BOOK VII. 



231 



the older they are, the dryer and better they are. The moulds in which the 

 cupels are moulded are of two kinds, that is, a smaller size and a larger size. 

 In the smaller ones are made the cupels in which silver or gold is purged 

 from the lead which has absorbed it ; in the larger ones are made cupels in 

 which sUver is separated from copper and lead. Both moulds are made out 

 of brass and have no bottom, in order that the cupels can be taken out of 

 them whole. The pestles also are of two kinds, smaller and larger, each 

 likewise of brass, and from the lower end of them there projects a round 

 knob, and this alone is pressed into the mould and makes the hollow part of 

 the cupel. The part which is next to the knob corresponds to the upper 

 part of the mould. 



-Little mould. 



-Inverted mould. C- 



PESTLE. 



Pestle. 



-Its knob. E — Second 



So much for these matters. I will now speak of the preparation of the 

 ore for assaying. It is prepared by roasting, burning, crushing, and wash- 

 ing. It is necessary to take a fixed weight of ore in order that one may 

 determine how great a portion of it these preparations consume. The 

 hard stone containing the metal is burned in order that, when its hardness 

 has been overcome, it can be crushed and washed ; indeed, the very hardest 

 kind, before it is burned, is sprinkled with vinegar, in order that it may more 

 rapidly soften in the fire. The soft stone should be broken with a hammer, 

 crushed in a mortar and reduced to powder ; then it should be washed 

 and then dried again. If earth is mixed with the mineral, it is washed in a 

 basin, and that which settles is assayed in the fire after it is dried. All mining 

 products which are washed must again be dried. But ore which is rich in 

 metal is neither burned nor crushed nor washed, but is roasted, lest that 

 method of preparation should lose some of the metal. When the fires have 



