of marble in low relief was frequently used for wall-decoration. The most notable example is the beautiful series of reliefs on the west front of Orvieto Cathedral, the work of Giovanni Pisano and his pupils in the early part of the 14th century. These are small reliefs, illustrative of the Old and New Testaments, of graceful design and skilful execution. A growth of branching foliage serves to unite and frame the tiers of subjects.
Of a widely different class, but of considerable importance in the history of mural decoration, are the beautiful reliefs, sculptured in stone and marble, with which Moslem buildings in many parts of the world are ornamented. These are mostly geometrical patterns of great intricacy, which cover large surfaces. frequently broken up into panels by bands of more flowing ornament or Arabic inscriptions. The mosques of Cairo, India and Persia, and the domestic Moslem buildings of Spain are extremely rich in this method of decoration. In western Europe, especially during the 15th century, stone panelled-work with rich tracery formed a large part of the scheme of decoration in all the more splendid buildings. Akin to this, though without actual relief, is the stone tracery—inlaid flush into rough flint walls—which was a mode of ornament largely used for enriching the exteriors of churches in the counties of Norfolk and Suffolk. It is almost peculiar to that district, and is an example of the skill and taste with which the medieval builders adapted their method of ornamentation to the materials in hand.
2. Marble Veneer.—Another widely used method of mural decoration has been the application of thin marble linings to wall-surfaces, the decorative effect being produced by the natural beauty of the marble itself and not by sculptured reliefs. One of the oldest buildings in the world, the so-called "Temple of the Sphinx" among the Giza pyramids, is built of great blocks of granite, the inside of the rooms being lined with slabs of semi-transparent African alabaster about 3 in. thick. In the 1st century thin veneers of richly coloured marbles were largely used by the Romans to decorate brick and stone walls. Pliny (H.N. xxxvi. 6) speaks of this practice as being a new and degenerate invention in his time. Many examples exist at Pompeii and in other Roman buildings. Numerous Byzantine churches, such as St Saviour’s at Constantinople, and St George’s, Thessalonica, have the lower part of the internal walls richly ornamented in this way. It was commonly used to form a dado, the upper part of the building being covered with mosaic. The cathedral of Monreale and other Siculo-Norman buildings owe a great deal of their splendour to these linings of richly variegated marbles. In most cases the main surface is of light-coloured marble or alabaster, inlaid bands of darker tint or coloured mosaic being used to divide the surface into panels. The peculiar Italian-Gothic of northern and central Italy during the 14th and 15th centuries, and at Venice some centuries earlier, relied greatly for its effects on this treatment of marble. St Mark’s at Venice and the cathedral of Florence are magnificent examples of this work used externally. Both inside and out most of the richest examples of Moslem architecture owe much to this method of decoration; the mosques and palaces of India and Persia are in many cases completely lined with the most brilliant sorts of marble of contrasting tints.
3. Wall-Linings of Glazed Bricks or Tiles.—This is a very important class of decoration, and from its almost imperishable nature, its richness of colour, and its brilliance of surface is capable of producing a splendour of effect only rivalled by glass mosaics. In the less important form—that of bricks modelled or stamped in relief with figures and inscriptions, and then coated with a brilliant colour in siliceous enamel—it was largely used by the ancient Egyptians and Assyrians as well as by the later Sasanians of Persia. In the 11th and 12th centuries the Moslems of Persia brought this art to great perfection, and used it on a large scale, chiefly, though not invariably, for internal walls. The main surfaces were covered by thick earthenware tiles, overlaid with a white enamel. These were not rectangular, but of various shapes, mostly some form of a star, arranged so as to fit closely together. Delicate and minute patterns were then painted on the tiles, after the first firing, in a copper-like colour with strong metallic lustre, produced by the deoxidization of a metallic salt in the process of the second firing. Bands and friezes with Arabic inscriptions, modelled boldly in high relief, were used to break up the monotony of the surface. In these, as a rule, the projecting letters were painted blue, and the flat ground enriched with very minute patterns in the lustre-colour. This combination of bold relief and delicate painting produces great vigour and richness of effect, equally telling whether viewed in the mass or closely examined tile by tile. In the 15th century lustre-colours, though still largely employed for plates, vases and other vessels, especially in Spain, were little used for tiles; and another class of ware, rich in the variety and brilliance of its colours, was extensively used by Moslem builders all over the Mahommedan world. The most sumptuous sorts of tiles used for wall-coverings are those of the so-called “Rhodian” and Damascene wares, the work of Persian potters at many places. Those made at Rhodes are coarsely executed in comparison with the produce of the older potteries at Isfahān and Damascus (see Ceramics). These are rectangular tiles of earthenware, covered with a white “slip,” and painted in brilliant colours with slight conventionalized representations of various flowers, especially the rose, the hyacinth and the carnation. The red used is applied in considerable body, so as to stand out in slight relief. Another class of design is more geometrical, forming regular repeats; but the most beautiful compositions are those in which the natural growth of trees and flowers is imitated, the branches and blossoms spreading over a large surface covered by hundreds of tiles without any repetition. One of the finest examples is the “Mecca wall” in the mosque of Ibrahim Agha, Cairo; and other Egyptian mosques are adorned in the same way (fig. 2).
Fig. 2.—One of the Wall-tiles from the Mosque of Ibrahim
Agha, Cairo. (10 in. square)
Another variety, the special production of Damascus, has the design almost entirely executed in blue. It was about A.D. 1600, in the reign of Shah Abbas I., that this class of pottery was brought to greatest perfection, and it is in Persia that the most magnificent examples are found, dating from the 12th to the 17th centuries. The most remarkable examples for beauty and extent are the mosque at Tabrīz, built by Ali Khoja in the 12th century, the ruined tomb of Sultan Khodabend (A.D. 1303–1316) at Sultaniyas, the palace of Shah Abbas I. and the tomb of Abbas II. (d. A.D. 1666) at Isfahān, all of which buildings are covered almost entirely inside and out.
Another important class of wall-tiles are those manufactured by the Spanish Moors, called “azulejos,” especially during the 14th century. These are in a very different style, being designed
