ROMAN ARCHITECTURE. I53 external wall of concrete faced with " opus mixtum " (page 117). At one end were the " carceres " or stalls for horses and chariots, with a central entrance for processions and two side entrances, and at the semicircular end was the " porta triumphalis." TRIUMPHAL ARCHES AND PILLARS OF VICTORY. These were erected to emperors or generals in honour of their victories. They consisted either of a single arch or of a central arch with a smaller one on either side. These rest on an impost, and have Corinthian or Composite columns on either side, and were adorned with architectural enrichments, statuary, and bas- reliefs relating to campaigns. An attic or surmounting mass of stonework was placed above, having a dedicatory inscription. (a.) The single-arched type, of which the central arch at Hyde Park Corner, London, is an example. The Arch of Titus, Rome (a.d. 81) (Nos. 47, 49, 69 a, c), commemorates the capture of Jerusalem in a.d. 70. On each side of the arch are semi-engaged columns of the Composite order, being the earliest known examples, and three-quarter columns occur at the angles. The archway has its soffit ornamented with deep coffers, in the centre of which is a relief of the apotheosis of Titus. The inner jambs have reliefs of the emperor in a triumphal car, being crowned by victory, on the one side, and the spoils taken from the Temple at Jerusalem on the other. The central keystones project considerably in order to support the main architrave, and are richly carved, as shown in No. 67 b. Other well-known examples of this type are the Arches of Trajan at Ancona (a.d. i 13), Trajan at Beneventum (a.d. 114) (No. 70 d), the Sergii at Pola, Augustus at Susa (Piedmont) (B.C. 7), Augustus at Aosta (Piedmont), Augustus at Rimini (a.d. 27), and Hadrian at Athens. The Arch of the Goldsmiths, Rome (a.d. 204) (No. 49), is not of arched construction, the opening being spanned by an entablature. {h.) The tlivee-arched type, of which the Marble Arch, London, gives a general idea. The Arch of Septimius Severus, Rome (a.d. 204) (Nos. 47, 57, 65, 66 and 70), built to commemorate Parthian victories, has detached Composite columns resting on pedestals. A description is given on each of the illustrations Nos. 57 and 65. The Arch of Constantine, Rome (a.d. 312) (No. 47), was built in honour of Constantine's victory over Maxentius, and is one of the best proportioned examples. It has detached Corinthian columns supporting an entablature, which returns round each column, and above the attic were originally a quadriga, horses, and statues.
