244 BOOK VII. 



leather, which sags about one hand's breadth ; next, the leather is folded 

 over and tied with a waxed string, and the dish catches the quicksilver 

 which is squeezed through it. As for the gold which remains in the leather, 

 it is placed in a scorifier and purified by being placed near glowing coals. Others 

 do not wash away the dirt with warm water, but with strong lye and vinegar, 

 for they pour these liquids into the pot, and also throw into it the quicksilver 

 mixed with the concentrates made by washing. Then they set the pot in a 

 warm place, and after twenty-four hours pour out the liquids with the dirt, and 

 separate the quicksilver from the gold in the manner which I have described. 

 Then they pour urine into a jar set in the ground, and in the jar place a 

 pot with holes in the bottom, and in the pot they place the gold ; then the 

 lid is put on and cemented, and it is joined with the jar ; they afterward heat 

 it tiU the pot glows red. After it has cooled, if there is copper in the gold 

 they melt it with lead in a cupel, that the copper may be separated from it ; 

 but if there is silver in the gold they separate them by means of the aqua 

 which has the power of parting these two metals. There are some who, 

 when they separate gold from quicksilver, do not pour the amalgam into 

 a leather, but put it into a gourd-shaped earthen vessel, which they place 

 in the furnace and heat gradually over burning charcoal ; next, with an iron 

 plate, they cover the opening of the operculum, which exudes vapour, and as 

 soon as it has ceased to exude, they smear it with lute and heat it for a short 

 time ; then they remove the operculum from the pot, and wipe off the 

 quicksilver which adheres to it with a hare's foot, and preserve it for future 

 use. By the latter method, a greater quantity of quicksilver is lost, and by 

 the former method, a smaller quantity. 



If an ore is rich in silver, as is rudis silver^', frequently silver glance, 

 or rarely ruby silver, gray silver, black silver, brown silver, or yellow silver, 

 as soon as it is cleansed and heated, a centumpondium (of the lesser weights) of 

 it is placed in an uncia of molten lead in a cupel, and is heated until the lead 

 exhales. But if the ore is of poor or moderate quality, it must first be dried, 

 then crushed, and then to a centumpondium (of the lesser weights) an uncia 

 of lead is added, and it is heated in the scorifier until it melts. If it is not 

 soon melted by the fire, it should be sprinkled with a little powder of the 

 first order of fluxes, and if then it does not melt, more is added little by little 

 untU it melts and exudes its slag ; that this result may be reached sooner, 

 the powder which has been sprinkled over it should be stirred in with an iron 

 rod. When the scorifier has been taken out of the assay furnace, the alloy 

 should be poured into a hole in a baked brick ; and when it has cooled and been 

 cleansed of the slag, it should be placed in a cupel and heated until it exhales 

 all its lead ; the weight of silver which remains in the cupel indicates what 

 proportion of silver is contained in the ore. 



We assay copper ore without lead, for if it is melted with it, the copper 

 usually exhsdes and is lost. Therefore, a certain weight of such an ore 



^'For discussion of the silver ores, see note 8, p. io8. Rudis silver was a fairly 

 pure silver mineral, the various coloured silvers v/sxe partly horn-silver and partly alteration 

 products. 



