Dolls’ eyes and artificial human eyes are made by well-trained operators working before a blow-pipe flame and manipulating tube and cane of delicately coloured tints to form the pupil and shell of the eye, the veins being pencilled on with thin threads of red-coloured glass. A considerable amount of skill and adaptation is necessary to do this class of work, and much depends upon the matching of the coloured cane glass used to give the natural effects. When properly made, so clever and natural are these glass imitations of the human eye that it is with difficulty that the ordinary observer can tell that they are not real. A skilled worker will make the artificial eye to fit the muscles of the socket and so move. In this way much ingenuity has been shown in fitting the eye sockets damaged during the war. Aventurine is a golden coloured glass containing minute yellowish spangles or crystals reflecting upon each other and giving its peculiar effect. This glass is obtained by the use of an excess of copper with strong reducing agents in the glass, whereby the copper is partially reduced within the glass, giving the pretty spangled effect. This glass is often used in the form of jewel stones, being cut and polished and fitted in ornaments. The process of making this glass was originated by the Italians, and for some time it remained a secret with them, and even now is styled “Italian aventurine.” Chrome aventurine is another form, giving a green, spangled effect. This is got by using an excess of chromium in the presence of reducing agents. The successful production of aventurine depends upon slowly cooling the molten glass so as to assist crystallisation. Mica schist, or flake mica, is used to give another curious effect in glass. A gathering of some dark-coloured glass is rolled or marvered upon a thin layer of flaked mica, and then a further gathering or coating of clear crystal metal is made. The whole is then blown and formed into some fancy ornament or vase. When finished, the glistening mica flakes show through against the coloured background, giving a curious silvery reflection. ------------------------------------------------------------------------ CHAPTER XIV OPTICAL GLASS