The building completed in this form we must remember was made up of vast masses of thin bricks, of which the mortar occupied probably a half of the aggregate; this had to thoroughly settle down and dry before the rest of the marble masonry was inserted, and the wall casings applied. The marble work, however, was all the while being prepared, and, the building once ready, the windows were inserted as screens in the openings previously left; marble jambs and lintels for the doors were placed in position also, with windows above them filling out to the brick arches. The walls were then sheeted with their marble covering, the vaults were overlaid with mosaic, and the pavement was laid down. In this way, as the bricklayers had not to wait for the masons, the carcase was completed in the shortest possible time; and by reserving the application of the marble until the structure was dry and solid, it was possible to bring together unyielding marble and brickwork that must have settled down very considerably. § 2. MARBLE QUARRIES. Much confusion exists as to the marbles of which the ancient writers speak; this has been occasioned necessarily by wrong identifications when but few ancient quarries had been recovered, and most unnecessarily by a persistence in using antique names for modern varieties, long after the true provenance has been discovered, when the ancient marbles are not “in the market.” It is the Italian names that have been corrupted in this way, and it would be a great advantage if they were discarded in England, or better still, used only in conjunction with the geographical names. In this case as the Italian names are descriptive, and, as many varieties of marble are found in the same or neighbouring quarries, we should get a safe nomenclature. Synnadan would thus be qualified as Pavonazzetto or Fior de Persico, and the banded varieties from Carystian, Proconnesian, or modern quarries might without confusion be called cipollino. In endeavouring to identify the marbles mentioned by the ancient writer on S. Sophia, we have made use of Salzenberg’s notes to the Poem of the Silentiary, and of the researches of Garofalo,[350] Corsi,[351] and C. O. Müller;[352] and we have also been helped by the practical knowledge of Mr. W. Brindley. The account of ancient marbles easily accessible in Professor Middleton’s _Ancient Rome_, 1892, is substantially an extract from Corsi.