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 calcined cobalt with two of flint powder, and one of pot-ash. At the bottoms of the crucibles in which the smalt is manufactured we generally find a regulus of a whitish colour inclining to red, and extremely brittle. This is melted afresh, and when cold separates into two parts; that at the bottom is the cobaltic regulus, which is employed to make more of the smalt; the other is bismuth.