To the Romans, therefore, is due the introduction of an arcuated construction with a well developed internal, and a partially developed external decoration. The early Christians adopted their forms of construction and decoration from the Romans. They were also indebted to them for the plans of the buildings, which became the types of the Christian sacred edifices during the middle ages. The Basilica (q. v.), or Roman court house and market-place, was found to be admirably adapted for early Christian worship, and the circular temples were the prototypes of the Christian baptisteries (q. v.) which usually accompanied the basilicas. In erecting their buildings, the Christians not only adopted the plans and mode of construction, but used the actual materials of the build ings of the Romans, many of which had been destroyed by the barbarians. Where such materials were abundant—as in t ome and central ltaly—the early Christian architecture very closely resembled that of the Roman buildings which had preceded it. But in more remote districts the builders, finding no ready-made materials at hand, had to design and prepare new ones. In doing so they followed as closely as they could the Roman originals, but their buildings partook more of the constructional than the decora tive elements of Roman architecture. The Roman ornament thus dropped out of use; and when, in process of time decoration was desired, each new people followed its own ideas. The traditional Roman decoration .thus became to a great extent lost, and new styles introduced. These new styles each retained some of the original Roman forms and modes of construction; and each style depended for its peculiar character on the particular Roman forms it retained and developed. Thus Constantine, and the archi tects of the Eact, seized upon time dome as the distinguishing feature of their style, and the architeCts of Lombardy adopted the plain tunnel-vault. The former style is called Byzantine (q. v.), and has been the type of all eastern mediaeval architecture; and the latter Romanesque (q. v.), and has been the origin of all the western architecture of mediceval Europe.
History.—From Lombardy—in those ages part of the German empire—the Roman esque style readily passed into Germany and Switzerland, and was also most naturally adopted in the s. of France, where examples of Roman architecture abounded. This architecture was carried out with various modifications in these different countries, all of which may have contributed to the general progress of the art; but, as might be expected, it is to the banks of the Rhine where the successors of Charlemagne chiefly dwelt, that we must look for the first step in the development of Gothic architecture, The following short sketch of the development of vaulting will show how this occurred.
The Roman basilicas, and, like them, the early Christian'churehes, were divided into a central nave with two side-aisles, the former separated from the latter by a row of columns on each side. These columns carried arches on which rested the side walls of the nave, which were carried sufficiently high to clear the roofs of the side-aisles, and admit windows to light the central nave. This row of windows afterwards became the Gothic clerestory (q.v.). The apse at the end of the nave was semicircular on plan, and was usually roofed with a vault in the form of a semi-dome. This feature was also
afterwards more fully developed in the chapels of Gothic churches. The nave aisles were originally roofed with wood, but, owing to: their frequent destruction by fire, it became necessary to cover the churches with a more kind of construc tion. Vaulting was then introduced, the Roman forms, of which many examples existed, being at first closely followed. To trace the progress of vaulting from the simple tunnel-vault of the Romans to the fully developed and magnificent groins of Gothic cathedrals, is a most interesting inquiry; and, indeed, includes the history of the development of Gothic architecture. There is one consideration which will to explain how the Roman arches were abandoned and new forms sought out. To the Roman emperors who built time splendid vaults of the baths, and who had a subdued world at command, materials and labor were a small consideration. They could, there fore, afford to build in a style which required perfect materials and workmanship. But mediaeval princes and bishops could obtain neither, except with great cost and trouble; to economize these, therefore, great skill and attention were required. It was necessary to study to avoid those large and expensive materials of which the Romans were so lavish, and to adopt the simplest and easiest forms of construction.
The first vaults tried were simple semi-circular tunnel-vaults. It was found that these, besides being very gloomy, required very massive walls to resist their thrust. An attempt was then made to relieve this thrust by tranverse arches across—at inter vals—under time tunnel-vault, to act as strengthening arches. Buttresses with a slight projection were applied outside to support these, and a beam of wood was somelimes introduced at the wall-head from buttress to buttress to assist in opposing the thrust of the vault. • This was time first attempt to throW the weight of the vault on single points. In the side-aisles, where the span was small, time Roman intersecting vaults were used; and as the roofs with tunnel-vaulting were found very gloomy and 'ill-lighted, it was desirable that similar intersecting vaults should be used to cover the main roof, in order to admit windows raised to light the vaulting. But how was this to be managed with the small materials at command? If the transverse arches AB, CD (fig I) are semi-circular, and the side-arches AC, BD the same—the vault being formed by two intersecting cylinders—then the intersecting groins AD and CB must be elliptical, This was a difficult form of construction: the mediaeval builders found it easier to construct semi circular groin arches with radius of one-half AD, and to fill in the triangular spaces ABE, etc., With slightly domed vaults. Here, then, we have the origin of the groin-rib, the development of which played so important a part Gothic vaulting. When the space to be covered was square, this form of vault was found to answer, and usually included two bays of the But this arrangement looked awkward externally, the win dows of the clerestOry not grouping well l'ith those of the side-aisles. A transverse arch was then introduced, carrying up the design from the nave piers to the vaulting. This form of vault is called hexapartite. All the above forms of vaulting were fully devel oped in the round arched styles of the Rhine.