初期キリスト教ローマ帝国の集中形式洗礼堂における洗礼室の建築構成

抄録

In the early Christian period, two types of structural system, the basilican and the centralized types, were employed in ecclesiastical architecture. These, it is said, eventually produced the domed basilica. With regard to the history of Western architecture, centralized ecclesiastical architecture plays an important role in the development of style. However, this building type has not been thoroughly elucidated except for the symbolic meaning of the dome. Therefore, the purpose of this paper is to clarify the present state of research by examining existing remains in terms of hypothetically possible reconstructions. The author's point of view is expressed in accordance with the notion in the existence of various enonces deducible from the remains as an archive. The idea of the architecture as originally set forth would thus be thought of as hidden, or covered, by the remains themselves. First of all, the literal concept of the "centralized" type of structure must be defined in clear terms. The author, first of all, defined constituent elements after examining various texts (Table 1) on the history of the architecture of this period. The nave forms considered are either polygons or circles excluding aside the case of the square which is difficult to distinguish from the longitudinal form. The distribution of remains is shown for the entire territory of the Empire in the Early Christian Period (Table 2). Significantly, neither type is restricted to a particular district. Instead, each must have been employed as an universal form of architecture in the Empire. Through further typological examination (Table 2), the architectural composition may be distinguished in several ways. From the previous distinction, we may isolate a binary contrast between octagonal and circular nave plans. Other such contrastive pairs include employment or absence of the nave columns, pillars, pilasters as well as the presence or absence of an apse toward the east. These typical configuration suggests an architectural principle inclined to reduce the difference between the remains in unity and simplicity of composition. The binary categories referred to above regard the interior nave elevation. In term of composition (Table 3) hypothetical reconstructions yield the following generalizations about architectural compositions. The interior elevation is divided into three tiers, one third of which corresponds to the dome; the interior is lighted mainly from the upper part of the exterior wall; finishing materials are differentiated in each tier. The elevation is synthesized, so to speak, from the system of linear composition, which corresponds to the system of column arrangement, and the planar composition, which corresponds to the walling system. As regards linear composition, a structural-type composition is replaced by a decorative-type composition. That is, the structural system is disguised as a decorative composition and might not function as the load-bearing system. Therefore, the linear composition indicates an ambivalent system in baptisteries. This visual system which controls the total composition functions as the chief architectural principle in the centralized baptisteries of the Early Christian Period.