1823.] Process of smelting Copper. 121 



to render it malleable, or, as it is termed, to bring it to the 

 proper pitch. The copper in this state is what is termed 

 dry. It is brittle, is of a deep-red colour inclining to purple, 

 an open grain, and a crystalline structure. In the process 

 of toughening, the surface of the metal in the furnace is first 

 well covered with charcoal. A pole commonly of birch is then 

 held in the liquid metal, which causes considerable ebullition, 

 owing to the evolution of gaseous matter, and this operation 

 of poling is continued, adding occasionally fresh charcoal, 

 so that the surface of the metal may be kept covered until from 

 the assays which the refiner from time to time takes, he perceives 

 the grain, which gradually becomes finer, is perfectly closed, so as 

 even to assume a silky polished appearance in the assays when 

 half cut through and broken, and is become of a light-red 

 colour. He then makes further trial of its malleability by taking 

 out a small quantity in a ladle, and pouring it into an iron mould, 

 and when set, beating it out while hot on the anvil with a sledge. 

 If it is soft under the hammer, and does not crack at the edges, 

 he is satisfied of its malleability, or as they term it, that it is in 

 its proper place, and directs the men to lade it out, which they 

 do m iron ladles coated with clay, pouring it into pots or moulds 

 of the size required by the manufacturer. The usual size of the 

 cakes for common purposes is 12 inches wide by 18 in length. 



The process of refining or toughening copper is a delicate 

 operation, requiring great care and attention on the part of the 

 refiner to keep the metal in the malleable state. Its surface 

 should be kept covered with charcoal, otherwise it will go back 

 between the rounds of lading, the cakes being allowed to cool 

 in the pot, and others laded thereon. In this case, fresh poling 

 must be had recourse to : over-poling is to be guarded against, 

 as the metal is rendered thereby even more brittle than when in 

 the dry state. Its colour becomes a light yellowish-red ; its 

 structure fibrous. When this is found to be the case, or as they 

 say, gone too far, the refiner directs the charcoal to be drawn off 

 the surface of the metal, and thus by taking down the side door, 

 and exposing the copper to the action of the air, it is brought 

 back to its proper pitch ; that is, it again becomes malleable. 



Are we to conclude from this, that copper in its dry state is 

 combined with a minute portion of oxygen? or that some oxide 

 of copper is diffused through, or combined with, the metal; that 

 it is deprived of this by poling, and is then rendered malleable ; 

 and that, when gone too far, it is combined with a minute portion 

 of carbon; that, like iron, either substance will render it brittle, and 

 that it is only malleable in a certain intermediate state when free 

 from both carbon and oxygen ?* Or is the effect of the pole merely 



• Another indication of the presence of oxygen in the dry copper, is afforded by tic 

 extraordinary action which it has upon the iron took ; they become bright, like iron in 

 a smith's forge, and are consumed much more rapidly than when the copper is in a 

 malleable state, 



