116 Mr. Vivian's Account of the [Feb. 



Process I. — The Calcination of the Ore. 



The copper ores, when discharged from the vessels in which 

 they are brought from Cornwall, are wheeled into yards or plots 

 contiguous to the works, and there deposited, one cargo over 

 the other, so that, when cut down perpendicularly to be carried 

 to the furnaces, a tolerably general mixture is formed of the ores 

 of the county. This is always desirable in a smelting work, as, 

 the ores being of different qualities and component parts, the one 

 acts as a flux for the other. A more accurate mixture, calculated 

 from the chemical analysis of each parcel of ore, might be prefera- 

 ble; but this on a large scale cannot be practised, as it would be 

 impossible to keep the ores separate, on the different wharfs in 

 Cornwall, to ship them separately, and to have sufficient space on 

 the wharfs at the works to receive them. 



The ore in the yard is weighed over to the calciner-men 

 in boxes, containing each one hundred weight. These are 

 carried on men's shoulders to the calciners, and emptied 

 into iron bins or hoppers, formed by four plates of cast iron 

 tapering to the bottom, placed over the roof of the furnace, and 

 supported by wrought iron frames resting on its sides. From 

 these bins, the ore is passed into the calciner through a hole in 

 the roof immediately below the bottom of the hopper. Two of 

 these bins are usually placed over each calciner, and nearly 

 opposite the side doors, so that the charge of ore, when let into 

 the furnace, may be conveniently spread, which is done by means 

 of long iron tools, called stirring rabbles. 



This charge of ore usually consists of three to three and a half 

 tons. It is distributed equally over the bottom of the calciner, 

 which is made of fire bricks or square tiles. The fire is then gradually 

 increased : so that towards the end of the process, which lasts 

 12 hours, the heat is as great as the ore will bear without being 

 fused or baked together. To prevent this taking place, and to 

 assist the disengagement of the sulphur, the ore is frequently 

 stirred during the operation, and fresh surfaces exposed. At the 

 expiration of the 12 hours, the charge is drawn out through holes 

 in the bottom of the calciner, of which there is one opposite to 

 each door, and, falling under the arch of the furnace, remains 

 there till it is sufficiently cool to be removed, when water is 

 thrown over it to prevent the escape of the finer particles ; it is 

 then put into barrows, and wheeled to the proper depots. In this 

 state it is called calcined ore. If the process has been well 

 conducted, the ore is black and powdery. The dark colour is 

 no doubt owing to a portion of the iron being oxidized during 

 the process, by which the ores acquire an increased degree of 

 fusibility. The quantity of iron oxidized during the first calcina- 

 tion is, however, small in proportion to the contents in the ore, 

 as the metal is protected from the action of the air by the mass 

 of earthy matter with which it is combined, and by the sulphur 



