Observations on the Purity of Standard Gold. 137 



hammers, afterwards pound it, bruise it, and wash it; and 

 finally, that the gold, when put into a close crucible, with 

 a little lead, salt, a little tin, and barley meal, was exposed 

 over the fire for rive days. 



The money-coiners of Darius certainly employed this 

 method, or a similar one, when this enlightened king wished 

 <o give his subjects ihe noble and useful example of a mint 

 made with the purest gold, similar to that of fine silver, 

 which his satrap Ariander afterwards did. 



To conclude: — It is not easy to form an intelligible idea 

 of the docimastic method, which Agatharchides has trans- 

 mitted to us. But if in the operation which he describes 

 there is no mention made of cementation, but of a true and 

 prolonged fusion, it remains to explain how we can re- 

 concile with the object in view, the employment of a close 

 crucible held over the fire, as he describes : far less can we 

 comprehend the use of the barley meal. 



When we reflect, however, on the ingenious method de- 

 scribed by Heilot as being practised at Lyons, in order to 

 refine, purifv, and separate cupelled silver from the small 

 quantity of lead which adheres to it after the first refining, 

 we may perhaps comprehend what is meant *. 



In Lyons they use crucibles thirteen inches high, and 

 five broad at their orifice. About three inches deep of 

 pounded charcoal is then put into the crucible and kept 

 down bv a lid, or rather a triangular piece of the crucible, 

 which is kept in its place. Oil this lid or false bottom 

 they put CO or 6 j pounds of long and thin ingots, in order 

 to be melted and purified. The wind furnace employed 

 for this purpose is 14 inches high, seven in diameter at the 

 grate, and nine at the top. The metal in melting was ob- 

 served to fall three inches from the edges of the crucible: 

 then, when it had acquired a sufficient degree of' heat, it was 

 seen to boil with the force and the agitation of' water ex- 

 posed to the heat of a strong fire ; and in this state it was 

 kept for seven or eight hours. 



The elastic fluid, which in this case is extricated from 

 the charcoal at the bottom of the crucible, produces the 

 agitation above alluded to; and it forms, as it were, a kind 



* It wou.ld be necessary, before deciding finally on the process detailed by 

 Agatharchides and that which is practised at Lyons, to repeat them, taking 

 the greatest care to apply the modern methods of chemical analysis, and 

 above all the pneumato-chemical apparatus: it would be necessary to de- 

 termine the nature of the gas, which passes through the melted siiver, and 

 ascert iin why the gas is formed under a certain pressure, and why it doet 

 out pass out through the pores of the crucible. The experiment of M. Fab- 

 broni does np£ seem to- mc to be conclusive. 



of 



