256 



BOOK VII. 



The 1st of 12 duellae of gold and 12 duellae of copper. 



These needles are not much used, because gold coins of that kind are 

 somewhat rare ; the ones chiefly used are those in which there is much 

 copper. Needles of the third kind, which are composed of gold, silver, and 

 copper, are more largely used, because such gold coins are common. But since 

 with the gold there are mixed equal or unequal portions of silver and copper, 

 two sorts of needles are made. If the proportion of silver and copper is 

 equal, the needles are as follows : — 



The 



Some make twenty-five needles, in order to be able to detect the two 

 scripula of silver or copper which are in a bes of gold. Of these needles, the 

 first is composed of twelve duellae of gold and six of silver, and the same 

 number of copper. The second, of twelve duellae and one sextula of gold, and 

 five duellae and one and a half sextulae of silver, and the same number of 

 duellae and one and a half sextulae of copper. The remaining needles are 

 made in the same proportion. 



Pliny is our authority that the Romans could tell to within one scripulum 

 how much gold was in any given alloy, and how much silver or copper. 



Needles may be made in either of two ways, namely, in the ways of which 

 I have spoken, and in the ways of which I am now about to speak. If 



