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design. The sculptor, being free from the restriction of construction, realuted his conception much in the same way as a scene-painter produce* a theatrical background. Aqueducts and Bridget. — Although at the present day aqueducts and bridges would be classed under the head of end • :..iM.-.-nrv i those built by the Romans are so fine in their conception and « _ that they take their place as monuments. The Pont-du-(jard near Nlmes, and the aqueducts of Segovia, Tarragona and Merida in Spain, and some of those in or near Rome, are of the simplest design, depending for their effect on their magnificent construction, their dimensions both in length and height, and the Kale given in the ranges of arches one above the other. Few of the Roman bridges have lasted to our day; the bridges of Augustus at Rimini ana of Alcantara in Spain may be taken as types of the design, in which we note that there are no architectural superfluities; the quality of the design depends on the graceful proportion of the arches and the fine masonry in which they arc built. Palatial Architecture. — By far the most magnificent group of palaces are those which were erected by the Caesars on the Palatine hill at Rome.

Commenced by Augustus and added to by his successors down to the reign of Severus, they cover an area considerably over 1,000,000 sq. ft., and comprise an immense series of great halls, throne room, banqueting hall, basilicas, peristylar courts, temple, libraries, schools, barracks, a stadium and separate suites for prince* and courtiers. The service of the palace would seem to have been carried on in vaulted corridors in several storeys, some of which on the north side, overlooking the Circus Maximus, must have been over 100 ft. in height. Except under the Villa Mills, the greater part of the plan has been traced ; and large remains of mosaic pavement* have been found in situ, and in the approaches, vaulted nails, some still retaining their stucco decoration. A similar variety of groups of every description of structure i* found at Tivoli, but spread over a very much larger area. The villa of Hadrian extended over 7 m. ; the works there were probably begun about A. p. 123, the first portion being his own residential palace.

In addition to the numerous halls, courts, libraries, &c., Hadrian attempted to reproduce some of the most remarkable monuments which he had seen during his long travels; the Stadium, Palaestra, Odeum, the two theatres, the artificial lake, Canopus and other features were, however, constructed in the Roman style. Built on a ridge between two valleys, the several buildings occupied various levels, so that immense terraces and flights of stairs existed throughout the site and, combined with the natural scenery, must have been of extraordinary beauty. The palace of Diocletian at Spalato, to which he retired after his abdication, constituted a fortress, three of its walls being protected by towers, the fourth on the south by the sea. For an account of its well-preserved remains see SPALATO. The emperor's own residence was on the south side, and had a gallery 520 ft. long overlooking the sea. The two main streets, with arcades on each side and crossing one another, divided the whole palace into four sections. One of these streets crossed from gate to gate, the other from the north gate led to the entrance into the palace of the emperor.

Private Houses. — The entire absence of the remains of the private houses of Rome, with the single exception of the house of Livia on the Palatine, would have left us with a very poor insight into their design were it not for the discovery of Pompeii (q.v.) and Herculaneum (q.v.). The descriptions given by Pliny of the lavish extravagance in the Roman nouses, and the employment of various Greek marbles in the shape of monolith columns and panelling of walls, are substantiated by those which are found in the Pantheon, in the palaces on the Palatine, and in Hadrian's villa at Tivoli; and these compared with what is found at Pompeii show that the latter was only a provincial town of second or third-rate importance, where painted imitations took the place of real marbles, and where the wall paintings were very inferior to those which have been discovered in Rome. (R. P. S.)