Zinc iJesilverizaliun. 85 



on an average 250 oz. of silver, are produced. The prices paid 

 for the silver in the ore in June, 1874, were for medium ore, 

 containing 25 per cent, of lead, for 100 oz. ore, $0,834 per oz. ; 

 for 200 oz. ore, 11.01; for 500 oz. ore, 11.17. In addition, the 

 freight to the works is paid, if it does not exceed $15.00 per 

 ton. One dollar per ton additional is ])aid for each unit of lead 

 above 25 per cent, and deducted in the same way. 



At the works of the Pennsylvania Lead Company, ores are no ■ 

 longer ti-eated, but silver lead and material containing silver are 

 purchased from all parts of the United States. The shaft-fur- 

 nace is used both for smelting the crasses and for the concentra- 

 tion of the copper matte which is produced from the residues con- 

 tciining copper. As the construction of this furnace is interest- 

 ing from several points of view, a drawing of it is given in 

 Fig. 3. It has charging-doors at two different levels, the lower 

 one. A, being used for the matte, and the upper, B, for the 

 ordinary crasses. There are thus two furnaces of different 

 heights in the same structure. The lower opening is bricked 

 up, and its charging-floor is not used while the crasses are being 

 charged. When sufficient matte has accumulated, the lower 

 charging-door, A, is opened. The upper part of the furnace 

 then serves only as a chimney. The lower part of the furnace is 

 built of common brick, laid up in ordinary mortar by a common 

 mason, up to the mantel, which is about eight feet from the 

 ground. Just under the mantel, a pipe with jets at short dis- 

 tances throws water over the surface of the outside of the brick, 

 the excess of which is caught in a trough. This water keeps the 

 furnace cool. The bricks melt off to within three or four inches 

 of the outside and then remain at this thickness. There are 

 four tuyeres, two at the back and one on each side. Three of 

 these are of phosphor bronze, and one of iron, which answers 

 just as well as the bronze. 



To put the furnace into blast, the hearth is filled with coal or 

 coke, and lighted, and this is kejjt up for three days, or until 

 the brasque is red hot. The blast is, during this time, blown in 

 through the Arendt's tap, C. When the furnace is ready, this is 

 filled with a plug of wood in which a hole is bored. The whole 

 crucible of the furnace is then filled with melted lead. The 

 furnace itself is then charged with one-third coke. When the 



