This chair is composed entirely of carved plates of ivory; scenes from the life of Joseph and other similar designs are represented, and these are surrounded by a great variety of small figures, which form a sort of framework around the principal parts; for example, animals and birds among vine-branches, and all arranged in a life-like and artistic manner. So large a work as this chair in ivory is unusual. The greater number of ivory carvings are upon small objects, such as drinking-cups and other vessels, book-covers and diptychs, or tablets for writing, of which fine specimens remain and are seen in art collections. Diptychs were carved ivory tablets, with the inner surface waxed for writing, and were used by the early Christians, as they had been by the ancients. The illustration given here is from the diptych of the Consul Areobrudus, and belongs to the year 506 (Fig. 73). The whole design upon it represents a contest with lions and bears; the scene is where--the circus gates being thrown open--the animals rush into the arena to be slain by the gladiators. Some diptychs are ornamented with subjects from the life of Christ and other religious themes. [Illustration: FIG. 72.--FROM THE CATHEDRA OF MAXIMIANUS.] About the beginning of the tenth century ivory-carving was much used for church purposes. The smaller altars were covered with it, the vessels used for the Holy Sacrament were made of it, magnificent covers for church books, were carved, and as much thought seems to have been given to the designs upon these small objects as had formerly been devoted to the splendid temples of the ancients. Ivory-carving extended from Byzantium into Germany and other Western countries, and along with it went the working in rich and precious metals, which had also been practised somewhat by the earlier Christians. [Illustration: FIG. 73.--DIPTYCH. _Zurich._] During the tenth century the metal works were very costly, and the different cathedrals and churches rivalled each other in possessions of this sort. Altar tables were covered with embossed metal plates, which were extended down from the top of the table to the floor, forming antependiums, as they are called, in the same way that those of cloth are now used. These plates of metal were worked into designs in relief, ornamented with delicate filigree work, with paintings in enamel, and even with rare antique cameos and exquisite gems. Crucifixes were also made of metals and richly adorned, as well as all the vessels and smaller articles used in the service and ceremonials of the church--incense-burners, candlesticks, tabernacles and reliquaries, or caskets for preserving relics. In the sacristies of many old churches and in art collections these rare, costly articles are still preserved, and are of great interest in the study of art.