much worked at an early period (see T.iv. xxvi. 27, xxxix. 44, and Varro, L.L. iv. 151). It is a very bad " weather-stone," but stands well if protected with stucco (Plin. H.N. xxxvi. 166). (2) Lapis Albanus, from Alba conga, of volcanic origin, a conglomerate of ashes, gravel' and fragments of stone; its quarries are still worked at Albano and Marino- This is now; called peperino, from the black scoriae, like peppercorns, with which the brown conglomerate mass is stadded. (3) Lapis Gabinus, from Gabii, 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 Tacit-us (Ann. xv. 43), it is fire-proof, and this is also the case with the Alban stone. Lapis Gabinus is now called sperone. (4) Silex (mod. selce), a lava from the now extinct volcanoes in the Alban Hills, used for paving roads; when broken into small pieces and mixed with lime and pozzolana it formed an immensely durable concrete. It is dark grey, very hard and breaks with a slightly conchoidal fracture (Plin. H.N. xxxvi. 135; Vitt. 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' riverAnio; a hard pure carbonate of lime, of a creamy white colour, deposited from running or dripping water in a highly 1 By the great flight of marble steps up to S. Maria in Ara Coeli. 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. (6) Pulvis. Puteolanus (pozzolana), o called from extensive beds of it at Puteoli—a volcanic pro-duct, 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 (lateres crudi) or kiln-baked (lateres cocti, testae). , The remarks of Vitruvius (ii. 3), seem to refer wholly to sun-dried bricks, of which no examples now exist in Rome. It is 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 (opus caementicium, Vitr. ii. 4, 6, 8), the most important of all the materials used, is made of rough pieces of stone, or of fragments of marble, brick,, &c., 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 stre'igth and coherence. Stucco; cement and Mortar (tectorium,opus hlbdrium 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 in. thick altogether; the lower coats were of lime and pozzolana, the finishing coats of powdered white marble, (opus albarium) suit-able 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" (Cie. In Veer. ii. 1, 52 seq.). 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. Marble appears to have come into use about the beginning of the 1st century s.c. Its introduction. was at first viewed with great Decors- jealousy, as savouring of Greek luxury. The 'orator flue Crassus was the first to use it in his house on the Palatine, materials. 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. 7). The temporary wooden theatre of the aedile 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. 5, 5o). . 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. p. 222), is of many qualities, from the purest creamy White and the finest grain to the coarser sorts disfigured with bluish grey Streaks. 1 In less solid constructions than those which have survived. until modern times bricks Were doubtless used by themselves. 2 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 quadratum of tufa or peperino, and opus reticutatum of tufa only.(Ex., the eleven Corinthian columns in the Borsa.) (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 ix. p. 399). (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 fpr statues, though some sculptors preferred it above all others, especially Pheidias and Praxiteles. (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. (Ex., the nineteen columns of the round, temple in the Forum Boarium'.) Nine chief varieties of coloured marbles were used in Rome. (1) Marmor Numidicum (mod. giallo antico; Plin. H.N. v. 22), from Numidia and Libya, hence also called Libycum, ColoareA is of a. rich yellow, deepening to orange and even pink., marbles. Enormous quantities of it were used, especially f or columns, wall-linings and pavements. (Ex., seven columns 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 I;uboea (Strabo x. p. 446), has alternate wavy strata of white and pale green—the "undosa Carystos" of Status (Silo. i. 5, 34). From its well-defined layers like an onion (cipolla) is derived its modern name. (Ex., columns of temple of Antoninus and Faustina. (3) Marmor Phrygium or Synnadicum (mod. pavonazzetto), from' Synnada in Phrygia (Strabo, xii. p. 577; Jqv, xiv. 307; Tibull. iii. 3, 13), is a slightly translucent marble, with rich purdie markings, violet verging on red. It was fabled to' be stained with the blood of Atys (Stet. Silo. i. 5, 37). (Ex., twelve fluted columns in S. Lorenzo fuori le Mura,.and four columns in the apse of,S. Paolo fuori, saved from the ancient nave of the basilica, burnt in. 1823.) (4) Marmor Iasium (probably the modern porta santa), from Iasus, is mottled with large patches of dull red, olive green and white. The holy doors ' of the four great basilicas are framed with it, hence its modern name. (Ex.; the slabs in front of the hemicycle of the Rostra and four columns in, S..Agnese fuori le Mum). (5) Marmor Chium, (probably the modern Africano), from Chios, is similar in the variety of its markings to the portasanta; 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) Marmor Taenarium (mod. rosso antico), from Taenarum in Laconia (Strabo viii. p. 367; Pliny, H.N. xxxvi. 158), is a very close-grained marble, of a rich deep red, like blood. As a rule it does net 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 ft: high in the Rospigliosi Casino dell' Aurora.) (7) The name Marmor Taenatium is also applied by the ancients to a black marble (nero entice) now no longer quarried. It is mentioned by Tibullus (iii. 3, 14) in conjunction with Phrygian and Carystian marbles; see also Prop. iii. 2, 9, and Plin. H.N. xxxvi. 135. (Ex., two columns in the choir of S. Giovanni in Laterano.) (8) Lapis Alydtius (verde antico), found at Atrax in Thessaly, 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. 59i xxxvii. 109); 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 bath§ 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, whose ancient` names are unknown.' From the latter part of the 1st century s.c. hard stones—granites and basalts—were introduced in great quantities. The basalts--i basanites "of Pliny,(xxxvi. 58)—are very refractpry, and Granites can only be worked by the help of emery or diamond dust. and The former was obtained largely at Naxos; diamond- basalt& dust drills are mentioned by Pliny (H.N. xxxvii. 200), The basalts are black, green and brown, and are usually free front spots or markings; examples of all three exist, but are corn, paratively rare. The red variety called " porphyry " was used in enormous quantities. It is the " porphyrites" of Pliny (H.N. These Nile quarries were worked during the 196 century, and many blocks were imported into Rome for the rebuilding of S. Paolo fuori le Mum. ' On the subject of Roman marbles, see Corsi, Delle pietre antiche (ed. 3, 1845), and Pullen, Handbook of Roman Marbles (London., 1894) ; also,Brindley in Transactions of the Royal Institute of British Architects (r887) A collection of moo specimens, originally formed by Corsi, is preserved in the museum at Oxford. 586 xxxvi. 57), 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 Lacedacmonia (Paus. iii. 21, 4; Plin. H.N. xxxvi. 55; Juv. xi. 175). It appears to have been mostly used for pavements and panels of wall linings. The granites used in Rome came mostly from near Philae on the Nile (Plin. H.N. xxxvi. 63). 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. 2, 67). The style of architecture employed in ancient Rome (see ARCHITECTURE, section Roman, and ROMAN ART) may be Arch,- said to have passed through three stages—the tecturst Etruscan, the Greek and the Roman. During the styles• 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, 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; it is found in the period following the Second Punic or Hannibalic War, and 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, such as Apollodorus of Damascus, who designed Trajan's forum and other buildings; on the other hand, a Roman, Cossutius, was employed on the building of the Olympieum at Athens, in the 2nd century B.C. Roman architects such as Vitruvius and C. Mucius 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).2 The Romans, however, though far below the Greeks in 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 semi-fluid 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 Pliny (H.N. xxxv. 154), quoting Varro, says that the decorations in painting and sculpture of the temple of Ceres near the Circus Maximus were the work of the first Greek artists employed in Rome, and that before that (c. 493 B.C.) " all things in temples were Etruscan." Vitruvius (iii. 3) says, " Ornantque signis fictilibus aut aereis inauratis eorum fastigia Tuscanico more, uti est ad Circum Maximum Cereris, et Herculis Pompeiani, item Capitolii " (cf. iv. 7, Vi. 3). 2 The frequent use of engaged columns is a peculiarity of Roman architecture, but it is not without precedent in Greek buildings of the best period, e.g. in the temple of Zeus at Agrigentum. Surface enrichments over the mouldings were used far more largely by the Romans than by the Greeks. 2 In the beautiful drawings of Choisy (L'Art de btltir chez les Remains, Paris, 1873) the structural importance of the brick used in vaults and arches is very much exaggerated.[THE ANCIENT CITY 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 ft. thick, while the brick facing averages scarcely 6 in. 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. The same applies to the superficial use of brick in all arches and vaults. Although, however, the setting of the concrete rendered the brick facing superfluous, it played its part in sustaining the fluid mass on its centring during the process of solidification. At first tufa only was used in opus quadratum, as we see in the so-called wall of Romulus. Next the harder peperino began to be worked: it is used, though sparingly, in the "Servian " Opus wall, and during the later Republic appears to have been guad- largely employed for exterior walls or points where there ratum. was heavy pressure, while other parts were built of tula. Thirdly, travertine appears to have been introauced about the 2nd 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) ft. thick in regular courses (the " isodomum " of Vitruvius) by 2 ft. across the end, and under the Republic often exactly 4 ft. long, so that two blocks set endways ranged with one set lengthways. They were 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. 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 ft. were used, and the courses varied in thickness—the " pseudisodomum " of Vitruvius. When tufa or peperino was mixed with the FIG. ,.—Example of Construction in which travertine, it was cut so as to range with the irregular courses of the latter. It is interesting 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 Au- many materials are used; upper part of one of the inner radiating walls under the cunei of the Colosseum. A, A. Marble seats on brick and concrete core, supported on vault made of pumice-stone concrete (C). B. Travertine arch at end of raking vault (C). D. One of the travertine piers built in flush with the tufa wall to give it extra strength. E, E. Wall of tufa concrete faced with triangular bricks, carrying the vaults of pumice concrete which support the marble seats. F. Travertine pier at end of radia- ting wall. G. Brick-faced arch of concrete to carry floor of passage. H, H. Tufa wall, opus quadratum. J, J, J. Line of steps in next bay. K, K. Surface arches of brick, too shallow to be of any constructional use, and not meant for ornament, as the whole was stuccoed; they only face the wall (which g u s t u s and the is about 4 ft. thick) to the average depth of temple of Fortuna 4 in. Virilis, so called) was inserted at points of special pressure, such as piers or arches (see fig.). The Colosseum is a particularly elaborate example of this mixed construction with three degrees of pressure supported by three different materials. A The use of mortar with opus quadratum is a sign of a comparatively 1 early date. It occurs, e.g. in the "Servian " wall on the Aventine Mortar and in the Tabularium. 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 Clamps. binding to give the joints a together was done smoothly cfitting surface. The actual lamps 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. Concrete is rarely found in connexion with opus quadratum; part of the " Servian " wall on the Aventine received a backing of concrete at a relatively late period Up to the 1st century B.C. it was faced with opus incertum—small irregularly shaped blocks of tufa, 3 to 6 in. across, with pointed ends driven into the concrete while it was soft, and worked smooth on the face only (see fig. 2). From the beginning Opus of the 1st century B.C. Opus reticulatum,' formed of rectangular tufa prisms laid in a regula: pattern like a reticu" net (whence the name), is found. It is very neat in ]atom. 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. Under the Empire brick quoins came into use (as may be seen, e.g. in the so-called palace of Caligula). Though in Rome opus reticulatum was almost 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. B B
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