Recognizing the near relationship between gems and coins, we here see that Constantine, shortly after he had established his empire in Byzantium, removed the pagan emblems from the coins of the empire, and issued others on which he caused to be impressed the legend illustrating and recording the peculiar incident of his conversion; to this was added a phœnix, emblematic of the renovation of his empire, together with the monogram of Christ, and the Angel of Victory, which in his vision had directed his course at the time of his conversion to Christianity and triumph over the pagan enemy. At the time of his baptism at Nicomedia he clad himself in a white robe, and from that time he never resumed the imperial purple. This incident was also engraved, and formed the subject of a design on a later coin. The engravers employed by Constantine were incisori of the highest rank of that period; none others were in favor. They executed portraits of his family, of his wife Fausta, of his sons, and of himself--in combat, in bust, on horseback, in imperial power; always laureated, and principally on cameos, very few intaglios being cut at this time. Several important examples have survived the rack and ruin of time, and may be seen in the Bibliothèque Nationale at Paris, the British Museum at London, the Royal and Imperial Collections of Vienna and St. Petersburg, and in my collection. These unique gems, those commissioned by Constantine, however, form a small proportion of the glyptic harvest from the Byzantine period. With Constantine commences the series of scriptural cameos, which continue during several years in Byzantia. The great number of cameos preserved from this epoch bearing scriptural subjects, which were ordered and engraved for reliquaries and every description of vessels, and for the adornment of altar book-bindings, for church and cathedral ceremonies, far exceeds in quantity those imperial portraits, and to an appreciator of distinctive specialties in a representative art collection they are more interesting. [Illustration: BYZANTINE.] After a few heads of Christ attributed to the Sassanians, we meet in the reign of Constantine the first gem portraits of our Saviour. These sacred portraits, even at times rudely rendered, have often more divinity in them than many similar subjects of a later period. The distinctive, most characteristic, Byzantine gems are the large series of scriptural cameos, designed in relief for the ornamentation of the sacred vessels and other paraphernalia on the altars of the churches at the Byzantine capital. [Illustration] MEDIÆVAL. The era in the decline in art was sensibly marked in the glyptic branch. The very rude and often grotesquely drawn designs we meet in this long period, the Middle Ages, may well be termed the dark days.