This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Origin of Roman Architecture. While the architecture of Egypt, as well as that of other early civilizations, probably contributed toward the style that was eventually produced and defined by the Greek artists, the Romans, by their conquest of Greece, at once acquired a unified and perfected architecture at almost the full height of its development. Not only were the buildings and architectural forms themselves perfected, but they were then being produced by the designers, architects, and artists who, as members of the subjugated nation, became the subjects of the more powerful race.
Thus the Romans became possessed of a perfected, if exotic, architecture; and we cannot therefore be surprised to find that the early Roman buildings were often Greek, in both their design and workmanship. This architectural style, although soon permanently affected in its development by Roman civilization, yet at first showed but slightly the influence of the arts of other foreign nations or races. The one notable exception was as regards the Roman adoption of the arch as the most important structural principle of their buildings.
The Arch and Vault. In taking up the progress of architecture at the period when the Greeks and other early nations yielded to the succeeding ruling race, the Romans; the difference in the vital principles underlying the structural elements of these two periods must be thoroughly understood. Throughout the Greek work we find that the lintel or supporting beam of wood or stone seems to be the only method of construction upon which they depended to any extent. The Romans, on the contrary, adopted the arch (see Fig. 96) to carry across all openings; and they further extended its use, in the form of a vault, to the covering of rooms or voids which they desired to roof in. The principle of this vaulted arch they had evidently borrowed directly from the Etruscans; a people of Asiatic origin living in northern Italy some ten or twelve centuries before Christ.
The arch itself dates back to a much earlier period. There are examples in Egypt of brick barrel vaults composed of three rings of voussoirs, built about 3500 B. C; but the Etruscans, by their use of cut stone instead of brick for this purpose, evidenced a much higher engineering skill, at least so far as an understanding of stereotomy was concerned. This same people continued to employ a form of construction consisting of overlapping layers of stonework, which may only indicate the transition from the lintel to the arch principle, or which may have been devised solely to imitate the interior appearance of a rock-cut tomb. This same scheme, we know, was used by the Egyptians, Assyrians, and Pelasgians, although it is best shown in the Etruscan tombs; and, because of the large size of the blocks of stone employed, it is frequently referred to as "Cyclopean" masonry. These tombs, round in plan, were constructed of layers of stonework, each layer projecting over the layer next below, until they met at the crown or apex of the resulting vault. This circular construction was then covered with earth or gravel, and the angles of the stone on the interior were dressed down to an even surface, suggesting by its outline the segment of an arch, as shown in Fig. 97. These tombs were built by the Pelasgic race in Italy probably between the years 1800 and 1500 B. C; but it remained for the Etruscans finally to define the principle of the voussoired arch of stonework. This principle the Romans borrowed and probably developed to a much higher degree than had ever been considered possible by its originators.
By adopting this principle, the Romans seldom required the column as a support for the lintel in the way that the Greeks had heretofore used it; and, as the arch required a heavier and stronger supporting member than the column in order to resist the thrust which it originated and transmitted, they were compelled to revert to the more solid pier of masonry for this pupose, which at once materially modified the appearance of their buildings. (See frontispiece).
Basilica of the Giants, Temple of Zeus, Agrigentum, Sicily. Showing Greek "engaged" columns.
Combination of Arch and Lintel Construction. The Romans, moreover, acquainted with the civilization and the architecture of the Greeks, demanded a more architectural effect than had satisfied the Etruscan builders; and therefore they adapted to their own purpose the architectural forms and Orders originated by the Greek artists, and even used them for ornamenting the otherwise plain wall surfaces of their various structures, in a way that the Greeks had never done. They employed a column, or partial column, placed against a plain wall surface-or engaged, as it is called, to the wall behind; as in the Tabularium, where an arcade on the side towards the Forum was decorated with engaged Doric columns, carrying an entablature. This is the earliest Roman instance of the use of the Orders in this fashion, and dates from about 78 B. C. The Temple of Fortuna Virilis (Fig. 123), in which the columns were engaged, with a plain wall surface between, after the fashion possibly suggested by one or two of the earlier Greek structures, is of a date earlier than the arcade of the Tabularium.
Fig. 97. Horizontal and Vertical Section of Pelasgic Arch Construction.
ROMAN -USE - OF - ARCH -AND -PIER.
A reference to Figs. 98 and 99 will show the radically different appearance given by thus applying an Order of architecture as an ornament upon the face of a method of construction complete in itself. In Fig. 98 is shown a simple arcade supported on plain piers (A, Fig. 100); and in Fig. 99 is drawn out a similar arcade ornamented by the application of the Doric Order to the face of these plain piers, after the fashion shown in plan at B, Fig. 100.