a kind of glass of a dark blue colour, which when levigated appears of a most beautiful colour; and if it could be made sufficiently fine, would be an excellent succedaneum for ultramarine, as not only resisting all kinds of weather, but even the most violent fires. It is prepared by melting one part of calcinated cobalt with two of flint powder, and one of potash. At the bottoms of the crucibles in which the smalt is manufactured, we generally find a regulus of a whitish colour inclined to red, and extremely brittle. This is melted afresh, and when cold, separated into two parts; that at the bottom is the cobaltic regulus, which is employed to make more of the smalt; the other is bismuth.