GLASS-Balls, which are circular or otherwise shaped hollow vessels of glass, may be coloured within, so as to imitate the semipellucid gems. The method of doing it is this: make a strong solution of ichthyocola, or isinglass, in common water, by boiling; pour a quantity of this while warm into the hollow of a white glass vessel; shake it thoroughly about, that all the sides may be wetted, and then pour off the rest of the moisture. Immediately after this, throw in red-lead, shake it and turn it about, throw it into many places with a tube, and the moisture will make it stick and run in waves and pretty figures. Then throw in some of the painter's blue smalt, and make it run in waves in the ball as the red-lead; then do the same with verdigris, next with orpiment, then with red lake, all well ground; always calling in the colours in different places, and turning the glass, that the moisture within may run them into the waves. Then take fine plaster of Paris, and put a quantity of it into the ball; shake it also nimbly about; this will every where stick firmly to the glass, and give it a strong inner coat, keeping all the colours on very fairly and strongly. These are set on frames of carved wood, and much esteemed as ornaments in many places.