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in moft parts, and is a fure mark of the fterility of the foil. 

 Its llalks fpread upon the ground, and fend out roots from 

 their joints; by which means, and by frequent (hcdding of 

 its feeds, as it flowers during the whole fummer, it foon 

 over-runs, and fills the land to a great diftance. Its leaves 

 are compofed of feveral lobes or wings, which are generally 

 placed along the mid-rib, and terminated by an odd one : 

 they are jagged at their edges, and are of a filvery colour, 

 efpecially on their under fide. It has been noticed by Mr. 

 Ray, that the root is fomewhat of the tap-rooted or parfnip 

 kind, and that hogs are very fond of feeding upon it. 



Silver, IVhite-hart. See White-hakt i'/Virr. 



Silver IVirs, is filver drawn through the holes of a wire- 

 drawing iron, and by this means reduced to the finenefs of 

 a thread or hair. The manner of drawing it, fee under the 

 article Gold /r«rc. See alfo Wire, andDuAwi.MG. 



Silver Bltiff', in Geography, a headland on the coaft of 

 South Carohna, at the mouth of the river Savannah. 



Silver Caya, a duller of rocks, lo miles S. of Grand 

 Cayes. 



Silver Creek, a river of America, in Kentucky, which 

 runs into the river Kentucky, N. lat. 37° 41'. W. long. 

 84° 40'. 



SILVER-GRAIN, in Vegetable Phyfwiogy, is defcribed 

 by Mr. Knight, Phil. Tranf. for 1801, 344, as confilling 

 of numerous thin plates, " diverging in every direftion from 

 the medulla to the bark, having little adhefion to each other 

 at any time, and lefs during fpring and iummer, than in au- 

 tumn and winter ; whence the greater brittlenefs of wood 

 in the former feafons." The fame writer remarks, that 

 thefe plates are vifible in every wood which he had examined, 

 except fome of the Palm tribe ; but are of a different width 

 in different kinds, lying between, and prefTing upon, the 

 fap-veffels of the alburnum. It may be obferved, that in 

 the oak " every tube is touched by them at ihort diltances, 

 and nightly diverted from its courfe. If thefe," continues 

 Mr. Knight, " are expanfible under changes of temperature, 

 or from any caufe ariling from the powers of vegetable life, 

 I conceive that tliey are as well placed as is poffible, to pro- 

 pel the fap to tiie extremities of the branches ; and their 

 reftlefs temper, after the tree has ceafcd to live, inclines me 

 to believe, that they arc not made to be idle whilll it con- 

 tinues alive." In fupport of this opinion, we would re- 

 mark, that the plates in qutllion are found where the fpiral 

 coats of the fap-vellcls either no longer exilt, or have loft 

 their clafticity. See Circulation of the Sap. 



SILVERING, the covering of any work with a thin 

 coating of filver. This operation is recommended by two 

 circumltaiices ; -viz.. the fuperior beauty of filver to that of 

 the cheaper metals, and alfo its fuperior wholefomenefs to 

 copper, braf';, or lead, for culinary purpofes, as it is not 

 corroded by vinegar and other weak acids. 



Silvering may be performed on the fame fiibllances, and 

 by fimilar methods with gilding ; which fee. But as works 

 or this kind are liable to taniilh and fpcckle, they are fel- 

 dom uled. But when this i'. the cafe, the coating of filver 

 fliould be much thicker than that of gold, becaufe other- 

 wife tiie fridtioii which is necedary for removing the tarnilh, 

 would foon wear off the filver fr.)m the mon. prominent 

 parts, and expofe to view the fiibjacent copper or brafs. 

 In order to avoid this inconvenience, fome have recom- 

 mended, when filverijig is admitted, a ilrmig varnilh, formed 

 of fome of the compofitions of mallic, landarac, the gums 

 animi or copal, and white rofin, to be put over it. 



The varnifti recommended in filvering leather may be ap- 

 plied to other jjurpofes. See Lacquer. 



The filver powder, called urgentum mufivum, may be either 



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tempered, in the manner of the fhell-gold, with gum-water, 



or rubbed over a ground properly fized ; and it will take a 

 very good pohfli from the dog's tooth or bumilhers ; and 

 hold its colour much better with a flight coat of varnifh over 

 it, than any true filver powder or leaf. 



The fizes for filvering, when they are ufed for this par- 

 pofe, ought not to be mixed, as in the cafe of gold, with 

 yellow, or bole armoniac, but with fome white fubitance, 

 whofc cffeft may prevent any fmall failures in covering the 

 ground with the filver from being feen. This may be done 

 with flake-white, or white-lead, when tiie fizes formed of 

 oil are ufed ; but whiting, or tobacco-pipe clay, with a little 

 lamp-black added to it, is the proper matter in the burnifli 

 fize for filvering, or wherever the glovers' or parchment fize 

 is ufed. 



It is ufual to filver metals, wood, paper, &c. 



The only metals to which filvering is applied are copper 

 and brafs, and very rarely iron ; and there are three modes 

 of performing this operation, -viz. hy amalgamation, by mu- 

 riated fil-vcr, and hy fdvcr in fubjiance. 'i'\\e Jirjl mode is 

 performed by adding plates of copper to a folution of ni- 

 trated filver, which will precipitate the filver in its metallic 

 Itate, and very finely divided ; fcrape this from the copper, 

 and let it be well wafiicd and dried. With half an ounce of 

 this powder, of common fait and fal ammoniac two ounces, 

 and one drachm of corrofive fublimate, well rubbed together, 

 make a parte by the addition of a little water, then clean the 

 vellel to be filvercd with a fmall quantity of diluted aqua 

 fortis, or by fcouring it with a mixture of common fait and 

 tartar. Rub it, when perfeftly clean, with the palte already 

 mentioned, until it is entirely covered with a white metalhc 

 coating ; which coating is an amalgam produced by the de- 

 compofition of the corrofive {ublimate bv means of the cop- 

 per, to the furface of which it applies very clofely and ex- 

 peditioufly. The copper thus filvered over is then to be 

 wafhed, dried, and heated nearly red, for the purpofe of 

 driving off the mercury : the filver remains behind and ad- 

 heres firmly to the copper, in a Hate capable of receiving a 

 high polilh. Thcyffonrf method of filvering is that by luna 

 cornea. For this purpofe, prepare the luna cornea in the 

 ufual manner, by pouring a folution of common fait into ni- 

 trate of filver, as Jong as any precipitation, occurs and boil- 

 ing the mixture ; then mix the white curdy matter thus ob- 

 tained with three parts of good pearl-a(h, one part of wafhed 

 whiting, and a little more than one part of common fait. 

 After the furface of the brafs, cleared from fcratches, has 

 been rubbed with a piece of old hat and rotttn ftone, in 

 order to remove any greafe, and then moillcned with fait 

 and water, a little of the compofilion, being now rubbed on 

 with the finger, will prefently cover the furface of the metal 

 witli filver. Then walh it well, rub it dry with loft rag, 

 and then, as the coat of filver is very thin, cover it with 

 tranlparent varnifli to prelerve it from tarnilh. .As this kind 

 of filvering is very impcrfetl, it is only ufed for the faces of 

 clocks, the fcales of barometers, or fimilar objects. (See 

 Luna Corma.) The third moiic of performing this opera- 

 tion is by means of filver in fubllance: and of doing this 

 there are three different methods. The firll is by mixing 

 together 20 grains of filver precipitated by copper, two 

 drachms of tartar, two drachms of common fait, and half a 

 drachm of alum ; and rubbing this conipofition on a per- 

 fectly clean lurface of copper or brafs will cover it witli a 

 thin coating of filver, which may be polilhed with a piece 

 of foft leather. Another and better method, called French 

 plating, conlills in buriiilliing down upon the furface of the 

 copper fucccllive layers of leuf-filvcr to any required thick- 

 nels. Altho'igh the Clver m this operation is more folid 



than 



