The celebrated Portland Vase is a glass cameo, of enormous proportions, and a work of the first century, in blue and white. There is a quaint legend connected with the famous stone cameo known as the Vase of St. Martin, which is as follows: when St. Martin visited the Martyr's Field at Agaune, he prayed for some time, and then stuck his knife into the ground, and was excusably astonished at seeing blood flow forth. Recognizing at once that he was in the presence of the miraculous (which was almost second nature to mediaeval saints), he began sedulously to collect the precious fluid in a couple of receptacles with which he had had the foresight to provide himself. The two vases, however, were soon filled, and yet the mystical ruby spring continued. At his wit's ends, he prayed again for guidance, and presently an angel descended, with a vase of fine cameo workmanship, in which the remainder of the sacred fluid was preserved. This vase is an onyx, beautifully cut, with fine figures, and is over eight inches high, mounted at foot and collar with Byzantine gold and jewelled work. The subject appears to be an episode during the Siege of Troy,--a whimsical selection of design for an angel. Some apparently mediaeval cameos are in reality antiques recut with Christian characters. A Hercules could easily be turned into a David, while Perseus and Medusa could be transformed quickly into a David and Goliath. There are two examples of cameos of the Virgin which had commenced their careers, one as a Leda, and the other as Venus! While a St. John had originally figured as Jupiter with his eagle! In the Renaissance there was great revival of all branches of gem cutting, and cameos began to improve, and to resemble once more their classical ancestors. Indeed, their resemblance was rather academic, and there was little originality in design. Like most of the Renaissance arts, it was a reversion instead of a new creation. Technically, however, the work was a triumph. The craftsmen were not satisfied until they had quite outdone the ancients, and they felt obliged to increase the depth of the cutting, in order to show how cleverly they could coerce the material; they even under-cut in some cases. During the Medicean period of Italian art, cameos were cut in most fantastic forms; sometimes a negro head would be introduced simply to exhibit a dark stratum in the onyx, and was quite without beauty. One of the Florentine lapidaries was known as Giovanni of the Carnelians, and another as Domenico of the Cameos. This latter carved a portrait of Ludovico il Moro on a red balas ruby, in intaglio. Nicolo Avanzi is reported as having carved a lapis lazuli "three fingers broad" into the scene of the Nativity. Matteo dal Nassaro, a son of a shoemaker in Verona, developed extraordinary talent in gem cutting.