A N- Y E S S A ON THE Origin, Nature, Ufes, and Properties, o F ARTIFICIAL STONE: TOGETFIER WITH Some Observations upon common natural Stone, Clays, and Burnt Earths in general. IN WHICH The Durability of the latter is Hiewn to be equal, if not fuperior, to the hardeft Marbles. BEING The Refult of many Experiments. By DANIEL PINCO T, Artificial Stone Manufafilurer. LONDON: Printed by Richard Hett ; And Sold by C. Marsh, at Charing-Crofs ; F./New- BERY, at the Corner or' St. Paul’s Church-Yard ; and by the Author, at the Manufadtory by King’s-Arms Stairs, Narrow Wall, Lambeth, oppofite Whitehall Stairs. M D C C L X X. [Price One Shilling and Six-pence.] Digitized by the Internet Archive in 2016 ^ ^ :gr https://archive.org/details/essayonoriginnatOOpinc INTRODUCTION. |^Sfe®^^3Rchitedure, or the art of raifing A regular and noble edifices, and tliem with proper or- naments, is a fcience that hath very much engaged the attention of great and ingenious men in every age and nation, fince its firft appearance in the world : and elegant buildings, adorned with wdl-chofen fculptures, are fo univerfally admired, that there is fcarce a man to be found who feels not a feniible delight in beholding them. Whoever obferves the ftrength, folidity, juft proportions, fine tafte in the larger fculp^ tures, high laboured finifhing of the lefler ornaments, and elegance of defign, ft ill dif- coverable in the remains of antique buildings, will be immediately convinced that neither ftudy, labour, nor coft were fpared in ac- complifhing thofe admirable piles. But filch rich and noble produdions are very rarely found among modern performances, A 2 though C 4 1 though we are not without ingenious and juftly efteemed architeds, who give proof of an ability in every refpecS equal to them, if they were poffeffed with the fame means. i But the changes of times, and a dif- ferent climate, altering the face of things, added to the exceeding great price of good fculptures, and the averfion of many perfons to plain buildings, which induces them to employ bad artifts for the fake of cheapnefs, (and perhaps fometimes for want of fldll enough to chufe good ones) may be the principal caufes of that vafl: heap of execrable ornaments (if I may call them or- naments) found about moft of our Englilh buildings. This is no where more notorious than in London, and its environs, where there are few houfes that are not more or lefs ftuck about with carvings, or fomething in imitation of them, performed in a mofi: miferable tafte : and what is dill worfe, this is not confined to private dwellings, fome of our public edifices being dreffed up with the fame poor embellifiiments, to the difgrace of a people who [ 5 ] who boaft of their knowledge In the polite arts. Again, if we turn our eyes Into the many gardens that are adorned with imagery, fuch a troop of diflortions prefent themfelves, as would incline a judicious beholder to believe the fculptors had intended to burlefque, and not imitate nature. And were it not de- fcending too low, we might take notice of that prodigious fwarm of vile unmeaning notchings, found In all the burying-places in the kingdom. Flence it is eafy to per- ceive, why fome who are judges of what is excellent in thefe works of art, ftudy a plain magnificence in their buildings ; neither chufing the heavy expence of good orna- ments, nor being able to bear the fight of bad ones. But the exceeding great price of cutting fine figures in marble, or even Portland ftone, prevents many more of the judicious from adorning their gardens, temples, &c, therewith ; contenting themfelves without fculptures, as they would be no better pleafed with a dull Apollo, a limping Diana, ^ The carvers call the cutting of grave-ftones, notching. A 3 a knock- s knock-krieed Hercules, or an impotent Mars, paired ivitb. an iil-fliaped Venus, than they would be in feeing the fimplicity o*f their plain manfions fpoiled by mock orna- ments, compofed of awkward holes, queer zigzags, and long unnatural fcratchings. But were perfons of fufficient fortune wil- ling to bear the expence of good fculp- turcs for ornamenting the outfides of their buildings, or to decorate their gardens with fine ftatues, buftos, vafes, &c. they are dif- couraged from doing it by the weather af this climate. For it is a certain and v/ell-known fadl, that the weather in this ifland has fo de- ftrudive an effed on Portland, Bath, and other rock ftone, and even marble itfelf, when expofed to the open air, that their furfaces are foon deftroyed, and in time the whole fo greatly impaired, that not only the beauty but defign and meaning alfo are loft; and this is moft of all feen in and near po- pulous cities, particularly in London, and its furrounding villages, where many of the modern artifts are eye-witnefles to the ruia of their own works* Thi$ E 7 ] This decay of marble and other ftone is not confined only to our own country, but attends all climates, is more or lefs vifible according to the different conftitutions of the air, and occafions over the whole globe fo broad and ftriking a fcene of deftruclion, that it caufes a painful fenfation in almoft every beholder. But it is mofl lamented by the antiquarian and the artift, the firft having thereby totally loft many infcriptions, whilft others are fo fpoiled as to render their read- ing very difficult and uncertain 5 and the latter having thereby been deprived of many bright examples, wffiich would have been well worthy of his imitation. From this, though but a ffiort view of things, it follows that the producing a ma- terial which will effcdually remove all the foregoing inconveniencies, muft certainly merit the attention not only of all who are concerned in buildings, and other works of elegance and ornament, but of the public in general. To (hew, therefore, that artificial ftone, compofed of proper materials, well manu- fadured and burnt, will fully anfwer the A 4 above [ 8 ] above piirpofes, is the principal defign of this treatifej in conjundlion with fome fpe- cimeos of fuch work which are adtoally performed. It has been the conflant defire of almoft every architedl and lover of the fine arts, for many years paft, that a work of this na- ture mi^ht be fet on foot, an or try for themfelves the following experiments. Colled fpecimens of feveral of the many clays which are brought to London for various purpofes; (or where this may not fuit on account of diflance, a fufficient num- ber may be found in almoft any county or diftrid, in this or any other kingdom.) Carefully examine them while raw or un« burnt, either by reducing them to dry poW“ cler, or diluting them in v/ater, or any other means, fo that their parts may be feparated as much as they can be 5 and hence fome of the component parts will be found as above deferibed. Then take fredi lumps of the fame clays, and, after drying, expofe each to different degrees of heat till they run in the fire, nicely Obferving the change of appear- ance throughout the whole operation. This may all be done at one operation, in a fmail B 2 wind [ 20 ] wind furnace, by putting in about twelve pieces of each fort, and drawing out one piece of each, at certain periods, as the heat is railed. This being done, make artificial clays of fuch materials or principles as are difcovered in the natural ones, expofing them, alfo, to the fame degrees of heat : then compare all together, and I am perfuaded, whoever does all this, will conclude, that clays are nothing more than the dull of ftones, fands, metals, folfils, &c. each con- taining its own proper principle of nature. Hence we may fee why alkaline and fome other falts, fulphurs, &c. are no more dif- cernable in raw clays than they are in other bodies, wherein though they exift, they are fo enveloped or locked up as not to be the ob- jedl of our fenfes, till by the force of fire they are fet at liberty; and clays, being compofed of the fame bodies, however fine the parts, are yet fufficient to hold thofe falts, &c. as firmly as in larger mafles. But when clays are expofed to fuch a degree of heat as to fet thofe falts at liberty, they im- mediately afiTift the vitrification, and are a ^ucond time locked up, and efcape our fenfes. It t 21 ] It may, alfo, be obferved, that moft of the clays now found have acquired a firm tough confiftence, by lying many years buried in large mafles 5 which, added, to their having thereby loft moft of their loofer falts, hath rendered them very unfit to promote vege- tation, unlefs long expofed to the open air, or mixed with other matter : whereas at their firft formation they muft have been more loofe, open, and replete with falts, and probably much more kindly to the growth of plants than that foil which hath lince covered them* This obfervation of clays growing tough by time, is confirmed by experience: for compofitions of fimilar natures are found to be thus affedled, if a proper degree of moifture is preferved in them. I will juft add, that that loofe blackifti foil or mould which covers great part of the earth, upon examination and a little re- flexion, will be found to be nothing more than the exuviae of nature, the ordure of animals, and divers other matter, acciden- tally thrown together. There could, there- fore, be none of it at the firft creation, nor B 3 much. [ 22 il much, till feme years after ; and confcir quently this was not at firft the upper ftra-** turn of the earth, as feme have thought. Having thus far (hewn what clays ori- ginally were, and now are, and compared the account, with what the philofophers fay of the fubiiding of the terreftrial matter at the creation, it naturally follows that the fineft parts or duft of all the other bodies, muft have been upheld or floated longer in the waters than the larger parts. This duft, at length fettling alfo, and taking in its way a proper portion of faits, became the upper layer of the ground, fully furnifhed with the principles requiflte for vegetation when aflifled by water, or for vitrification when, expofed to fire, Whoever will compare, what is contained in feveral books, which treat of making glafs, enamels, porcelain, &c, and which deferibe chymical procefTes on minerals and folTiIs, with what hath been advanced above, concerning the original for- mation and conflituent parts of clays, will not only find a confirmation of what has been faid ; but may make other difeoveries both ufeful and entertaining, as well as fave , himfclf ( 3 himfelf the trouble of trying thofe experi-* ments mentioned a page or two paft. As a conclufion of this part, we may ob- ferve, that, according to philofophers, anti- quaries, and the foregoing defcription of earth or clay, our firfl proportion feems to be true, in all points; as the firft facrificers muft have difcovered fome parts of their altars converted into firm ftones. A phenomenon like this, muft certainly have been very furprifing to perfons fo un- acquainted with the properties of natural bodies, as the firft inhabitants of the world muft have been. And what could more command the attention of perfons upon the fearch for whatever they apprehended might render their fttuation more agreeable, than to fee that the fame fire which con fumed the viftim and the wood, made the altar ftrong and indifibluble ? This being once known, it was exceeding eafy to find, that while the clay was foft, it might by the hand be fafliloned at pleafure : and thus in all probability began the art of making ftone of burnt earth, and divers vef- fels for domeftic ufes, B 4 Nor [ H ] Nor may it feem extravagant to fappofe that this difeovery was not only the firft in the world that contained curiofity as well as great ufefulnefs, but that it might be the mother of another, perhaps equal, if not fuperior, in value. For a defire of more knowledge in thofc firft inhabitants being awakened by the for- mer difeovery, they might, by obferving a variety in the matter of the earth, be na- turally led to fearch deeper ; and when they fell on a vein of metalliferous earth, fome of which was either accidentally or delignedly, for fome purpofe or other, put in the fire, the metal would foon become a frefh objedl of their attention. But though this difeovery may feem as eafily made as the former, yet its application to various purpofes was much more difficult, and muft have required a con- fiderable length of time and experience to bring about in any tolerable degree of per- fedlion. Yet we are affured that it was in pradlice in the days of Adam. This is, alfo, a farther confirmation of the antiquity of the former difeovery : for with-^ out ftones of burnt earth they could not well m ake t 25 ] make proper furnaces for purifying their ores. But fhould fome fay that they might have ufed for this purpofe raw clay, the con- fequence is ftill the fame; for they mufi: have been firft convinced that the clay would endure the fire. Nor is it eafy to conceive how they could fail in producing glafs, though in a very li- mited manner: for, in the courfe of their operations by fire, either in burning clays, or fmelting ores, bright drops of glafs muft frequently be found, which they might break from the parts to which they ftuck, keeping them carefully till they had a proper quantity, after which they might be melted all together. And this I am inclined to think was the only known way of making, or rather finding, glafs, till many ages after the Deluge, which rendered it fo fcarce and valuable as it fqems to have been in thofe early times. I cannot quit this part of the fubjedl, without obferving, that however incoofider- able the ftudy of clays may appear to fome, yet they certainly contain ftifficient .matter, not only to exercife ufefully the mind^ bat, 5 alfo. [ 26 J aifo, to afford no fmall degree of gratifica- tion to the curiofity of the ingenious and Ipeculative : and like other things which arc negleded on account of their commonnefs, might lead to the explanation of many a phenomenon at prefent myfterious. SECT. IL Aving in the foregoing part taken notice of the antiquity of the art of making artificial (lone, or as it was formerly (and perhaps more properly) called, ffone of baked or burnt earth, we £hall, in this part, take a brief furvey of the progrefs of it in the firfl: and fome following ages of the world, with a few remarks concerning its application to various purpofes in feveral na- tions; and alfo offer an obfervation or two on the properties thereof, and of natural rock ffone, from whence will appear the effential difference between the two Ipecies. Whether any of the cities or other buiid- ‘ ings before the flood v/ere of burnt earth. or brick, is not certainly known ; yet the affir- 5 mative t 27 1 mative appears by much the more probable fuppofition : for, allowing what hath been advanced in the former part to have any truth on its fide, it follows that the fuffi- ciency of the material for fuch purpofes mufl: have been known. Again, the building of altars might fug- geft a plain opening to the art of raifing walls 5 and fome well known and very early tranfadions of the poftdiluvians nearly con- firm the matter. The readinefs which men difcovered, al- moft diredly after the Flood, for building a city and a tower with llones of baked earth, and their knowing fo well the necefllrv of burning them thoroughly, plainly indicated, either their having experience herein them- felves, or their being taught by fome who were poflefied of fuch experience by former works. For that it was a convidion of the firength and durability of burnt earth, that determined them in its favour, in preference to natural ftone, appears pretty plain from the text 5 which (hews, that they intended the building for a perpetual monument of their name and place, as well as for a ge- ' neral [ 28 ] neral rendezvous. But this knowledge of the permanency of thorough burnt brick, they could not have had, from their own expe- rience as to time, that being evidently too fliortj nor did they know enough of the caufes of the cohefion or decay either of na- tural or artificial bodies, to come at it by reafoning : they muft, therefore, have been taught it, which appears to be really the cafe; for Noah and his fons were all not only then alive among them, but lived many years after, and had lived long enough in the old world to know the arts therein pradifed ; and undoubtedly taught not only the above, but many others alfo to their feveral tribes, and that even for many years after the dif- perfion of mankind; and thus the know- ledge of thefe and many other things was fpread all over the world. Hence it is probable that this bufinefs was in pradice long before the Deluge. It is, however, very well known to have been in great ufe a few ages after, and from many hints which may be gathered from ancient writings, and fome rare pieces that have been found, it appears that men foon grew pretty [ 29 ] pretty dexterous in handling thefe earthen materials : and as they made veffels for do- meftic ufes tolerably handfome, fo alfo it feems probable that the firft idolaters made their gods therein. If we compare the fa- cred writings with the firft accounts of pagan mythology, it may not appear extravagant to fuppofe that images of Noah and his fons, with certain figures or hieroglyphics, figni- fying their teaching arts to the people, and their other adions, were the firft works of this kind that were performed in the world : and in time, as men loft or corrupted what had been taught them concerning the true God, they deify *d thefe ancient fathers, and worfhipped their images, giving them va- rious names according to their feveral lan- guages, or varying ideas. Thus, in all probability, began the making of imagery, and with it idolatry, the progrefs of which appears to have been fo rapid that in a few ages it might be a query whether gods or men were the more numerous, tn this fituation, it would have been a little wonderful if a people fo very fond of god- making, ftiould mifs doing it in a material fo [ 3 ° 3 fo iackily a[dapted to the purpofe as clay, though they foon ufed other materials alfo. Hence arofe their having a tradition that God made the firft man of tempered clay, which, being impregnated with the celeftial fire, took life, and became flefh and blood : and when perfons found that their men of clay, by common fire, became lafting ftones, it required but very little prieftly jumbling to form the ftory of Prometheus. But thus to follow the ufes that have been made of this material would be endlefs, and of no fervice j and even to mention all the greater infiances thereof in the world would only ferve to fwell this work to a needlefs bulk. I fhalf, therefore, confine myfelf only to fome re- marks on its ufe in China, Greece, Italy, and England, the reafon of which choice will foon appear. Whoever hath travelled into China, or read their hiftory, muft know how much the Chinefe boaft of the great antiquity and per- fection of this art in their empire, and of their being the firft difeoverers of it, parti- cularly of that juftly efteemed ware which they formerly called the precious jewel : and k [ 31 1 k is true that till of late, they have borne away the prke from all other nations, as to the finenefs of the material itfelf. But were their oldeft records better under- ftood, or their later hiftorians more faithful, their claim to being the original inventors would have no better foundation than fuch claim would have if made by any other na- tion, as to burning earths in general 3 for the Chinefe are moft probably the offspring of Abraham by his concubines, which I could prove, were it worth the pains. As to the perfection of their ware, if the matter were fairly examined, it might be found that the difcovery thereof was more owing to accident than defign : for in the courfe of fo mighty a work as digging up, tempering and mixing the clay with proper matter, moulding and burning the bricks, or rather (tones, for building that prodigious wall efteemed one of the wonders of the world, added to their having ready at hand the fineft clay hitherto difcovered, they might eafily be led to that knowledge which they afcribe to their own great fagacity ; and not- withfianding what they fay of the vaft anti- quity [ 32 ] quity of their fine ware, it does not appear to be fo old as the building of that wall. As to their painting and glazing they are modern. Having made mention of the Chinefe wall, it brings into my mind a remark thereon of Ilbrand Ides’s, in his travels over land from Mofcow to Peking, which is to the following effed:: Upon his furveying that ftupendous in- ftance of human labour, and feeming not to know that the materials thereof were burnt earth, he expreffes fome wonder that a wall, which had ftood upwards of two thoufand five hundred years, fhould ftill have the ap- pearance of one that had not been built above twenty ; it being remarkably clean, and not growm over with mofs and weeds, as old walls ufually are. This remark naturally introduces the in- tended obfervations on the eflential difference between natural and artificial ftone ; which obfervations, though they may here feem wrong placed, and have the air of a digref- fion, can have no ill effed on a fubjed like this. Upon [ 33 ] Upon that fingle circumftance taken no-* tice of by the noble traveller above named, if no other had ever mentioned the materials of that famous wall, we might have fafely concluded that it was built of artificial and not natural ftonCy as may be feen by the lead reflection on what follows. That fpecles of whitifli rock done com- monly ufed in buildings, hath a great de- pcndance on a certain degree of moiflnre for the maintenance of its texture. Thefe Hones, being a little dried, greedily imbibe the moiflure of the air, if fitly expofed thereto, which is a nourifhment and fup- port to their ftrength 5 and where the heat of the fun, during its prefence, deprives their furfaces of more moiflure than can be fupplied in his abfence, the flone is foon defaced^ Experience, alfo, fhews that if ftones of this texture have their pores locked or rather choaked up by any refinous or oily matter, as varnilh or paint, fo that the moiflure of the air cannot freely enter their fiirfaces, they become weak and rotten much fooner than otherwife they would 5 and rf their moiflure is quite exhaufled by C the [ 38 ] the force of fire, they in appearance feem to take a different mode of exigence, as in making lime. Again, the pores of Hones being in a con- tinued connedlon throughout their whole fubftances, and their communication with the earth not being intercepted, they will re- ceive frefh moifture therefrom, which, added to what they receive from the air, may be the reafon why Hone buildings are more de- cayed at top than at bottom, and why they are never found to periih from their centers outward. Hence, alfo, they have frefli fup- plies of the principles requifite for vegeta- tion 'y and their moiHure being fufficient for the nouriilinient of certain moffes whofe roots find proper room to extend their fibres in the deep pores of the Hone, thefe moffes form lodgements for duH mixed with feeds of other plants, which, growing and annually dying, leave frefii feeds and matter. Thus at length fo great an cncreafe enfues as to cover the whole building, if totally negkded ; and hence the lower ruins of buildings are pre- ferved many ages after their tops are gone to duH. [ 35 3 This vegetable cloathing on flone is con^ ftantly feen, except the afpedt or general litnation is unfavourable, and then a worfe confequence takes place : for where thefe vegetables are denied growth the (lone is deftroyed, it being obfervabie that where ftones are covered with mofies^ &c. their furfaces are preferved, and, on the contrary, where the pne cannot grow the other is con- tinually wafting which confirms our lead- ing propofition, viz. that rock ftones have a dependance on a certain degree of moifture for the maintenance of their texture. We now return again to artificial ftone, wliere, though the outward appearance is nearly the fame, the internal properties are totally difierent, and far fuperior to all the common forts of rock ftone ; provided the artificial be made of the beft materials, and properly burnt, as that of the Chinefe wall muft. have been, according to the foregoing remark* * There are mariV other obfervations, cn fitvatioriS, mat- ter in the air contradictory to the nature of {lone, accidents in its firft formation, ill management in workmen, &c. Scc.i. omitted for want of room. C 2 The [36] The difference between the former and thk, arifes from its coheCon being an indif- Toluble bond, which is not the cafe in any known natural bodies. Its pores are few, irregular, and have little or no communica- tion with each other. It receives neither benefit or injury from the air, the earth, or their moifture. Whether its fmall uncon- nected pores are by any means choaked up, or left open, it matters not j yet it holds on its furface paint or varnifli more firmly than any other fubftance I know of. It neither has any inherent moifture, nor, upon a fo- reign fupply, will it retain a fufiiciency there- of long enough to fupport the growth of any known vegetable, except it be laid in a lituation conftantly moift. But as thefe properties in this material will be more fully treated of in another place, they are here but juft mentioned in the form of meer aiTertions, only to fhew the effential difference between the two fpe- cies of ftone; and that if Ifbrand Ides had bccn converfant in things of this nature he would not have wondered at the permanency and deannefs of that wonderous wall. But, f 37 ] But, befides this wall, there are, according to the teftimony of fome travellers, many buildings in China, the greater part of which are of the fame materials, although the country abounds in marble ; and perhaps the Chlnefe may have reafon to wifh that their forefathers had ufed more marble, and lefs of their fine clay. The next fubjedl that (hould prefent itfelf to our view, is the ufes that were made of burnt earths by the ancient Greeks and Romans. But as thefe, as well as the other works of thofe renowned artifts, have already been the fubjedl: of treatifes by feveral antiquaries ; and as many fpecimens thereof are to be found in the cabinets of the curious, a par^ ticular defcriptlon is here pafled overj and, inftead thereof, fome obfervations are offered by way of comparifon between thofe excel- lent artifts above named and the Chinefe, with regard to their differing earths. A little confidcration v/ill make it appear a very unlucky circumftance, that the know- ledge or poffeffion of the fineft and moft dur- able material that could be adapted to the life of performing fine fculptnres fhould be ftiut [ 38 ] lip in a corner of the world, among a people notorious for being bad defigners, and who have fcarce any of that knowledge which gave fo great fame to the Greek and Roman artifts ; while thefe either had not, or knew not, the ufe of any other earths proper for burning but fuch as were coarfe and of a bad colour. Yet even on thefe they frequently beftowed much fkill and labour ; and hence it is plain that if they had been pofieffed of thofe finer materials, they would have made a much more noble ufe thereof than thofe who had them. Had this really been the cafe, it would not be abfurd to fuppofe that they, inftead of covering their burnt earths with marble, would rather have covered mar- ble with burnt earth. Hov/ever, from what is now feen of their works, it is evident they would have made many fine fiiatues and other curious fculptures therein, the remains of which would now have been more va- luable than thofe of marble. The next review, is of what hath been done of this kind in England ; and here but little can be faid, except it be to expofe or reprove the dullnefs of my countrymen, the 5 cafe [ 39 ] cafe here being quite different, from both the foregoing. For the Chinefe have both fine marbles and fine days; the Greeks and Romans have fine marbles, and, as far as is difcovered, but homely days : but the Eng- lifh have fine days, and but homely ftones. They are, therefore, the more interefled in a bufinefs of this nature, and yet they have moft negleded it. I cannot here fay any thing more to the purpofe than what is found in a book that was publifhed about fixty-fix years ago, intitled The Country Pur chafer y or Builders DiBioiiaryy a part of which is here tranfcribed. The author, difcourfing on brick-making, mentions fome improvements therein as pro- pofed by one Mr. Worlidge ; who, among other articles, fpeaks of earthen pipes for- merly made for the conveyance of water un- der ground at Portfmouth in Hampfliire, and of grates and backs of chimneys made by Sir John Winter formerly of Charing- Crofs: then, after fpeaking of the applica- tion of thefe materials to door and window frames, he ( Mr, Worlidge ) fays ^Mhis is one of the moft feafible aiid profitable C 4 opera- [ 4 ° ] operations I know In England to be neg- lefted.” (Then the author himfelf goes on. ) It is really my thoughts, much might be done concerning making of chimney- “ pieces, ftone moldings, and architraves for doors and windows, and architraves or fafcias for fronts of buildings, &c. if that men of this profeffion would but fet their minds to work, to contrive fome good compofition of earth, and a way to manage it well in moulding, burning, &c. But (the more is the pity,) men of this pro- feffion are like the materials they work upon, viz. heavy and lumpidi. ‘‘ It might be made a query, whether a compofition of earth fomething like to common crockers earth, would not in fome meafure anfwer the defign, fince it is apparent, that whatever form the crockers are pleafed to put their earth into, it retains it after drying and burning, al- though crocks, and fuch like things, are formed very thin : now, fuppqfe that chimney pieces, or the like, were made in ** molds, and dried and burnt, when they ‘‘ came ' fC [ 41 ] came to be fet up, if they v/ere not “ thought fmooth enough, they might he polifhed with fharp fand and water, or a piece of (harp fand, ftone, and water. Or ‘' were there but care taken of fuch things, “ as thefe, (which are for ornament as well “ as ufe) when they are half dry or more in the air, then let them be polilhed over “ with an inftrument for the purpofe, either “ of copper or iron, or fome hard body, and then leave them till they are dry enough “ to burn : ’tis my thoughts fuch would not “ want much polifhing afterwards. “ And let me further add, I am very apt “ to think that ingenious men of this orofef- " lion, might make very handfome and beau- " tiful chimney pieces, ftone moldings for “ doors, &c. fit for noblemens houfes, and " all others that would be at the charge, “ What I would here propofe, is by way " of glazing, as potters do their fine earthen ware, either white or any other colour, or “ it might be vein’d in imitation of marble, “ or be painted and anneal’d with figures “ of various colours, or fome hiftory, per- fpedlive or the like, which would be much cheaper. [ 42 ] “ cheaper, if not alfo as durable, and every whit as beautiful as marble itfelf. And had 1 time, and room in this fmall treatife, I could here have added the me- thods of glazing, and painting of various ^‘ Colours, to haVe encouraged the lovers of fuch arts, to fet their heads at work at it, fo that I am inclined to think, we rather want art, or ingenuity, and induftry, than ^‘ materials to fatisfy our greateft curiofity in building. ’Tis not the bafenefs of our Englifli ** materials, but w^ant of fkill and diligence in managing them, that makes our Englifh Buildings, in the leaft meafure inferior to any foreign ones : I well remember an in- ftance of this nature, wdiich was an ob- fervation of an Engliih ambaiTador, which “ was this, (viz.) that we ought not to be difcouraged v/ith our ignoble materials for building, which we ufe in England, in comparifon of the marbles of Alia and Numidia ; for, faith he, I have often, at Venice, view^ed with much pleafure, an ‘‘ antiporch, after the Greek manner,, ereded by Andreas Palladio upon eight columns of [ 43 3 of the Roman order, the backs of ftone without pedeftals, the fliafts or bodies of “ meer brick, three feet and half in dia- meter below, and confequently thirty-five feet high, as himfelf hath defcribed them in his fecond book. Than which, faith the ambaffador, mine eyes never yet beheld any ‘‘ columns more ftately of ftone or marble, for the bricks were firft formed in a circu- lar mold, and were cut before they were ‘‘ burnt, into four quarters or quadrants, or more than four parts, for he could not “ certainly tell how many the fides were, afterwards in laying, jointed fo dofe and ‘‘ nicely, and the points concenter’d fo ex- acftly, that the pillars appear one entire “ piece. And therefore I would not have Eng- lifhmen be difbeartned, that we do here “ want thofe firm and folid ftones, which nature hath furnidied other nations with, but rather to exercife their ingenuity, to fupply ourfelves by art, with thofe things which Providence hath thought fit we ftiould want, unlefs we would do fo. And [ 44 ] And if we can but bring fuch things to perfeftion, which have been here hinted “ at, it may hereafter redound to the honour of the Englifh nation. I mention thefe things here purely to ftir up inquifitive per- fons, to endeavour after an improvement of fuch arts, and that they might not be fo ftupid, as to fuppofe that either they, or their forefathers, were arrived at the /le plus ultra of this or any other art. And to perfjade them if poffible to throw ojfif that flothful and dangerous principle of refting contented with being pofieft of the fame degree of knowledge, which our predeceffors had before us, and of thinking that they have fkill enough, be-* caufe the barbarous part of the world ‘‘ doth not pradlife fo much as they. But I would very fain, if it lay in my power, prevail upon mechanicks, to fee what im- provements in their profeffions, they can bring forth."’ This quotation fliews the ftate of thefe matters in the time of its author, who feems not to have known that making artificial .done was in pradlice feveral hundred years before. [ 45 ] before. For it appears that there are fev^^ if any, of our cathedral churches, from five to feven hundred years ftanding, but what have fome parts made in thefe materials, ei- ther of the burnt or unburnt fpecies ; but (if I miftake not) they are moftly of the lat- ter, or that fort which hardens in the air only. But herein, if I am not greatly mif- i taken, the Engllfh fall infinitely fhort of the fkill of the ancient Egyptians ; for I have long fufpefted that porphyry, granite, and other hard marbles, (no quarries of which can be found,) are compofitions. I could fupport this fuppofition by experiments, the account of which muft at prefent be omitted. During the reigns of the two lafl; Henrys, the burnt kind feems to have been pretty much in ufe, fevcral in fiances of which might be produced 5 but one may be fuffi- cient. In taking down an old gate which lately flood near Whitehall, there were found buftos of eight Roman emperors, in as many niches, all of burnt earth, and not in the leaft de- cayed by the weather. They are now in the [ 46 1 the cuftody of Thomas Sandby, Efq; archi- tedf at Windfor Great Park, It is obfervable that in the times o-f the above performances very little was known of moulds proper to deliver thefe kinds of ma- terials with any certainty. Moft part, there- fore, if not all thofe ancient works muft have been done by immediate modelling, which may be the principal reafon why the pradice thereof was difcontinued 5 as it is pretty welji known how few modellers, particularly good ones, were then in this kingdom. Nor does there appear to have been any revival of this bufinefs till about forty years ago, when a confiderable undertaking of this kind, (profeflfedly under the name of artifi- cial fione,) was fet up by one Mr. Holt, at Lambeth, oppofite York Stairs, w^ho alfo wrote a fmall treatife fetting forth the excel- lence of his manufadare ^ which treatife is the firft in fiance, that I can remember, where the nanae, artificial ftone, is applied to burnt earths j for whenever this name hath oc- curred in other authors, it feems to mean thofe compofitions which acquire hardncls in the air pnly. L 47 ] The plan upon which the above manu- fadbure was conduced was exadly the fame as defcribcd by the author above quoted ; though Mr. Holt, in his book, talks much of his fecret compofition, and afcribes the whole to his own Invention, (as fome others have done fince.) From ftveral circumftances, it appears that this work met with tolerable encourage- ment for fome years, till, the projeQor dying, the whole affair died alfo. But, it is evi- dent fVom a confiderabie quantity of broken pieces now in my poireffion, that fuch a work could not have held many years in great efteem without improvement, had its author lived 5 there being neither tafle in the de- Iigns, nor neatnefs in the execution, though time has proved the materials durable in the fevereft trials. It is all covered on one fide with an earthen ware, white glaze ; and fome of it is poorly painted v^ith blue orna^ ments, baflcets of flowers, &c, Mr. Langley the architedl, alfo, made many things of this fort; particularly fome buftos, faid to be tolerably executed. What ■„ V,. [ 48 } What hath been attempted in this bufinefs by feveral hands for fome years part is too well known to need any defcription. But it may be obferved, in general, that whatever improvements have of late been made in thefe manufactures, they appear to be intirely owing to the unwearied diligence of feveral ingenious men who have fearched this king- dom for proper materials to make porcelain, and to their endeavouring therein to equal the Chinefe. I freely acknowledge that it was from fome fuch I had thofe bints which rendered my experiments fuccefsful ; and the public may be affured that if my prefen t undertaking fhould meet with any tolerable encouragement, I will exert what abilities I have, yet farther to improve fo pleafant and ufeful an art. N. B. There are fome notices which I have met with, in the courfe of many acci- dental converfations with perfons who have travelled, and vylth whom at prefent I have no acquaintance. Several of them have cb- ferved, that there are to be fecn in the Mo- gul’s empire and other parts of the continent, c fo:ne f 49 3 fome very Ancient buildings of a whitifli ftone, fufpecled to be artificial, and fuppofed to have been built foon after the Flood. I juft mention this by way of enquiry, that travellers, when they meet with fuch objefts, may endeavour to inform them- felves in this matter, which is eafily done, thus : Break from fome part of the building a fmall piece, ( if no bigger than a nutmeg it will do ) heat it llowly till at length it may be put in a fmart fire, then increafe the heat to a degree that would melt glafs. Let it cool gently, and the difcovery is made. For if the ftone is burnt earth, it will not fuffer injury hereby, unlefs perhaps it be a little more glaffified : but if it is natural rock ftone, it will be a calx or limed. Any intelligence of this fort conveyed to me I ihall eftcem a favour. D SECT. [ 50 ] Sec t. III. Avlng, in the foregoing part, given a general account of artificial ftone, fo far as relates to its origin and progrefs in pad times ; it is the bufinefs of this part to attempt fuch an explanation of its nature and properties as to recommend its ufe in future ; and to prove that the ftrength and durability of the burnt fpecies is fuperior to white marble or common rock ftone* Artificial ftone, as hath been before ob- ferved, is of two kinds, (viz.) unburnt and burnt 5 and thefe differ as little in their out- ward appearances, as was, in the farmer part, obferved of the burnt artificial and natural ftone 3 and have, alfo, the fame eftential differences in their natures and properties, arlfing from the fame different caufes in their cohciion ; the firft being by the mi- ni firy of water, and the other by fire. Though the laft of thefe is the principal f ilijcft of this work, it may not be amifs to offer ibmc farther obfervations on the former, as [ 5 > ] as It appears mort: probable that this was iii as great ufe in ancient times as the other' and is dill an objedl worthy the attention of all Vv^ho are concerned in building. As the component parts, as well as thd caufe of their cohefion in this fpecies of done, are (or at lead fliould be) the very fame with thofe of natural done, its nature and properties will be the fame alfo: that is, the materials thereof fhould be fo chofen and prepared, that upon forming the mafs to its intended fhape, the fined parts may take fo orderly a difpofitlon as to be firmly held in contact by the common power of grai^ity, in conjundion with a due degree of moiduro and combining falts ; which, from many ex- periments, appears to be univerfally the cafe in natural dones. This may in fome meafure be obferved in the operations on common mortars, ducco, plaider of Paris, and many others, and were there due care taken to redore certain acid principles which were driven off by the fire in burning the dones for fuch purpofes, their drength, upon being re-made and dried to a proper degree in the air, would D 2 be [ 52 ] be equal, and fometimes fuperior, to what they had in their priftine ftate : for when Hones are burnt till they become a calx or lime, the falts that remain in them are moflly of the alkaline kind, and require to he duly balanced by fome fuitable acid, in order to render them indiffoluble ^ which appears to be the reafon why fcum'd milk, and fome other liquids containing certain degrees of acidity, are known to make thefe bodies more Hrong and durable > and fome mineral acids perform this Hill better.' The idea of fixing, or rendering alkaline falts indiffoluble by balancing acids, may to fome appear new ; but in this cafe, the matter feems demonffrated by fadt, or I am greatly deceived by my own experiments : for according thereto, com- pared with fome natural appearances, the ftonefylng principle in fome waters, the ef- fedts of which are fo often feen, arifes from mineral adds, in conjundlion with that fpe- cies of falts which upon burning natural ftones are found therein. This I could farther explain by feveral experiments, compared with fome obferva- tions f 53 ] tions on the changing hardneffes of ftone^ and ftony matter, in their feveral ftages, from their moifted: fituation in the earth or quarry, to their dried date in the air. But thefe, with many other things of this nature, mud: here be omitted for want of room. There are various other methods of mak- ing artificial done without burning ; as by cementing their parts with gummous and divers other glutinous liquids, or by oily or refinous mixtures; but the infufRciency of all thefe for any good purpofes, renders them undeferving of any farther notice. Having thus run over a few particulars, towards explaining what principles fliould be attended to, in making the mod perfect un- burnt artificial done ; I proceed immediate- ly to the confideration of that fpecies, whofe firm texture is a partial vitrification, or which hath glafs for its bond of cohefion. As I have, in a former part, given fome defcription of clays in general, and therein (hewed, fo far as I have difcovered them, what are the various materials in their com- pofitions ; and as, alfo, by comparing them with certain well known fafe, I have ex- D 3 plained [ 54 3 plained the means whereby they fo con- llaiitly become fuch half-vitrified indiiTolublp fiibfiaPiCcs, after being expofed to fuitablp degrees of heat ; what has been offered may afford fufficient teflimonies touching the nature of burnt earths in general, the permanency of which, when properly fired, is univerfally known by the conftant applir cations thereof to divers purpofes, in nu- fnerous forms, fuch as bricks, tiles, pot- tery, &c. Having, therefore, treated on thefe infer rior kinds, there only remains porcelain, and the befi: artificial ffone, as matters for farther confideration. Thefe laft, being in the Ifridfeft fenfe but one fpecies, and having the fame identical confeituent parts, need no other diffindions, than fine and coarfe ; the degrees of grinding being proportioned to ilich magnitudes as are required in their ap- plication. But the fineft of thefe, being well known as an article in common ufe, and having already been treated of in other books, may here be paffed over, that we may bring forward the principal fubjed in- tended, viz. an explanation or proof of that propq- [ 55 ] propofition, which (lands as a title to this fedion, and may be thus (lated. That kind of artificial (lone, which hath all the requifites hereafter defcribed, is far fuperior, in (Irength and durability, to white marble, or common rock (lone. Thefhorteft method for accomplifhing this, with any tolerable evidence, to thofe who have not hitherto ftudied, upon what principles fuch bodies exift, may be by (irft offering fome general remarks on their ingredients fingly; fecondly, by naming thofe requlhtes which conftitute a found well-fini(hed piece of work; and then, by (riewing whereon thofe requifites depend. Hereby we (liall form diftind heads, the feveral explanations of which will not only lay open the nature of fuch compofitions, but, alfo, prove, that their cohehon is really glafs ; w'hence it muft follow, from common obfervation, and well-known experience, that our firff propo- fition is true, provided things are ponduded as here defer ihed. For though diverfe com- pofitions, called artificial done, have been, and hereafter may be produced by perlbns wholly ignorant of the nature or properties D 4 of [ 56 ] of their ingredients fingly, or of their eftedls when combined yet a competent know- ledge herein, befides conftant circumfpeclion through every operation, is abfolutely necef- fary to the performance of thefe works, with their proper requifites. To proceed, with all poffible clearnefs, it fliould be firft obferved, that thefe expref- fions, vitrifiable, unvitrifiable, too much or too little of vitreous materials, &c. muft be underftood in limited fenfes, meaning only, that they are fuch, or otherwife, as expofed to determined degrees of heat. Again, various combinations, each con- taining feveral ingredients for producing ei- ther partial or entire vitrifications, may be fo compofcd, that fome are glaflified with moderate heats 3 and another fet requires lomething more ; whllft a third clafs de- mands intenfe fire, to awaken their vitreous principles. Hence thefe fubftances attain feveral degrees of hardnefs ; it being ob- , fervable, that glafs and glaffy bodies are more or lefs ftrong, according to the different forces of fire requiiite to their vitrification. Let it be oblerved, bye the bye, that the weakcld t 57 1 weakeft of thefe are known to endure the weather beyond marble. Things being thus premifed, I pafs on, and ohferve that as all clays arc compofitions, fo likewife every combination, made by art, with fimilar in- gredients and properties, may be called clay, though fome particular principles of the firft are purpofely omitted in the laft. Hence we have two claffes of clays, viz. natural, and artificial. Notwithftanding there is fuch an infinite variety of natural clays in this kingdom, not one hath hitherto been found fuflicient, without other ingredients, to make artificial ftone, with all its requifites 3 the reafons of which, regarding their general fpecies, need no mention, being already obvious. Yet there are fome few, which, judging only from appearances, bid fair for the purpofe, being fine, and if in fmall fubjed:s, are, when expofed to moderate heats, of middling firength, and well coloured. Thefe, from experiments, appear in the main thus com- pofed : for a bafis they have fine fands and calxes, much lead and fome tin, both na- turally calx’d, and iron, and firong fluxing falts, blended with bituminous principles, &c. c ail [ 58 ] all which being Intimately united, by long lying together, are become tough and foapy. Hence, in artificial clays they make good auxiliaries, but bad principals ^ it being evi- dent to thofe Ikilled in thefe matters, that this fet of ingredients, proportioned as they are in nature, mu ft be infufficient for large works, the vitrifiable parts being too tender and abundant, as will appear hereafter. This being the cafe, recourfe muft be had to ar- tificial days. Thefe may be divided into two forts 3 one without, the other with, a certain portion of natural clays. The firfi: kinds are mofi: excellent, their component parts being only fuch bodies as are free, both from fluxing and colouring metals, or tinging fulphurs ; or at lead:, pof- fefiing none but what are volatile, like the blacknefs in flints, pebbles, &c. x^nother property of thefe ingredients, is a perfed uni- formity in their effeds, through every ope- ration. The vitreous parts, alfo, are of that fort, before noted for being mofi; obfiinate in the fire, or requiring the ftrongeil heats to vitrify them. Thefe compofitions, when properly burnt, have at once the firength of porphyry. [ 59 ] porphyry, and the brilliant whitenefs of the fineft ftatuary marble ; but, on account of certain inconveniences, they become at pre- fent too expenfive for common ufe : and therefore, till a farther difeovery can be made, for w^orking them with more free- dom, we muft be content with lowering the quality, by mixing fome portion of the natural clay. Thus is produced the next ciafs of artificial clays, the nature of which will more fully appear from the means whereby the following requifites are pro- duced, or their contrary avoided. Good artificial ftone fhould, in the fird: place, retain perfedly the form it receives from the mould ; fecondly, exadtnefs in its dimenfions ; thirdly, it ihould be free from cracks, or fire flaws 3 fourthly, it fhould be equally burnt, or have an even firmnefs throughout its whole fubftance 5 fifthly, it' fhould have but fmall unconnedled pores 5 and lafUy, a bright ftone colour fliopld grace the whole. To begin with the Firfl of thefe, which is a perfedf retenftpn of figure, or maintaijiing exactly [ 6o ] exacily that particular fhape received from the mould ; this may well be efteemed a leading rcqaifite, fince a want thereof renders all the reit utterly ufelefs. In the general relation, concerning this material, it hath been deferibed as a fub- ftance whole cohefion and ftrength depend on a partial vitrification. It is eafy to con- ceive, that there is in thefe compofitions, confidering their intended applications, a ne- ceffity for limiting their vitrification, or ren- dering it but partial; for, were this total, any particular device would be impradlicable, without a very difterent, and more expenlive mode of operation. On the contrary, were the portion of vitreous matters omitted, there would not be the leaf!: degree of ftrength ; and, of the many gradations between thefe extremes, there mufi: be but one that befl maintains a balance ; whence it will appear, that the unvitrifiable ingredients fupply the office of fapporters to their fufible com- panions ; and that thefe two grand prin-- ciples require not their quantities, but their powers, to be in exadt equilibrium ; for the vitrifiable parts being rendered too abundant by [ 6i ] by an intenfe heat, the fupporters will float, and hence diftortions muft enfue. Again, it is requiiite that the unvitrifiable materials be of fuch a nature, that during pro- per heats, they may retain fufiicient firengtb, not only to fupport the neareft adjoining parts, while in fufion ; but alfo, that a fmall portion thereof may fuftain the entire w’eight of the whole fubjeft. There is a difficulty attending this, that exceeds whatever is ob- fervable in any other kindred operation. Eefldes the above-mentioned circumflan- ces, there are a variety of others that are pro- dudtive of deficiencies, not only in this, but alfo in the next reqoifite, to which we pro- ceed, confidering them together, as being nearly conneded. Therefore, Secondly^ Several pieces, delivered from the fame mould, ffiould, when burnt, not only retain exadly equal diaienfions, but alfo poffefs that dimenfion particularly required. Notwithflanding a precife prododion of this requifite is within reach, provided the manufadurer under (lands the conftitution of his materia! i yet, experience hath proved, by E 62 ] by fevefal inflances of miftake, that it de^ mands, in many refpe(fts, a fcrupulous aftnefs, far exceeding what is required in fmaller works of porcelain; both with re-^ gard to the choice, and alfo the adjufting of the proportions of its component parts. For, all clayey compofitions diminifli in their magnitudes by drying and burning; and this diminution not only varies continually^ by diverfity of accidents, either through in-^ equality of moifture during moulding, or by irregular heats in burning. But in number- lefs degrees, according to the very different qualities of natural clays, and the propor- tions thereof, that are incorporated with the other ingredients, all thefe things require condant attention, fince there are compofi-* tions, that by drying and burning, leffen their extent a fourth part ; whilft, on the contrary, others decreafe but a thirtieths That which is made by myfelf, for com- mon purpofes, loofes one part in twenty- three: but even this is no longer certain, than while the manufadlurcr’s eyes are open ; for, the conflitutions of natural clays, not only in diverfe forts, but in feveral famples from [ 63 ] from the fame pit, are fo various and un- certain, that no {landing recipe can^be per- formed 3 every frefh parcel of clay demand- ing new experiments to determine the pro- portions. This abatement of exteniion is the caufe of failure in the next requifite before men- tioned, which was. Thirdly^ Freedom from cracks, or fire- flaws. Though thefe are frequently but of fmall confequence, they fhould, if poiTible, be avoided, being defeds : yet, in fome pieces, they are almofl unavoidable, there being few fubjeds that have not, by neceffity, their entire weight fuftained only ^by fome one part. Confequently, the whole is not equally at liberty to decreafe its extent 3 and hence, in ponderous fubjeds, notwithftanding di- verfe contrivances, and much care, chafms or flaws will fometimes happen. Nor is this marvellous, when it is confidered, that, at the very inllant the cafts are delivered from their moulds, a diminution commences, 3 [ 64 1 and continues not only through drying, with- out, but alfo in the furnace, until their moifture is entirely exhaufted. Then the encreafing heat immediately produces an ex- paniion, w^hich afcends in conjundlion with the fire, making the calls exceed the limits of their firft moift flate, (provided the com- pofition lofes not more than a twentieth part of its volume.) Again, falling from in- tenfe heat until quite cold, they defcend to a lefs extent than at their greateft unburnt drynefs. Yet, notwithiranding thefe great, and nearly fudden changes, many fubjedls are produced perfedly found. ' Fourthly^ An equal, and almoft impene- trable, firmnefs, throughout the whole fub- fiance, is a moil: important requifite in that material which deferves the name of artifi- cial ftone 5 a deficiency herein being certain deftrudlion, when expofed to much moiflurc ^and fevere frofts. For whatever fubjedls have only their furfaces hardned, whilft their centers remain fcarce any thing more than dried clay, muft, by the hrft moifl feafon, be furnifhed with water fufficient to pervade, and [ 65 ] and fill all their interfiices, fo as to increafe the volumes of their unburnt centers, which, immediately, or in the firfl: fevere froft, muft burft to pieces the enclofing crufts : to ex- plain which, it is well known, that clay, being only dried, increafes its volume upon the accefiion of moifture j and experience teaches, that when thefe fine clayey bodies , are burning in fubjeds of confiderable thick- nefles, they attain a red heat on their furfaces, fome time fooner than in their centers, and if their vitreous ingredients are of the ten- dereft clafs, an external vitrification com- mences too foon; and, of confequence, there muft be, either an unequal ftrength, or the luperficies are damaged in hardening the in- ternal fubftance, or, at beft, much time and fuel muft be fpent in burning, to gain but a poor produdion. Therefore, to avoid thefe but too common errors, and bring forth pro- per effeds, the vitrifiable ingredients ftiould be of the rnoft obdurate clafs, by which means fcarce any degree of fufion will be produced, until the heat is intenfe. Hence the pores are kept or left open till an equal force of fire hath penetrated the whole fub- E ftance [ 66 ] ftance; and then, one pitch of heat per- forms, nearly all at once, the required vitri- fication. It muft be granted, that compofitions thus formed, are, in the fire, rather hazardous : but _no buyer will complain hereof, fince the danger lies altogether on the fide of the manufacflurer. For any thing lefs then a due pitch of heat will leave the fubjeds too foft or weak, even on the furface ^ and therefore difcover- able : whilfl: on the contrary, a fmall matter too much of fire will melt down and deface the whole. By this choice of ingredients, and by nice- ly adjufting their proportions, a fmall piece, only a quarter of an inch in thicknefs, de- mands the fame degree and even durance of heat with others of the largeft required magnitudes. Fifthhy The pores"' fhould be fmall and unconneded, thereby denying to water that free admiffion and palTage, which frequently occafions inconveniencies in natural done. ' The [ h ] The advantages ariling from this requifitc are eafily comprehended, fince it renders this material much fuperior, for diverfe pur- pofes, to moft others in prefeiit ufe. The means produdive hereof are de- fcribed under the foregoing requifite; for that being properly effedfed, this follows of coLU’fe, Yet, as there are compofitions which, by nature, mufl: either be dcfedlive herein, or injured in other refpedts by burning; and as fome fpecimens thereof have been, and may again be offered to the public, an ob- fervation or two thereon may not appear unneceffary. When the vitreous matters are not only of the tendered: clafs, but alfo in too fmall quantities fufficiently to envelope the unvi- trifiable ingredients, the cohelion mufl: be weak, eonfifting only in a few paints of contadl, thereby leaving the pores large and continued, as in the loofeft natural ftone. And if fome of the unvitrified parts are nearly^ and others wholly calx’d, which is too much the cafe where raw fand is a large ingre- dient, fuch ftone muft imbibe moifture with E 2 near [ 68 ] near the greedinefs of common lime, be- fides having or being liable to all the defeds mentioned under the foregoing heads, and w^iil, at beft, be no better than ordinary earthen ware. Such are thofe compofitions whofe greateft excellence ischeapnefs, having for their prin- cipal parts natural clays, the other ingre- dients being only employed as openers, to fave the fubjeds from flying to pieces through a Ipeedy acceflion of the fire. Thefe, pro- vided they have but a cafe-hardening heat, will to the eye appear very fair. But a fair appearance fhould be produced by much better means than flack burning, as will be feen under the next requiflte, which was, LaJUy^ A bright flone colour^ neither the dull rednefs of common terra cotta’s, nor a chalky whitenefs, being efteemed agreeable. A brilliant colour in the finer branches of porcelain-making is reckoned one principal requiflte; and, except glazing, is the only thing wherein the Englifla have been ex- celled by the Chinefe. The difficulties herein arife from our Britifh clays, which contain too confiderable 2 P01‘- [ 3 portions of tinging mineral fulphurs^ lead and iron. But the effedls of thefe principles become ftill more obvious, when expofed to that durance of intenfe heat requifite to burning large fubjeds^ the two firft producing a heavy yellowifh opacity, and the lad, becoming an imperfect or foul crocus martis^ yields a dull red colour ; to remedy which, as well as other inconveniencies already mentioned, the fmalleft quantity poffible of natural clay fhould be ufed, and the other ingredients chofen as deferibed under the head of pure artificial clays. By thefe means, a fmall pro- portion of thofe colouring being difperfed among larger quantities of coloiirlefs mate- rials, they only Ijaread an agreeable tlndure over the wholes and notwithftanding thefe compofitions are fomething more expenfive than thofe under the foregoing head, their additional beauty and ftrength fufficiently balance the account. What I have advanced concerning the feveral requifites of the mod perfedl artificiai done, may be fafely depended upon, being the refuk of aftual experiments, made with E 3 clofc [ 70 ] €lofe attention, and is a real defcriptlon of the compofition which I make for common ufe. From hence it is very obvious, that the principle of cohefion and ftrength, in all, and every kind of burnt ea^th, is a partial vitrification ^ or in other words, that the bond which unites and holds together their parts, from the coarfeft brick, to the fineft porcelain, is neither more, nor lefs, than real glafs : all the various denominations of thofe bodies partaking of one common nature, and differing only in degree of perfedion. It follows too, that the fiirength of a com- pofition will be proportionate, to its finenefs or purity, provided always it be fufficiently burnt; for a due degree of heat mufi: ever be confidered as effential to ftrength ; and where that due degree is attained, I think I have demonftrated, that thofe bodies w^e have been confidering, are equal, if not fu« perior, to any known natural bodies, in point of durability. This truth has as many fads and monuments to fapport it, as would fill a volume to appeal to them diftindly. Some are known to have frood near three thoufand, others [ 71 ] Others from two to one thoufand years 5 not to mention abundance of later date, in a!- moft all parts of the world : and there is no reafon to be affigned why that which is now made, fliould not be as durable as the oldeft of thefe monuments. But as I am convinced, that the bed compofition in the world mud fail, unlefs thoroughly burnt, I would drongly recommend to all whom it may concern, that they take a little pains to become judges in this particular. The ex- periment I propofe to them is ea(y and cer- tain. Get of the manufadurer a piece of his burnt compofition, not lefs than an inch thick, break it, and put one half in warm water for fome hours, increafing the heat of the water to boiling: then break the wa» tered piece, and it is foon difeovered if the center and fuperficies are equally hard ; and if the wet piece be as hard as the dry. If no failure is found under this ted, it is properly burnt, and will never decay in the weather. Were this caution duly attended to, the manufaflure of artificial done would become E 4 more [ 72 ] more exteniive and ufeful than mofl: people are aware of. Of the Ufe and Application of Artificial Stone. S I would treat my fubjed: impartially. I fhall begin with pointing out the inconveniencies which attend it. And it is eafy to conceive, that a compdition made foft enough to caft in a mould, out of which it is to be taken while moid, ihould incur much hazard, and occafion much trouble, v/hen thrown into a form, whofe length is difproportioned to its thkknefs. To give a more determinate idea of the difproportion I fpeak of, I (hall juft mention, that I have produced a piece, near four feet long, nine inches broad, and two inches thick, which was quite ftraight and found ; bu." the ex- traordinary hazard and trouble attending fuch piece, through every operation, after its difcharge from the mould, till it goes into the fire, as well as the danger of warping while in it., mufl: of courfc add to the expence. Pieces [ 73 3 Pieces that are very large and unweildy, have alfo as many inconveniencies, and thus far the ufe of artificial ftone, may feem to be more limited than the natural. But thefe difadvantages are counterbalanced by a pro- perty in the former of holding cement, with a firmnefs fuperior to the latter ^ and the joints may be made as fine as in any mate- rial whatever, fo that if a fubjedl be too long for its bulk, or too large for convenient management, it can be cut into feveral pieces, and fo joined after burning, as to appear one in tire ftone. Again, as thofe productions are caft in moulds, and the price of the model and mould muft fall on the cafis that are made from it ; fo upon fingle fubjeCts there can be no great faving of expence, unlefs modelled in the compofition itfelf, which in fome cafes may be done with advantage: or elfe, when the fiibjeCt is fo important, that a fia- tuary would make a perfeCt model in clay, before he carves it in ftone; then the mak- ing a mould from that clay, and fo pro- ducing a caft, would fave expence on a fingle fubjeCt, Once more : In plain mafonry, fuch as [ 74 ] plinths, facies and fhafts of columns, Tuf- can bafes and capitals, and things of like workmanfhip, there will be little or no faving. We have now been conGdering artiGcial ftone under its greateft poffible difadvan- tages 3 notwithftanding which, it has a juG: claim to the attention of every builder, not only on account of fuperior ftrength and beauty, but of cheapnefs alfo, and that in every kind of ornamental work. The faving here is very conGderable over natural Gone, and that in proportion to the enrichment. As for inftance, more in the pound will be faved in Corinthian than in Ionic capitals, and more in thefe than in Doric, BeGdes, things which are fcarce pradic- able in natural Gone, or not without pro- digious expence, may be produced in this compoGtion at a very moderate rate. In Giort, the artificial Gone here offered to the public, is equal to every wifh of the curious, being little inferior to marble in ap- pearance 3 not fo liable to damage by a blow 3 when broken, it may be joined with more eaie and Grmnefs3 and if ever fo foul, may be [ 75 ] be cleaned without the leaft injury' to the furface. The defire of thofe gentlemen in particular is hereby gratified who have been long in fearch for a material that would en- dure the weather, in order to have cafts from the beft antique ftatues, buftos, vafes, &c. placed on the outfides of their build- ings, and in their gardens : an end which cannot be anfwered by plaifter of Paris, neither by lead, in which, as it requires fre- quent painting, the charader is foon loft. Thus may the moft admired works of antiquity be tranfmitted to the lateft pofte- rity. I cannot avoid mentioning another cir- cumftance in this material favourable to the curious, which is, that in forming a figure, group, or any fiibjed whatever, it is eafy to make perforations of various fizes and di- redions, in a manner almoft, if not quite impradicable in any other fubftance : fo that fuch as are defirous of playing fountains, may indulge the moft luxuriant fancy with- out much extraordinary expence. Nor is it lefs adapted to infide than outfide orna- ments. As a fpecimen I ftiall only mention chimney^ [ 76 3 chimney-pieces, now to be feen at the ma- nufaftory, which may with great propriety be_ brought into the moft elegant buildings, being only to be exceeded by ftatuary- marble itfelf. It would be endlefs to enumerate the fub- jedls of curiofity and ufe in which the appli- cation of this material would obviate thofe objedions which lay againft the execution in other materials : the judicious obferver will foon make the difcovery, the manu- fadory being open to his infpedion. POST- [ 77 ] POSTSCRIPT. S INCE the foregoing work was finlihed and in the prefs, many frefh inftances of difingenuity, prejudicial to this manu- failure, have occurred, which obliges me to enlarge on a hint mentioned in the laft page of the Introdudlon. Many of the mafons, and fome other workmen, particularly the lefler mafters, (for fome of the greater deferve praife) not- withftanding they are confcious of fuperior merit in this manufadture, yet are ufing their utmoft efforts to overturn it ; and that by pradices fo mean that I am almoft afhamed to mention them. One meafure they take is by deterring mo- dellers from working for the manufadory* telling them that they will ’be defpifed by the whole trade, as forwarding a work it is their intereft to fupprefs. Again, when their employers lignify an inclination to ufe this material, they imme-> diately [ 78 ] diately cry out, O Sir ! why will you have artificial ftone ? nature muft certainly be better than art ; it is but an imitation, and a meer makefliif t Is it not more to your credit to have real ftone than to ftick up lumps of earthen ware ? This I have known to be the cafe after they have been fent by gentlemen to examine the material, and when, before my face, they have been forced by conviddion, againft: their will, to acknowledge its great fuperiori- ty to the beft Portland. Even after all this, they have gone back to their employers, and prejudiced them againft it by the above falfe reprefentations. Much more of this fort might be pro- duced, but this may fuffice to caution gentle- men againft yielding implicitly to what their workmen fay. Were it worth while to re- tort, I might afk whether our forefathers called the introdudlion of glafs in windows a makeftiift, as this was artificial, and horn was natural; and I might, alfo, with juftice call the ufing natural ftone a makeftiift, and as poor a one too, in comparifon with arti- * This tetm has been greatly ufed. 2 ficial. , [ 79 ] ficial, as It would now be called to ufe horn for windows inftead of glafs. What is it but a makelhifr, for perfons, againft their inclinations, to alter defigns, and put up with an inferior order of architedlure, or abate fome of the ftandard ornaments of a fuperior, to fave expence in carving ; whilft in arti- ficial ftone, there would need no fuch altera- tion in defign, or abatement of ornament? Certainly I am not too bold in afferting that there is fcarce in this kingdom (except the perfons above-mentioned) a man to be found fo weak as, after due examination, to be- ftow carving on any kind of Englifh rock- ftone whatever. Some perfons, in order to hinder the pro- grefs of this work, have aflferted that it will not endure above feven years. I hereby call upon fuch perfons to prove their affertions, provided they do it publicly^ for I will not enter into private debates. THE END. .»■ ., y aJ -V'. - -t , f 41 . >f i:'’hr- If, .- > -A^\' , ., -j- T-i.^3!'.. /:en*v;}.,f;v'. %■ -If I' ■^.. 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