The natural consequences followed, that the exports in glass from Venice to foreign countries became lessened, so much so that the workmen of Murano complained of being thrown idle for several months in the year. [Illustration: Fig. 300.—Venetian Enamelled Glass; Fifteenth Century. (S.K.M.)] Venetian glass has been made in many colours, such as blue, green, purple, amber, and ruby, and in variegated mixtures of clear or transparent and opaque glass. The clear variety is remarkable for elegance of shape and fantastic designs of handles or wings, consisting of twisted and knotted interlacings, which were generally executed in blue or red colours and attached to the sides of wine-glasses and other vessels (Fig. 301). One beautiful variety of glass is clouded with a milky-like opalescent tint, which is supposed to be produced from arsenic. The opaque white glass is made by the addition of oxide of tin to the usual ingredients. [Illustration: Fig. 301.—Venetian Glass of the Sixteenth Century. (J.)] [Illustration: Fig. 302.—Venetian “Vitro di trina.” (S.K.M.)] Glass was made by the Venetians to imitate precious stones, were streaked, splashed, or spotted with various colours, gold, and copper; the aventurine spotted glass was obtained from a silicate of copper. The _latticinio_ variety was formed of rods of transparent glass enclosing lines of opaque white glass forming patterns. The _vitro di trina_ is the so-called lace-glass (Fig. 302); the latter and the mosaic-like or _mille-fiori_ glass were made by the Venetians in imitation of the Roman varieties. Another variety was that known as _a reticelli_, in which ornament of opaque network sometimes enclosed air bubbles. That known under the German name of _Schmelz_ is the variegated or marble opaque glass made in the Murano furnaces, which imitated chalcedony, lapis lazuli, tortoiseshell, and jasper. Crackled glass was made by the sudden cooling of the half-blown material; this was again heated and drawn out in order to increase the spaces between the crackled lines. In the sixteenth century the forms of the Venetian glass vessels were of the Renaissance type; the long shanks and the wide bowls gave them an appearance of elegance and grace. The light and thin character of the material had also a great deal to do with the fragile look of elegance in Venetian glass of this period; the glass of the former (fifteenth) century was of a much thicker kind. The lightness and superior strength of Venetian glass was due to the absence of lead in its composition, which is so much used in the modern flint glass. The materials of the composition of the clear Murano glass are supposed to be—one part of alkali, obtained from ferns, moss, lichen, or seaweed, and two parts of pebbles of white quartz or fine clean white sand, and a small quantity of manganese, all well mixed together and melted in the furnace.