Revh•al of Roman ..architecture, and its present state The church of St Sophia, erected at Constantinople, under the emperor Justinian, about the year 637, by the Greek architects Anthemius and Isodorus, forms an in termediate link between the ancient Roman architecture, and that revived about the latter end of the 15th, and beginning of the 16th century. In Plate CLXXI II, we have given a plan and section, from which it will be seen that the outlines of this structure resemble those of the temple of peace at Rome. It has also, like it, the win dows and other openings covered by simicircular arches; but instead of having the central part covered by a ground vault, it is surmounted by a spherical dome, in the man ner of the Pantheon, but differing from that edifice in rising only about one-third of its chord-line, whereas that in the Pantheon rises one-half. Where columns are used in the recesses from the middle aisle, they have base mouldings, but no square plinths under them: the upper member of their capitals has sonic resemblance to the Ionic, the other part seems an awkward imitation of the vase of the Corinthian. The spaces between the columns are covered by arches springing immediately from the top of the caps, as in the temple of Faunus at Rome. The faces of the large square piers are covered with rectangular pannels. But the, whole details are misera bly inferior to either the Greek or ancient Roman archi tecture ; and the frequent failures which took place in attempting to construct the dome, though under the di rection of the best Greek architects of the age, are proofs of the degenerate state of the art at that period. The following short account of the manner in which the archi tects proceeded with this dome will, 1% c have no doubt, be satisfactory to the reader, and prove instructive to the young architect. On the angles of a square of about 115 feet, four piers were erected, and carried up to near ly the same height, where arches were turned between them. The angular spaces between the archivolts of those arches were worked up so as gradually to form a complete circle at the level of the top of the arches.
Upon this circle the dome was raised. The pressure of the eastern and western arches was resisted by walls, al most solid, running north and south, two in each direc tion, for about 90 feet. The small semi-dome which co vered the circular recesses, were intended to resist the north and south arches ; but they proved insufficient, for a few months only after the dome Was completed, it gave way towards the cast, fell down, and carried with it the semi-dome on that side. The architect then added to the eastern piers, by filling up some vacuities, and re constructed the dome. But the resistance at the cast end was still insufficient, for before it was completed it fell a second time. Ile then constructed strong buttresses against the wall of a square cloister, which surrounded the central building, and from thence carried arched but tresses over the interval to the main building, and a third time raised the dome, taking care to diminish the thick ness, and for lightness to make use of pumice-stone. But after all, lie found it necessary to fill up the arches on the north and south sides with others of smaller dimensions.
The early Christian churches were built with a great number of columns, because those were found ready worked among the ruins of ancient edifices. When this mode of supply failed, towards the end of the 10th cen tury, the clumsy workmen were obliged to substitute massy piers and arcades.
If we were to follow the practice of architecture as it succeeded in point of time, we ought here to introduce and describe specimens of the Gothic school ; but for simplicity and distinctness, we prefer following the Ro man to its revival and present state, reserving the Gothic to the latter end of this article.
Previous to producing specimens of the different vari ations of style which have taken place in the course of the last 400 years, we shall endeavour to discuss the com ponent parts of a building ; which being generally appli cable, we are unavoidably led to consider frequently as connected both with ancient and modern practice.