BOOK VII.

231

the older they are, the dryer and better they are. The moulds in which thecupels 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 purgedfrom the lead which has absorbed it; in the larger ones are made cupels inwhich silver is separated from copper and lead. Both moulds are made outof brass and have no bottom, in order that the cupels can be taken out ofthem whole. The pestles also are of two kinds, smaller and larger, eachlikewise of brass, and from the lower end of them there projects a roundknob, and this alone is pressed into the mould and makes the hollow part ofthe cupel. The part which is next to the knob corresponds to the upperpart of the mould.

A —Little mould. B —Inverted mould. C—Pestle. D —Its knob. E —Second

pestle.

So much for these matters. I will now speak of the preparation of theore 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 maydetermine how great a portion of it these preparations consume. Thehard stone containing the metal is burned in order that, when its hardnesshas been overcome, it can be crushed and washed; indeed, the very hardestkind, before it is burned, is sprinkled with vinegar, in order that it may morerapidly 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 washedand then dried again. If earth is mixed with the mineral, it is washed in abasin, and that which settles is assayed in the fire after it is dried. All miningproducts which are washed must again be dried. But ore which is rich inmetal is neither burned nor crushed nor washed, but is roasted, lest thatmethod of preparation should lose some of the metal. When the fires have