5o6 BOOK XL 



of de-silverized lead, or of litharge, as will make it possible to obtain from that 

 alloy a liquation cake containing two and a quarter centumpondia of lead, 

 in which manner in four of these cakes there will be three centumpondia of 

 copper and nine centumpondia of lead. The lead which hquates from these 

 cakes weighs seven centumpondia, in each centumpondium of which there is 

 a quarter of a libra of silver and a Uttle more than a sicilicus. About seven 

 undue of silver remain in the exhausted hquation cakes and in the Uquation 

 thorns, if we may be allowed to make common the old name {spinae=i\iovns) 

 and bestow it upon a new substance. If in three-quarters of a centumpondium 

 of copper there is less than three-quarters of a libra of silver, or three-quarters 

 and a semi-uncia, then as much rich lead must be added as wiU produce one 

 of the proportions of silver in the copper-lead alloy above mentioned ; this 

 is the " third " alloy. To this is added such an amount of de-silverized lead 

 or of litharge, that a hquation cake made from it contains in aU two and 

 three-quarters centumpondia of lead. In this manner four such cakes will 

 contain three centumpondia of copper and eleven centumpondia of lead. 

 The lead which these cakes liquate, when they are melted in the furnace, 

 weighs about nine centumpondia, in each centumpondium of which there is 

 a quarter of a libra and more than a sicilicus of silver ; and seven unciae of 

 silver remain in the exhausted hquation cakes and in the hquation thorns. 

 If, however, in three-quarters of a centumpondium of copper there is less than 

 ten-twelfths of a libra or ten-twelfths of a libra and a semi-uncia of silver, 

 then such a proportion of rich lead is added as wiU produce in the copper-lead 

 alloy one of the proportions of silver which I mentioned above ; this is the 

 " fourth " alloy. To this is added such a weight of de-silverized lead or of 

 Htharge, that a hquation cake made from it contains three centumpondia of 



this table that with the increasing richness of copper an increased proportion of lead was 



added, so that the products were of similar value. It has been assumed (see footnote 13 



p. 509), that Roman weights are intended. It is not to be expected that metallurgical 



results of this period will " tie up " with the exactness of the modern operator's, and it has 



not been considered necessary to calculate beyond the nearest pennyweight. Where two 



or more values are given by the author the average has been taken. 



1ST Charge. 2nd Charge. 3RD Charge. 4TH Charge. 



Amount of argenti- 

 ferous copper . . 211. 8 lbs. 211. 8 lbs. 211. 8 lbs. 211. 8 lbs. 



Amount of lead . . 564.8 ,, 635.4 .. 776.6 ,, 847.2 ,, 



Weight of each cake . . 193.5 ,, 211. 5 ,, 247.1 ,, 264.75,, 



Average value of 



charge . . . . 56 ozs. 3dwts. 62 ozs. 4dwts. 64 ozs. 4dwts. 66 ozs. 7dwts. 



Per cent, of copper.. 27.2% 25% 21.4% 20% 



Average value of ori- 

 ginal copper per ton 207 ozs. 4dwts. 251 ozs. 3dwts. 299 ozs. i5dwts. 332 ozs. 3dwts. 



Weight of argenti- 

 ferous lead liquated 

 out . . . . 423.6 lbs. 494-2 lbs. 635.4 lbs. 706 lbs. 



Average value of liqu- 

 ated lead per ton. . 79 ozs. 79 ozs. 79 ozs. 85 ozs. 



Weight of residues (re- 

 sidual copper and 

 thorns) . . . . 353 lbs. 353 lbs. 353 lbs. 353 lbs. 



Average value of re- 

 sidues per ton .. 34 ozs. 34 ozs. 34 ozs. 34 ozs. to 38 ozs. 



Extraction of silver 

 into the argenti- 

 ferous lead . . 76.5% 73.4% 79% 85.3% 



