the remains of Pompeii show, was an invention of the later Hellenistic age. Reduced copies of statues are found in the decoration of such capitals in the baths of Caracalla; the capitals with Victories and trophies in S. Lorenzo Fuori also belonged to a building of pagan times.
But the specific achievement of the Roman architect was the artistic application of a new set of principles—those which are expressed in the arch, the vault and the dome. The rectilinear buildings of the Greeks, with their direct vertical supports, gave place to vaulted structures in which lateral thrust was called into play. The aesthetic effect of the curves thus brought into prominence was well understood by the Romans; and they were the inventors of the decorative combination of the Greek orders with the arcade. More than this, the erection of vaults and domes of wide span, rendered possible by the use of concrete, gave to the Roman architect the opportunity of dealing artistically with internal spaces. A simple yet grandiose example of this may be found in the Pantheon of Hadrian. Circular buildings were a common feature in Italian architecture;[1] the temple of Vesta, which doubtless represented the primitive hut or dwelling of the king, always had this form, and the theme was repeated with many variations, from the well-known circular temple in the Forum Boarium to the fantastic structure with broken outlines at Baalbek. But in the Pantheon the artist lays stress, not on the exterior, which possesses no special effect, but on the interior, whose proportions are carefully determined and give a most impressive result. The same may be said of the great halls of the Imperial Thermae, and as time went on more elaborate architectural schemes were devised to meet the requirements of the Christian Church.
(b) Sculpture.—It was pointed out above that in the late Republican period specifically Roman art was practically confined to portraiture. Of this we have many fine examples, such as the so-called Domitius Ahenobarbus of the Braccio Nuovo (Plate I. fig. 1); and there is a series of busts which possess a special interest in that some of them have been claimed as portraits of Scipio Africanus. The example in the Museo Capitolino (Plate I. fig. 2), with a modern inscription, though executed in the 2nd century A.D., is clearly copied from a famous Republican original. The baldness of the head has been thought to be derived from the technique of the waxen imagines, in which the hair was painted; the presence of a scar above the temple, which has given rise to various theories, merely betokens the unsparing realism of the Republican artist. In monumental sculpture our earliest datable example is the altar of Domitius Ahenobarbus, already referred to (Plate II. fig. 10). The ceremonial scene of the suovetaurilia fills the centre of the composition; to the left we see the dismissal of veterans for whom diplomata are being prepared; to the right the troops on active service, both horse and foot, are represented. The artist was clearly inspired by statuary and other types of earlier date, which are grouped in a somewhat loose composition. Augustan art is adequately represented by the Prima Porta statue of the emperor, discovered in 1863 in the Villa of Livia and now in the Braccio Nuovo (Plate III. fig. 17). The attitude of the figure is that of an imperator addressing his army; but there is a characteristic blending of the real with the ideal, for the emperor is not only bareheaded but barefoot, and beside him is a tiny cupid riding on a dolphin, which indicates the descent of the Julian house from Venus. We note, too, how the Roman artist—or the Greek artist interpreting the wishes of the Roman—is scarcely more concerned for the total effect of his work than for the significant details of the decoration. The chasings of the corselet display, as a central subject, the restoration by the Parthian in 20 B.C. of the standards taken from Crassus at Carrhae (53 B.C.). Not content with this, the artist has added a group of personifications indicating sunrise—Sol, Caelus, Aurora and the goddess of the morning dew—as well as Apollo, Diana, Mars and the earth goddess, and two figures symbolical of the western provinces, Gaul and Spain. It is also to be noted that the statue shows abundant traces of its original polychrome tints—brown, yellow, blue, red and pink. It must have been executed later—probably not much later—than 13 B.C., when Augustus returned from the West, and therefore belongs to the same period as the Ara Pacis Augustae, dedicated January 30, 9 B.C. This altar stood in a walled enclosure with two entrances, measuring 11½ by 10½ metres. The walls, with their plinth, were about 6 metres in height, and were decorated internally with a frieze of garlands and bucrania, and externally with two bands of relief, the lower consisting of conventional scrolls of acanthus varied with other floral motives, and teeming with bird and insect life, the upper showing processions (Plate II. fig. 11) passing from east to west. The most interesting of these is that on the south wall, which included Augustus himself, the flamines and the imperial family.[2] On the western face, towards which the processions are directed, we find a scene of sacrifice, with a landscape background, in which the ideal figures of senate and people appear. To the east front (apparently) belongs the beautiful group of the earth goddess (Tellus) and the spirits of air and water (Plate II. fig. 13). It is impossible to deny the incongruity of this composition with the realistic procession which adjoins it, and we can only suppose that the artist borrowed the group from some Hellenistic precursor and used it in that blend of the real and ideal which, as we saw, was the keynote of the new imperial art.
The lack of public monuments which can be assigned to the Julio-Claudian period is only in part supplied by those of private significance; the most important of these are the sepulchral cippi and other altars, decorated sometimes with figure-subjects, but largely with plant and animal forms rendered with the utmost naturalism. The altar with plane leaves in the Museo delle Terme (fig. 38), though perhaps not later than Augustus, is typical of the spirit in which vegetable forms were treated under the first dynasty. We may take a female portrait discovered in a 1st-century house on the right bank of the Tiber (Plate I. fig. 3) as an example of the portraiture of this period, which shows great technical merit but a touch of conventionality.
The sculpture of the Flavian period finds its best-known example in the reliefs of the Arch of Titus. This has but a single archway; the piers had no sculptured decoration, and the narrow frieze which surmounts the architrave is perfunctorily executed. But the long panels on either side of the passage, which represent the triumph of Titus and the spoils of Jerusalem, have been deemed (by Wickhoff) worthy of a place in the history of art beside the masterpieces of Velazquez—the “Hilanderas” and the “Surrender of Breda”; and