BOOK VII. 



255 



The gth needle of 15 duellae of silver and 9 duellae of gold. 



loth 

 nth 

 12th 

 13th 

 14th 

 15th 

 i6th 

 17th 

 i8th 

 19th 

 20th 



2ISt 



22nd 

 23rd 

 24th 



14 

 13 

 12 

 II 

 10 



9 

 8 



7 

 6 



5 

 4 

 3 

 2 



I 



pure gold 



ID 



II 



12 

 13 

 14 

 15 

 16 



17 

 18 



19 

 20 

 21 

 22 

 23 



By the first eleven needles, when they are rubbed on the touchstone, we 

 test what proportion of gold a bar of silver contains, and with the remaining 

 thirteen we test what proportion of silver is in a bar of gold ; and also what 

 proportion of either may be in money. 



Since some gold coins are composed of gold and copper, thirteen needles 

 of another kind are made as follows : — 



