118 Mr, Vivian's Account of the [Feb. 



and the oxides of iron and other metals that were mixed with 

 the copper. The oxide of iron gives them a black colour. The 

 silex or quartz remains in part unfused, and gives the slags a 

 porphyritic appearance. 



In this process, the copper is concentrated, and a mass of 

 stuff with which it was combined in the ore got rid of. The 

 granulated metal usually contains about one-third of copper. It 

 is thus four times as rich as the ore, and must consequently 

 have diminished in bulk in the same proportion. Its chief com- 

 ponent parts are sulphur, copper, and iron. 



The most important point to be attended to in this process is to 

 make a fluid good mixture of earthy and metals, so that the copper 

 which is combined with the sulphuf-, may from its greater specific 

 gravity, settle at the bottom, and yield clean slags. This object 

 is effected chiefly by means of metallic oxides, the slags from 

 Process 4, which are melted with the ore, being almost wholly 

 black oxide of iron. When the ores are very stubborn or diffi- 

 cult to melt, a box of fluor spar is added to the charge, but it is 

 not desirable to increase the bulk of matter in the furnace unless 

 required. 



The men work round the 24 hours, and commonly melt in this 

 time five charges. Under favourable circumstances, as fusible 

 ore, strong coal, furnace in good repair, they even do six charges. 

 They are paid by the ton. 



Process III. — Calcination of the Coarse Metal, the Product of 



the first Fusion. 



This is conducted in precisely a similar manner to the calcin- 

 ing of the ore The charge is nearly of the same weight ; but as 

 it is desirable to oxidize the iron, which is more readily effected 

 in this process than in the ore calciners, where it is protected 

 from the action of the air by the earthy matters with which it is 

 combined, the charge remains 24 hours in the furnace, and dur- 

 ing that time is repeatedly stirred and turned. The heat during 

 the first six hours should be moderate, and from that time gra- 

 dually increased to the end of the operation. 



Process IV. — Melting of tht Coarse Metal after it has under- 

 gone Calcination. 



This is performed in furnaces precisely similar in construction 

 to those in which the ore is melted ; and with the calcined metal 

 are melted some slags from the last operations in the works which 

 contain some oxide of copper, as likewise pieces of furnace bot- 

 toms impregnated with metal, the proportion of each varying 

 according to the stock or to the quality of the calcined metal. 



The chemical effect which takes place is, that the oxide of cop- 

 perin the slags becomes reduced by a portion of the sulphur which 

 combines with the oxygen, and passes off as sulphurous acid gas, 

 while the metal thus reduced enters into combination with the sul- 



