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BOOK VII.

good, for the cupels made from them, since they are not sufficiently dry,frequently crack and break in the fire and absorb the metals. If ashes ofbeech or similar wood are not to be had, the assayer makes little balls of suchashes as he can get, after they have been cleared of impurities in the mannerbefore described, and puts them in a baker’s or potter’s oven to bum, and fromthese the cupels are made, because the fire consumes whatever fat or dampthere may be. As to all kinds of ashes, the older they are the better, for it isnecessary that they should have the greatest possible dryness. For thisreason ashes obtained from burned bones, especially from the bones of theheads of animals, are the most suitable for cupels, as are also those ashesobtained from the horns of deer and the spines of fishes. Lastly, some take theashes which are obtained from burnt scrapings of leather, when the tannersscrape the hides to clear them from hair. Some prefer to use compounds,that one being recommended which has one and a half parts of ashes from thebones of animals or the spines of fishes, and one part of beech ashes, and half apart of ashes of burnt hide scrapings. From this mixture good cupels aremade, though far better ones are obtained from equal portions of ashes ofburnt hide scrapings, ashes of the bones of heads of sheep and calves, andashes of deer horns. But the best of all are produced from deer horns alone,burnt to powder ; this kind, by reason of its extreme dryness, absorbs metalsleast of all. Assayers of our own day, however, generally make thecupels from beech ashes. These ashes, after being prepared in themanner just described, are first of all sprinkled with beer or water, to makethem stick together, and are then ground in a small mortar. They are groundagain after being mixed with the ashes obtained from the skulls of beasts or fromthe spines of fishes ; the more the ashes are ground the better they are.Some rub bricks and sprinkle the dust so obtained, after sifting it, into thebeech ashes, for dust of this kind does not allow the hearth-lead to absorbthe gold or silver by eating away the cupels. Others, to guard against thesame thing, moisten the cupels with white of egg after they have been made,and when they have been dried in the sun, again crush them ; especially if theywant to assay in it an ore or copper which contains iron. Some moisten theashes again and again with cow’s milk, and dry them, and grind them in asmall mortar, and then mould the cupels. In the works in which silveris separated from copper, they make cupels from two parts of the ashes ofthe crucible of the cupellation furnace, for these ashes are very dry, and fromone part of bone-ash. Cupels which have been made in these ways alsoneed to be placed in the sun or in a furnace ; afterward, in whatever waythey have been made, they must be kept a long time in dry places, for theolder they are, the dryer and better they are.

Not only potters, but also the assayers themselves, make scorifiersand triangular crucibles. They make them out of fatty clay, which isdry 5 , and neither hard nor soft. With this clay they mix the dust of oldbroken crucibles, or of burnt and worn bricks ; then they knead with apestle the clay thus mixed with dust, and then dry it. As to these crucibles,B Spissa, —“Dry.” This term is used in contra-distinction to pingue, unctuous or "fatty.”