[Illustration: Fig. 290.—Geometric Mosaic, Church of Ara Cœli, Rome.] Gaddi followed the style and aims of Cimabue; his work was poetic in conception, and in his execution he leaned to the Byzantine methods, but in drawing and composition he was greatly excelled by the Roman mosaicist Toriti. The celebrated Roman family of the Cosmati were excellent mosaicists. Giovanni Cosmato, son of the elder artist of that name, executed some fine work on the tomb of Gonsalo Roderigo in the Church of S. Maria Maggiore, and on monuments in S. Maria sopra Minerva. A variety of mosaic was much used in Italy at different times, the earliest dating from the sixth century, which consisted in decorating pulpits, screens, and small altars with a geometric inlay of small squares and lozenges of gold and coloured tesseræ which were inserted into grooves of white marble (Fig. 290). About the year 1351, Pietro Cavallini, a native of Rome and a supposed pupil of the painter Giotto, was commissioned to execute some mosaics in the Church of S. Maria Transtevere at Rome. The design and style of these works were strongly influenced if not partly copied from the frescoes of Giotto in the Arena Chapel at Padua. Cavallini also executed in mosaic the celebrated Navicella, from the design by Giotto, which decorates the vestibule of the old basilica church of St. Peter’s at Rome. This work represents a ship in which the Apostles are seen, and Christ and Peter are figured walking on the sea. With the exception of a few notable works in St. Peter’s at Rome, in St. Mark’s at Venice, some unfinished work of Domenico Ghirlandaio (1449-95), and the work of Pesselli in the Church of Or-San-Michele at Florence (1416), the fifteenth century was not a prosperous period for mosaic. This is accounted for by the rapid development of the Italian schools of painting, which advanced during this century with incredible swiftness, and as painting advanced, mosaic decoration retreated before its more popular rival. The mosaicist had to make room for the fresco painter, who soon became the successful competitor of the former in the work of church decoration. Regarding the mosaics of St. Mark’s at Venice, it may be stated that they date from the eleventh century to the nineteenth.