304 METALS. 



on the continent of Europe, the ore, after being pounded and assorted, 

 is piled up in high pyramidal mounds, which mounds are covered with 

 mortar, sod, &c, and have a chimney at the center. Hemisphc ricaJ 

 cavities are dug on the upper surface for the purpose of receiving the 

 sulphur during the roasting, which arrives liquified at the surface. This 

 process lasts about six months. In England, at Swansea, where the 

 ores are carried for reduction, the calcinations are performed more rap- 

 idly in a reverberatory furnace ; and this is especially necessary when 

 the ores' do not contain a sufficient proportion of iron pyrites to furnish 

 enough sulphur to sustain the combustion. After calcination, the ore is 

 black and powdery. In the Swansea establishments, the calcined ore 

 is introduced into the furnace, (a reverberatory smaller than that used 

 for calcination,) and is spread over the bottom, 1 cwt. at a time. The 

 heat is raised, and the furnace closed. When fusion has taken place 

 the liquid mass is well rabbled or stirred, so as to allow of the complete 

 separation of the slags from the metal ; afterwards the slags are skimmed 

 off. Then a second charge is added, and after a similar process, a 

 third charge, if the furnace is deep enough to receive it without the 

 metal's flowing from the door. After the last charge is reduced also, 

 the tap-hole is opened, and the metal flows out into water, where it is 

 granulated. The slags if not free from metal are again returned to the 

 furnace, when other charges are put in. This granulated metal is 

 usuaily about one-third copper ; it contains sulphur, copper, and iron. 



This coarse metal is next calcined, just as the ore was first calcined ; 

 by which the iron is oxydized. The charge remains in the furnace 24 

 hours, and is repeatedly stirred and turned. 



It is then transferred to the furnace for melting, and there melted 

 along with some slags from the previous fusion. The sulphur reduces 

 any oxyd and the whole fuses down. The slags are skimmed off and 

 the furnace tapped : the metal is again drawn off into water. In this 

 state it contains about 60 per cent, of copper, and it is called fine 

 metal. The fine metal is then calcined like the coarse metal ; and next 

 it is melted as before. It results in a coarse copper containing 80 to 90 

 per cent, of pure metal. 



The coarse copper is then roasted in the melting furnace ; the air 

 drawing in large quantities over the copper in incipient fusion, oxydizes 

 the iron and the volatile substances are driven off. The metal is fused 

 toward the end of the operation, which is continued from 12 to 24 

 hours, and is then tapped into sand beds. The pigs formed are cov- 

 ered with black blisters and they are cellular within. The copper is 

 then remelted in a melting furnace ; it is heated slowly to allow of any 

 farther oxydizing that may be necessary. The slag is removed and the 

 metal is examined from time to time, by taking out soms of it, and 

 when it is in the right condition, it is next subjected to the process of 

 toughening. It is now brittle, of a deep red color inclining to purple 

 with an open grain and a crystalline structure ; the copper in this state 

 is what is termed dry. The surface of the melted metal is first cov- 

 ered with charcoal ; a pole, commonly of birch, is held in the liquid 

 matter, causing considerable ebullition ; and this poling is continued, 

 with occasional additions of charcoal, till it is found in the assays taken 



What are the several steps in reduction ? 



