The colour of this kind of glass is usually green and the decorations are enamelled or painted in grisaille; as a rule the German cups and wine glasses of the seventeenth century are richly decorated (Fig. 305). In the German wine-glasses known as “flügelgläser” is seen an imitation of the Venetian “winged glasses” (Fig. 301). [Illustration: Fig. 305.—Decorated German Vases; Seventeenth Century. (S.K.M.)] Bohemian glass of the seventeenth century is noted for its clearness and good quality, and illustrates the advancement made in the art of engraving on glass. The engraved work was done with a diamond point as in etching, with the lapidary’s wheel, and by means of biting the glass with fluoric acid; the latter method is said to have been discovered by Henry Schwanhard of Nüremberg in 1670. John Schäper was a very clever glass engraver and decorator of this period. A beautiful kind of German glass is known as Kunckel’s ruby glass, the originator of which was the director of the Potsdam glass works, where he produced this variety about 1680. Many relics of glass vessels and beads have been found in Roman tombs, and in various parts of England, of a greenish or blue colour. These may have been imported or may have been made in England, but there is no certain evidence of this. Glass vessels for drinking purposes have been found which are believed to have belonged to the Anglo-Saxon period (Fig. 306). The material of these is thin, the colour is generally of a pale straw tint, and strips of thickened glass ornament the outside, arranged in the nature of parallel lines, or wound spirally to produce a kind of network decoration. [Illustration: Fig. 306.—Anglo-Saxon Drinking Cup. (S.K.M.)] Venetian glass found its way to England in the sixteenth century; in the inventories of Henry VIII. (1529) and of Robert, Earl of Leicester (1588), large quantities of Venetian glasses are mentioned as belonging to the above. Some Muranese glass workers were engaged at this time (1550) in the service of the King of England. The name of an Italian—Jacob Vessaline—is mentioned as a glass maker who worked at Crutched Friars in the beginning of Elizabeth’s reign (1557), and in the year 1589 there were supposed to be fifteen glass houses in England. Sir Robert Mansel was a prominent glass maker of the seventeenth century; he obtained patents in the year 1616 for the making of window glass and all kinds of vessels, and from the remains of glass objects that were found on the site of Princes Hall, in Broad Street, London, it is believed that his works were on that spot.