Page:Cyclopaedia, Chambers - Volume 2.djvu/467

 POR

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POR

The Chinefe make another Kind of Porcelain, which they paint and bake twice; and for this fecond Baking they have a kind of little Ovens on purpofe. When very lmall, they are made of Iron ; otherwile, of a kind of Bricks an Inch thick, a Foot high, and half a Foot broad; made of the fame Earth with the Porcelain Cafes. The biggett ot thefe Furnaces does not exceed five Foot in Height, ana three in Diameter; and being made much in form ot Bee- Hives the Bricks are arch'd a little, to form the Catyity the better. The Hearth is of Earth half a Foot high, form'd of two or three Ranges of Bricks; and on this Maf- five is the Furnace built. Around the Furnace, at the dirtance of about half a Foot, is rais'd a Shell of common Bricks, join'd to the Furnace itfelf, by a kind of Arcbou- tant of Earth, which ferve to ftrengthen it. They ufual- ly build four or five of thefe Furnaces at equal Diftances from each other. At the bottom of the Shell are Holes to give Air to the Fire when lighted : A-top is an Aper- ture, which they cover up with a piece of the baked Earth, when the Porcelains are laid in the Furnace.

The Porcelains, here, are not inclos'd in Coffins, as in the common Furnaces; the Furnace, itfelf, ferving that purpofe; and being fo exaftly clos'd, that they receive no other Impreffion of the Fire, but that of the Heat of the Charcoal difpos'd in the Hearth, at the bottom of the Fur- nace, as well as a-top of the Vault, and in the Interval between the Furnace and the Shell, or Brick- Wall.

To prepare the Porcelains for a fecond Baking, they muft have had their Varnifh in the common manner, and have pafs'd the great Furnace : In this State they are painted with various Colours, after which, without gi- ving them any new Varnilh, they are rang'd in Piles in the little Furnace ; fetting the little ones over the larger, in form of Pyramids.

This fecond Baking is fometimes intended to preferve the Luftre of the Colours the better, and at [the fame time to give them a kind of Relievo. But more ufually, its Defign is to hide defective Places, by covering them over •with Colours : But the Artifice is ealily found out, by paf- fing the Hand over them.

When the Workman judges his Porcelains enough baked, he takes off the Piece that covers the Aperture ; and if the Works appear glittering, and the Colours glowing, he takes out theChatcoal ; and when the Furnace is cold, the Por- celain too. .

How beautiful foever the modern Porcelain may be; the Taeft for Antiquity, which reigns in China, as well as in Europe, gives the antient Porcelain a Value far above that of the modern t It muft be own'd, the Antient feems finer as to the Matter, more perfect as to the Baking, and of a more pleafant Calf, both as to the White of the Ground, and the other Colours; yet 'tis certain the moft able and difcerning may be deceiv'd herein : And there are Workmen who make it their bufinefs to counterfeit the antient Porcelain, call'd Koutom, in the modern.

The Matter of thefe falfe Koatoms is a yellowifh Earth, found near Kimtetchim : There is nothing particular in the firfl part of the Procefs, except that they are made thicker, and that they are varnifh'd with an Oil drawn from the yellow Stone, mix'd with the common Oil, which gives them a kind of Sea-green Hue. When taken out of the Furnace, they throw it into a fatty Broth, made of Capons, igc- in which they boil it a fecond time ; they then bury it in the filthieft Sink they can find for a Month or fix Weeks, or more, according as they would give it the grea- ter appearance of Antiquity. Befides their Thicknefs and their Colour, thefe falfe Antiques referable the true ones in this ; that they do not refound when ftruck, nor even give the leaft buz, when held to the Ear.

Notwithflanding the vaft Quantity of Porcelains made in almoft all the Provinces of the Empire of China ; they ftill continue very dear ; tho' not near fo dear, as antiently. The Chinefe Annals tell us of Times wherein a fingle Urn coft ninety or an hundred Crowns on the fpot. What chief- ly occafions the extraordinary Price of this Commodity, efpecially in Europe, is, befide the great Profits of the Merchants in Europe, and their Factors in China ; that it rarely happens a Furnace fucceeds rhroughout; that it is frequently quite fpoilt, fo that upon opening it, in lieu of fine Porcelains, is found a hard unform'd Mafs, into which both the Porcelains, and their Coffins, are converted either by Excefs of Heat, or fome ill Qualities in the Matter.

Another reafon of the Dearnefs of Porcelain, is, that the Ingredients it is made of, and the Wood wherewith it is burnt, grow more and more fcarce : One may add a third reafon for the exceffive Price of Porcelains to the Europeans ; and 'tis this, that moft of thofe fent to Europe are form'd on new Models, frequently very odd, and dif- ficult to fuccced in ; which, yet, for the fmalleft Defects, are turn'd on the Manufact urer's hands : and he not being able to difpofe of them to the Chinefe, becaufe not to their

Tafte, nor for their Ufe, Is forc'd to charge the Porcelain he delivers, the higher, to pay himfelf for thofe refus'd.

The French have been thefe fifteen Years attempting to imitate Porcelain ; The firft Effays made at Rouen,' ate faid to have fucceeded tolerably well ; and M. Saveiy tells us, are now carry'd to fuch a point in the Manufac- turies of Faffl, and S. Cloud, that the French Porcelains want nothing to make them of equal Value with the Chinefe, but to be brought five or fix thoufand Leagues, In effea, for the Finenefs of the Grain of the Matter, the Beauty and Form of the Veffels, the Exactitude of the Defign, and the Luftre of the Colours, at leaft the Blues; the French are not much behind the Chinefe. But their grand Defect is in the White of the Ground, which is u. fually dingy and dull ; and eafily diftinguifhes itfelf from the pure fprightly White of the Chinefe.

Porcelain; is alfo a kind of little white Sea-fhell, found along with the Sponges ; and current in feveral Parts of AJia, Africa, and America, by way of Money. See Coin.

Authors have hitherto been of opinion, that thefe Shells were the Matter whereof the Porcelain, or CteM-Ware, was made. They are of fome ufe in Medicine, and are pre- ferred pounded or broken, in manner of Pearls. See Pearl.

PORCH, a kind of Veftible fupported by Columns; much ufed at the Entrance of the antient Churches, Tem- ples, $3c. See Vestible.

In the antient Architecture, Porch was a Veftible, or a Difpofltion of infulated Columns, ufually crown'd with a Pediment, forming a Covert Place before the principal Door of a Temple or Palace,

When it had four Columns in Front, it was call'd a 1e- traftyle ; when fix, Exajlyle ; when eight, Oiloftyle ; when ten, Decaftyle, iSc.

Vitruvms calls it Pronaos and Prodomos. When it has Iron Gates, it is call'd PropyUum.

PORE, a little Interftice, between the Particles of Mat- ter which conttitute Bodies; either empty, or fill'd with fome infenfible Medium. See Body and Matiee.

Condenfation, and Rarefaction, are only perform'd by doling and opening the Fores. See Rarefaction and Condensation.

The Tranfparency of Bodies is ufually fuppos'd to arife from their Pores being directly oppofite to one another. See Transparency.

The Matter of infenfible Perfpiration is convey'd thro' the Pores of the Cutis. See Perspiration.

The Word Pore is form'd from the Greek »o{©-, Aper- tltre, or 2)ucJ, thro' which a Thing paffes.

Sir Ifaac Newton fhews, that Bodies are much more rare, and porous, than is commonly believ'd : Water, e.gr. is 19 times lighter, and confequently rarer than Gold ; and Gold itfelf is fo rare, as very readily, and without the leaft oppofition, to tranfmit Magnetic Effluvia, and ea- fily to admit Quickfilver into its Pores, and to let Water pafs thro' it : for a concave Sphere of Gold hath, when fill'd with Waterj and folder'd up, upon preffing with a great Force, ler the Water fqueeze thro' it, and itand all over its outfide, in multitudes of fmall Drops like Dew, without burfting or cracking the Gold: whence it may be concluded, that Gold hath more Fores than folid Parts ; and by confequence that Water hath above forty times more Fores than Parts. See Gold.

The Magnet tranfmits its Virtues without any Diminution or Alteration, thro' all cold Bodies that are not magnetic; as Gold, Silver, Brafs, Glafs, Water, £i?e. See Mag- net.

The Rays of Light, let them be either Bodies actually coming to us from the Sun, or only Motions or Impreffions upon the Medium, move in right Lines, and are hardly e- ver, unlefs by grear chance, reflected back again in the fame right Line, after their Impingence upon Objects ; and yet we fee that Light is tranfmitted to the greateft Diftances thro' pellucid Bodies, and that in right Lines. See Ray, &c.

Now how Bodies fhould have Pores fufficient for thefe Effects, may be difficult to conceive, but not impoflible : For Sir Ifaac ftiews, that the Colours of all Bodies arife from their Particles being of fuch a determinate Size or Magnitude. Wherefore, if we conceive thofe Particles to be fo difpos'd, as that there is as much Porofity, as there is of Matter ; and in like manner thofe Particles to be com- pos'd of others much lefs, and that have as much in- terfpers'd Vacuity or Space, as their Quantity of Matter amounts to ; and fo on, till we come to folid Particles with- out Pores : then, if in any Body there be (for inftance) three of thefe Sizes of Particles, and that the laft be of the folid, or leaft fort ; that Body will have feven times as much Vacuity as folid Matter. If four fuch Degrees, and the laft be leafli and folid, that Body will have fifteen

times