[ 627 J

gold. All these compositions were bright and transpa-rent, without any scum on the surface or regulus at thebottom. The last exhibited a multitude of small sparklesinterspersed through its whole substance, which gave it abeautiful appearance in the mass, though in the lapidarieshands they were found to be imperfections, arising fromair bubbles. It is pretty remarkable, that in several repe-titions of this experiment, in a glasshouse furnace as wellas in my own elaboratory, the product was always full ofthese brilliant specks.

Glass of lead and glass of antimony make likewise a goldcoloured glazing for porcelain and earthen ware. Thefinest gold glazing is said to be made with an addition ofsilver. A glass of lead is prepared by melting minium orlitharge with a third or a fourth part of its weight of pow-dered flint. This yellow glass, reduced into fine powder,is either sprinkled on the porcelain made red hot, or mixedwith beer or other glutinous liquids to a due consistence,and applied with a pencil : the ware is then placed in thefurnace, under a muffle, till the glass begins to melt,whichis known by its glistening j after which, while warm fromthe fire, it is moistened with a diluted solution of silver,and baked again. Or the powdered glass of lead is moist-ened with the silver solution, then melted, and the glazingof the ware finished in one process, by applying on it thiscompound glass. After the baking, the glazed vessels,while still red hot, are held over the smoke of burningstraw, 6cc.

Gold coloured glasses without metallic substances.

There are sundry earthy bodies, as chalk and gypsum,which make a yellow colour in glass, especially when thevitrification is procured with borax or alcaline salts.These glasses however have generally more or less of a

M m m m green