the Sulphureous we of Copper hy Lead, 1^7 



filver. Hence the graduated arrangement of the chemical attraftions of fulphur, with r*r 

 fpedl to the metals mentioned, is as follows : 



SULPHUR, LEAD, 



IRON, SILVER. 



COPPER, 



6. When the fulphur is faturated with copper, it can no longer diffolve any portion of 

 lead and filver. 



7. Silver and lead have a very ftrong chemical attradion for each other. 



Inferences from thefe fundamental Principles, 



From thefe aflertions, unqueftionably proved by experience, it follows, that if copper-mat^ 

 the fulphur of which (the proportion having been fo much altered by roafting, as to be fatu- 

 rated with copper, is made to be penetrated by lead in fufion, the lead muft then take up all 

 the filver which it contains, and in fuch a manner, that no part of the lead can be diflblvcd 

 by the fulphur contained in the copper-mat. 



But it would be very wrong to conclude, that the filver can be completely extrafted 

 from thisroafted copper-mat, mftelyby fubjefling the lead, together with the copper-mat 

 to a melting heat. For the le-ad, on account of its eafier fufibility, would melt fooner than 

 the copper-mat, fink down to the hearth of the furnace, and by its greater fpecific gravity 

 always remain beneath the fufed copper-mat; and confequently it would deprive this laft 

 of its filver merely at the furface, with which it is in contaft, and no farther. If, there- 

 fore, it be wiflied to obtain the intended obje£l, it will be neceflary that the fluid copper- 

 mat (hould be forced to rife through the lead in fufion, and to penetrate it entirely. 



It is on this circumftance, that the charafteriftic and moft eflential part of my new 

 method depends. 



It confifts in the management, by which the copper-mat (duly roafted, and in which the 

 fulphur is faturated with the copper) is made to rife immediately, and during Its fufion 

 through the melted lead. I might call this new method an amalgamation of fufed topper-mat 

 ivith fufed lead. 



The poffibility of efFcfting the conditions, requifite for this purpofe, appears very eafily 

 from hydroflatical principles. — Let the fpace of the outward floor, or hearth B, Fig. i, 

 Plate VIII. be conne£ted with the cavity of the furnace A, by means of a hole (o). Now 

 if there be only melted lead in the furnace, it will ftand on the outward hearth, equally as 

 high as in the furnace itfelf. Suppofe its horizontal furfaee to be as marked {be); then if 

 the melted copper-mat in the interior furnace A, which is of lefs fpecific gravity, be aboVc 

 that height, it will rife by the laws of the equilibrium in the outward hearth B. 



The fecond chief condition is obtained, by an eafy management of the fire employed to 

 effeQ the fufion. This melting furnace has a recurved bottom, and is provided with an 

 outward hearth, {Vorderheerd) and a draining hearth {Stichheerd) . Its eflfential form of 

 oonftrudlion is fuflTicientlylhewn in die drawing, before referred to. In this manner the 



U 2 hearth 



