BOOK XI. 541 



the work of smelting, one of whom smelts, while the other takes out the 

 thick cakes from the forehearth. These cakes are only "dried," and from 

 the " dried " cakes copper is again made. 



The " slags "*° are melted continually day and night, whether they have 

 been drawn off from the alloyed metals with a rabble, or whether they adhered 

 to the forehearth to the thickness of a digit and made it smaller and 

 were taken off with spatulas. In this manner two or three hquation cakes 

 are made, and afterward much or little of the "slag," skimmed from the 

 molten alloy of copper and lead, is re-melted. Such hquation cakes should 

 weigh up to three centum pondui, in each of which there is half an uncia of 

 silver. Five cakes are placed at the same time in the furnace in which 

 argentiferous lead is liquated from copper, and from these are made lead 

 which contains half an uncia of silver to the centumpondium. The exhausted 

 liquation cakes are laid upon the other baser exhausted liquation cakes, from 

 both of which yellow copper is made. The base thorns thus obtained are 

 re-melted with a few baser " slags," after having been sprinkled with con- 

 centrates from furnace accretions and other material, and in this manner six 

 or seven liquation cakes are made, each of which weighs some two centum- 

 pondia. Five of these are placed at the same time in the furnace in which 

 silver-lead is liquated from copper ; these drip three centumpondia of 

 lead, each of which contains half an imcia of silver. The basest thorns 

 thus produced should be re-melted with only a little " slag." The copper 

 alloyed with lead, which flows down from the furnace into the fore- 

 hearth, is poured out with a ladle into oblong copper moulds ; these cakes 

 are " dried " with base exhausted liquation cakes. The thorns they produce 

 are added to the base thorns, and they are made into cakes according to the 

 method I have described. From the " dried " cakes they make copper, of 

 which some add a small portion to the best " dried " cakes when copper is 

 made from them, in order that by mixing the base copper with the good it 

 may be sold without loss. The " slags," if they are utilisable, are re-melted 

 a second and a third time, the cakes made from them are " dried," and from 

 the " dried " cakes is made copper, which is mixed with the good copper. The 

 "slags," drawn off by the master who makes copper out of "dried" cakes, 

 are sifted, and those which fall through the sieve into a vessel placed under- 

 neath are washed ; those which remain in it are emptied into a wheelbarrovi? 

 and wheeled away to the blast furnaces, and they are re-melted together 

 with other " slags," over which are sprinkled the concentrates from washing 

 the slags or furnace accretions made at this time. The copper which flows out 



'"There are three principal " slags " mentioned — 



1st. Slag from " leading." 



2nd. Slag from " drying." 



3rd. Slag from refining the copper. 

 From the analyses quoted by various authors these ran from 52% to 85% lead oxide, 

 5% to 20% cuprous oxide, and considerable silica from the furnace bottoms. They were 

 reduced in the main into liquation cakes, although Agricola mentions instances of the 

 metal reduced from " slags " being taken directly to the " drying " furnace. Such liquation 

 cakes would run very low in silver, and at the values given only averaged 12 ozs. per ton ; 

 therefore the liquated lead running the same value as the cakes, or less than half that of the 

 " poor " lead mentioned in Note 17, p. 512, could not have been cu]:)elled directly. 



