Rome" instances this cupola as "a remarkable example of the extraordinarily skilful use of concrete by the Romans. It is cast in one solid mass, and is as free from lateral thrust as if it were cut out of one block of stone. Though having the arch form, it is in no way constructed on the principle of the arch. The walls of the great rotunda which supports the dome are nearly 20 feet thick, cast in concrete, with the thin facing of brick which afterwards became so common, although examples of the time of Augustus are very rare. The actual mass of concrete used is very much reduced by a series of recesses formed in the drum. Those in the interior form large niches for statues and altars, and were enriched with marble columns and other decorations. Other semicircular chambers set at intervals between the internal niches were probably formed to diminish the mass of concrete required, and also to admit the air into its interior so as to hasten its setting."

Internally the cupola is divided into deeply sunk square coffers; and although the outside of the dome is not an important feature in the external design of the building, in its original state it must have looked like a mound of shining gold, as it was then covered with tiles of gilt bronze. These plated tiles were stripped off in A.D. 663 by the Emperor Constans II. The present lead covering was put on in 1454. The internal effect of the dome, with its single central hypæthral opening. 25 feet in diameter, forming a frame to the blue sky, makes it unlike any other building in the world; and even now, although stripped of the greater part of its marble linings, it is still one of the most stately of edifices.

The beautiful works of art which remain to us of the time breathe the living spirit of Greek design-witness the Pompeian vase and fountain [page 231]. They are undated; but as Pompeii was destroyed in A.D. 79, they are clearly well within the first period of GræcoRoman art.

An arch in honour of Titus, of which nothing but its inscription now remains, had been erected in the Circus Maximus during his lifetime, in A.D. 80; but the arch in marble on the hill-top or Summa Sacra Via, and known as the Arch of Titus, was erected by Domitian in honour of Vespasian and Titus to commemorate the taking of Jerusalem. Of this arch the central portion only is original: the sides were restored in 1823.

In the twelfth century the tower of a fortress known as the Turris Cartalaria, or Record Tower, was partly built over the Arch of Titus, and the remains of this building can still be traced. The capitals of the engaged columns on each side of the arch are said to be the earliest existing examples of the composite order. The jambs of the archway are ornamented with reliefs representing the triumphal procession of Titus and his army after the fall of Jerusalem. In the spandrils of the arch are winged Victories bearing trophies, and the keystones have figures of Fortuna and Roma. The soffit of the arch is richly coffered, and has a relief of the apotheosis of Titus borne upwards by an eagle. There is a small sculptured external frieze.

Under my middle period I would include Trajan's Column (A.D. 114) [pp. 236-37]. The Emperor's ashes, deposited in a gold vase, were placed in the chamber formed in the interior of the pedestal of the Column, which, built of large blocks of Greek marble, is 97 feet in height. The diameter immediately above the base is about 12 feet. A colossal bronze statue of the Emperor formerly stood upon the top of the capital, which very closely resembles one of the Doric order. Bands of sculpture in low relief ranged in twenty-three tiers, and illustrative of Trajan's two campaigns against the Dacians, are coiled round the column, which has an internal staircase. The pedestal carrying the column is decorated with reliefs of arms and trophies, and on one of its sides is a tablet with a dedicatory inscription, and under it is the doorway to the spiral staircase. An eagle supporting a garland of flowers is placed at each angle above the cornice of the pedestal.

Among my illustrations is a conjectural restoration of the theatre at Ostia supposed to have been built by Trajan. Ostia, situated at the mouth of the Tiber, about fifteen miles from Rome, was one of the great commercial centres of the empire, and its famous harbours, constructed by Claudius and Trajan, received merchandise from all quarters of the world. It had vast granaries of corn, from which the imperial city received its constant supply.

The Arch of Severus, which, with the rest of the buildings I am about to mention, comes under the final period, was erected in A.D. 203 in honour of Severus and his sons Caracalla

and Geta and in commemoration of victories in Parthia and other Eastern countries. The base is of travertine lined with slabs of marble. Elsewhere the arch is constructed of massive blocks of white Pentelic marble. After the death of Severus and the murder of Geta, said to have been stabbed in his mother's arms by Caracalla, the latter in his foolish endeavours to extinguish the memory of his ill-fated brother ordered all statues and reliefs of Geta to be destroyed and his name to be erased from the inscriptions. Traces of the erasure are visible on this arch, as the holes are still existent by which the bronze letters of Geta's name and titles were fastened to the marble. The capitals of the order are designed in a debased composite

style. The sunk coffered soffits and enriched mouldings and centre flowers of the three arches. are rather coarsely executed.

The reliefs are poor works of art, but interesting for their representations of historical events, such as the siege of Carræ, the relief of Nisibis effected by Severus in A.D. 195, victories in Mesopotamia, the taking of Babylon, and the subsequent defeat of the Parthian king Artabanus. There are winged Victories bearing trophies, and figures representative of the four seasons in the spandrils of the central arch. The spandrils of the side arches contain reliefs of the river gods of the conquered countries-the Euphrates, the Tigris, and two tributaries. The pedestals of the columns have life-sized representations of captives driven by Roman soldiers. There is a long inscription of the titles and honours of Severus and Caracalla inserted in the large panel of the attic.