ARCH, TRIUMPHAL, a structure which the Romans used to erect across their roads or bridges, or at the entrance of their cities, in honour of victorious generals or emperors. They were of' two kinds. Temporary arches were made of wood, on the occasion of a triumph. The others were permanent struc tures, built first of brick, afterwards of hewn stone, and lastly made of, or at least cased with, marble. Their general form is that of a parallelopipedon, which has an opening in the longer side, and sometimes a smaller opening on each side of the large one. These openings are arched over with semicircular arches, and the fronts are decorated with co lumns and their accessories on lofty pedestals : the whole is surmounted by a heavy attic, on the faces of which inscriptions were generally placed.
Triumphal arches were erected under the republic. Under the emperors these monu ments became very numerous, and were over charged with ornaments. One erected to Augustus at Rimini has the widest opening of the ancient arches, the gateway being 31 feet. Of the triumphal arches remaining at Rome, that of Titus is the oldest. This arch is or namented with sculptures representing the triumph of Titus, and the ornaments of the temple of Jerusalem which he brought as spoils to Rome. But arches were also raised in honour of emperors for benefits conferred on their country on some particular occasions ; such is the fine arch of Trajan on the old mole of Ancona. Another fine arch in me mory of Trajan exists at Benevento ; it is ornamented with fine rilievi, and is in very good preservation. All these are single
arches; but others have two smaller archways, one on each side of the great central one. These are consequently oblong in their shape, and have a heavier appearance than the single arch. Two of these triple arches still exist at Rome, that of Septimius Severus, and that called the arch of Constantine.
There are other arches in various parts of Italy, at Aquino, Aosta, and Pola in Istria, and several in the south of France, of which those of Nismes and Orange are the best preserved. There are several arches in Syria and in Bar bary, particularly one at Tripoli, and another at Constantina. In modern times triumphal arches have been raised in imitation of the Roman arches. Those of the gate of St. Denis and the gate of St. Martin, at Paris, were raised in honour of Louis XIV. Bonaparte also had one constructed on the place du Carousel, after the model of the triumphal arch of' Septimius Severus at Rome. The much larger arch, the 'Arc de l'Etoile,' at the Barrriere de Neuilly, was commenced in 1806, after the battle of Austerlitz, and has only recently been finished (1847.) Another arch (L'Arco della Pace) which was begun by Bonaparte's order at Milan, on the opening of the famous road across the Simplon, has since been completed by the Austrian government. In London there is a single arch at Hyde Park Corner.