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of gold. 



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 : — 



