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delicate ornamental part, the modelling, ena-melling, painting, gilding, &c. which difplaysfo much exquifite beauty and which requiresa combination of perfeverance, fkill, and prac-ical nicety of management, that is hardly equal-led in any other chemical manufacture.

The intimate mixture of the ingredients ufedin pottery is of great importance to the beauty,compadtnefs and foundnefs of the ware. For-merly the wet clay and ground flint (or what-ever was the other material) were beatentogether with great and long-continued manuallabour, no more water being added than wasneceflary to render the clay thoroughly plaftic.This laborious (and therefore expenfive) methodhas now been laid afide in the larger potteries,and the ingenious way has been fubftituted ofbringing each material firft to an impalpablepowder, and diffufing them feparately in asmuch water as will bring them to the confid-ence of thick cream, mixing them in dueproportion by meafure, and when thoroughlyftirred together, evaporating the fuperfluouswater till the mafs is brought to a due conflu-ence for working.

The following is the common procefs ufedin StafFordfhire for making the ordinary ware.The materials are a fine clay brought chieflyfrom Devonfhire, and a filiceous ftone calledChert , or elfe common flint reduced to powderby heating red, hot, quenching in water, andthen grinding by wind-mills to a fubtle powder.Each material is pafied through fine brafs fieves,then difl'ufed in water, mixed by meafure, andbrought to a plallic ftate in the way juft men-tioned. A lump of this is then thrown on thepotter’s wheel, and by the workman’s handsaflifted by a fmall blunt iron knife-blade it isfafhioned into the fhape required, when circular,fuch as cups, faucers, plates, &c. but when madeoval, or to any pattern form, it is moulded on aplafter model. Handles and fpouts are thenftuck on if required, and the piece after beingagain fmoothed and the fhape more accuratelytouched up, is fet to dry for fome days in awarm room, where - ifc becomes fo hard as tobear handling without altering its fhape. Whendry enough, it is enclofed along with manyothers in baked clay cafes of the fhape ofband-boxes, called feggars, which are made ofthe coarfe clays of the country . Thefe are nextranged in the kiln or furnace fo as to fill itexcept a fpace in the middle for the fuel.Here the ware is baked till it has remainedfully red-hot for a confiderable time, which in

the larger kilns confumes io or 15 tons of coal,after which tire fire is allowed to go out, andwhen all is cooled, the feggars are taken outand their contents unpacked. The entire con-tents of one kiln will fometimes exceed 30,000different pieces of pottery. The ware is thenin the ftate of bifeuit; it is perfect pottery, veryhard, beautifully white with a flight fhade ofyellow, and of a fmooth furface, quite void ofglofs, much refembling a clean egg-fhell.

The next procefs is the glazing, which isperformed on all pottery intended for domefticufe. For this purpofe the bifeuit ware is dippedin a tub containing a mixture of about 60 partsof litharge, 1 o of clay, and 2o of ground flint,diffufed in water to a creamy confidence, andwhen taken out enough adheres to the piece togive an uniform glazing when again heated.The pieces are then again packed up in thefaggars, with fmall bits of pottery interpofedbetween each, and fixed in a kiln as before.The glazing mixture fufes at a very moderateheat and gives an uniform gloffy coating, whichfinifhes the procefs when it is intended for thecommon white ware. But the painting andgilding, each require feparate procefies.

Something may be added in this place on theppttery employed in chemical operations. For-merly when chemifts made their own crucibles,muffles, See. this was a very important branchof practical knowledge to every chemift, but atprefent this is almoft wholly confined to themanufacturer, and we are only able to pointout fome of the leading circumftances whichdetermine the goodnefs of pottery ware for oneor other purpofe.

Some very eminent chemifts, among whomwe may enumerate Glauber, Agricola, andPott, a have paid particular attention to thisfubjedt, and that enlightened manufacturer,the ’i'.e Mr. Wedgev/ood, has introduced afpecies of ware which anfwers fome importantpurpofes better than any hitherto invented.

Three important requ'fltes are demandedto ccnftitute a perfect pottery for all chemicalpurpofes, namely, infuflbility at any heat; coin-pactnefs of texture fo as to retain'faline andother fluxes in fufion without being materiallyadted on by them, or allowing them to tranf-pire; and endurance of fudden changes of tem-perature, particularly fudden heating withoutcracking or giving way in any degree.

Thefe three requisites however have beenfound impradticable to be united in the fameware, which has led to the neceffity of feledting

Mem. dc l’-Acad. de Berlin, for 1750 .