At lona flourished abbot Adamnan, so distinguished by his participation in the great paschal controversy, A. D. 705 ; and he supplies the architectural antiquary with the know ' ledge so much desired. We owe. the information to a sin gular contingency. After a long pilgrimage and continued residence in the Holy Laud, a Gaulish bishop, named Areulphus, driven to the Ilehrides, became the guest of the Culdee monastery. Here he related his perils, describing the holy places he had visited ; and the " Selellus de Locis Saudis" coutains his narrative.
Rarely has any work been transmitted with more pecu liarity and authenticity. Adamnan wrote upon his tablets, from the actual dictation of the stranger ; the notes so taken became the hook we now possess. The Holy Sepulchre, as might be anticipated, was the main object of Adanman's curiosity ; and in addition to the verbal description, Arcul phus drew a plan of the buildings. upon the tables with his own hand. This plan Adamnan copied in his manuscript ; he speaks of his drawing with extreme humility, calling it a vile figuration ; but, as will be seen by comparing it with the plan of San Stefimo Rotondo, it affords valuable information. The church was wholly of stone, of wonderful rotundity," supported by twelve columns ; having, as it would seem, three aisles ; it was entered by four doors; and the sepulchre itself was illuminated by twelve lamps, burning day and night in honour of the twelve apostles. Since Adainnan speaks of three walls, we must suppose that the interior circle marks the columns, and the lines were probably staircases, leading to an upper church or gallery. When Aculphus saw the Holy Sepulchre, it had been somewhat damaged by the Persians, and it was subsequently ruined by the Arabs; y et, as the existing church still retains the original shape, we do not doubt but that it was rebuilt upon the original tbundations.
Other churches were built by Constantine, at Jerusalem, Antioch, Nicomedia, Mambre, Heliopolis, Rome, and Con stantinople, but new remain to the present day, few, at least, that have not been materially altered. Perhaps the most perfect specimen remaining is the church of S. Constantia ; the burial-place of the daughter of Constantine ; it is circular in plan, and divided by concentric rows of pillars, front which spring arches to support the roof. The model from which it m as constructed w as es idently identical with that of the Holy Sepulchre, even were it not that structure itself. It is the
opinion of some, that the form of circular churches was derived from that of heathen temples of the kind, such as those of Vesta, or Minerva Medica; this, however, does not seem to be the case, for although they are both circular in plan, they are of entirely different construction and arrangement. The temple has its columns on the exte rior, supporting an entablature, while the clinch has its detached columns arranged in concentric circles within, con nected by arches springing from the capitals, forming one or more aisles; the arrangement, it will be acknowledged, is totally dissimilar, and the mere outline cannot have much weight in the consideration.
But some have gone still further, and claimed the very- struc tures themselves for heathen temples: the building mentioned above is supposed by such to be an ancient temple of Bac chus; but as Mr. Knight, in his beautiful work on this sub ject, says, '• Fins opinion is principally founded on the mosaics with which the ceiling of the aisles is adorned, and which represents vine-leaves and grapes. But the vine is a Christian emblem, and is so frequently- introduced in the decoration of Christian places of worship, that little weight can be attached to this circumstance. The architecture of this building is in contbrmity with the sty le of the time of Constantine, and not in conformity with that of a much earlier date." The filet is, the circular is the most natural form for sepulchral chapels, where the chief object is a tomb, placed in the centre. Other similar chapels are still in existence, of which, probably, the most remarkable, is that of S. Stephen. Baptisteries were likewise frequently of the same form, as is that of S. John Lateran, hut more fre quently octagonal, and sometimes octagonal within and circular without. All such buildings seem to have been simply baptisteries or sepulchral chapels; the form is totally unfitted for the requirements of the Christian liturgy, nor do they seem to have been employed for such pur pose, with the exception, perhaps, of the church of the Holy Sepulchre, and this was not purely circular, but had parts of different plan attached to it, something like to the Temple Church, London. The form is very suitable fin• a baptistery. See Pours CHURCHES.