CHAPTER XIX
TERRACOTTA IN ROMAN ARCHITECTURE AND SCULPTURE
Clay in Roman architecture—Use of bricks—Methods of construction—Tiles—Ornamental antefixae—Flue-tiles—Other uses—Inscriptions on bricks and tiles—Military tiles—Mural reliefs—List of subjects—Roman sculpture in terracotta—Statuettes—Uses at Rome—Types and subjects—Gaulish terracottas—Potters and centres of fabric—Subjects—Miscellaneous uses of terracotta—Money-boxes—Coin-moulds.
The uses of clay among the Romans were, as may be supposed, much the same as among the Greeks and Etruscans, in architecture, in sculpture, and for household implements. The main differences are that in some cases—as in architecture—its use was more extensive at Rome, in others less; and that generally the products of this material in Roman workshops are inferior to those of the Greeks. But the technical processes are in the main identical with those employed by the Greeks, and consequently much that has been said in Chap. III. of this work need not be here repeated.
I. Architecture
1. BRICKS AND TILES
The Romans divided the manufacture of objects in clay into two classes: opus figlinum or fine ware, made from argilla or creta figularis; and opus doliare, for tiles and common earthenware.[[2395]] We begin, then, as in the chapter on the Greek uses of clay, with the latter division, including the use of this material in Roman architecture, and primarily in the making of bricks and tiles. It must be borne in mind, however, that the structural use of bricks of clay, such as we employ at the present day, was unknown to the Romans; they only used what we should call tiles, and even these were only employed structurally, as a facing to walls and vaults of concrete; no walls were ever built of solid brick, and even in those of seven inches thickness the bricks are built on a core of concrete. Nor were the bricks allowed to appear on the outer face of the building, at least before the second century of the Empire; they were always faced with a coating of marble or stucco.
Nevertheless, the general use of bricks or tiles was most extensive, and they were employed as tiles for roofing houses, as bricks for walls and vaults, and even for columns, as slabs for pavements, for furnaces and for covering graves, and in tube form for conveying water or hot air; they are found in temples, theatres, and baths, and are used for cisterns and fountains, and in aqueducts and military fortifications. They were called lateres, because, says Isidorus, “they were broad, and made by placing round them four boards.”[[2396]] The kilns were called laterariae, and the makers laterarii; to make bricks was lateres ducere, fingere,[[2397]] or (with reference to the baking only) coquere. The word later seems to be employed indiscriminately for sun-dried (crudi) and baked bricks (coctiles),[[2398]] without the qualifying epithet, but testa is also used when burnt brick is intended.[[2399]] The sun-dried bricks were the earlier and simpler form, used for building walls and cemented together with clay or mud.[[2400]] Vitruvius in his account of brick-making (ii. 3) only refers to this kind, and apparently never mentions baked bricks except in passing allusions. He describes three kinds, to which he says the Greeks gave the respective names of genus Lydium, pentadoron, and tetradoron (see Vol. I. p. [95]). The two latter are exclusively Greek, but the first-named, 1½ by 1 foot in dimensions, answers to the Roman tegula sesquipedalis.[[2401]] A frequent arrangement, he says, was to employ half-bricks in alternate courses with the ordinary sizes, which served to bind the walls together and present an effective as well as a stable appearance. This information is repeated by Pliny, copying almost word for word.[[2402]]
Among the Romans two dimensions were in general use, as may be inferred from the frequent mention in inscriptions or elsewhere of the sesquipedales and of bipedales,[[2403]] or two-foot bricks, as we shall have occasion to show later. Being very flat and thin in proportion to their size, these bricks rather resemble tiles, as has been already noted; they are generally square, or at least rectangular. But there were also tegulae bessales or bricks measuring two-thirds of a foot square, i.e. about 8 inches, and triangular bricks, equilateral in form, with a length varying from 4 to 14 inches. The latter are the kind used in all existing Roman walls of concrete with brick facings. The thickness varies from 1¼ to 2 inches. They are not always made with mechanical accuracy, the edges being rounded and the sides not always parallel. In military works they were often used alternately with flint and stone (see below, p. [337]), as we see them in England, at Colchester, Dover, Verulam, and many other places.[[2404]] At Verulam the tiles are arranged in three horizontal layers at intervals of about 4 feet, with flint and mortar between. They were also used for turning the arches of doorways, and for this purpose tegulae bipedales were cut into pieces, so as only to tail a few inches into the concrete which they cover. Complete squares were introduced at intervals to improve the bonding.[[2405]]
The pillars of the floors of hypocausts were formed of tegulae bessales, and sometimes also of two semicircular bricks joined so as to form a circle, varying from 6 to 15 inches in diameter.[[2406]] Occasionally the upper bricks diminished in size, in order to give greater solidity to the structure. The bricks or tiles forming the upper floors were from 18 to 20 inches square; in some cases, as at Cirencester,[[2407]] these were flanged tiles (see below).
The general size of Roman bricks was, in the case of the sesquipedales, 1½ by 1 Roman foot; but variations are found, such as 15 by 14 inches. For the bipedales Palladius recommends 2 feet by 1 foot by 4 inches. The great building at Trier known as the Palace of Constantine is built of burnt bricks, 15 inches square by 1¼ inch thick.[[2408]] Prof. Middleton notes tiles in Rome of 12, 14, and 18 inches square,[[2409]] and Marquardt[[2410]] states that bricks found in France measure 15 by 8 to 10 inches; others (the bessales) 8 by 8 by 3 inches. A complete circular brick, measuring 7½ inches across by 3¼ inches thick, and impressed with the stamp of the eleventh legion, was found at Dolae near Gardun, and is now in the museum at Spalato.[[2411]]