and the Inconvenience of AJh Cupelh. 21^ 



the head, and, having luted it round with foft clay, make 

 fire in the fire-hole as for the common operations of refining. 



When the lead is in complete fufion, and the mafs is 

 covered with fcum and charred ftraw, make the fcum or 

 drofs run off by the gutter for the litharge with a bit of 

 board al)out a foot in length, in the middle of which is faft- 

 ened a rod of iron of fufiicient length to ttaverfe the furnace 

 and about a yard more. 



When the lead has been well fcummed feveral times, and 

 becrins to be red, make the bellows aft, but at firft gently ; 

 ari-ange the nozzles of them in fuch a manner, that the wind 

 ifluinir from both may be dircfled to the centre of the cu- 

 pell ; and in order that the wind may be always reverberated 

 on the mafs, adapt to the extremity of each nozzle a fmall 

 round piece of iron plate. This kind of valves, which the 

 French refiners call papUlons, is employed for refining 

 according to the German method. They are fufpendc by 

 hinges at their upper part : at each ftrokeof the bellow- they 

 are half raifed, and they reverberate the wind on the lead, 

 which accelerates its oxidation. 



After all the drofs or fcum is removed, and when the lead 

 has become exceedingly red, and covered with a ftratum of 

 litharce, form, with a fmall iron hook deRined for that pur- 

 pofe, a fmall gutter in the fand of the cupell, which muft be 

 dug deeper, gradually and with caution, until the bottom of 

 it be on a level with the mafs. The litharge then, driven by 

 the wind of the bellows towards the anterior part of the fur- 

 nace, will run by this gutter and fall on the floor of the foun- 

 drv, as is the cafe in the common operations of refining. 



When the refiner obferves tliat no more litharge remains 

 in the neiglibourhood of the gutter, he will Hop the flowing 

 ott'with a fmall quantity of moiftened afhes : but as foon as 

 the lead again becomes covered with oxide, the gutter muft 

 be opened, and mull be dug in proportion to the diminutioa 

 of tliemafs, taking care that no lead efcapes, and particu- 

 larly towards the end of the operation ; for it would carry 

 with it a irreat deal of filver, which would be loft. You mull 

 proceed in this manner till the filver has acquired its vivid 

 colour; taking care to increafe the fire in proportion to the 

 diminution ot the mafs; efpecially when the operation is 

 nearly terminated, becaufe the lilver then is collefted toire- 

 ther : and, as it is much more dillicidt to be kept in fufion 

 than ilie (mail quantity of lead which remains united with it, 

 it could be refined only in an imperfedl manner at an infuf- 

 ficient temperature; and inftcad of alK)ut a twentieih of lead, 

 which the filver generally contains in the German refining- 

 O 4 lioules, 



