112 COMPARATIVE ARCHITECTURE. be compared as follows : — (a.) The Romans never became a sea- faring people like the Greeks, nor did they send out colonists of the same description to all parts of the then known world. (b.) There were few rival cities in Italy at this period (a condition which was altered in after times, pages 230, 234, 405, 476), and the small towns, being less jealous of their separate independence, the Roman power could be built up by a gradual absorption of small states, a process that was never completed by Athens or Sparta. The position of Italy enabled her to act as the intermediary in spreading over the continent of Europe the arts of civilization. ii. Geological. — The geological formation of Italy differs from that of Greece, where the chief and almost the only building material is marble. In Italy marble, terra-cotta, stone, and brick were largely used even for the more important buildings. In Rome the following materials were at hand: — Travertine, a hard limestone from Tivoli ; Tufa, a volcanic substance of which the hills of Rome are mainly composed ; and Pepcrino, a stone of volcanic origin from Mount Albano. Besides these. Lava and Pozzolana, derived from volcanic eruptions, and excellent sand and gravel were plentiful. The existence of Pozzolana (a clean sandy earth) found in thick strata in the district, gave the Romans a material which contributed largely to the durability of their architecture, for it has extraordinary properties of hardness, strength and durability, when mixed into concrete with lime. The walls were generally formed of concrete and were faced in a decorative way with brick, stone, alabasters, porphyries, or marbles of all kinds, hewn from countless Oriental quarries by whole armies of workmen, Roman architecture, as it spread itself over the whole of the then known world, was influenced naturally by the materials found in the various parts where it planted itself, but concrete, in conjunction with brick and stone casing or banding, was the favourite material ; although in Syria, notably at Palmyra and Baal bee, and in Egypt the quarries supplied stones of enormous size, which were used locally. iii. Climate, — The north has the climate of the temperate region of continental Europe ; central Italy is more genial and sunny ; while the south is almost tropical. iv. Religion. — The heathen religion of ancient Rome being looked upon as part of the constitution of the state, the worship of the gods came eventually to be kept up only as a matter of state policy. The emperor then received divine honours, and may almost be described as the leader of the Pantheon of deities embraced by the tolerant and wide-spreading Roman rule. Officialism therefore naturally stamped its character on the temple architecture, A list of the chief Roman deities is gien on page 46, V, Social and Political. — ^In early times three chief nations dwelt in the peninsula. In the central portion (or Etruria) lived
