Chapter 11

ROMAN ARCHITECTURE.

BOOKS RECOMMENDED: As before, Anderson and Spiers, Baumeister, Reber. Choisy, _L’Art de bâtir chez les Romains_. Desgodetz, _Rome in her Ancient Grandeur_. Durm, _Die Baukunst der Etrusker_; _Die Baukunst der Romer_. Lanciani, _Ancient Rome in the Light of Modern Discovery_; _New Tales of Old Rome_; _Ruins and Excavations of Ancient Rome_. De Martha, _Archéologie étrusque et romaine_. Middleton, _Ancient Rome in 1888_.

+LAND AND PEOPLE.+ The geographical position of Italy conferred upon her special and obvious advantages for taking up and carrying northward and westward the arts of civilization. A scarcity of good harbors was the only drawback amid the blessings of a glorious climate, fertile soil, varied scenery, and rich material resources. From a remote antiquity Dorian colonists had occupied the southern portion and the island of Sicily, enriching them with splendid monuments of Doric art; and Phœnician commerce had brought thither the products of Oriental art and industry. The foundation of Rome in 753 B.C. established the nucleus about which the sundry populations of Italy were to crystallize into the Roman nation, under the dominating influence of the Latin element. Later on, the absorption of the conquered Etruscans added to this composite people a race of builders and engineers, as yet rude and uncouth in their art, but destined to become a powerful factor in developing the new architecture that was to spring from the contact of the practical Romans with the noble art of the Greek centres.

+GENERAL CHARACTERISTICS.+ While the Greeks bequeathed to posterity the most perfect models of form in literary and plastic art, it was reserved for the Romans to work out the applications of these to every-day material life. The Romans were above all things a practical people. Their consummate skill as organizers is manifest in the marvellous administrative institutions of their government, under which they united the most distant and diverse nationalities. Seemingly deficient in culture, they were yet able to recast the forms of Greek architecture in new moulds, and to evolve therefrom a mighty architecture adapted to wholly novel conditions. They brought engineering into the service of architecture, which they fitted to the varied requirements of government, public amusement, private luxury, and the common comfort. They covered the antique world with arches and amphitheatres, with villas, baths, basilicas, and temples, all bearing the unmistakable impress of Rome, though wrought by artists and artisans of divers races. Only an extraordinary genius for organization could have accomplished such results.

The architects of Rome marvellously extended the range of their art, and gave it a flexibility by which it accommodated itself to the widest variety of materials and conditions. They made the arch and vault the basis of their system of design, employing them on a scale previously undreamed of, and in combinations of surpassing richness and majesty. They systematized their methods of construction so that soldiers and barbarians could execute the rough mass of their buildings, and formulated the designing of the decorative details so that artisans of moderate skill could execute them with good effect. They carried the principle of repetition of motives to its utmost limit, and sought to counteract any resulting monotony by the scale and splendor of the design. Above all they developed planning into a fine art, displaying their genius in a wonderful variety of combinations and in an unfailing sense of the demands of constructive propriety, practical convenience, and artistic effect. Where Egyptian or Greek architecture shows one type of plan, the Roman shows a score.

+GREEK INFLUENCE.+ Previous to the closing years of the Republic the Romans had no art but the Etruscan. The few buildings of importance they possessed were of Etruscan design and workmanship, excepting a small number built by Greek hands. It was not until the Empire that Roman architecture took on a truly national form. True Roman architecture is essentially imperial. The change from the primitive Etruscan style to the splendors of the imperial age was due to the conquest of the Greek states. Not only did the Greek campaigns enrich Rome with an unprecedented wealth of artistic spoils; they also brought into Italy hosts of Greek artists, and filled the minds of the campaigners with the ambition to realize in their own dominions the marble colonnades, the temples, theatres, and propylæa of the Greek cities they had pillaged. The Greek orders were adopted, altered, and applied to arcaded designs as well as to peristyles and other open colonnades. The marriage of the column and arch gave birth to a system of forms as characteristic of Roman architecture as the Doric or Ionic colonnade is of the Greek.

+THE ROMAN ORDERS.+ To meet the demands of Roman taste the Etruscan column was retained with its simple entablature; the Doric and Ionic were adopted in a modified form; the Corinthian was developed into a complete and independent order, and the Composite was added to the list. A regular system of proportions for all these five orders was gradually evolved, and the mouldings were profiled with arcs of circles instead of the subtler Greek curves. In the building of many-storied structures the orders were superposed, the more slender over the sturdier, in an orderly and graded succession. The immense extent and number of the Roman buildings, the coarse materials often used, the relative scarcity of highly trained artisans, and above all, the necessity of making a given amount of artistic design serve for the largest possible amount of architecture, combined to direct the designing of detail into uniform channels. Thus in time was established a sort of canon of proportions, which was reduced to rules by Vitruvius, and revived in much more detailed and precise form by Vignola in the sixteenth century.

In each of the orders, including the Doric, the column was given a base one half of a diameter in height (the unit of measurement being the diameter of the lower part of the shaft, the _crassitudo_ of Vitruvius). The shaft was made to contract about one-sixth in diameter toward the capital, under which it was terminated by an _astragal_ or collar of small mouldings; at the base it ended in a slight flare and fillet called the _cincture_. The entablature was in all cases given not far from one quarter the height of the whole column. The +Tuscan+ order was a rudimentary or Etruscan Doric with a column seven diameters high and a simple entablature without triglyphs, mutules, or dentils. But few examples of its use are known. The +Doric+ (Fig. 42) retained the triglyphs and metopes, the mutules and guttæ of the Greek; but the column was made eight diameters high, the shaft was smooth or had deep flutings separated by narrow fillets, and was usually provided with a simple moulded base on a square plinth. Mutules were used only over the triglyphs, and were even replaced in some cases by dentils; the corona was made lighter than the Greek, and a cymatium replaced the antefixæ on the lateral cornices. The Ionic underwent fewer changes, and these principally in the smaller mouldings and details of the capital. The column was nine diameters high (Fig. 43). The +Corinthian+ was made into an independent order by the designing of a special base of small _tori_ and _scotiæ_, and by sumptuously carved _modillions_ or brackets enriching the cornice and supporting the corona above a denticulated bed-mould (Fig. 44). Though the first designers of the modillion were probably Greeks, it must, nevertheless, be taken as really a Roman device, worthily completing the essentially Roman Corinthian order. The +Composite+ was formed by combining into one capital portions of the Ionic and Corinthian, and giving to it a simplified form of the Corinthian cornice. The Corinthian order remained, however, the favorite order of Roman architecture.

+USE OF THE ORDERS.+ The Romans introduced many innovations in the general use and treatment of the orders. Monolithic shafts were preferred to those built up of superposed drums. The fluting was omitted on these, and when hard and semi-precious stone like porphyry or verd-antique was the material, it was highly polished to bring out its color. These polished monoliths were often of great size, and they were used in almost incredible numbers.

Another radical departure from Greek usage was the mounting of columns on pedestals to secure greater height without increasing the size of the column and its entablature. The Greek _anta_ was developed into the Roman pilaster or flattened wall-column, and every free column, or range of columns perpendicular to the façade, had its corresponding pilaster to support the wall-end of the architrave. But the most radical innovation was the general use of engaged columns as wall-decorations or buttresses. The engaged column projected from the wall by more than half its diameter, and was built up with the wall as a part of its substance (Fig. 45). The entablature was in many cases advanced only over the columns, between which it was set back almost to the plane of the wall. This practice is open to the obvious criticism that it makes the column appear superfluous by depriving it of its function of supporting the continuous entablature. The objection has less weight when the projecting entablature over the column serves as a pedestal for a statue or similar object, which restores to the column its function as a support (see the Arch of Constantine, Fig. 63).

+ARCADES.+ The orders, though probably at first used only as free supports in porticos and colonnades, were early applied as decorations to arcaded structures. This practice became general with the multiplication of many-storied arcades like those of the amphitheatres, the engaged columns being set between the arches as buttresses, supporting entablatures which marked the divisions into stories (Fig. 45). This combination has been assailed as a false and illogical device, but the criticism proceeds from a too narrow conception of architectural propriety. It is defensible upon both artistic and logical grounds; for it not only furnishes a most desirable play of light and shade and a pleasing contrast of rectangular and curved lines, but by emphasizing the constructive divisions and elements of the building and the vertical support of the piers, it also contributes to the expressiveness and vigor of the design.

+VAULTING.+ The Romans substituted vaulting in brick, concrete, or masonry for wooden ceilings wherever possible, both in public and private edifices. The Etruscans were the first vault-builders, and the Cloaca Maxima, the great sewer of Republican Rome (about 500 B.C.) still remains as a monument of their engineering skill. Probably not only Etruscan engineers (whose traditions were perhaps derived from Asiatic sources in the remote past), but Asiatic builders also from conquered eastern provinces, were engaged together in the development of the wonderful system of vaulted construction to which Roman architecture so largely owed its grandeur. Three types of vault were commonly used: the barrel-vault, the groined or four-part vault, and the dome.

The barrel vault (Fig. 46) was generally semi-cylindrical in section, and was used to cover corridors and oblong halls, like the temple-cellas, or was bent around a curve, as in amphitheatre passages.

The groined vault is formed by the intersection of two barrel-vaults (Fig. 47). When several compartments of groined vaulting are placed together over an oblong plan, a double advantage is secured. Lateral windows can be carried up to the full height of the vaulting instead of being stopped below its springing; and the weight and thrust of the vaulting are concentrated upon a number of isolated points instead of being exerted along the whole extent of the side walls, as with the barrel-vault. The Romans saw that it was sufficient to dispose the masonry at these points in masses at right angles to the length of the hall, to best resist the lateral thrust of the vault. This appears clearly in the plan of the Basilica of Constantine (Fig. 58).

The dome was in almost all Roman examples supported on a circular wall built up from the ground, as in the Pantheon (Fig. 54). The pendentive dome, sustained by four or eight arches over a square or octagonal plan, is not found in true Roman buildings.

The Romans made of the vault something more than a mere constructive device. It became in their hands an element of interior effect at least equally important with the arch and column. No style of architecture has ever evolved nobler forms of ceiling than the groined vault and the dome. Moreover, the use of vaulting made possible effects of unencumbered spaciousness and amplitude which could never be compassed by any combination of piers and columns. It also assured to the Roman monuments a duration and a freedom from danger of destruction by fire impossible with any wooden-roofed architecture, however noble its form or careful its execution.

+CONSTRUCTION.+ The constructive methods of the Romans varied with the conditions and resources of different provinces, but were everywhere dominated by the same practical spirit. Their vaulted architecture demanded for the support of its enormous weights and for resistance to its disruptive thrusts, piers and buttresses of great mass. To construct these wholly of cut stone appeared preposterous and wasteful to the Roman. Italy abounds in clay, lime, and a volcanic product, _pozzolana_ (from Puteoli or Pozzuoli, where it has always been obtained in large quantities), which makes an admirable hydraulic cement. With these materials it was possible to employ unskilled labor for the great bulk of this massive masonry, and to erect with the greatest rapidity and in the most economical manner those stupendous piles which, even in their ruin, excite the admiration of every beholder.

+STONE, CONCRETE, AND BRICK MASONRY.+ For buildings of an externally decorative character such as temples, arches of triumph, and amphitheatres, as well as in all places where brick and concrete were not easily obtained, stone was employed. The walls were built by laying up the inner and outer faces in _ashlar_ or cut stone, and filling in the intermediate space with rubble (random masonry of uncut stone) laid up in cement, or with concrete of broken stone and cement dumped into the space in successive layers. The cement converted the whole into a conglomerate closely united with the face-masonry. In Syria and Egypt the local preference for stones of enormous size was gratified, and even surpassed, as in Herod’s terrace-walls for the temple at Jerusalem (p. 41), and in the splendid structures of Palmyra and Baalbec. In Italy, however, stones of moderate size were preferred, and when blocks of unusual dimensions occur, they are in many cases marked with false joints, dividing them into apparently smaller blocks, lest they should dwarf the building by their large scale. The general use in the Augustan period of marble for a decorative lining or wainscot in interiors led in time to the objectionable practice of coating buildings of concrete with an apparel of sham marble masonry, by carving false joints upon an external veneer of thin slabs of that material. Ordinary concrete walls were frequently faced with small blocks of tufa, called, according to the manner of its application, _opus reticulatum_, _opus incertum_, _opus spicatum_, etc. (Fig. 48). In most cases, however, the facing was of carefully executed brickwork, covered sometimes by a coating of stucco. The bricks were large, measuring from one to two feet square where used for quoins or arches, but triangular where they served only as facings. Bricks were also used in the construction of skeleton ribs for concrete vaults of large span.

+VAULTING.+ Here, as in the wall-masonry, economy and common sense devised methods extremely simple for accomplishing vast designs. While the smaller vaults were, so to speak, cast in concrete upon moulds made of rough boards, the enormous weight of the larger vaults precluded their being supported, while drying or “setting,” upon timber centrings built up from the ground. Accordingly, a skeleton of light ribs was first built on wooden centrings, and these ribs, when firmly “set,” became themselves supports for intermediate centrings on which to cast the concrete fillings between the ribs. The whole vault, once hardened, formed really a monolithic curved lintel, exerting no thrust whatever, so that the extraordinary precautions against lateral disruption practised by the Romans were, in fact, in many cases quite superfluous.

+DECORATION.+ The temple of Castor and Pollux in the Forum (long miscalled the temple of Jupiter Stator), is a typical example of Roman architectural decoration, in which richness was preferred to the subtler refinements of design (see Fig. 44). The splendid figure-sculpture which adorned the Greek monuments would have been inappropriate on the theatres and thermæ of Rome or the provinces, even had there been the taste or the skill to produce it. Conventional carved ornament was substituted in its place, and developed into a splendid system of highly decorative forms. Two principal elements appear in this decoration--the acanthus-leaf, as the basis of a whole series of wonderfully varied motives; and symbolism, represented principally by what are technically termed _grotesques_--incongruous combinations of natural forms, as when an infant’s body terminates in a bunch of foliage (Fig. 49). Only to a limited extent do we find true sculpture employed as decoration, and that mainly for triumphal arches or memorial columns.

The architectural mouldings were nearly always carved, the Greek water-leaf and egg-and-dart forming the basis of most of the enrichments; but these were greatly elaborated and treated with more minute detail than the Greek prototypes. Friezes and bands were commonly ornamented with the foliated scroll or _rinceau_ (a convenient French term for which we have no equivalent). This motive was as characteristic of Roman art as the anthemion was of the Greek. It consists of a continuous stem throwing out alternately on either side branches which curl into spirals and are richly adorned with rosettes, acanthus-leaves, scrolls, tendrils, and blossoms. In the best examples the detail was modelled with great care and minuteness, and the motive itself was treated with extraordinary variety and fertility of invention. A derived and enriched form of the anthemion was sometimes used for bands and friezes; and grotesques, dolphins, griffins, infant genii, wreaths, festoons, ribbons, eagles, and masks are also common features in Roman relief carving.

The Romans made great use of panelling and of moulded plaster in their interior decoration, especially for ceilings. The panelling of domes and vaults was usually roughly shaped in their first construction and finished afterward in stucco with rich moulding and rosettes. The panels were not always square or rectangular, as in Greek ceilings, but of various geometric forms in pleasing combinations (Fig. 50). In works of a small scale the panels and decorations were wrought in relief in a heavy coating of plaster applied to the finished structure, and these stucco reliefs are among the most refined and charming products of Roman art. (Baths of Titus; Baths at Pompeii; Palace of the Cæsars and tombs at Rome.)

+COLOR DECORATION.+ Plaster was also used as a ground for painting, executed in distemper or by the encaustic process, wax liquefied by a hot iron being the medium for applying the color in the latter case. Pompeii and Herculaneum furnish countless examples of brilliant wall-painting in which strong primary colors form the ground, and a semi-naturalistic, semi-fantastic representation of figures, architecture and landscape is mingled with festoons, vines, and purely conventional ornament. Mosaic was also employed to decorate floors and wall-spaces, and sometimes for ceilings.[13] The later imperial baths and palaces were especially rich in mosaic of the kind called opus Grecanicum, executed with numberless minute cubes of stone or glass, as in the Baths of Caracalla and the Villa of Hadrian at Tivoli.

[Footnote 13: See Van Dyke’s _History of Paintings_, p. 33.]

To the walls of monumental interiors, such as temples, basilicas, and thermæ, splendor of color was given by veneering them with thin slabs of rare and richly colored marble. No limit seems to have been placed upon the costliness or amount of these precious materials. Byzantine architecture borrowed from this practice its system of interior color decoration.