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the profit was to depend on tlie. lead alone. Itmay be further obferved that the filver is forthe molt part accompanied by antimony whichhardens the lead and greatly deteriorates itsquality except this ingredient is driven off;now the only economical method of getting ridof it is by the very fame procefs by which thefilver is obtained; thus a double advantage en-fues, the fiver is feparated from the lead, andthe lead by being at the fame time deprived ofthe antimony, is rendered fofter and more mar-ketable.

The proportion of filver contained in galenais extremely variable. The richeft that wehave heard of was formerly dug in BrunghillMoor in the diftrift of Craven in Yorkfhire ;it contained about 230 oz. of filver per ton oflead. The Cardiganfhire mines, near Plinlim-mon, in the reign of Charles I. afforded a leadwhich yielded Ko oz. per ton. The Durham and Weftmoreland leads, by which the North-umberland refineries are at prefent fupplied,yield upon the average about 17 oz. of filverper ton. The large refinery at Poullaouen inBrittany , is fupplied with lead of various quali-ties, the average produce of which, exceeds 39oz. per ton. Of the different procefles carriedon at this eftablifhment, an excellent accounthas been publifhed/ of which we fhall give anabridgement, noticing at the fame time, thofeparticulars in which it is inferior to the beftEnglifh pradlice.

The ore, which is very largely mixed withgangue, is firft drefled by hand and afterwards{tamped and waffled by means of the commonapparatus. Being* thus brought to the confift-ence of fand, and containing, befides argentifer-ous galena, a fmall portion of blende, of ironpyrites and of the earthy gangue, it is deliveredto the fmelter. The reduction of the ore iseffected at two proceffes; the firft, which isroafting, is performed in a common reverbera-tory. Here it is expofed at firft to a brightred heat, which however is gradually dimi-niflied as the fulphur is volatilized for fear ofbringing the mafs to a ftate of fufion. Inabout an hour’s time the furface of the orebegins to clot, which is the fignal for turning itover with long fpades, in order to expofe frefhfurfaces to the adfion of the heat. If this bu-fmefs is duly performed, in about five or fixhours the fulphureous vapours will have nearlyceafed, and in confequence, the flame playingon the furface of the ore will have changedfrom blue to reddifli white, thus fhewing that

f Beaunier & Gailois in _

the roafting is compleat. The fecond procefscommences by throwing upon the furface ofthe half-oxydated ore a few fpadefuls of char-coal, and puflung the fire vigouroufly; by thistreatment, globules of melted lead begin toexude and collect in a mafs in the cavity orbafon of the furnace, with the unreduced partfloating on its furface. In about an hour, oran hour and a half, a fufficient quantity ofmelted metal is colledled for the firft running;upon which a little quicklime is thrown in,which coagulates the fluid fcorise, and thefe be-ing raked to the fide, the bafon is pierced withan iron bar, and difcharges the melted metalwhich it contains into a hemifpherical refervoiradjoining the furnace. The channel formedby the bar is now clofed with clay, and inabout an hour after the firft running a fuffici-ent quantity of metal is collected in the bafonfor a fecond, which is performed exactly in thefame manner as the firft. In proportion as thefeoff® become more and more poor, a greaterheat is required to keep them fufficientiy fluidfor the globules of reduced lead to fall readilythrough, fo that after from eight to nine run-nings have been taken it is not worth while toexpend any further quantity of fuel uponthem ; they are accordingly removed from thefurnace, and another charge of frefh ore is im-mediately thrown in. The lead after it hasflowed from the furnace into the refervoir iscovered with pulverized charcoal, and remainsuntouched for fome time, that the fcorias andother impurities may rife to its furface; whenthis has taken place, the fubftances floating onthe metal are fkimmed off, and its furface iscovered with fawduft and fmall chips of wood,to which is added, by fmall pieces at a time,about 1 f lb. of rofin; in the mean time themelted metal is ftirred about vigoroufly tocompleat its purification; as foon as the flamedeclines, the lead is removed with iron ladles,and poured into moulds. A fingle charge ofore weighs about 26 quintals and yields about13 i quintals of metal and more than 7 quintalsof fcorix, containing 30 per cent, of metal,which are reduced by a fubfequent procefs in ablaft furnace.

The lead being thus extradted from the ore,the next thing to be done is to obtain the filverin a feparate ftate which is diftufed through thewhole mafs of lead; for this purpofe cupella-tion muft be had recourfe to. I11 the articleAssay we have noticed the theory of cupella-tion, and the method of performing it in the'ourn. des Mines, No. 93,