BOOK X. 475 



the channel, mixed with charcoal, the scum, as one might say, of the lead ; 

 the lead makes this scum when it becomes hot, but that less of it may be 

 made it must be stirred frequently with the bar. 



Within the space of a quarter of an hour the crucible absorbs the lead ; 

 at the time when it penetrates into the crucible it leaps and bubbles. Then 

 the master takes out a Uttle lead with an iron ladle, which he assays, in order 

 to find what proportion of silver there is in the whole of the alloy ; the 

 ladle is five digits wide, the iron part of its handle is three feet long and the 

 wooden part the same. Afterward, when they are heated, he extracts with 

 a bar the litharge which comes from the lead and the copper, if there be any 

 of it in the alloy. Wherefore, it might more rightly be called spuma of lead 

 than of silver^*. There is no injury to the silver, when the lead and copper 

 are separated from it. In truth the lead becomes much purer in the crucible 

 of the other furnace, in which silver is refined. In ancient times, as the 

 author Phny^^ relates, there was under the channel of the crucible another 

 crucible, and the litharge flowed down from the upper one into the lower 

 one, out of which it was lifted up and roUed round with a stick in order that 

 it might be of moderate weight. For which reason, they formerly made it 

 into small tubes or pipes, but now, since it is not rolled round a stick, they 

 make it into bars. 



If there be any danger that the aUoy might flow out with the litharge, the 

 foreman keeps on hand a piece of lute, shaped like a cylinder and pointed at 

 both ends ; fastening this to a hooked bar he opposes it to the alloy so that 

 it will not flow out. 



Now when the colour begins to show in the sUver, bright spots appear, 

 some of them being almost white, and a moment afterward it becomes 

 absolutely white. Then the assistant lets down the water-gates, so that, the 

 race being closed, the water-wheel ceases to turn and the bellows are still. 

 Then the master pours several buckets of water on to the silver to cool it ; 

 others pour beer over it to make it whiter, but this is of no importance since 

 the silver has yet to be refined. Afterward, the cake of silver is raised with 

 the pointed iron bar, which is three feet long and two digits wide, and has a 

 wooden handle four feet long fixed in its socket. When the cake of silver has 

 been taken from the crucible, it is laid upon a stone, and from part of it the 

 hearth-lead, and from the other part the htharge, is chipped away with a 

 hammer ; then it is cleansed with a bundle of brass wire dipped in water. 

 When the lead is separated from the silver, more silver is frequently found 

 than when it was assayed ; for instance, if before there were three unciae and 

 as many drachmae in a centumpondium, they now sometimes find three unciae 

 and a half 3*. Often the hearth-lead remaining in the crucible is a palm 

 deep ; it is taken out with the rest of the ashes and is sifted, and that which 

 remains in the sieve, since it is hearth-lead, is added to the hearth-lead^'. 



'*The Latin term for litharge is spuma argenti, spume of silver. 



^^Pliny, XXXIII, 35. This quotation is given in full in the footnote p. 466. Agricola 

 illustrates these "tubes" of litharge on p. 481. 



'^Assuming Roman weights, three unciae and three drachmae per centumpondium 

 would be about 82 ozs., and the second case would equal about 85 ozs. per short ton. 



^'Agricola uses throughout De Re Metallica the term molyhdaena for this substance. 



V 



