BYZANTINE ARCHITECTURE. 197 support the arcli." This was done by shaping the block of marble which formed the capital so that a simple transition from the square block to the circular shaft of the column was formed. Further, as Messrs. Swainson and Lethaby say, the numerous round shafts of S. Sophia exhibit a remarkable and beautiful structural expedient, by which the neckins^^ is entirely suppressed, and bronze annulets surround the shafts under the capital and above the base. These prevent the shafts from splitting— a likely result, since the monolithic shafts had to be set up contrary to the direction of the quarry bed — and also the lead seating from being forced out by the superincumbent weight. The science of construction acquired by the Romans descended to the Byzantines, for the walls were formed with a brick facing and concrete core — a method also employed for vaults, bridges, and aqueducts. The building procedure was developed some- what as follows : — the general form of the building being more or less decided, the first thing necessary was to collect monolithic marble shafts, and it " was necessary to have a certain knowledge where such might be quarried or otherwise obtained, before even the foundations were prepared, for the columns decided the height and points of support of the building. These shafts once assured, the body of the structure was proceeded with as a brickwork shell without further dependence on the masons, who were only required to prepare the bases, capitals, and cornices, everything else being completed as a brick ' carcass.' " The building was thus made of vast masses of thin bricks, with mortar joints of equal thickness ; and when this had settled down and dried, the walls were sheeted with their marble covering, the vaults overlaid with mosaic, and the pave- ment laid down. In this way the carcass was completed at once, the bricklayers not having to wait for the masons ; and, further, by reserving the application of the marble until the structure was dry and solid, it was possible to bring together unyielding marble and brickwork with large mortar joints that must have settled down very considerably This independence of the different parts of the structure was a leading idea in Byzantine construction, and is obviously necessary when the quantity of mortar is so great that the bricks become secondary in height to the joints. Brick, moreover, was the material preferred in the construction of walls, and lent itself to all the caprices of the architect ; for as interiors were always lined with marble and mosaics, or decorated ^yith frescoes, such walls were the most suitable for the recep- tion of these kinds of ornamentation. Bricks being so much used, it is not surprising that the Byzantines took great pains in their manufacture when it is remembered that they employed them in their military as well as in their ecclesiastical and domestic architecture. The form of these varied a great deal, but the
