METALLURGICAL COLLECTIONS. 
93' 
oxidised copper ores and slags ; and the white metal , or pimple 
metal , resulting from this fusion yielded, on roasting, a crude 
variety of copper, called blister copper , which was subsequently 
refined by exposure to oxidising influences in a reverberatory 
furnace. During these operations the sulphide of iron in the 
ore was converted into an oxide, which, combining with the 
siliceous matters present, formed a fusible slag ; and the iron 
being thus removed, the sulphide of copper suffered decompo- 
sition, its sulphur being evolved as sulphurous acid, whilst the 
oxide of copper (cuprous oxide), formed during refining, was 
reduced in the final operation of toughening. The Welsh process, , 
more or less modified, is still extensively employed. 
In the process of toughening, the surface of the copper is well 
covered with anthracite, and a pole , usually of green birch, is 
held in the liquid metal, the evolution of gaseous matter causing 
considerable ebullition. This operation of poling is continued 
until the metal is found to be in the best condition. The 
operation requires great care ; both under poling and over 
poling being found injurious. Some specimens in this case 
illustrate Mr. Weston’s process of refining copper by addition 
of a compound of copper and phosphorus. 
Copper passes into the market in the conditions of cake (ingot) 
and sheet copper of various descriptions. Granulation may be 
effected by pouring the metal in a molten state into a vessel 
pierced with holes, supported over a cistern of water. When it 
falls into hot water the copper assumes a rounded form, and is 
called bean shot, and when into cold water, from its assuming a 
ragged appearance, it is called feathered shot. Copper is also 
cast, chiefly for exportation to the East Indies, in pieces of the 
length of six inches, and weighing about eight ounces each ; 
these are called Japan copper . 
Table Case 38. — In this Case are exhibited some specimens 
illustrating certain Continental processes of copper smelting. 
The treatment of the remarkable Kupferschiefer or copper- 
slate (p. 78) is here illustrated. This schist, which is extensively 
smelted in the neighbourhood of Mansfeld, in Prussian Saxony, 
contains on an average not more than three or four per cent, of 
copper, with a small proportion of silver, about lOlbs. to the ton 
of copper. After calcination for a considerable time in large 
heaps, the ore is mixed with a certain amount of slag and flux in 
the form of fluor-spar, and the mixture smelted in a blast furnace ; 
the product being subjected to successive roastings, until at 
length a concentrated regulus is obtained from which the silver 
is extracted, and the copper-bearing residuum subsequently 
smelted, At the time this series was obtained the silver was 
extracted by Augustin’s method, which is accordingly here 
illustrated, but at present a different process is adopted. Ex- 
amples of the rosette copper formerly made at Mansfeld are 
here shown. A little water was thrown on to the bath of molten 
copper, in a hemispherical basin, in order to determine the 
