168 Mr. H. L. Pattinson on Smelting Lead Ore, 8$c. 



a high temperature, and Lead, under the same circumstances, becom- 

 ing rapidly converted into the state of a protoxide ; which, when form- 

 ed in the large way, is called Litharge. The refining process is 

 therefore performed, by exposing the Lead containing Silver to a strong 

 blast of air, at a high temperature, in a furnace properly constructed to 

 allow the Litharge to separate as it is formed, and to admit of the con- 

 tinual introduction of Lead as the operation proceeds, and the ready 

 removal of the cake of Silver obtained at the end of the process. 



The furnace for this purpose is called a Refining-furnace, a plan, lon- 

 gitudinal section, and cross section, of which, Plate I. Figs. 2, 3, and 

 4, very clearly display its construction. It is a small reverberatory 

 furnace, the fire-place of which A, Plate I. Fig. 4, is very large, com- 

 pared to the size of its body B, rendering it capable of exciting an in- 

 tense heat. Some of the objects to be attained in the construction of 

 this furnace already stated, render it necessary that its bottom should 

 be moveable, in consequence of which, an open space is left quite 

 through under the body of the furnace, from back to front, which is 

 formed by two walls of brick work a b, Figs. 2 and 4. The distance 

 of these walls in front, at a b, Fig. 4, is 36 inches ; but they approach 

 together at the back of the furnace, and at g h, Fig. 2, the space be- 

 tween them is but 28 inches, which, to prevent a draught of cold air 

 underneath the furnace bottom, is closed with iron doors. At the 

 height of 16 or 17 inches from the floor two strong iron bars are laid 

 across between these walls, and firmly secured in the brick-work at each 

 end ; both these are shewn at c c, Figs. 2 and 3, and the front one at c, 

 Fig. 4. Above these bars, and at the height of 27 inches from the 

 floor, a plate of cast iron, having an elliptical opening in the middle, 

 the transverse and conjugate diameters of which are 46 and 28 inches 

 respectively, is laid across, from wall to wall, as shew at d d, Plate I. 

 Fig. 2, and in section at d d, Figs. 3 and 4. Instead of a square plate, 

 as shewn in the figure, a broad elliptical ring, supported by bearers, is 

 sometimes used ; but, in either case, the brick-work forming the body 

 of the furnace, is built upon this plate, and is made to extend to, and 

 surround, the edge of the elliptical opening ; except a small aperture 



