EXPERIMENTS ON VARIOUS ALLOYS OF COLD. 153 



pofing that hard gold foffered, in every cafe, lefs by fridlon 

 than that which is moderately duftile, (which is not however 

 the fa6t,) and allowing that ftandard gold may, by a mixed 

 alloy, be rendered as hard as gold reduced by copper to 

 18 carats, without changing the ftandard proportion of gold, 

 yet it would be very difficult always to make fuch ftandard 

 gold of an uniform degree of hardnefs. Aloreover, by fome 

 experiments which Mr.H. purpolely made at the Mint, upon the 

 rolling and ftamping of gold of different qualities, it evidently 

 appeared, that gold equal in hardnefs to that of 1 8 carats, 

 could not be employed with advantage; for, the additional 

 labour which was required for the rolling and ftamping of 

 this hard gold, the frequent failure in maknig the impreflion, 

 and the battering and breaking of the dies, fully proved, that 

 the expence and difficulty attending the working of fuch 

 gold, would by no means be compenfated by any fmall degree 

 of durability which it might poftefs over any other. 



The extremes of duftility and of hardnefs being therefore ^°'^ °^ ^J^P^- 

 equally objectionable, it follows of courfe, that gold of mo- j,g^^ 

 derate du6tility muft be that which is the beft adapted for 

 coin ; and, as nothing but filver or copper can be employed 

 to alloy gold which is intended to be coined, it may be here 

 obferved, that whatever might have been the original motive 

 for introducing the prefent ftandard of 22 carats, yet it ap- 

 pears, from the experiments lately defcribed, that this pro- 

 portion of y^ of the above-mentioned metals, is (every cir- 

 cumftance being confidered) the beft, or at leaft as good as 

 any, which could have been chofen. 



There is, however, fome difference in the quality of gold, 

 when alloyed with the ftandard proportion of filver, of filver 

 and copper, and of copper, which requires to be con- 

 fidered. 



Gold alloyed with one-twelfth of filver, is of a fine but Gold alloyed 

 pale yellow ; it is very dudile ; it is eafily rolled, and may ^/"^^fg^J.' '^ 

 be ftamped without being annealed ; it conlequently does 

 not require to be blanched j and, after the complete procefs 

 of coining, the furface and every part remains of an uni- 

 form quality, fo that, by wear, it does not appear of different 

 colours. 



Thefe properties are certainly much to be valued ; but the 

 objedions to this kind of ftandard gold are, 



1ft. 



