The Romans used both stone and brick with extraor- dinary skill in their buildings. These materials were employed with great ingenuity and varietj^ both with and without mortar. The Romans adopted from the Etruscans the round arch and its consequence, the round vault. Arching and vaulting are the chief character- istics of Roman architecture. By using these they were able to erect massive and lofty structures of pleasing lightness and with economy of material. Indeed, with- out the arch Roman architecture would not have had an existence. By the use of the arch and the vault Roman architecture has given rise to the Byzantine style, and, through this, has inspired all subsequent architecture. Through the arch Roman architecture forms the connecting-link and the transition medium from the art of antiquity to the art of mediaeval and modern times. The Romans used the vault as the tran- sition to the dome, and thus, through half-domes, to the light and airy architecture of the Byzantines. They also built circular temples, which, originally at least, were more usually consecrated to Vesta, with a simple circular cell, surmounted by a dome, as in the Pantheon. From the traditions of their early Etruscan neigh- bors they preferred the square cell to the Greek rec- tangidar oblong cell in their rectangular temples. Es- pecially was this the case in Rome itself. The temples they built in other parts of the empire, especialh' in (Jreece and the former Greek colonies, were built after the plan of Greek originals; but these were decorated after the modified Greek manner, which the Romans adopted at the metropolis.
The Romans greatly modified all the styles of Greek architecture. To the Doric they added the Tuscan base. This gave the order much wider adaptability to the uses for which the Romans wished to emjjloy the style; that is. in forming colonnades and pilasters to many kinds of buildings, whether circular, elliptical, or rectan- gular. They were less fortunate in the modification of the Ionic order, which they adopted from a single known (Jreek original, making volutes face all four sides of the capital. As half-columns or pilasters this modification was more fortunate. The Ionic order was only used by them as an intermediate style, in the second storv of buildings, never in temples or other buildings a single story in height. The Corinthian order, which had
hardly obtained its full capacity of development under the Greeks, was most happily used by the Romans. The Ionic volute, in a modified form, was introduced in the midst of the Acanthus. Thus was taken the first step to the complete union of the Ionic and Corinthian styles in the so-caUed composite order, which is the most characteristic and original decorative feature in Roman architecture, though it was doubtless elaborated by the hands of Greek workmen under the Roman'rule. The capitals of columns and the entablatures were ofren covered with an amount of elaborate decoration which finalh- became overpowering, and almost destructive of good architectural effect. See Order.
In considering the classes of buildings erected bj' the Romans, the student of Egyptian or Greek art is sur- prised at the small number of temples constructed by the Romans in comparison with other edifices. The no- blest monument of Roman architecture is the Pantheon, which is preserved almost in its entirety. Of other famous temples, as that of Jupiter Capitolinus, there are now no remains. The most magnificent temple built under the Roman dominion was that of Jupiter Olympus at Athens. The temples at Palmyra and Baalbee surprise by their size and the magnitude of the blocks of stone used in their erection, but in architect- ural elegance and purity they are very defective.
Of buildings of civil architecture the forum may first be considered. The forum was used, as by the Greeks, as a place for marketing, for assembling the people for the transaction of public business, for the election of officers, and for other purposes. The forum was sur- rounded by colonnades. These were fre(iuently richly decorated. Besides the original Roman forum, various emperors laid out others, which served similar purposes. In the further development of the public life, the trans- action of a portion of public affairs was transferred to special buildings, of which the basilicas are the most important. In the basilicas were held the courts of justice and the exchange for merchants: finally shops and libraries were added, and the basilicas al- most served the varied purposes of the forums. The basilicas were generalh' rectangular and oblong in shape, though some were nearly square and were vaulted. The oblong basilicas usually had a round apsis at one end. These two forms furnished the starting-points for the two great early styles of Christian architecture — the oblong, for the so-called basilican churches in Italy; and the vaulted ones, for the Byzantine style in Constantinople. Thus we find in the Roman basilica the most important specific connecting-link between classical and Christian architecture. See Basilica.
Triumphal arches form a most important feature of Roman architecture. They were very stately in form and costly in execution. This use of the arch they had doubtless derived from the Etruscans. The most important arches to signalize victories are those of Septimus Severus, Titus, and Constantine. The arch of Titus has peculiar interest to Christians, inasmuch as upon a bas-relief on the inside of the arch are cut models of the seven-branched candlestick and other ves- sels of the Temple service which Titus carried with him to Rome after his conquest of .Jerusalem. Arches were erected in many cities to commemorate also the erec- tion of public works of great extent by the emperors or other public officials. See Arch.