CHAP. XXIII. WEAR OF COIN. 175 



perfect knowledge of assaying that then existed 

 the small quantity of those inferior metals could 

 not easily be detected. 



It has been shown by the experiments of Mes- 

 sieurs Cavendish and Hatchett that if our English 

 standard gold, consisting of two parts of alloy in 

 twenty-four, were to have that alloy formed of a 

 mixture of iron and tin, the loss by friction would 

 be five times as much as it is with the kind of alloy 

 applied at the mint 1 ; if the alloy were copper and 

 tin it would be nearly four times as much. There 

 is no reason to conclude that the ancients ever 

 used any alloy except tin, iron, and copper, and 

 we may conclude therefore that the loss on their 

 gold coins was from four to five times as great as 

 would be experienced on the modern English gold 

 coins. 



The maximum of durability for gold coins 

 seems to be fixed at twenty-two parts in twenty- 

 four of pure gold with the appropriate alloys. 

 When the fineness ascends or descends from that 

 point, the consumption by abrasion is increased. 

 Thus the experiment of Mr. Cavendish and Mr. 

 Hatchett shows, as before stated, that gold of the 

 finest quality that can be worked, viz. of twenty- 

 three carats and three quarters fine, suffers a loss 

 of four times that of the standard of twenty-two 

 fine. On the other hand, the coins below that 



1 See note, page 1 70. 



