014 



COPPER 



construction ; they vary in their dimensions and in the number of their openings 

 according to the operations for which they are intended. There are five of them : 1. 

 The calcining furnace, or calciner ; 2. The melting furnace ; 3. The roasting furnace, 

 or roaster; 4. The refining furnace ; 5. The heating or igniting furnace. 



1. The Calcining Furnace rests upon a vault, c, into which the ore is raked down 

 after being calcined ; it is built with bricks, and bound by iron bars, as shown in 

 the elevation, ./fy. 501. The hearth, B v,figs. 502 and 503, is placed upon a level with 

 the lower horizontal binding bar, and has nearly the form of an ellipse, truncated at 

 the two extremities of its greater axis. It is horizontal, bedded with fire-bricks set 

 on edge, so that it may be removed and repaired without disturbing the arch upon 

 which it reposes. Holes, not visible in the figure, are left in the sole before each 

 door c c, through which the roasted ore is let fall into the subjacent vault. The di- 

 mensions of the hearth B B, vary from 17 to 19 feet in length, and from 14 to 16 in 

 breadth. The fire-place &,jig. 503, is from 4J to 5 feet long and 3 feet wide. The 

 bridge or low wall b, fig 504, which separates the fire-place from the hearth, is 2 feet 

 thick, and in Messrs. Vivians' smelting-works is hollow, as shown in the figure, and 

 communicates at its two ends with the atmosphere, in order to conduct a supply of 

 fresh air to the hearth of the furnace. This judicious contrivance will be described in 

 explaining the roasting operation. The arched roof of the furnace slopes down from 

 the bridge to the beginning of the chimney/, figs. 501, 503, its height above the hearth 

 being at the first point about 26 inches, and from 8 to 12 at the second. 



Such calcining furnaces have five doors, cccc, fig. 503, and one for the fire-place, 

 as shown at the right hand in fig. 501 ; four are for working the ore upon the reverbera- 

 tory hearth. These openings are 12 inches square, and are bound with iron frames. 

 The chimney is about 22 feet high, and is placed at one angle of the hearth, as at/, 

 fig. 503, being joined by an inclined flue to the furnace. 



For charging it with ore, two hoppers E E, are usually placed above the upper pirt 

 of the vault, in a line with the doors ; they are formed of four plates of iron, 

 supported in an iron frame. Beneath each is an orifice for letting the ore down into 

 the hearth. 



These furnaces serve for calcining the ore and matts: for the latter purpose, indeed, 

 furnaces of two stories are sometimes employed, as represented in fig. 507. The 

 dimensions of each floor in this case are a little less than the preceding. Two doors, 

 cc,fig. 501, correspond to each hearth, and the workmen, while employed at the upper 

 story, stand upon a raised moveable platform. 



2. Melting Furnace, figs. 505 and 506. The form of the hearth is, in this case, also 

 elliptical, but the dimensions are smaller than in the calcining furnace. The length 

 does not exceed 11 or Hi feet, and the breadth varies from 7 to 8. The fire-place is, 

 however, larger in proportion, its length being from 3J to 4 feet, and its breadth from 

 3 to 3 ; this size being requisite to produce the high temperature of the furnace. It 

 has fewer openings, there being commonly three ; one to the fire-place at D, a second 

 one, o, in the side, kept generally shut, and used only when incrustations need to be 

 scraped off the hearth, or when the furnace is to be entered for repairs ; and the third 

 or working door, G, placed on the front of the furnace beneath the chimney. Through 

 it, the scoriae are raked out, and the melted matters stirred and puddled, &c. 



The hearth is bedded with infusible sand, and slopes slightly towards the side door, 

 to facilitate the discharge of the metal. Above this door is a hole in the wall of the 

 chimney (fig. 506) for letting the metal escape. An iron gutter, o, leads it into a pit, 

 K, bottomed with an iron receiving-pot, which may be lifted out by a crane. The pit, 

 M. is filled with water, and the metal becomes granulated as it falls into the receiver. 

 These melting furnaces are surmounted by a hopper r, as shown fig. 505. 



