EARLY CHRISTIAN ARCHITECTURE.
Basilicas in Rome and Italy.
DURING the first three centuries the Christian religion was discredited and persecuted; and though many interesting memorials of this time (some of them having an indirect bearing upon architectural questions) remain in the Catacombs, it is chiefly for their paintings that the touching records of the past which have been preserved to us in these secluded excavations should be studied. Early in the fourth century Constantine the Great became Emperor, and in the course of his reign (from A.D. 312 to 337) he recognised Christianity,  and made it the religion of the State. It then, of course, became requisite to provide places of public worship. Probably the Christians would have been, in many cases, reluctant to make use of heathen temples, and few temples, if any, were adapted to the assembling of a large congregation. But the large halls of the baths and the basilicas were free from associations of an objectionable character, and well fitted for large assemblages of worshippers. These and other such places were accordingly, in the first instance, employed as Christian churches. The basilica, however, became the model which, at least in Italy, was followed, to the exclusion of all others, when new buildings were erected for the purpose of Christian worship; and during the fourth century, and several succeeding ones, the churches of the West were all of the basilica type. What occurred at Constantinople, the seat of the Eastern Empire and the centre of the Eastern Church, will be considered presently.
There is probably no basilica actually standing which was built during the reign of Constantine, or near his time; but there are several basilica churches in Rome, such as that of San Clemente, which were founded near his time, and which, though they have been partially or wholly rebuilt, exhibit what is believed to be the ancient disposition without modification.
Access is obtained to San Clemente through a forecourt to which the name of the atrium is given. This is very much like the atrium of a Roman house, being covered with a shed roof round all four sides and open in the centre, and so resembling a cloister. The side next the church was called the narthex or porch; and when an atrium did not exist, a narthex at least was usually  provided. The basilica has always a central avenue, or nave, and sides or aisles, and was generally entered from the narthex by three doors, one to each division. The nave of San Clemente is lofty, and covered by a simple wooden roof; it is separated from the side aisles by arcades, the arches of which spring from the capitals of columns; and high up in its side walls we find windows. The side aisles, like the nave, have wooden roofs. The nave terminates in a semicircular recess called “the apse,” the floor of which is higher than that of the general structure, and is approached by steps. A large arch divides this apse from the nave. A portion of the nave floor is occupied by an enclosed space for the choir, surrounded by marble screens, and having a pulpit on either side of it. These pulpits are termed “ambos.” Below the Church of San Clemente is a vaulted structure or crypt extending under the greater part, but not the whole, of the floor of the main building.
The description given above would apply, with very slight variations, to any one of the many ancient basilica churches in Rome, Milan, Ravenna, and the other older cities of Italy; the principal variations being that in many instances, including the very ancient basilica of St. Peter, now destroyed, the avenues all stopped short of the end wall of the basilica, and a wide and clear transverse space or transept ran athwart them in front of the apse. San Clemente indeed shows some faint traces of such a feature. In one or two very large churches five avenues occur,—that is to say, a nave and double aisles; and in Santa Agnese (Fig. 156a) and at least one other, we find a gallery over the side aisles opening into the nave, or, as Mr. Fergusson puts it, “the side aisles in two stories.” In many instances we should find no atrium,  but in all cases we meet with the nave and aisles, and the apse at the end of the nave, with its arch and its elevated floor; and the entrances are always at the end of the building farthest from the apse, with some sort of porch or portal.
The interest of these buildings lies not so much in their venerable antiquity as in the fact that the arrangements of all Christian churches in Western Europe down to the Reformation, and of very many since, are directly derived from these originals. If the reader will refer to the description of a Gothic cathedral in the companion volume of this series, it will not be difficult for him to trace the correspondence between its plan and its general structure and those of the primitive basilica. The atrium no longer forms the access to a cathedral, but it still survives in the cloister, though in a changed position. The narthex or porch is still more or less traceable in the great western portals, and in a kind of separation which often, but not always, exists between the westernmost bay of a cathedral and the rest of the structure. The division into nave and aisles remains, and in very large churches and cathedrals there are double aisles, as there were in the largest basilicas. The nave roof is still higher than the aisles—the arcade, in two stories, survives in the usual arcade and triforium; the windows placed high in the nave are the present clerestory. The apsidal termination of the central avenue is still retained in almost all Continental architecture, though in Great Britain, from an early date, it was abandoned for a square east end; but square-ended or apsidal, a recess with a raised floor and a conspicuous arch, marking it off from the nave, always occupies this  end of the church; and the under church, or crypt, is commonly, though not always, met with. The enclosure for the choir has, generally speaking, been moved farther east than it was in the basilica churches; though in Westminster Abbey, and in most Spanish cathedrals, we have examples of its occupying a position closely analogous to that of the corresponding enclosure at the basilica of San Clemente. The cross passage to which we have referred as having existed in the old basilica of St. Peter, and many others, is the original of the transept which in later churches has been made more conspicuous than it was in the basilica by being lengthened so as to project beyond the side walls of the church, and by being moved more westward. Lastly, the two ambos, or pulpits, survive in two senses. They are represented by the reading desk and the pulpit, and their situation and purpose are continued in the epistle and gospel sides of the choir.
The one point in which an essential difference occurs is the position of the altar, or communion table, and that of the Bishop’s chair, or throne. In the classic basilica the apse was the tribunal, and a raised seat with a tesselated pavement occupied the central position in it, and was the justice-seat of the presiding judge; and in the sweep of the apse, seats right and left, at a lower elevation, were provided for assessors or assistant-judges. In front of the president was placed a small altar. The whole of these arrangements were copied in the basilica churches. The seat of the president became the bishop’s throne, the seats for assessors were appropriated to the clergy, and the altar retained substantially its old position in front of the apse, generally with a canopy erected over it. This disposition continues in basilica churches to the present day.  At St. Peter’s in Rome, for example, the Pope occupies a throne in the middle of the apse, and says mass with his face turned towards the congregation at the high altar, which stands in front of his throne under a vast baldacchino or canopy; but in Western Christendom generally a change has been made,—the altar has been placed in the  apse where the bishop’s throne formerly stood, and the throne of the bishop and stalls of his clergy have been displaced, and are to be found at the sides of the choir or presbytery.
Many basilica churches were erected out of fragments taken from older buildings, and present a curious mixture of columns, capitals, &c.; others, especially those at Ravenna, exhibit more care, and are noble specimens of ancient and severe architectural work. The illustration which we give of part of the nave, arcade, and apse of one of these, Sant’ Apollinare in Classe, shows the dignified yet ornate aspect of one of the most carefully executed of these buildings (Fig. 157).
In some of these churches the decorations are chiefly in mosaic, and are extremely striking. Our illustration of the apse of the great basilica of St. Paul without the walls (Fig. 158) may be taken as a fair specimen of the general arrangement and treatment of the crowd of sacred figures and subjects which it is customary to represent in these situations; but it can of course convey no idea of the brilliant effect produced by powerful colouring executed in mosaic, the most luminous of all methods of enrichment. The floor of most of them was formed in the style of mosaic known as “opus Alexandrinum,” and the large sweeping, curved bands of coloured material with which the main outlines of the patterns are defined, and the general harmony of colour among the porphyries and other hard stones with which these pavements were executed, combine to satisfy the eye. A splendid specimen of opus Alexandrinum, the finest north of the Alps, exists in the presbytery of Westminster Abbey.
Another description of building is customarily met with in connection with early Christian churches,—the  baptistery. This is commonly a detached building, and almost always circular or polygonal. In some instances the baptistery adjoins the atrium or forecourt; but it soon became customary to erect detached baptisteries of considerable size. These generally have a high central portion carried by a ring of columns, and a low aisle running round, the receptacle for water being in the centre. The origin of these buildings is not so clear as that of the basilica churches; they bear some resemblance to the Roman circular temples; but it is more probable that the form was suggested by buildings similar in general arrangement, and forming part of a Roman bath. The octagonal building known as the baptistery of Constantine, and the circular building now used as a church and dedicated to Santa Costanza in Rome, and the celebrated baptistery of Ravenna, are early examples of this class of structure. Somewhat more recent, and very well known, are the great baptisteries of Florence and Pisa.
A few ancient circular or polygonal churches remain which do not appear to have been built as baptisteries. One of these is at Rome, the church of San Stefano Rotondo; but another, more remarkable in every way, is at Ravenna, the church of San Vitale. This is an octagonal building, with a large vestibule and a small apsidal choir. The central portion, carried by eight arches springing from as many lofty and solid piers, and surmounted by a hemispherical dome, rises high above the aisle which surrounds it. Much elegance is produced by the arrangement of smaller columns so as to form a kind of apsidal recess in each of the interspaces between the eight main piers.
Another feature which has become thoroughly identified with church architecture is the bell-tower, or campanile.  This appendage, there can be no doubt, originated with the basilicas of Italy. The use of bells as a call to prayer is said to have been introduced not later, at any rate, than the sixth century, and to this era is attributed a circular campanile belonging to Sant’ Apollinare in Classe at Ravenna, a basilica already alluded to. The circular plan was, however, exceptional; the ancient campaniles remaining in Rome are all square; they are usually built of brick, many stories in height, and with a group of arched openings in each story, and are generally surmounted by a low conical roof.
The type of church which we have described influenced church architecture in Italy down to the eleventh century, and such buildings as the beautiful church (Fig. 155) of San Miniato, near Florence (A.D. 1013), and the renowned group of Cathedral, Baptistery, Campanile, and Campo Santo (a kind of cloistered cemetery) at Pisa, bear a very strong resemblance in many respects to these originals; though they belong rather to the Romanesque than to the Basilican division of early Christian architecture.
 ‘Gothic and Renaissance Architecture,’ chap. ii. p. 6.