in natural history, a mineral substance approaching to the nature of the lapis lazuli, found in the East Indies, and of great use in the Chinese porcelain manufactures, being the finest blue they are possessed of. This stone is found in the strata of pit-coal, or in those of a yellowish or reddish earth in the neighbourhood of the veins of coal. There are often found pieces of it lying on the surface of the ground, and these are a sure indication that more will be found on digging. It is generally found in oblong pieces of the size of a finger, not round, but flat. Some of this is very fine, and some coarse and of a bad colour. The latter is very common; but the fine sort is scarce, and greatly valued. It is not easy to distinguish them at sight, but they are found by experiment; and the trying one piece is generally sufficient for judging of the whole mine, for all that is found in the same place is usually of the same sort.

The manner of preparing it for use is this: They first wash it very clean, to separate it from the earth or any other foulness it may have; then lay it at the bottom of their baking furnaces; and when it has been thus calcined for three or four hours, it is taken out, and powdered very fine in large mortars of porcelain, with stone pestles faced with iron. When the powder is perfectly fine, they pour in boiling water, and grind that with the rest, and when it is thoroughly incorporated, they add more, and finally pour it off after some time settling. The remainder at the bottom of the mortar, which is the coarser part, they grind again with more water; and so on till they have made the whole fine, excepting a little dirt or grit. When this is done, all the liquors are mixed together, and well stirred. They are suffered to stand two or three minutes after this, and then poured off with the powder remaining in them: this is suffered to subside gradually, and is the fine blue used in their belt works, our common flint serving for the blue of all the common china ware.