In 1316 Andrea of Ognibene executed, for the Cathedral of Pistoia, an altar-front, which has come down to us, and must have been followed by more important works. Then come Pietro and Paulo of Arezzo, Ugolino of Siena, and finally Master Cione,[18] the author of the two silver bas-reliefs still to be seen on the altar of the Baptistery of Florence. Master Cione, whose school was numerous, had for his principal pupils Forzane of Arezzo and Leonardo of Florence, who worked on the two most noted monuments of the goldsmith’s art which time and depredations have respected--the altar of Saint-Jacques at Pistoia, and that same altar of the Baptistery to which the bas-reliefs of Cione were afterwards adapted. During more than a hundred and fifty years the ornamentation of these two altars, of which no description can give an idea, was, if we may so say, the arena wherein all the most famous goldsmiths met. At the end of the fourteenth century Luca della Robbia, who, as we have seen, distinguished himself in ceramic art, and afterwards Brunelleschi, no less great as an architect than as a sculptor, came forth from the studio of a goldsmith. At the same period shone Baccioforte and Mazzano of Placentia, Arditi the Florentine, and Bartoluccio, master of the famous sculptor Ghiberti, to whom we owe those doors of the Baptistery, which Michael Angelo pronounced worthy of being placed at the entrance to Paradise. [Illustration: Fig. 103.--Shrine of the Fifteenth Century. (Collection of Prince Soltykoff.)] It is well known that the execution of these doors was, in 1400, submitted to competition; and it may be said, in honour of the goldsmith’s art, that Ghiberti, vying with the most celebrated competitors--for among them were Donatello and Brunelleschi--owed his triumph, perhaps, to the simple fact that he had treated, as it were by habit, his model with all the delicacy of the goldsmith’s art. And it must be added, and to the praise of the great artist, that although in great reputation for sculptured works of the highest importance, he adhered faithfully all his life to his first profession, and considered it not derogatory even to manufacture jewellery. Thus, for example, in 1428 he mounted as a signet for Jean de Medicis, a cornelian said to have belonged to the treasury of Nero, and he set it as a winged-dragon emerging from a cluster of ivy leaves; in 1429, for Pope Martin V., a button of the cope, and a mitre; and in 1439, for Pope Eugene IV., a golden mitre, embellished with five and a half pounds weight of precious stones,--its front representing Christ surrounded by numerous cherubs, and at the back the Virgin in the midst of the four Evangelists. During the forty years employed in the execution of the doors of the Baptistery, Ghiberti continued to derive assistance from several goldsmiths, who, so guided, could not fail in their turn to become skilful masters.