120 Mr. Vivian's Account of the [Feb; 



other metals still combined with the copper are oxidized. The 

 charge is from 25 to 30 cwt. The metal is fused towards 

 the end of the operation, which is continued for 12 or 24 

 hours, according to the state of forwardness when filled into 

 the furnace, and is tapped into sand beds. The pigs, are 

 covered with black blisters, and the copper in this state is known 

 by the name of blistered copper. In the interior of the pigs, the 

 metal has a porous honeycombed appearance, occasioned by the 

 gas formed during the ebullition which takes place in the 

 sand beds on tapping. It is in this state fit for the refinery, the 

 copper being freed from nearly all the sulphur, iron, and other 

 substances, with which it was combined. 



Another mode of forwarding the metal for the refinery, still 

 practised in some works, is by repeated roastings from the state 

 of blue or fine metal ; this, however, is a more tedious method 

 of proceeding. 



The oxidizing processes, whether conducted in a calciner or 

 furnace, depending on the admission of atmospheric air into the 

 body of the furnace, are greatly assisted by a patent, the exclu- 

 sive right to which we purchased of Mr. Sheffield, the inventor, 

 by which a constant stream of fresh air is kept passing over the 

 metal. This is effected by means of a channel formed in the 

 middle of the bridge, communicating with the external air at its 

 two extremities, and with the interior of the furnace by square 

 holes formed in the bridge at right angles with the channel. 

 This has a very powerful effect in forwarding the process, and 

 not only promotes the oxidation of the metals, but has the effect 

 of igniting and consuming the coal smoke, assists in the disen- 

 gagement of the sulphur, and, by keeping the bridge cool, admits 

 of a more regular heat throughout the furnace. 



Process VIII. — Refining or Toughening. 



The refining furnace is similar in construction to the melting 

 furnaces, and differs only in the arrangement of the bottom, 

 which, is made of sand, and laid with an inclination to the 

 front door instead of to one side, as is the case in those furnaces 

 in which the metal is flowed out ; the refined copper being 

 taken out in ladles from a pool formed in the bottom near the 

 front door. The pigs from the roasters are filled into the fur- 

 nace through a large doorln the side. The heat at first is mode- 

 rate, so as to complete the roasting or oxidizing process, should 

 the copper not be quite fine. After the charge is run down, 

 and there is a good heat on the furnace, the front door is taken 

 down, and the slags skimmed off; an assay is then taken out by 

 the refiner with a small ladle, and broken in the vice ; and from 

 the general appearance of the metal in and out of the furnace, 

 the state of the fire, Sec. he judges whether the toughening pro- 

 cess may be proceeded with, and can form some opinion as 

 to the quantity of poles and charcoal that will be required 



