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being here needed ; nor any Thing, but to put them in the Fire"; Where the Lead evaporating, leaves the Silver pure. The Indians, who, till the Arrival of the Spaniards, knew nothing of the Uie of Mercury, melted none but of this Kind of Mineral. The Roffcler, is another black Mineral diflinguifhed by whetting and rubbing it againft Iron, which turns it red. 'Tis very rich, and the Metal it yields, of the beft Sort. The Loroche burns like Talc, and looks as if filvercd ; tho' it does not yield much. The 'Pace is a yel- low red, very foft, and found almoft broke in Pieces; 'tis not rich. The CobriJJo is green, and half friable. Tho' the Silver be vifible, yet 'tis exceedingly difficultly drawn from it, by Realbn of the Copper wherewith 'tis intermixed. Laftly, the Arannear, which is only found in Potofi, and that only in the Mine of Cotamito, eonfifts of Thteads of pure Silver, interwove like a Silver Galoon, that has been burnt to get out the Silk.
The Silver-Veins, of what Quality foever, are ufually richer in the Middle than towards the Extremes. But the richeft Places are thole where the Veins interfect. 'Tis reckoned a gteat Addition to the Richnefs of a Mine to be near a River, for the Advantage of Mills to grind Oar. At Lipes and Potofi, for Jnflance, the Caxon of Oar null yield Ten Marks to defray Expenccs ; whereas, at Lanava, there need not above Five.
The mod ufual Way of feparating the Silver from the Oar, is by what they call <pigues. See Pignes. Some- times, however, they ufe nothing but Fire frequently repeat- ed ; or Aqua Fortis.
What renders the Working of rhe Mines exceedingly dan- gerous, is the Exhalations arifing from them ; which are even felt on the Out fide ; and make an Impreflion on Ani- mals grazing in the Neighbourhood ; but in the In-fide, ilupify the Miners, none of whom can bear lb poifonous an Air above a Day together. Sometimes 'tis lo fatal, that it kills, on the Spot ;' and obliges them to (lop up the Veins again, whence it exhales. 1'he Mines of 'Potofi, are much the lead fubiccl to them ; and yet, without the Herb 'Para- guay, the Infufion whereof is taken by the Miners, as we do rhat of Tea, thole Mines mull be foon abandoned. Tho' the Mines of Potofi and Lipes, flill keep up their Reputation, yet are there leveral diicovered within thefe few Years, that exceed them much in Richnefs .- Such are the Mines of Oruro, Eighty Leagues from Arica, and thofe of Ollachea, near Cl'fco, opened in 17 12. 'Tis rematkakle, that mod of the Mines in America are found in cold and barren Places.
The Method of Separating Silver from the Ore, in Europe, is the lame as that of Gold: That is, by Means of Quick- silver ; with this Difference, that for Silver, ro every Fifty Hundred Weight of Ore, is added One Hundred Weight of Rock-Salt, "or lome other natural Salt. That curious Operation may be feen at length under the Article Gold.
To feparate the Silver from the Mercury, wherewith 'tis amalgamated; they have a Furnace open a-top ; and the Aperture covered with a kind of Capital made of Earth, of a Cylindrical Form ; that may be clapp'd oe, or taken off at Pleafure. The Mais of Silver, and guick-filver, being laid in the Furnace, the Capital applied, and the Fire light- ed underneath ; by this Means, the gtiick-filver rais'd by the Action of the Fire, in Form of Vapour, is caught in the Capital, and taken thence, to be ufed in the Second Ope- ration.
The Standard of fine Silver is 12 Penny-weights, each confiding of 24 Grains. When 'tis below this, it mull be raifed to it by Refining; which is uiiially performed by means of Lead. In order to this, a Coppel is fill'd with a Mixture of Brick allies, and Afhes of a Bullock's and other Bones. 'Tis fct on the Fire, and heated red hot ; in which State the Sliver and Lead are put in together, in the Proportion of a Pound of Lead to Eight Ounces of Silver, and even lomewhat more Lead, if the Silver be very coarfe. As thefe Two Metals melt together, the Copper, be- fore mixed with the Silver, diffipates in Smoak, or goes away with the Scum ; and lb does the Lead it lelf; leaving the Silver alone in the Coppel, in its proper Degree of FUaenefs. In this Method of Refining, wherein 6 or 7000 Pounds may be refined at once ; the Metal is drawn out of the Coppel Two ways ; the one by plunging in it, while flill liquid, a thick Bar of Iron, round which, the Silver flicks in Form of a Shell, or Crud ; repeating this again and again : The other, is by letting the Coppel ftand till 'tis cold ; in the Bottom whereof, the Silver fixes in Form of a Cake.
Befides the Refining of Silver with Lead, there is ano- ther Manner of doing it with Salt-Petre ; the Manner whereof, fee defcribed under the Article Refining.
But both the one and the other are tedious and trouble- fome ; when performed on large Quantities. This occafion- ed M. Homberg to endeavour to fhotten the Operation ; which he effected with good Succefs. His Method is; To calcine the Silver with Half its Weight of common Sul- phur 5 and aftet melting the whole together, to call a Quan-
tity of Steel Filings upon it, at feveral Times : Upon this- the Sulphur quits the Silver, and joins it lelf to the Iron and both are converted into Scoria, which fwim on the&/- <ver$ and the Metal it lelf is found pure at the Bottom of the Crucible.
The Effay of Silver is alfo made by the Coppel, in the fame Manner as the refining by Lead. It the Silver, after this Effay, preferve its Weight, 'tis Standard ; if it lofe, the Grains, or even Penny-weights of its Diminution, are account- ed. See Essay : See alio Standard.
SiLVER-H-'«'e, is Silver drawn thro' the Holes of a Wire- drawing-iron, and by this Means reduced to the Finenefsof a Thtead or Hair. The Manner of drawing it, lee under the Article Gold-wire.
SiLVER-Zea/, is that the Gold-beaters have reduced in. to fine, thin Leaves, to be tiled by Gilders, s£c. See Gold- Leaf.
o7?e//-SitvER, is made of the Shreads of Silver Leaves, or of the Leaves themfelves : Ufed inPainting and Silvering cer- tain Works. Shell-Silver is prepared after the fame Manner as Shell-Gold. See Gold.
Silver, inChymillry, is called Luna, Moon ; and leve- ral Preparations are made from it : Particularly, a Lintlure of Silver, by diffblving thin Silver Plates, or Silver Shot in Spirit of Nitre ; and pouring the DifTolutian in another Veffel full of Salt-water. By this Means, the Silver is im- mediately precipitated in a very white Powder, which rhey wadl feveral Times in Spring- Warer. This Powder they put in aMatrals ; and pour reef ified Spirit of Wine, and Vola- tile Salt of Urine upon ir. The whole is left to diged in a moderate Heat for Fifteen Days ; dufing which, the Spirit of Wine affumes a beautiful Sky-blue Colour, and becomes an Ingredient in feveral Medicines. This is alfo called 'Potable Silver, or Argentina To-labile. Silver is likewilb converted into Crydals, by means of the lame Spirit of Ni- tre ; and 'tis this is called Vitriol of Silver. The Lapis Iufer- nalis is nothing but Silver diffolved in Aqua Fortis, and left to crydallize.
^f«'f/t-SiLvER. See Mercury.
Silvering, the Covering of any Work with Silver- Leaf. 'Tis ufual to Silver Metals, Wood, Paper, gfc. Which is performed either by Fire, by Oil, or by Glue. Metal-Gildctsy?/-jer by the Fire: Painter-Gilders, all the other Ways. See Gilding.
SILVESTR1S, a red Grain ufed to Dye in Scarlet. The Tree that produces it, is peculiar to the Province of Guatimala in ive-iu Spain. 'Tis not unlike the Tree that produces the Cochineel, only in this, that the Fruit con- taining the Grain Silveftris, is fomewhat longer than that of the Cochineel-Tree : When the Fruit of the former is ripe, it opens of it felf, and calls out its Seed upon a gentle lhaking ; and the Fildians gather it in Eatthen Plates fet under the Tree for the Purpofe. Eight or Ten of thefe Fruits do not yield above an Ounce of Seed ; whereas Four of the Cochineel Fruits, yield an Ounce of Inlecfs. The two Drugs are much like one another, as to the Eye, but prove very different ; the Tincture of Cochineel being infinitely more beautiful than that of Silveftris : See Cochineel.
SIMA, in Architecture, a Term ufed by Wdjkis, and fome other Writers, for what we otherwife call Cymatium or Simatmm. See Cymatium.
SIMAT1UM or SIMAISE, in Architeflure : See Cy- matium. Simatmm and Cymatium, are generally con- founded together ; yet, in effect, they ought to be diflin- guifhed : the latter being the Genus, and the former the Species. Simatium of Sima, cainous, according to Felibien, is the laft and uppermoff Member of grand Comiches, cal- led particularly the great 'Doucine or Gula retla ; and by the Greeks, Fpithides. In the Antique Buildings, the Simatium, a top of the Doric Corniche, is generally in Form of a Cavetto, or Semi-Scotia; as we fee particularly in the The- atte of MarcelhlS: This, fome modern Architects have imi- tated ; but in the Ionic Order, the Simatium is always J IDoucine. The Simatium, or Doncine, then, is diftingui/hed from the other Kinds of Cymatia, by its being camous.
S1MEL1UM, a Term purely Latin, lignifying a lit* Table, with Ranges of little Cavities therein, for rhe dtt- poling of Medals in Chronological Order. The Word, is but ill wrote: It mould rather be Cymelium, as be'"g formed of the Greek Ks/!«Ai», Curiofities, or a Cabinet ot precious Things. We more ufually lay, A Cabinet of Me- dals, than a Simelium.
SIMILAR, in Arithmetic and Geometry. Thofe Things are laid to be Similar, or alike, which cannot be diftm- guifli'd but by their Com-prefence ; that is, either by j™? ^ diately applying the one to the other, or lome other Third to them both. There is nothing, therefore, found in one of the Similar Things, but is equally found in the other ; that is, if you note all the Things 'in A, which may oe difcerned and conceiv'd, without affirming anv other; an > in like Manner, note all the Things in B. which may
