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luted, and placed in a wind-furnace : the sire was gradu-ally railed, so as to make the crucibles of a moderatelystrong red heat, and continued in this state for fix or sevenhours. The fire being then suffered to decay, and thecrucibles taken out and examined, the glass was found inall to have become porcelain. In the upper chamber,most remote from the action of the fire, the pieces were ingeneral fibrous, and some of the thick ones not changedthroughout: in the lower chamber, more immediatelyexposed to the sire, where the matters intermixt with theglass were the fame as in the upper one, the fibres hadin most of the pieces disappeared, and given place tograins. There did not seem to be any differences, thatcould be ascribed to the quality of the cementing matters,in the internal colour, hardness, texture, or the regularsuccession of the changes ; though, in external appear-ance, the differences were very considerable.

All the pieces, which had been surrounded with soot,with charcoal, or with mixtures of the two, were exter-nally of a deep black colour : where small proportions ofsoot or charcoal were mixed with white earths, the por-celain turned out of a brown colour, deeper or lighter,according as the inflammable ingredient was in greater orless quantity. Judging that the dark colour, which thefoot or charcoal communicate, might be burnt off by fireassisted by the action of the air, I put some of the blackpieces into a crucible, which was placed open in a blastfurnace, and excited the fire, for above an hour, to asgreat a degree as the porcelain seemed capable of bearingwithout beginning to melt : the colour resisted this heat,continuing as deep a black as at first.

The coloured clays, boles, ochres, powdered.red bricks,and the sands which burn red, gave likewise differentshades of brown, inclining more or less to blackish, red-

2 dish.