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on the outside, Is very well fitted for many kinds' of ule-fid vessels.

Green glass mortars, or planes for levigation, may beadvantageously changed into this hard porcelain, greatlyexceeding the hardness of any kind of marble, and noill substitute for agate or porphyry. Mortars and levi-gating planes of this kind seem for some purposes particu-larly excellent, as for the grinding of enamels, which,though they should wear off some of the matter of thebaked glass, as well as of marble or alabaster, yet cannotbe so much injured by the little they receive from the for-mer, which is analogous to their own composition, as bythe greater quantity they receive from the latter, which isof very different quality.

Glass vessels, intended for bearing the fire, may, byconverting them into porcelain, be made capable of bear-ing it in a much greater degree, and rendered much lessliable to crack. As vessels of this porcelain have in theseintentions manifest advantages above glass, they have ad-vantages also above all the other porcelains and earthen'wares. The unglazed earthen wares permit saline liquorsto soak through them ; those which are glazed have theirglazing corroded by acids ; the compact stone wares, andthose in general which have clay in their composition, asall the common wares necessarily have, are corroded andpartly dissolved by certain acids in a boiling state, parti-cularly by the vitriolic : while the porcelain from glassis neither affected by these causes, nor so liable to be in-jured by hastily exposing it to the fire. I know of nomaterial, so proper, and so commodious, for evaporatingvessels, or others, that shall be proof against all kindsof saline liquors.

There are some vessels also, which may be figuredmore perfectly, and with less expence, in this kind of

porcelain