BOOK XL 523 



long ; its sharp edge is a palm wide ; the round end is three digits thick ; the 

 wooden handle is four feet long. 



The master throws pulverised earth into a small vessel, sprinkles water 

 over it, and mixes it ; this he pours over the whole hearth, and sprinkles 

 charcoal dust over it to the thickness of a digit. If he should neglect this, 

 the copper, settling in the passages, would adhere to the copper bed-plates, 

 from which it can be chipped off only with difficulty ; or else it would adhere 

 to the bricks, if the hearth was covered with them, and when the copper is 

 chipped off these they are easily broken. On the second day, at the same 

 time, the master arranges bricks in ten rows ; in this manner twelve 

 passages are made. The first two rows of bricks are between the first and 

 the second openings on the right of the furnace ; the next three rows are 

 between the second and third openings, the following three rows are 

 between the third and the fourth openings, and the last two rows between 

 the fourth and fifth openings. These bricks are a foot and a palm long, two 

 palms and a digit wide, and a palm and two digits thick ; there are seven of 

 these thick bricks in a row, so there are seventy all together. Then on the 

 first three rows of bricks they lay exhausted liquation cakes and a layer five 

 digits thick of large charcoal ; then in a similar way more exhausted 

 liquation cakes are laid upon the other bricks, and charcoal is thrown upon 

 them ; in this manner seventy centumpondia of cakes are put on the 

 hearth of the furnace. But if half of this weight, or a little more, is to be 

 " dried," then four rows of bricks will suffice. Those who dry exhausted 

 liquation cakes^" made from copper " bottoms " place ninety or a hundred 

 centumpondia^^ into the furnace at the same time. A place is left in the front 

 part of the furnace for the topmost cakes removed from the forehearth in 

 which copper is made, these being more suitable for supporting the exhausted 

 liquation cakes than are iron plates ; indeed, if the former cakes drip copper 

 from the heat, this can be taken back with the liquation thorns to the first 

 furnace, but melted iron is of no use to us in these matters. When the cakes 

 of this kind have been placed in front of the exhausted liquation cakes, the 

 workman inserts the iron bar into the holes on the inside of the wall, which 

 are at a height of three palms and two digits above the hearth ; the hole to 

 the left penetrates through into the wall, so that the bar may be pushed back 



'"A further amount of lead could be obtained in the first liquation, but a higher tem- 

 perature is necessary, which was more economical to secure in the " drying " furnace. 

 Therefore, the " drying " was really an extension of liquation ; but as air was admitted the 

 lead and copper melted out were oxidized. The products were the final residual copper, 

 called by Agricola the " dried " copper, together with lead and copper oxides, called by him 

 the " slags, " and the scale of copper and lead oxides termed by him the " ash-coloured 

 copper." The German metallurgists distinguished two kinds of slag : the first and principal 

 one, the darrost, and the second the darrsdhle, this latter differing only in that it contained 

 more impurities from the floor of the furnace, and remained behind until the furnace cooled. 

 Agricola possibly refers to these as " more liquation thorns," because in describing the 

 treatment of the bye-products he refers to thorns from the process, whereas in the description 

 of " drying " he usually refers to " slags." A number of analyses of these products, given 

 by Karsten, show the " dried " copper to contain from 82.7 to 90.6% copper, and from 9.4 

 to 17.3% lead; the "slag" to contain 76.5 to 85.1% lead oxide, and from 4.1 to 7.8% 

 cuprous oxide, with 9 to 13% silica from the furnace bottoms, together with some other 



*^If Roman weights, this would equal from 6,360 lbs. to 7,066 lbs. 



